Progressive Crop Consultant - March/April 2020

March/April 2020

Spray Calibration and Coverage: The Basics of Spray Application The Start of Irrigation in Almonds The Brown Marmorated Stink Bug Is (Still) Invading California M A R C H /A P R I L 2 0 2 0

CO T T O N REVIEW pages 33-80

June 3, 2020 5 page See details for

Alm nd Day June 24, 2020

PUBLICATION

5 : Issue 2 March / April 2020 Volume www.progressivecrop.com

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March / April 2020

PUBLISHER: Jason Scott Email: jason@jcsmarketinginc.com EDITOR: Marni Katz ASSOCIATE EDITOR: Cecilia Parsons Email: article@jcsmarketinginc.com PRODUCTION: design@jcsmarketinginc.com Phone: 559.352.4456 Fax: 559.472.3113 Web: www.progressivecrop.com

IN THIS ISSUE

4 10 16 20

26

Selecting the Right Rootstock in California Prune Production

Richard Buchner

Farm Advisor Emeritus Tehama County

Spray Calibration and Coverage: The Basics of Spray Application

The Start of Irrigation in Almonds: Early Season Irrigation Management Impact Tree Health All Season Economic Trends in Almond Production: New UC Ag Issues Center Study on Costs and Returns for Almond in California Shows Product Costs Have Increased Substantially

Kent M. Daane

4

Dept. of Environmental Science, Policy, & Management, UC Berkeley

Margaret L. Ellis

Franz Niederholzer

UCCE Farm Advisor for Colusa, Sutter, and Yuba Counties

Dr. James M. Olvey Ph.D.,

Allan Fulton

Greg Palla

Brittney Goodrich

UCCE Specialist, Department of Agricultural and Resource Economics, UC Davis

Ian Grettenberger

UCCE Field Crops Specialist

Bob Hutmacher

UCCE Cotton Specialist and AES Agronomist

President, O & A Enterprises, Inc. San Joaquin Valley Quality Cotton Growers Association

Davide Scaccini

Dept. of Agronomy Food Natural Resources Animals and Environment, University of Padova, Legnaro, Padova, Italy

Lynn M. Sosnoskie

UCCE Weed Science Farm Advisors

Judith M. Stahl

UUCCE Weed Science Farm Advisors

Dept. of Environmental Science, Policy, & Management, UC Berkeley

Dr. Peter Ako Larbi

Dr. Mauricio Ulloa

Kurt J. Hembree

The Brown Marmorated Stink Bug Is (Still) Invading California

UCCE Farm Advisor for Butte, Glenn and Tehama Counties

Plant Science Department, California State University, Fresno UCCE Irrigation and Water Resources Advisor, Tehama, Shasta, Glenn, and Colusa Counties

10

Luke Milliron

UCCE Agricultural Application Engineering Specialist, Kearney Agricultural Research and Extension Center

USDA-ARS Plant Stress and Germplasm Development Research, Lubbock, TX

33 COT TON REVIEW

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The articles, research, industry updates, company profiles, and advertisements in this publication are the professional opinions of writers and advertisers. Progressive Crop Consultant does not assume any responsibility for the opinions given in the publication.

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S EL E CT ING T HE R I GH T R O O TS T OC K IN CA L IFOR NI A PRU N E PRODUC T I ON

By LUKE MILLIRON | UCCE Farm Advisor for Butte, Glenn and Tehama Counties FRANZ NIEDERHOLZER | UCCE Farm Advisor Colusa, Sutter, and Yuba Counties ALLAN FULTON | UCCE Irrigation and Water Resources Advisor, Tehama, Colusa, Glenn, & Shasta RICHARD BUCHNER| Farm Advisor Emeritus Tehama County A tree at the Yuba rootstock trial site that likely died of a bacterial canker infection sometime after leafout in 2018 (photo courtesy of L. Milliron).

R

oots are the unsung heroes of orchard plantings. They operate out of sight and are relatively difficult to examine and characterize. The roots, of course, anchor the trees to the soil and take up water and essential mineral elements.

They also store carbohydrates and synthesize materials. Because roots play these key roles, rootstocks can influence scion vigor, growth and performance. Rootstocks vary in their tolerance to different soil types and conditions and their resistance to soil borne diseases and nematodes As soil treatment options become increasingly limited, more restrictive and less effective, the priority to identify a genetic solution to solve or reduce the replant issue is of increasing interest. One genetic solution is to find or develop rootstocks to help manage soil related problems, such as soil borne fungi/bacteria, nematodes and 4

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soil acidity and excess salts. Of additional interest are root and tree characteristics imparting canopy size control, good anchorage and little or no root suckering.

The California prune industry has historically utilized just five rootstocks, Myrobalan 29C, Myrobalan seedling, Marianna 2624, Lovell peach and Marianna 40. The Prune Production Manual (UC ANR # 3507) has a very good chapter describing the traditional rootstock choices. You can find the production manual for sale at anrcatalog. ucanr.edu and as an e-version through Google Books. Recognizing the need for identifying additional rootstocks for California prune production, University of California farm advisors and campus-based faculty with funding from the California Prune Board designed and planted two replicated rootstock experiments in 2011 to evaluate 15 rootstocks

March / April 2020

for prune production. These rootstocks have diverse genetic backgrounds within the Prunus family (plum, peach, almond, etc.).

Replicated rootstock trials in growers’ orchards in Butte County and Yuba Counties allow UC researchers to evaluate a total of 15 rootstocks (Table 1, pg. 6) under very different soil, irrigation, and yield potential.

The Butte plot is planted on Farwell clay adobe and the lighter textured Nord Loam soil types; this ground was previously planted to almonds on Lovell (peach) rootstock. In contrast, the Yuba site is planted on more typical prune ground (Kilga clay loam) and is prune following prune. The Butte site has tighter spacing at 12.5 feet in-row and 17 feet between rows (205 trees per acre), compared to 16 feet in-row and 18 feet between rows (151 trees per acre) at Yuba. The Butte plot is drip irrigated, while the Yuba plot has micro sprinklers.

The differences in soil, crop history, tree density, irrigation, and resulting vigor at the two replicated trial sites allows for a rigorous evaluation of these rootstocks.

Tree Survival

Roger Duncan a pomology farm advisor based in Stanislaus County, who has done extensive trialing of rootstocks for almond production, has noted that rootstock choice is like an insurance policy. Although there is no perfect rootstock, careful rootstock selection can help guard against disaster.

These two trial sites have illustrated an incredible range in rootstock survival, which helps illustrate a varying ability of these rootstocks to guard against disaster at two very different sites. Following a wet winter which delayed soil preparation in 2011, both the Butte and Yuba sites experienced extensive mortality and were significantly replanted in 2012. However, even after replanting in 2012, the rootstocks have experienced very different rates of survival.

Percent tree survival since the 2012 replanting was assessed at both sites in 2019 (Table 2, pg. 7). Survival ranged from 10 percent (Empyrean 2) to 97 percent (Atlas) at the Butte site, and 37 percent (HBOK 50) to 100 percent (Viking and Lovell) at the Yuba site. The two rootstocks that are only planted at a single site each have

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standard, had a mere 63-percent survival as of 2019, while Marianna 30 and HBOK 50 fared even worse, each at 37-percent survival. In contrast, Viking, Atlas, Krymsk 86, Lovell and Rootpac-R all had between 93- and 100-percent survival.

Vigor and Yield

Satellite image of the UCCE prune rootstock plot in Yuba County. Although tree loss was likely from multiple causes, bacterial canker was a significant player. Note gaps of six trees (number of trees in a replicate), despite rootstock treatments with large, healthy canopies surrounding these gaps (Google©, Imagery Maxar Technologies ©2019, and U.S. Geological Survey map data ©2019).

Continued from Page 4 had dramatically different results, with the disastrous 10 percent survival of Empyrean 2 at Butte, compared to the 93 percent survival of Rootpac-R at Yuba.

There are other notable differences and similarities in survival between the two sites. Myrobalan 29C, Myrobalan seedling, and HBOK 50 have all had higher survival rates at the Butte site, potentially due to bacterial canker susceptibility at the Yuba location. At both sites, Atlas and Viking, which were planted in 2012 (not available in 2011), have had excellent survival (97 to 100 percent). Marianna 40 and Marianna 2624 have also had decent survival (80 to 87 percent). Finally, Marianna 30 has had very low survival at both sites (43 and 37 percent at Butte and Yuba, respectively).

are six trees in length (i.e. the number of trees in a rootstock treatment replicate, see related photo). Although there are several causes of tree loss in the plot, certain rootstocks have had very low survival in the same areas of the orchard where other rootstocks have 100-percent survival and vigorous growth. For example, Myroblan 29C an industry

The satellite image of this plot clearly shows several gaps of missing trees that Progressive Crop Consultant

The 2017 harvest at the Butte site shows that a larger trunk, measured as trunk cross sectional area (cm2), generally higher dry yield (pounds per tree), and smaller fruit size (Table 3, pg. 8).

Among the smaller trunk size and lower yielding trees were Krymsk 1, HBOK 50, Marianna 58, Empyrean 2 and Citation.

Among the largest and highest yielding

Table 1: Rootstocks being evaluated in Butte and Yuba Counties Heritage (P. = Prunus)

Bacterial canker susceptibility has greatly colored the results at the Yuba location.

Land with a history of the disease likely has ring nematode, and may also have sandy or low pH soils, low tree nitrogen status, or a clay/shallow hardpan. For land with a history of bacterial canker, having a prune orchard with a high rate of survival at maturity is no small feat.

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The first mechanical harvest in the two trials was in 2017 and yield data continues to be taken. In addition to the Butte site having tighter spacing (205 trees/acre, compared to 151 at Yuba), the tree trunks have generally been larger, and yields per tree higher than Yuba. The 2017 yield results at Butte offer a valuable glimpse into the vigor of these rootstocks, since it was a very high yielding and unthinned crop, which helps illustrate the yield potential of these rootstocks.

These high, unthinned yields were unsustainable and in 2018 there was poor return bloom at the site and low yields.

March / April 2020

Table 2: Percent Tree Survival Butte Rootstock 2019

Myrobalan 29C Atlas Viking Marianna 30 Lovell Marianna 40 Marianna 2624 Myroblan seedling Krymsk 86 Citation Rootpac-R Empyrean 2 Marianna 58 HBOK 50 Krymsk 1 Average:

Yuba

90% 97% 93% 43% 70% 86% 80%

ab a a bc ab ab ab

63% 97% 100% 37% 100% 87% 83%

ab a a b a a a

93% 77% 53%

a ab abc

73% 97% 80% 93%

ab a a a

10% 73% 77% 43% 70%

c ab ab bc

77% 37% 80% 79%

ab b a

Table 2 Percent tree survival at the Butte (September) and Yuba (June) sites in 2019. Values followed by the same letters are not significantly different at 95 percent using Tukey’s HSD. The numerically highest and lowest values are highlighted in each column.

were Myrobalan 29C, Atlas, Viking, Marianna 30 and Lovell. Similar yield and trunk size differences between rootstocks have been found subsequently at both sites. Of course, all rootstock trials that impose the same spacing across the plot disadvantage lower vigor rootstocks that could have been placed at a higher density.

Although there are similarities in yield performance of the rootstocks at both sites, there are some notable differences between sites. Rootpac-R, which isn’t planted at the Butte site, has had middle of the pack trunk size and yield at Yuba. Another notable difference is that Krymsk 86 is a fairly average vigor and yield rootstock at Butte but is among the largest and highest yielding at Yuba.

Anchorage & Suckering

In addition to survival and vigor (and resulting yield potential), there are other attributes that are important to growers.

Anchorage is key since growers need trees to stand up on their own and not be blown over, as well as provide a straight up-and-down trunk for shaker harvesting.

Degree of lean was measured with the level feature in the iPhone at both rootstock plots with one person pushing against the

tree and another person measuring the deflection. Although rootstocks at the Yuba site had greater lean (there were notable wet soil conditions at the time of measurement), the rootstocks had similar relative lean to one-another at the two sites. Marianna 58 and Krymsk 1 had among the greatest angles of deflection, while Viking and especially Krymsk 86 showed little deflection at either site.

Removing suckers is a costly and cumbersome activity. In addition, rootstock suckers may offer a route for systemic herbicides to be taken up and damage the tree. Rootstocks suckers were rated on a one to five scale, with one being the fewest suckers and five being extensive and large suckers.

Again, the two sites offered many similarities in rootstock performance.

Myroblan seedling had the most rootstock suckers at both sites, while many rootstocks including Atlas, HBOK 50, Viking, Citation, Marianna 58, Lovell and Marianna 40 had few, if any suckers.

Rootstocks with Potential Problems Many of the rootstocks haven’t performed well when survival, lean, and suckering were evaluated.

Many of those same underperforming rootstocks also tend to be on the lower vigor and lower yielding end of the spectrum. Krymsk 1 and Marianna 58 had among the highest lean, and in-addition Krymsk 1 had low survival at Butte and was among the lowest yielding rootstocks. HBOK 50 also had high lean, poor survival at Yuba, and poor yield at Butte. Empyrean

2 which was only at Butte, had a mere 10-percent survival by 2019. Myroblan seedling had the worst suckering and had high lean at Yuba. The industry standard Myroblan 29C has performed well at Butte but has had low survival under the bacterial canker conditions in Yuba. Marianna 30, despite been among the highest yielding rootstocks per tree at Butte has had very low survival at both sites.

Rootstocks with Evident Strengths

Krymsk 86, Viking, and Atlas have all had very high survival at both rootstock trial sites. In addition, Krymsk 86 has been among the highest yielding at Yuba, and Atlas and Viking have been high yielding at both sites. Krymsk 86 has maintained its reputation for excellent anchorage, while Viking also showed little lean at both sites. Finally, both Viking and Atlas had a sucker rating of zero at both

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Continued from Page 7

Table 3: 2017 Butte Rootstock Experiment Harvest Comparisons

rootstock plots.

2016 Trunk Size (cm 2 ) 46 a

Dry Yield (lbs./tree) 18 a

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Where Is Rootstock Selection in the Industry Headed?

Atlas, Viking, and Krymsk 86 have all shined at these two rootstock plots.

Krymsk 86 is the only one of these that is so far seeing significant adoption in the prune industry. Following widespread adoption of Krymsk 86 in the Sacramento Valley for almond production, Krymsk 86, known for its superior anchorage and tolerance to wet feet, has been planted now in many new prune orchards. Like the higher vigor at the Yuba site and in contrast to the middling vigor at Butte, we have heard from growers that Krymsk 86 has been a high vigor rootstock in their plantings. Just as with growing almonds on Krymsk 86, growers should test for and be wary of planting Krymsk 86 where nematodes, particularly root-knot, are present.

As described in an article in the September/October issue of Progressive Crop Consultant (progressivecrop. com/2019/10/californias-prune-orchardof-the-future) choosing a higher vigor rootstock and/or planting at a tighter spacing leads to capturing more sunlight and having a higher yield potential.

However, when hand pruning large prune trees can cost $1,000 per acre, many growers are adopting mechanical hedging, and some progressive growers have had an increased interest in low vigor rootstocks.

A couple of these growers have begun trialing low vigor inducing rootstocks in high density plantings, in hopes that low vigor rootstocks will reduce pruning expenses. Low vigor, high density and potentially trellised plantings, stand in stark contrast to the vigorous rootstocks that have stood out in these two trials.

The choice between high and low vigor rootstock may prove to be one of the key defining choices where the California prune industry heads in the coming years.

We want to sincerely thank an amazing team of UC researchers, as well as support from dryer managers at Sunsweet Growers Inc. This work is made possible by the generous funding support of the California Prune Board.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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S P RAY C A L I B R AT I O N A N D C O V E R A G E :

THE BASICS OF SPRAY APPLICATION

By DR. PETER AKO LARBI | UCCE Agricultural Application Engineering Specialist, Kearney Agricultural Research and Extension Center

A

ir-assisted sprayers discharge tank mix as tiny spray droplets into an airstream that transports the droplets to the target tree or vine canopy. The mixture of air and spray droplets, known as the spray cloud, expands in both the vertical and horizontal dimensions as it moves away from the sprayer’s outlet. The speed of the air reduces drastically after exiting the sprayer and then continues to reduce gradually with distance away from the sprayer. Because the sprayer is moving, however, the spray cloud appears as having been bent backwards.

Why is it important? Calibration is best practice in pesticide spray application. When done correctly, it is a sure way to know how much material you would actually be applying to your crop. Incorrect calibration or not calibrating at all can result in inaccurate application rate, ineffective application, and illegal residues on the treated crop. Accurate calibration will lead to effective pest control while minimizing waste and negative environmental impact. Above all, accurate sprayer calibration will ensure compliance with the law as represented by the pesticide label.

If we consider the continuous forward movement of the sprayer to be in short steps of equal lengths, we can determine the time the sprayer spends in each step by dividing the step length by the travel speed.

We can then multiply the time by the flow rates of the air and spray liquid to know the volumes of air and spray discharged in each step movement. The volume of spray is what is applied in each forward step and the volume of air is how much is available to carry the applied spray. The slower the travel speed, the higher the volume discharged; the faster the travel speed, the lower the volume discharged.

When should it be done? Ideally, sprayer calibration should be done at the beginning of the growing season and whenever there is a significant change in conditions.

Examples of changes in condition that may require calibration include: Change in ground condition (e.g. soil type, soil wetness, ground cover); change in target condition (e.g. crop type, canopy size, canopy density); change in spray material condition (e.g. density). Although not all the calibration steps may be necessary in response to a change, adjustments should be made to the components that are directly affected by the change. For instance, if only ground condition has changed, then only travel speed would have to be determined again and appropriate adjustments made. However, if a global positioning system (GPS) based speedometer device or mobile app is in use, then it may not be necessary to check speed again. This is because readings of GPS-based speedometers are not affected by changes in tire traction due to ground cover.

During the spray application, immediate tree or vine canopies adjacent to the sprayer are the target canopies (Figure 1). Each tree or vine is bound by a ground area equal to row spacing times tree spacing. It is sufficient and most efficient for the air to carry spray droplets to the target, not beyond.

This is because spray droplets carried beyond the target tend to either fall to the ground or potentially drift away by the wind when they miss canopies in the subsequent rows. However, the air speed and volume should be enough to cause the spray to penetrate the target canopy. This means that travel speed and air volume of the sprayer should be matched to the canopy size and density. Also, the number of nozzles used should not result in too much spray applied over and/or under the canopy. Effective spraying will result if the spray is strategically directed toward the target.

Continued on Page 12

Sprayer Calibration: What, Why, When and How What is it? Sprayer calibration is the adjustments made to a sprayer based on measurements taken to ensure that the correct amount of material (spray mix or active ingredient) is applied.

Figure 1. Basics of spray application.

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March / April 2020

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Figure 2. Various ways to determine travel speed.

Continued from Page 10 How should it be done? A major objective of sprayer calibration is the idea of optimizing the application. There are different ways to do it, but with the same or similar outcome. The steps could be as follow: 1) determine travel speed; 2) assess air profile to determine number of nozzles; 3) select nozzles; 4) measure sprayer output; 5) adjust sprayer output; and 6) assess spray coverage.

STEP 1: Determine Travel Speed This should be done with the sprayer tank about half-full and the fan running.

Materials needed: Measuring tape, flagging flags, stopwatch, calculator, clipboard, GPS device (e.g. smartphone).

Method 1 – Manual known distance method: Measure a known distance, D, (typically 100 or 200 feet) with a measuring tape in the orchard or vineyard where you would be spraying. Use marking flags to clearly indicate the distance. Using a stopwatch, measure the time, T, it takes for the sprayer to travel the marked distance at a preselected gear setting. Repeat this for at least three times in total and determine the average time. Calculate the speed, S, as: S (mph)=0.68 (D (ft))/(T (s)) When two people are available, in addition to the operator, person A should stand adjacent to the starting flag with one hand up (Figure 2a). Provide enough distance for the sprayer to attain the speed before reaching the starting flag. Once a predetermined feature on the tractor/ 12

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flagging tape on the vine adjacent to the marking flag to aid the operator’s visibility.

Note the tree spacing, TS. Providing enough distance for the sprayer to attain speed before reaching the starting flag, measure the time it takes for the sprayer to travel the marked distance at a preselected gear setting. The number of trees passed by the sprayer, NT, is Figure 4. Various nozzle configurations with different the count excluding degrees of missing target canopy. the starting tree but including the ending tree. sprayer (e.g. front of tractor/sprayer, center Repeat time measurement for a total of front wheel, etc.) reaches the starting of at least three times and determine point, person A should lower the raised the average. Calculate the speed as: hand to indicate to person B to start measuring the time with a stopwatch. Once S (mph)=0.68 (NT ×TS(ft))/(T (s) the predetermined feature on the tractor/ sprayer reaches the ending flag, person B Method 3 – Automatic tracking method should stop measuring the time and then record the elapsed time on a clipboard.

Drive the sprayer for about 100 ft or more while observing the speed reading on a When only one person is available, in GPS device (a smartphone with a GPS addition to the operator, fix the marking speedometer app can be used for this). flags in the sprayer’s path (Figure 2b).

Repeat the observation for at least three Provide enough distance for the sprayer times in total and determine the averto attain the speed before reaching the age. If the tractor pulling the sprayer is starting flag. Once the front of the tractor equipped with a GPS monitor, then speed touches the starting flag, start measuring measurement may not be necessary. the time with a stopwatch. Again, once the front of the tractor touches the ending STEP 2: Assess Air Profile to flag, stop measuring the time and then Determine Number of Nozzles record the elapsed time on a clipboard.

Materials needed: Flagging tape, digital camera When only the operator is available, (e.g. smartphone). fix the marking flags in the sprayer’s path. Provide enough distance for the sprayer to attain the speed before reaching the starting flag.

Maintaining sitting posture, start measuring the time with a stopwatch the moment the starting flag disappears and stop measuring just when the ending flag disappears. Record the elapsed time on a clipboard.

Method 2 – Manual tree passed method: Count about 10 or more trees or vines and fix two marking flags in an adjacent mid-row in the path of the sprayer (Figure 2c). Additionally, you can tie pieces of

March / April 2020

Figure 3. To assess the air profile, attach about 4 feet of flagging tape to each nozzle on the sprayer manifolds.

Start the fan and observe the aloft flagging tapes from behind the sprayer. (All photos courtesy of P. Larbi.)

Method: Attach about 4 feet of flagging tape to each nozzle on the sprayer manifolds. Start the fan and observe the aloft flagging tapes from behind the sprayer (Figure 3). Take a photo of the scene with a camera for reviewing. From the photo, determine the number of nozzles and their position that are well directed on the target canopy. Turn off nozzles that miss the target canopy. To better understand why this is necessary, see Figure 4(pg. 12).

Also, attach a piece of flagging tape to the target tree or vine canopy and the next adjacent canopy in the path of the air. Drive the sprayer across the taped locations at the determined travel speed with the air running and observe the tapes on the canopies.

If the tape on both canopies are sufficiently aloft, the air might be too much (Figure 5a). Adjust the air if the sprayer is equipped for that, considering the target canopy size and density. Otherwise, increase the travel speed to adjust the air (Figure 5b). Another option is to partially cover the fan inlet using a so called ‘Cornell doughnut’ (Figure 5c and 5d). Ideally, an automated means of adjusting the fan intake would be best.

STEP 3: Select Nozzles Materials needed: Calculator, clipboard, nozzle catalog, nozzle selection mobile app Method: Knowing the desired application rate, AR, and row spacing, RS, determine the total sprayer output per side, SO, from all open nozzles as:

SO (gpm)=(AR(gpa)×S(mph)×RS(ft))/ If the spray volume is intended to be uniform on each side, then divide SO by the determined number of nozzles to get the desired nozzle flow rate. Use this number to select the nozzle from a nozzle catalog.

However, SO can be split into different fractions for upper nozzles and lower nozzles. A common configuration for trees is 2/3 for upper nozzles and 1/3 for lower nozzles. Whatever the split ratio, the total should amount to

the calculated SO. Various available software applications and mobile apps can be used to aid this determination.

STEP 4: Measure Sprayer Output This should be done with the sprayer stationary. Alternate methods to that presented here exist.

Materials needed: Measuring pitcher, stopwatch, calculator, clipboard, automatic nozzle calibrator, flow meter, pressure tester.

Continued on Page 14

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Continued from Page 13 Method:With the sprayer running in a fixed position, confirm that the pressure gauge reading is accurate using a tool. Start spraying and collect spray water from each nozzle for 1 min using a measuring pitcher and record the values in fluid ounces (oz). These should be the nozzles that will be used for the spray application. Calculate the flow rate of each nozzle as: FR (gpm)=(collected volume (oz))/128

Repeat the measurement and determine the average.

Calculate the sprayer output by multiplying the average FR by N, for uniform application. For non-uniform application, do this separately for the upper and lower sections and sum them up.

Alternatively, you can automatically measure the flow rate by using a flow meter (e.g. SpotOn™ calibrator). Also, you can use a manifold patternator to observe uniformity

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of nozzle flow across all nozzles.

STEP 5: Adjust Sprayer Output There are two adjustments that can be applied to the sprayer output in order to achieve the desired application rate, if the measure sprayer output is off. The first is adjusting the travel speed, while the second is adjusting the pressure.

Adjusting travel speed: The adjusted travel speed, S2, can be obtained as: S_2 (mph)=(〖AR〗_1 (gpa)×S_1 (mph))/(〖AR〗_2 (gpa) ) where, AR1 = application rate obtained with the actual measured sprayer output in Step 4 AR2 = desired application rate in Step 3 S1 = travel speed measured in Step 1.

Adjusting operating pressure: The adjusted operating, P2, can be obtained as: P_2=(〖〖SO〗_2〗^2 (gpm^2)×P_1 where, SO1 = measured sprayer output in Step 4SO2 = desired sprayer output in Step 3 P1 = intial operating pressure

STEP 6: Assess Spray Coverage Attach water sensitive cards (yellow cards that turn blue when moist) to different locations in the target canopy. Run the sprayer and apply water similar to the intended application. Evaluate the spray coverage to ensure that it is suitable. Make adjustments as necessary to obtain a suitable coverage.

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Prolonged wet early season conditions have been linked to the “yellowing Krymsk” and “yellowing Rootpac-R” problem in young orchards. A yellowing ‘Monterey’ almond tree on ‘Rootpac-R’ rootstock in July of 2017. Similar yellowing symptoms have been seen in some young Monterey on ‘Krymsk 86’ trees, particularly in wet springs. All photos courtesy of Luke Milliron.

EARLY SEASON IRRIGATION MANAGEMENT IMPACTS TREE HEALTH ALL SEASON

By LUKE MILLIRON | UCCE Farm Advisor Butte, Glenn and Tehama Counties and ALLAN FULTON | UCCE Irrigation and Water Resources Advisor, Tehama, Colusa, Glenn, & Shasta

O

ne of the motivations for making good water management decisions early in the growing season is to reduce the risk of root and crown diseases that can eventually kill almond and other tree species. These diseases need three elements to infect and damage a tree: a susceptible host plant, a pathogen, and favorable environmental conditions.

A second motivation for diligent early season water management is that even in the absence of a pathogen like Phytophthora, root death due to waterlogging alone can damage or kill trees. Prolonged wet early season conditions have been linked to the “yellowing Krymsk” and “yellowing Rootpac-R” problem in young orchards. This problem which is most often associated with the ‘Monterey’ variety, often resolves itself with careful soil moisture monitoring. Similarly, in older orchards, over-watered conditions in 16

Progressive Crop Consultant

March through May have been linked to the lower limb dieback (LLD) problem.

Both conditions show that early season water management can greatly impact tree health much later in the season.

You can read more about “yellowing Krymsk” at: sacvalleyorchards. com/almonds/foliar-diseases/yellowing-krymsk/ and about LLD at: thealmonddoctor.com/2014/05/16/ lower-limb-dieback-almond/ Early season water management influences the environment where roots grow by affecting soil temperature and aeration and can be pivotal in how much tree decline occurs. Trees are expensive.

The money and effort spent to establish them is lost, more costs lie ahead to replace them, and production is lost.

Choosing the Best Time to Start Irrigating Each season you need to decide when to start irrigating. It can be difficult to March / April 2020

choose the best time to start irrigation.

There are a lot of different information sources you can use to make this decision. You can copy practices that you observe around you, evaluate soil moisture, consider the weather and evapotranspiration loss of the crop (ETc), or take a plant-based approach. Utilizing multiple information sources is highly recommended. However, utilizing the plant-based monitoring approach of stem water potential readings with a pressure chamber (or “pressure bomb”) has a distinct advantage over the others.

The pressure chamber directly determines the water status experienced by the trees, while the other sources, such as ET or soil moisture, although helpful, are indirect.

The pressure chamber gauges the amount of positive gas pressure (in pressure units, e.g. bars) required to balance the level of water tension in a plant sample (e.g. leaf; see related graphic). The level of water tension in a leaf expresses the

Continued on Page 18

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could result in irrigating too soon.

Using Information to Delay the First Irrigation

Possible lower limb dieback symptoms in July of 2019 in a mature orchard in Durham, CA. In older orchards, over-watered conditions in March through May have been linked to the lower limb dieback (LLD) problem.

Continued from Page 16 degree of effort utilized to pull water all the way through the tree from the soil.

Relying on an indirect information source, particularly an approach like beginning irrigation when your neighbor does, when the surface soil has dried out, or irrigating on the first hot day,

Research in walnut orchards in California’s Tehama and Stanislaus counties has found that the start of irrigation can be delayed by waiting for mild to moderate water status when measured with the pressure chamber.

Some observed benefits have been a minimum 10-percent reduction in energy for pumping, less tree stress during harvest season, and no impact on edible kernel yield. A managed (informed) delay in the start of irrigation may allow for deeper root activity late in the season. It’s possible that a strategy that starts the irrigation season too early promotes a shallow root system at the expense of deeper root development.

This is completely contradictory to the conventional wisdom in walnut and almond production that early season irrigation allows for “banking of water” to help avoid high water stress at harvest.

UC researchers plan to investigate this managed irrigation delay in almonds in the northern Sacramento Valley.

Before UC researchers begin to see results from this work in almonds, it is best to be cautious in choosing a level of stem water potential with the pressure chamber to trigger the first irrigation of the season. From everything

Schematic showing how water potential is measured in a severed leaf and stem (petiole) using a hand-held pump-up pressure chamber. Source: Adapted from Plant Moisture Stress (PMS) Instrument Company.

18

Progressive Crop Consultant

March / April 2020

we currently understand, waiting for a tree water status of -2 bars below the fully watered baseline before applying the first irrigation represents a low risk irrigation decision that could benefit long term tree and root health. To learn more about the pressure chamber, stem water potential, the fully watered baseline, and how to go about getting equipment and taking measurements, check out our series at: sacvalleyorchards. com/manuals/stem-water-potential/

Monitoring Weather—Crop Evapotranspiration (ETc)

If using the pressure chamber isn’t appealing, or a second source of information is desired, monitoring the weather and evapotranspiration crop losses is an option.

This method is sometimes called a “water budget,” because it is analogous to budgeting money. Soil water storage in the crop root zone equates to a balance in a checking or savings account. ET equates to a debit from the account and significant rainfall or irrigation equates to a deposit or credit into the account. Water budgeting approximates the soil moisture level in the root zone rather than measuring it with soil moisture sensors.

Weekly ET reports are available during the irrigation season online or can be delivered weekly by email. ET is estimated based upon real-time weather measurements at regional CIMIS weather stations. Estimates are for trees with at least 50 percent canopy cover and need to be adjusted downward for smaller trees. Each report provides a real-time estimate of ET in inches for the past seven days, an estimate for the next seven days, and keeps a running total for the season. Accumulations begin at leaf-out for each crop which enables their use to help decide when to begin the irrigation season. It is important to know the hourly water application rate (inches/hour) of your irrigation system.

Using an example from the 2018 season, if we followed each weekly report from February 16 to May 3 for the Gerber South CIMIS weather station, it showed that cumulative ET for almonds was 7.51 inches while cumulative rainfall for the same period was 5.26 inches and resulted in a 2.25-inch soil moisture deficit. This assumed that all of the rainfall was effectively used in the orchard which is a site-specific consideration that needs to be adjusted accordingly in the water budget. Dividing this 2.25-inch soil

moisture deficit by a water application rate of 0.07 inch per hour (i.e. an almond orchard with 124 trees per acre with one 16 gph microsprinkler per tree) equates to 32 hours of irrigation or the equivalent of two 16-hour irrigation sets that suit PG&E off-peak rates. Choice of set length is site-specific depending on irrigation system and soil type; however, it is best to minimize ponding conditions that can starve roots of oxygen and provide favorable disease conditions.

For help with your own ET calculations see: sacvalleyorchards.com/et-reports/ The previous example provides context on how this deficit relates to the irrigation system capacity. It is left to the irrigation manager’s judgement to continue to delay the beginning of irrigation to protect tree and root health, begin irrigation by partially refilling the soil moisture deficit (i.e. one 16-hour irrigation set), or begin irrigation and fully replace the soil moisture deficit. If this information were paired with the pressure chamber measurements and the

stem water potential measurements were still within -2 bars of the fully irrigated baseline, the manager may have more peace of mind about continuing to delay the first irrigation.

used. Refer to the UC ANR article Soil Moisture Sensor Selection is Confusing for more insight: sacvalleyorchards.com/blog/soil-moisture-sensor-selection-is-confusing/

Monitoring soil Moisture Depletion

The Judgment of the Irrigation Manager

If neither the pressure chamber nor water budgeting appeal to you or you are looking for a supplement to one or both methods, directly monitoring soil moisture is an option. Checking soil moisture by hand is a very basic method to evaluate soil moisture conditions.

There are many online stores where soil augers can be purchased (examples include: JMC Backsaver, AMS samplers, Forestry Suppliers, and Ben Meadows).

For interpretation of soil moisture in collected samples, the USDA-National Resource Conservation Service also offers a nicely prepared publication with color pictures titled Estimate Soil Moisture by Feel and Appearance.

There are also a wide variety of soil moisture sensors that can also be

Stem water potential readings with a pressure chamber, evapotranspirationbased water budgets and soil moisture monitoring all bring different and valuable information to the decision of when to first irrigate almonds. Stem water potential readings with the pressure chamber offer the most direct measure of tree irrigation need. In addition, adopting this practice may both save water and encourage valuable deep root development. No matter if you choose to adopt one, or all three of these monitoring approaches, the irrigation-manager’s careful judgement is most important.

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Continued from Page 20

Economic Trends in Almond Production New UC Ag Issues Center Study on Costs and Returns for Almond in California Shows Product Costs Have Increased Substantially

By BRITTNEY GOODRICH | UCCE Specialist, Department of Agricultural and Resource Economics, UC Davis

T

he University of California Agricultural Issues Center (UC AIC) and the Department of Agricultural and Resource Economics at UC Davis work with UC Cooperative Extension Farm Advisors and Specialists to compile cost studies for crops and livestock produced in California.

These costs and return studies are used by growers, bankers, crop consultants and many others to aid in a range of farm decisions from what to plant to production specifics.

Often policy makers and researchers use these cost studies as well. The current and archived cost studies can be found at: https:// coststudies.ucdavis.edu/ UC AIC recently released new cost and return studies for almond production in California.

These 2019 regional cost and return studies for almonds are available for the Sacramento Valley, and the Northern and Southern San Joaquin Valley. This recent update of almond studies presents an opportune time to explore trends in almond cost and returns for the most recent two decades.

Before digging into graphs and figures, it’s important to discuss the elements of the cost study. The cost and return studies are meant to be used as a guide for growers, and actual costs and returns will vary depending on the specifics of the operation, growing conditions, and orchard characteristics. Therefore, it is necessary to specify underlying assumptions for orchards represented. It is not feasible to represent the infinite number of almond 20

Progressive Crop Consultant

production scenarios out there. The following are some of the basic assumptions of 2019 cost study for the Northern San Joaquin Valley. For the full list of assumptions for each study listed in the charts, see the cost and return studies themselves.

Interest rates are 5.25% for operating loans and 6% for long-term investments.

The cost studies go into detail about the following cost categories, and provide a look at costs and returns at various yield and price combinations.

Cost of pumping irrigation water from an established well is $100 per acre-foot.

Operating costs: Any costs associated with almond production practices in a given year, including pesticide and fertilizer applications, irrigation water, labor, harvesting, interest on operating loan.

The orchard consists of 100 acres of almonds with a density of 130 trees per acre.

No specific variety is listed.

The useful life of the orchard is expected to be 25 years.

A new micro-sprinkler irrigation system is installed during orchard establishment.

The expected yield at maturity is 2200 lbs per acre at an expected price of $2.50/lb.

March / April 2020

Land value is $25,200 per producing acre.

Cost of pollination is 2 hives per acre at $200 per hive.

Cash overhead costs: Expenses paid that are not for a particular enterprise and should be assigned to the whole farm operation, such as office and accounting expenses, assessments, field sanitation, or equipment repairs.

Non-cash overhead costs: Annual depreciation and interest cost for farm investments. Examples include depreciation on farm machinery, well/irrigation systems, annual establishment costs, etc.

Establishment costs: Total pre-plant, planting and accumulated costs for non-bearing years.

Establishment costs are amortized (spread out) over the useful life of the orchard.

Total costs: Sum of operating, cash overhead, interest and non-cash overhead costs.

Continued on Page 22

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These two steps are critical to achieving top yields at harvest.

Demands for zinc, magnesium, and other micronutrients reach peak demand timing during rapid leaf and root development.

Soils are often cold and wet during this time which limits nutrient availability and uptake hindering root and leaf growth and chlorophyll development. Satisfying peak nutrient demands are critical to maximizing yield potential. Zinc is the cornerstone for leaf, root and vascular system development. Manganese and molybdenum play a key roles in nitrogen metabolism. Iron, magnesium, copper and manganese are backbones of chlorophyll development and structure. Shortages of one or more of these nutrients will limit yield potential. Applying Micro SeaMix and Sysstem Leaf Max with fungicide or insecticide sprays at rapid leaf-out is an ideal way to meet early season almond nutrient needs while simultaneously reducing plant stress. Maximizing

leaf surface area ensures the photosynthetic factory is capable of supporting and sizing a large nut crop.

At petal fall, nut cell division is not yet finished and it is important to support the final stages of this process with foliar phosphorus and calcium. Foliar applications are important as cold and/or wet soils combined with limited root activity at this time limit uptake of these important nutrients. Vigor SeaCal supports uptake of phosphate for increased cell division leading to increased nut size.

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remained similar at around $4,500 per acre.

Operating costs per acre also increased between 2016 to 2019. Much of the increase in operating costs was due to increasing labor $5,000 Between 2016 and 2019, and pesticide costs, as well as increases in the total costs of almond operating loan interest rates. Figure 2 shows $4,000 production per-acre various cost categories as a percentage of increased substantially total operating costs for 2002, 2011 and 2019 Operating, $2,717 (Figure 1). The driver of $3,000 almond production. In 2002, pesticides, labor this is a large increase and harvest comprised more than 60 percent of total operating costs. While that number Non-Cash Overhead, in non-cash overhead $2,000 $2,469 costs. The primary dropped to roughly 43 percent in 2019, over increases in this cost time, pollination, irrigation and fertilizer costs Establishment, $758 $1,000 category between 2016 have increased to make up a much larger portion of total operating costs for almond growCash Overhead, $538 and 2019 are increases $in establishment costs ers. Irrigation costs may continue increasing as 1998 2002 2006 2011 2016 2019 and land values. Interest a percentage of total operating costs given imFigure 1: Sample Per-Acre Costs of Establishing and Producing Almonds in the Northern San Joaquin Valley Using Micro-Sprinkler rates in 2016 were 3.25 plementation of the Sustainable Groundwater Irrigation, 1998, 2002, 2006, 2011, 2016, and 2019 (in 2019 dollars) percent compared Management Act (SGMA), however it is Sources: University of California Agricultural Issues Center Sample Cost and unclear what the effects of this regulation will Returns Studies: https://coststudies.ucdavis.edu/. US Bureau of Economic with 6 percent in 2019, Analysis, GDP Price Deflator. increasing establishbe (for SGMA resources see http://groundwa30% ment costs substantially. ter.ucdavis.edu/SGMA/). Pollination fees will 25% According to USDA likely continue their trend upward as well, National Agricultural though growers may be able to reduce pollina20% Statistics Service, tion costs through decreasing the number of 15% average irrigated land colonies per acre, planting self-fertile varieties 10% values in California or making mutually beneficial contractual 5% increased by 8 percent arrangements with the beekeeper (Goodrich, 0% on average from 2016 2019; Champetier, Lee, and Sumner, 2019).

2002 2011 2019 to 2019. Factoring land Irrigation Pollination Fertilizer Pesticides Labor Harvest Figure 2: Cost Categories as a Percentage of Total Operating Costs for values into the cost Trends in Almond Returns Almond Production in the Northern San Joaquin Valley Using Microof production allows Figure 3 shows the Blue Diamond average base Sprinkler Irrigation, 2002, 2011 and 2019 Source: University of California growers to consider the rate for nonpareil meats from 2004 to 2018 (in Agricultural Issues Center Sample Cost and Returns Studies: https://coststudies.ucdavis.edu/ opportunity cost of their 2019 dollars to adjust for inflation). Since 2016, investment in the almond orchard. Even if prices have been lower than the 2004-2018 Continued from Page 20 a grower owns the land he or she plans to average of $3 per pound. Uncertainty in trade establish an orchard on, he or she might issues have resulted in decreased demand for Looking over these cost studies can help be better off renting out the orchard and almonds in a number of countries (Sumner, growers and crop advisors make sure investing those rental revenues elsewhere. Hanon and Matthews, 2019). For example, they are incorporating all costs when making crop production decisions.

Continued on Page 24 Total Costs, $5,725

Percent of Total Operating Costs

$ /Acre (in 2019 dollars)

$6,000

Figure 1 displays per-acre costs of almond production over time. All costs are adjusted to 2019 dollars to account for inflation. It is clear from the figure that from 1998 to 2016, inflation-adjusted total costs of almond production 22

Progressive Crop Consultant

45,000

$5.00

40,000

$4.50 $4.00

35,000

$3.50

30,000

Planted Acres

Trends in Almond Costs To outline the trends in almond production costs, I use the 1998, 2002, 2006, 2011, 2016 and 2019 UC AIC cost and return studies for establishing and producing an almond orchard in the Northern San Joaquin Valley using micro-sprinkler irrigation. This provides an approximate idea of how costs have developed over time. The trends in most cost categories should be similar across the state, however there may be noticeable differences in certain aspects across regions, ex: land values, water costs, etc.

Nonpareil Average Price

25,000

$3.00

Southern San Joaquin $2.50

20,000 $2.00 15,000

$1.50 Northern San Joaquin

10,000

$1.00 Sacramento Valley

5,000

0

$0.50

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

$0.00

Figure 3: Planted Almond Acreage by Region and Nonpareil Average Base Rate ($/lb in 2019 dollars), 2004-2018 Sources: 2018 Almond Acreage Report, USDA NASS, CDFA. Blue Diamond Payment History 2004-2018. US Bureau of Economic Analysis, GDP Price Deflator.

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23

almond exports to China were down 24 percent between 2018 and 2019 (Almond Board of California, 2019). This decreased demand has led to lower almond prices, and with future trade agreements still uncertain, it is unclear how prices will move going forward.

The prices a grower receives will vary by quality, size and variety. Figure 4 shows average variety prices as a percentage of nonpareil. In 2016 and 2017, other varieties were discounted fairly heavily in comparison to nonpareil, while in other years discounts were not quite as large. What impacts the size of these discounts? The relative supply and demand of nonpareil compared with other varieties. Figure 4 also displays nonpareil production as a percentage of total production from Butte/Padre, Butte, Monterey, Carmel, and Fritz. In 2017 and 2018, nonpareil production was relatively high compared to these other varieties. The large supply of nonpareil almonds drives down the price relative to other varieties, shrinking the associated premium.

Trends in Planted Acreage Figure 3 also shows planted acreage from 2004 to 2018 by region along with the average price of nonpareil. The planted acreage trends by region look relatively similar. Over the last five years, the largest almond producing region (Southern San Joaquin Valley) has seen planted acreage drop off significantly. Water availability concerns as well as relatively low prices are likely the driving issues here. The Northern San Joaquin Valley has also seen acreage drop off, but not as substantially as its southern counterpart. Planting in the Sacramento Valley has stayed relatively consistent over the last decade or so.

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Figure 5. Planted Almond Acreage by Variety, 1998-2018 Source: 2018 Almond Acreage Report, USDA NASS, CDFA.

Closing Remarks Overall, net returns from almond production have likely narrowed over the last decade due to increasing costs of production. Land values and interest Figure 5 shows planted acreage for some of the rates have increased, increasing the main almond varieties. Toward the middle of costs of establishing an almond orchard. the series, one sees the large planted acreage Pollination, irrigation and fertilizer costs for most varieties due to relatively high prices have increased as a percentage of total in 2004-05. Over time, acreage plantings operating costs, while almond prices have stabilized at lower levels. The increase have remained at relatively low levels over in self-fertile almond acreage is noticeable the last few years. The fact that acreage in the mid 2010s. Operating cost savings is still being planted suggests that the from pollination and fewer equipment passes potential net returns remain relatively through the orchard were likely driving this strong compared with other crops in trend (Champetier, Lee and Sumner, 2019).

California.

Price discounts for the Independence variety in comparison to nonpareil have stabilized, from References: as low as 2 to 4 percent discount in 2013-14, Almond Board of California. 2019. to on average of 11 percent over the last four “Almond Almanac 2019” years for Independence compared to nonpareil.

24

2016

Monterey

Figure 4: Variety Price as a Percentage of Nonpareil Price and Nonpareil Total Yield as Percentage of Butte/Padre, Butte, Monterey, Carmel, and Fritz Yield Sources: Blue Diamond Payment History 2013-2018. Almond Board of California Almond Almanac 2013-2019.

Planted Acreage by Year

Continued from Page 22

Variety Price as Percentage of Nonpareil

Nonpareil production Other variety production

March / April 2020

Champetier, A., H. Lee, and D.A. Sumner. 2019. "Are the Almond and Beekeeping Industries Gaining Independence?" Choices. Quarter 4.

Goodrich, B.K. 2019. "Contracting for Pollination Services: Overview and Emerging Issues." Choices. Quarter 4.

Sumner, D.A., T. Hanon and W.A. Matthews. 2019. “Implication of Trade Policy Turmoil for Perennial Crops” Choices. Quarter 4. Available online: University of California Agricultural Issues Center Sample Cost and Returns Studies. Available online: https://coststudies.ucdavis.edu/

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The TheBrown BrownMarmorated MarmoratedStink StinkBug Bug IsIs(Still) (Still)Invading InvadingCalifornia: California: Is Is The The Voracious Voracious Pest Pest AA Threat Threat ToTo Pistachio Pistachio Production?

Production?

By JUDITH M. STAHL | Dept. of Environmental Science, Policy, & Management, UC Berkeley KENT M. DAANE | Dept. of Environmental Science, Policy, & Management, UC Berkeley DAVIDE SCACCINI | Dept. of Agronomy Food Natural Resources Animals and Environment, University of Padova, Legnaro, Padova, Italy

T

he brown marmorated stink bug (BMSB), Halyomorpha halys, has caused significant yield losses in fruit and nut crops around the world.

Its appearance in California around fifteen years ago was no surprise after it had already invaded large portions of the country, especially the mid-Atlantic states. Here, we give background information and an overview of the brown marmorated stink bug biology, its current status within California and its potential to impact pistachio production.

Invasion History of the Brown Marmorated Stink Bug

Originally, BMSB was known only in China, Korea, and Japan. With increasing global trade and transport, it started, like many other species, spreading to new parts of the world. Outside of its native range, it was first identified from samples in Allentown, Pennsylvania, in 2001, but the earliest confirmed sighting of the invasive stink bug already occurred five years prior. That invasive species are present for years before their 26

Progressive Crop Consultant

official recognition is common since they generally arrive in low numbers and have to build up their populations before they can cause any damage—which then generally attracts attention and alarm.

In the case of the brown marmorated stink bug, regular interceptions, for example, in the UK and New Zealand show that it probably travelled in transport crates or shipping containers to the US, and later to Europe, Canada and Chile.

Shipping containers provide BMSB adults (the overwintering stage) with shelter and protection. Other favored overwintering sites are other human-made structures, including homes, garages, barns, etc.

This, in combination with their likely arrival at trade hubs such as large cities, and their tendency to form overwintering aggregations that can consist of hundreds or even thousands, has led to them being classified as a ‘nuisance pest’. Indeed, unlucky homeowners have struggled with up to 25,000 BMSB hiding in their walls, attics, and other living spaces during the winter. Of concern for farmers in California is BMSB movement from urban shelters into agricultural crops.

March / April 2020

Biology of the Brown Marmorated Stink Bug

The brown marmorated stink bug biology is similar to many of our native stink bugs and shares many traits with leaffooted bugs and smaller ‘true bugs’.

They have an egg, nymph, and adult stage. Adult BMSB are about half an inch long, with a brown body and white striped antennae and legs. In California, they can be confused with Euschistus species or the predatory Roughshouldered stink bug Brochymena; the website www.StopBMSB.org has a helpful compendium with pictures and detailed descriptions. After mating, adult female BMSB lays up to ten egg masses, often consisting of about 28 lightly blue-green colored eggs, over the span of her life, which can last several months. The nymphs undergo five instars until they reach the adult stage. The red-brown and black first instar nymphs can be seen sitting around the egg mass after hatching, feeding on the symbiotic microorganisms that will make it possible

Continued on Page 28

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An adult of the brown marmorated stink bug. (Photo courtesy of W. Wong)

Continued from Page 26 to digest their various host plants. After that, they start wandering off in search of food. Second to fifth instar nymphs are black and white in appearance and can walk rather long distances for their small size, for example fifth instars can walk 65 ft within only four hours.

Both the nymphs and the adults feed by inserting their needle-like mouthparts into a variety of plant tissues including stems, leaves, and especially reproductive structures, secreting digestive enzymes and sucking up the liquified plant material. The mechanical damage and specifically the chemical changes due to the excreted enzymes can lead to discoloration, deformation and the abortion of fruiting structures, all of which make the crop unmarketable. Many stink bug species are known mainly as secondary pests in various crops. Often, an individual species has different host plants to fulfill their nutrient requirements and can therefore behave as a pest in different crops or take refuge in a naturally occurring host.

The brown marmorated stink bug has more known host plants than other stink bugs; in the US alone, more than 170 plant species have been reported, many of them economically important crops. These include vegetables, leguminous crops, fruits, nuts, and ornamentals. In the first big outbreak year, 2010, damage caused by BMSB to apple production of the mid-Atlantic states led to economic losses of $37 million. Other examples, from Georgia 28

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A nymph of the brown marmorated stink bug investigating a pistachio.

(Photo courtesy of K. Daane)

and Russia, include the destruction of the hazelnut crop, which is highly important for these regions, to such an extent that the government paid citizens for every bucket full of stink bugs. In contrast to those stories, BMSB crop damage has been relatively quiet in California and the rest of the West Coast.

sites, trap catches have actually been decreasing for several years. The current situation therefore sees BMSB spreading in California, but at a low density apart from localized larger populations. The bad news is that, in addition to almonds, many California specialty crops are either known or potential hosts.

The Brown Marmorated Stink Bug in California

Damage Potential in Pistachios

Not long after the brown marmorated stink bug was reported on the East Coast, in 2002, the first individual was discovered in a storage unit in California.

Like most invasive species, there can be years between the first interceptions of individuals and the establishment of a reproducing population. Consequently, the first established brown marmorated stink bug populations in California were not reported until 2006 in the Los Angeles area and 2013 in Sacramento.

The following year, 2014, monitoring efforts were put into place and, since then, the invasive stink bug has been shown to be established, or at least been detected, in most California counties (https://cisr.ucr.edu/invasive-species/ brown-marmorated-stink-bug).

However, presence and abundance are two separate matters. The warm climate allows the invasive insect to complete two generations per year and BMSB damage has been reported in several almond orchards near Modesto, Calif.

The stink bugs have also been sighted in commercial peaches, but most sightings still occur in urban centers rather than agricultural areas, often associated with the common ornamental tree, the tree of heaven (which is also from Asia).

Good news is that in many monitoring

March / April 2020

To assess the threat of the brown marmorated stink bug to California’s pistachio production, we conducted trials under Central Valley conditions by caging terminal branch endings with pistachio clusters were caged, just after bud-break, and exposing the developing nuts to BMSB for a five-day feeding period. Trials were conducted throughout the season to account for hardening of the pistachio shell and changing temperatures. As a comparison, clusters were also exposed to adults of two native species that feed on pistachios, the flat green stink bug Chinavia hilaris and a leaffooted bug, Leptoglossus zonatus.

Native true bugs common in pistachios can be grouped by their size: ‘small bugs’ like mirids are more abundant early in the season and cannot pierce the pistachio shell later in the season, while ‘large bugs’ like stink bugs and leaffooted bugs continue to cause damage during mid- and late-season. The insertion of their needle-like mouthparts and the secretion of digestive enzymes can result in external damage, brown to black lesions of the outer fruit layer, the ‘epicarp lesions’ that can stain the outer shell and lower market value. Especially after mid- to late-season feeding, epicarp

lesions often appear with a delay or not at all, hiding the internal damage: if the insect’s mouthparts reach the endosperm tissue, it can become necrotic or lead to aborted nuts. Along with direct damage, the feeding can lead to fungal infections, ‘stigmatomycosis’, that result in blackened, foul-smelling kernels.

We found that, one to two weeks after feeding, BMSB caused similar amounts of external nut damage (i.e., epicarp lesions) as did the native species tested. However, by following clusters development and damage throughout the season, we noticed more epicarp lesions formed later in the season in the BMSB exposed cages.

Shortly before harvest in September, there were significantly more damaged nuts per cluster (based on epicarp lesions) in BMSB cages than in the green stink bug or leaffooted bug cages, independent of when the feeding occurred during the season. This indicates that adults of the brown marmorated stink bug can cause more external damage than our native large bug pests. However, the

more important internal damage criteria such as the number of necrotic kernels, aborted nuts or kernels with stigmatomycosis were not different between these large bug pest species tested.

The brown marmorated stink bug may generally cause more crop damage than other large bugs because of their feeding behavior or saliva composition - this is still being investigated, but the main factor that makes them such an important pest are the sheer numbers in which they occur in affected areas, such as Virginia. In California’s Central Valley, this is generally not the case, at least at this time. One potential explanation for this phenomenon are the hot and dry summers in the Central Valley, as well as the large-structured agriculture, with thousands of contiguous acres of commercial agriculture, that may make it difficult for BMSB nymphs to switch host plants to access all their required nutrients.

‘The brown marmorated

stink bug has the potential to cause at least as much damage in pistachios as our native stink bug and leaffooted bug species. This is, however, dependent on its abundance in the respective areas, which is currently low.’ caged first instar BMSB nymphs on different California specialty crops throughout the last two seasons and showed high nymphal mortality. This could explain the low overall abundance of BMSB in the Central Valley—it’s just too hot and dry. They were generally more likely to

To point this out, in another trial we

Continued on Page 30

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areas, which is currently low.

‘The first line of defense

is monitoring. Take into account that border rows are generally more affected than the inside, especially if the orchard or field is close to woodlands or preferred host plants, like the tree of heaven.

Common sampling programs include sweep and beat samples as well as visual counts, but those methods have not proven to be as reliable as pheromone traps.’

Continued from Page 29 reach the adult stage on almond than on pistachio, which could be explained by the close relation of almond to one of their favorite host plants, peach. This is also in line with the records of brown marmorated stink bugs in California almonds, but so far not in pistachio. Still, even on almond survivorship was low.

To conclude, the brown marmorated stink bug has the potential to cause at least as much damage in pistachios as our native stink bug and leaffooted bug species. This is, however, dependent on its abundance in the respective

What You Can Do If You Suspect You Have Brown Marmorated Stink Bugs In case BMSB becomes a bigger issue in California, there are a number of measures that can be taken. The first line of defense is monitoring. Take into account that border rows are generally more affected than the inside, especially if the orchard or field is close to woodlands or preferred host plants, like the tree of heaven. Common sampling programs include sweep and beat samples as well as visual counts, but those methods have not proven to be as reliable as pheromone traps.

There are many different trap types available of which the most effective one is the black pyramid trap, and the most economic one a clear sticky trap that can be mounted on a pole. The lure most commonly used is a blend of the aggregation pheromone of BMSB and the closely related oriental stink bug (Plautia stali).

Trap counts can be used to determine insecticide applications as opposed to calendar-based applications, but the system is still being optimized because it is more difficult to relate trap catches with BMSB densities in the orchard than it is for other pests. Pheromones and insecticides can also be combined in ‘attract and kill’ methods using for example ‘bait trees’ that are equipped with pheromone lures and are sprayed in regular intervals.

This can ideally reduce pest populations with only a small area affected by the insecticides, thereby protecting natural enemies, decreasing the risk of secondary pest resurgence, and reducing costs. Research efforts to make these systems commercially available are currently underway on the east coast.

A female of the samurai wasp Trissolcus japonicus parasitizing eggs of the brown marmorated stink bug. (Photo courtesy of Warren H. L. Wong)

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When the brown marmorated stink bug first started threatening yields in the mid-Atlantic states, growers applied insecticides registered for native stink bugs such as pyrethroids and neonicotinoids, which unfortunately failed to provide complete control of this

March / April 2020

External and internal stink bug induced pistachio damage: epicarp lesions (marked with red ‘X’) top, and kernel necrosis bottom. (Photos courtesy of J. Stahl and K. Daane)

invasive species. Part of the failure was due to the combination of a very mobile insect and products with a short residual activity.

It is also easier to kill the overwintering adults than the subsequent generations, so once population densities are high during the season, application efficacy is reduced.

One reason to back off of pesticide treatments for low densities of BMSB are its natural enemies. Many predators are feeding on different life stages of this bug, although the levels of control in California are still not clearly known. There are a number of native parasitic wasps that attack the egg stage of stink bugs, including this invasive stink bug. However, since the brown marmorated stink bug is a novel host for them, they have yet to adapt to it; often, their offspring are not able to develop within the eggs of the

Continued on Page 32

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Continued from Page 30 brown marmorated stink bug. Currently, BMSB control in the United States by resident natural enemies is not sufficient to reduce population sizes significantly and prevent crop losses. There is, however, a parasitic wasp that could make a difference: Trissolcus japonicus, also known as ‘the samurai wasp’.

The Samurai Wasp

To the naked eye, the samurai wasp looks just like any other of our native

egg parasitoids that attack stink bugs: it is smaller than a grain of sand, mostly black, and completely harmless. But unlike its relatives, it has the same area of origin as BMSB and is very well-adapted to this host. In Asia, the samurai wasp is the most important natural enemy keeping the brown marmorated stink bug in check.

Like its host, it has made its way to North America and Europe. After first being discovered in the eastern part of the US in 2014, it spread, presumably with multiple new introductions from Asia, to the West, and has recently been recovered in the Los

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March / April 2020

Adult Euschistus (top) and Brochymena (bottom) species, lookalikes of the brown marmorated stink bug that can be found in California pistachios.

Note that Euschistus is missing the brown-white banded antennae and Brochymena has ‘rough shoulders’ as well as an uneven front. (Photos courtesy of K. Daane)

In California, most growers have so far been luckier than their colleagues on the east, and there are no indications that that will change soon; but the brown marmorated stink bug has been full of surprises and considering that it has the potential to severely impact SJV nut production, everyone should continue to be calm but vigilant.

For a list of references please email judithmstahl@berkeley.edu.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

Annual

COTTON REVIEW March / April 2020

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A look at the latest research addressing the most pressing issues in California cotton including: Disease resistance and variety screening, sticky cotton, contamination, insect management and control, water management, weed management, and nutrition management.

Research is coordinated and funded by Cotton Incorporated (CI), the California Cotton Alliance (CCA), and the California Cotton Ginners and Growers Association (CCGGA).

IN THIS REVIEW

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48

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36 Biocontrol

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March / April 2020

OVERVIEW OF ONGOING COTTON RESEARCH IN CALIFORNIA D

espite reduced acreage in recent years, research in California cotton is alive and well. In fact, with the establishment of a coordinated research meeting held every September, research in California cotton is as strong and harmonized as it has ever been.

Growers, Gin Managers and industry leaders come together in September to review research proposals on California cotton and make sure that funds are spent wisely and effectively in a coordinated manner. This ensures what limited resources the industry does have are stretched to the maximum extent possible to keep California cotton in the forefront.

Research dollars are focused on addressing California cotton’s most pressing needs as identified by the industry at this time.

They are in order of ranking: 1. Diseases (FOV resistance, variety screening, seed and soil treatments, pathology work in lab and field plus Seedling Disease issues) 2. Sticky Cotton (Development of better detection and measurement system and

standards and continue educational efforts) 3. Contamination (Research ways to detect plastic in the seed cotton and eliminate where possible) 4. Insect Management and Control (Efficacy screening of new and old products and promote intro of new chemistries with low VOC, focus on Lygus and Aphid control) 5. Water Management (Regional with varying soil types and irrigation methods with emphasis on efficiencies, conservation, nitrogen, and salt management) 6. Weed Management (Resistance Management to existing products and introduction of new chemistries)

Funds from Cotton Incorporated (CI), the California Cotton Alliance (CCA), and the California Cotton Ginners and Growers Association (CCGGA) are coordinated and used to fund this critical research.

Funds from CCGGA come through an assessment on cotton planting seed by the California Crop Improvement Association (CCIA).

The following are papers on the most recent research as compiled by CCGGA. Please take this opportunity to thoroughly review this document and come to understand how growers’ money is being spent to preserve the California cotton industry and help address its biggest challenges.

7. Nutrient Management (Focus on nutrient management while taking into account factors of soil type, irrigation method, efficiencies, etc.)type, irrigation method, efficiencies, etc.)

March / April 2020

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COTTON REVIEW

CONTROLLING HERBICIDERESISTANT AND PERENNIAL WEEDS IN CALIFORNIA COTTON

By LYNN M. SOSNOSKIE and KURT J. HEMBREE | UCCE Weed Science Farm Advisors

C

otton is susceptible to weed interference, especially following emergence, as many weed species can outgrow and outcompete the newly germinated seedlings. This includes a weed native to California - Palmer amaranth (Amaranthus palmeri)- whose season-long germination phenology and high rate of photosynthesis enhances its ability as a crop competitor. Palmer amaranth interference significantly affects the growth and yield of most agronomic crops, with cotton being one of the more sensitive commodities. In addition to direct impacts on yield, Palmer amaranth can also interfere with harvest efficiency. Research has suggested that mechanical harvesting of cotton with Palmer amaranth at densities greater than six plants per 30 feet of row was impractical because of the potential for damage to equipment. Additional reports noted that the frequency of work stoppages increased as Palmer amaranth densities increased because of the need to repeatedly dislodge weed stems from the harvester.

Currently, glyphosate is the predominant herbicide applied in California cotton for weed control.

According to data derived from the California Department of Pesticide Regulation (CDPR) pesticide use reports, glyphosate was applied to 438,305 cotton acres in 2016, which is eight times more treated acreage than the next most commonly applied active ingredients (paraquat and oxyfluorfen). The use of glyphosate is not limited solely to cotton; glyphosate is an important component of weed control programs in a diverse array of crops, including almonds, alfalfa, corn, grapes, pistachios, and walnuts. The extensive

Continued on Page 38 36

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COTTON REVIEW

Continued on Page 37 March / April 2020

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COTTON REVIEW

Figure 1a. Glyphosate-resistant Palmer amaranth in cotton in Madera County (2019).

(Photos courtesy of L. Sosnoskie)

Continued from Page 36 use of glyphosate across commodities and over time has resulted in the selection for glyphosate-resistance in six species in California, including Palmer amaranth (Figures 1a and 1b).

Pesticide use reports indicate that California cotton growers do not regularly use residual herbicides on their planted acres; pendimethalin and flumioxazin were applied to less than half of California’s cotton acres in 2016, suggesting that growers are relying, heavily, on post-emergence measures (including glyphosate, hand-weeding, and cultivation) for weed control.

Palmer amaranth has an exceptionally high growth rate, which allows the species to rapidly exceed height limits for chemical control. For example, glufosinate applications should be made to small (<3” in height) Palmer amaranth to prevent weed escape and regrowth.

In 2019, a trial was undertaken in Fresno, Calif., to describe the growth of Palmer amaranth in response to emergence date and to determine how 38

Progressive Crop Consultant

Figure 1b. Palmer amaranth infestation in an almond orchard in Merced County (2019).

quickly Palmer amaranth can overcome most herbicide label height limits.

Palmer amaranth seed was collected in September of 2018 from a population growing alongside an agronomic crop field in Merced County. Seed were planted into 1.7-gallon pots containing all-purpose garden soil on April 21, April 28, May 30 and June 18, 2019.

Palmer amaranth emerged on April 24th, May 2, June 2 and June 21 and were thinned to a density of one plant per pot (10 pots total per planting date). Palmer amaranth growth and development was recorded for each individual pot every second day until 20 days after emergence (DAE).

Growing degree days (GDD) were calculated for each observation window using UC IPM models and Palmer growth regressed against GDD to predict critical stages (3 and 6 inches in height) for Palmer management.

All Palmer amaranth in this study reached a height of 3 inches by six to 10 DAE (Figure 2, pg. 39). Palmer emerging on April 24th and May 2nd reached a height of six inches 14 to 16 DAE, whereas Palmer amaranth emerging on June 2nd and June 24th

March / April 2020

reached a height of 6 inches 12 DAE. Plant heights at 20 DAE were 11.5, 8.5, 20.0 and 21.3 inches for the April 24th, May 2nd, June 2nd and June 21st emergence dates, respectively.

To standardize Palmer growth across all observation periods, plant heights were regressed against accumulated GDD using a second-order polynomial model; a threshold base temperature of 50 degrees F was used in the computation (Figure 3, pg. 40). Results indicated that the observed SJV Palmer amaranth population requires 175 to 180 GDD to achieve a height of 3 inches and 270 to 275 GDD to reach a height of 6 inches. This model can serve as a basis for predicting Palmer amaranth development in the future. Understanding the relationship between the accumulation heat units and plant growth makes it possible to predict when Palmer could become too large for control during a growing season regardless of yearly variation in temperature.

If Palmer amaranth escapes herbicide (or cultivation) treatments, hand-weeding may be needed to prevent Palmer

COTTON REVIEW amaranth from producing seed that can be returned to the soil seedbank.

Remember: female Palmer amaranth can produce up to a million seed per plant, which can support an infestation for many years to come. When hand-weeding, plants should, ideally, be removed entirely from the field to prevent them from becoming re-established. Even plants that are cut off at or near the base of the stem can re-sprout and achieve reproductive maturity.

Palmer amaranth height (inches) vs DAE 27.0 24.0 21.0 18.0 15.0 12.0 9.0

6.0 Escapes are not uncommon as Palmer amaranth can grow rapidly and 3.0 outpace many control efforts. If plants become established in the field and 0.0 2 4 6 8 10 12 14 16 18 20 hand-weeding is necessary, be sure to remove as much of the weed biomass as 24-Apr 2-May 2-Jun 21-Jun possible to prevent plants from growing Figure 2. Palmer amaranth height (inches) two to 20 DAE as affected by emergence date. and achieving reproductive maturity.

Field Bindweed Perennialization

Field bindweed (Convolvulus arvensis) is another species that has become problematic in California cotton, particularly in crop rotation systems that are characterized by drip irrigation and reduced tillage. In addition to negatively impacting cotton yield, bindweed can serve as an alternate host for the silverleaf whitefly, the honeydew from which is a primary source of sugars that can result in sticky cotton lint.

can regrow from root buds following above-ground biomass removal. Field bindweed seed collected in Merced County in 2018 was scarified using boiling water to induce germination.

Seed were planted into 1.7-gallon pots containing all-purpose garden soil on April 17 and June, 2019, representing

Continued on Page 40

Field bindweed is a deep-rooted (up to 20 feet) and spreading perennial vine, Management guidelines often suggest that field bindweed is susceptible to control at the seedling stage, although there is limited information to suggest when newly emerged field bindweed vines assume the characteristics of perennial plants.

Personal communications between weed scientists have indicated that field bindweed seedlings could survive defoliation attempts as soon as 3 WAE. In 2019, a trial was undertaken in Fresno, Calif., to describe the growth of seedling field bindweed and to determine when the vines take on the characteristics of perennial plants; specifically, the study was designed to evaluate at what stage field bindweed

March / April 2020

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39

COTTON REVIEW germination. Results from this study suggest that field bindweed seedlings may not remain sensitive to certain control measures for more than 4 weeks after emergence. Studies to examine seedling development and responses to contact and systemic herbicides will be conducted during the fall of 2019/winter of 2020.

Palmer amaranth height (inches) vs GDD (base 50 F) 24 21 18 15 12

Field Bindweed Response to Trifluralin and Pendimethalin

9 6 3 0

0

100

200

300

400

500

600

Figure 3. Palmer amaranth height (inches) regressed against GDD. Y = 5E-05x2 + 0.0084x – 0.0247 where Y = inches and x = GDD.

Continued from Page 39 two runs of the trial. Bindweed emerged on April 20 and June 4, respectively. Four replicate bindweed seedlings were physically defoliated (by removing all aboveground biomass at the soil line) at either 2, 4, 6, or 8 WAE and their compensatory growth measured two weeks after the cutting treatment (WAT). A second set of seedlings were destructively harvested at 2, 4, 6, and 8 WAE to describe biomass accumulation at the time of cutting.

vines, the seed of field bindweed should not be ignored. Bindweed seed can remain viable in the soil for decades (Weaver and Riley 1982) suggesting that infestations can re-occur even if rhizomes are successfully eradicated from a site. Anecdotal evidence indicated that newly emerged seedlings could take on the characteristics of perennial vines, rapidly, following

Results from previous studies in processing tomatoes have shown that trifluralin pre-plant incorporated (PPI) can suppress perennial field bindweed vines (Sosnoskie and Hanson 2015). However, most cotton growers do not regularly apply this active ingredient in their systems; with respect to pre-emergence herbicides, pendimethalin (which is in the same chemical family as trifluralin) is more commonly used.

Studies were initiated at the UC Westside Research and Extension Center in Five Points California in May 2019 to describe the response of field bindweed to trifluralin and pendimethalin relative to an

Results indicate that the ability of field bindweed to regrow following defoliation increased with plant age (Table 1, pg. 41). Field bindweed seedlings defoliated at 2 WAE did not re-sprout by two weeks following cutting; no viable above- or below-ground tissue was observed and recorded. Thirty-eight percent of field bindweed seedlings defoliated at 4 and 6 WAE survived the cutting treatment and re-sprouted.

One average, 0.5 to 3.0 grams of stem/ leave and root tissue were recovered at 2 WAT. One hundred percent of the field bindweed defoliated at 8 WAE survived the cutting treatment and produced 13.1 and 35.9 grams of above- and below-ground tissue, respectively.

While most management practices are focused on controlling rhizomatous 40

Progressive Crop Consultant

Figure 3. Field bindweed in cotton in Merced County (2019).

March / April 2020

COTTON REVIEW Table 1: Field Bindweed biomass accumulation (grams) at 2, 4, 6, and 8 weeks after emergence and subsequent regrowth (biomass accumulation in grams) following defoliation.

At time cuttting Belowground biomass (g)

Survival (%)

Aboveground biomass (g)

Belowground biomass (g)

2

Aboveground biomass (g)

0.2

0.2

0.0

0.0

0.0

4

1.7

1.6

37.5

0.5

0.9

6

9.3

9.7

37.5

1.1

3.0

8

27.3

21.5

100.0

13.1

35.9

120.0 100.0 80.0 60.0 40.0 20.0

n

u 12 n -J u 14 n -J u 16 n -J u 18 n -J u 20 n -J u 22 n -J u 12 n -J u 26 n -J u 28 n -J u 30 n -J un 2Ju l 4Ju l 6Ju l 8Ju l 10 -J u 12 l -J u 14 l -J u 16 l -J ul

-J

10

Ju

8-

6-

Ju

n

0.0

Treflan

Prowl H20

UTC

Figure 4. Bindweed cover (% of area occupied by vines) in response to trifluralin and pendimethalin.

Percent (%) Vine Cover 120.0 100.0 80.0 60.0 40.0 20.0

Ju 16 n -J u 18 n -J u 20 n -J u 22 n -J u 12 n -J u 26 n -J u 28 n -J u 30 n -J un 2Ju l 4Ju l 6Ju l 8Ju l 10 -J u 12 l -J u 14 l -J u 16 l -J ul

14 -

Ju n

12 -

Ju n

10 -

un

0.0

8J

Few pre-emergence or pre-plant incorporated herbicides are registered for the suppression of perennial field bindweed vines. Trifluralin, a dinitroaniline microtuble inhibitor, has been shown to inhibit vine emergence while pendimethalin has not. Results from the 2019 trial demonstrated that vine cover in the trifluralin treatments was reduced by 50 percent or more relative to the untreated check and pendimethalin treatments (Figures 4-5). There were no differences between pendimethalin and the UTC.

By July 16, mean bindweed cover in the trifluralin plots was 45 percent, whereas cover in the pendimethalin and UTC plots were 88 percent and 93 percent respectively. Flowering didn’t commence until June 27 in all treatments (<1% - trifluralin, 11% - pendimethalin, 27% - UTC) (Figure 5). Trifluralin also reduced flowering potential on July 8; however,

by July 16, 90 percent of emerged vines were flowering in all treatments.

Pendimethalin and trifluralin control

Percent (%) Vines Flowering

un

untreated check. Trifluralin (24 oz/A Treflan) and pendimethalin (24 oz/A Prowl H2O) were applied on May 24 and physically incorporated to a depth of three inches. Individual plots were 13.5 feet in width and 50 feet in length. An untreated check (UTC) was also included. Bindweed pressure in the trial was considered to be significant; approximately half of the study site was covered in vines two weeks before the initiation of the trial.

To ensure sufficient contact between the herbicide and the soil surface, the trial location was repeatedly disked to remove standing vegetation. Bindweed cover and flowering was assessed weekly from June 6 until July 16.

6J

Cutting Treatment (WAE)

Two weeks after cuttting

Treflan

Prowl H20

UTC

Figure 5. Bindweed flowering (% vines flowering) in response to trifluralin and pendimethalin.

a similar spectrum of weeds; if field bindweed is a concern in a field, growers may want to consider the use of trifluralin for vine suppression.

Continuing Research

A field trial to evaluate the combined effects of residual and postemergence herbicides and cultivation on vine control and cotton growth is ongoing

and will be reported on at a later date.

Results describing bindweed control in response to fall applied herbicides will also be presented later.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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41

COTTON REVIEW

MANAGEMENT OF KEY COTTON ARTHROPOD PESTS WITH INSECTICIDES AND ACARICIDES

REFINEMENT OF USE FOR COTTON IPM SYSTEMS

By IAN GRETTENBERGER | UCCE Field Crops Specialist Objectives of Research 1.) Develop an expanded database on the current efficacy of labeled/ recommended insecticide and acaricide products on key insect and mite pests of cotton in the San Joaquin Valley and document the influence of these products on beneficial arthropods with the objective of providing better guidelines on pesticide use.

2.) Evaluate the effectiveness of new candidate insecticide/acaricide products on key San Joaquin Valley cotton pests, the impact of these new compounds on populations of beneficial arthropods, and devise strategies for deploying these new products.

3.) Examine factors, including insecticide-related, environmental, and agronomic factors, which influence management of cotton arthropod pests with registered and experimental insecticides, emphasizing insects that threaten lint quality.

Introduction

We must maintain a multifaceted IPM approach to sustain an efficient and stable system of pest management in California cotton and to improve overall profitability. Insecticides remain a key component of effective management of arthropod pests in cotton. Furthermore, management of insect pests is a critical aspect of managing sticky cotton. California has a reputation for producing high-quality cotton, and successfully managing whiteflies and aphids and the resulting havoc they can create with lint quality is key to maintaining this reputation.

Up-to-date data on insecticide efficacy are in constant demand by growers and PCAs, as are data on how given insecticides can fit within an IPM 42

Progressive Crop Consultant

program. The results from this project will clearly be used nearly immediately.

Regulatory actions involving insecticides are ongoing and likely inevitable in California’s agricultural sector, which can lead to uncertainty and changes to what tools are available to control arthropod pests. In recent years, several insecticides, such as several organophosphates, Temik®, and endosulfan, have been lost due to marketing decisions (probably hastened by regulations). Use of several EC formulations in cotton have been limited due to VOC regulations in the SJV – dimethoate, abamectin, etc.

Concerns about off-site movement (via water and air) have threatened registrations and use of chlorpyrifos and pyrethroid products (and several premixes that contain a pyrethoid).

Belt® insecticide was removed from the market although it was promoted and thought to be a reduced-risk material for beet armyworm (and other species) control. Recently, numerous insecticides, especially neonicotinoid products, are being scrutinized due to the ongoing honeybee/pollinator concerns with proposed regulations potentially having significant impacts. There are a variety of neonicotinoid products used by the industry that could be influenced by future regulations. Registrations of “new” i nsecticide products such as Transform® are threatened and have been delayed (on again and off again) as well due to the pollinator issue.

Transform will not be available for the upcoming season in California. During the last growing season, chlorpyrifos was slated from removal from the marketplace. This has clearly left a gap in tools for late-season management of aphids and whiteflies. The overall effect of the losses or lack of registrations is very problematic and makes

March / April 2020

pest management more challenging.

Products are also being removed from the “toolbox” because of the build-up of insecticide resistance in pests, which are constantly evolving.

Organophosphates are typically not useful for lygus management, and pyrethroid insecticides may be useful for lygus for one application per season due to resistance. Spider mite control options have been available and numerous, but there appears to be some slippage in performance in recent years in other field crops. Given the ability of spider mites to develop resistance in multiple regions and cropping systems, this is not a surprise. Presently, whitefly control options are still in place although during some “application windows” there are now a shortage of options. Mid-season aphid management is still viable as long as the neonicotinoid products are available, but late-season there is a critical void with the loss of chlorpyrifos. Maintaining effective aphid and whitefly IPM programs is essential to addressing the threat of sticky cotton to the industry.

The challenges from development of insecticide resistance and regulatory actions are best addressed with wellplanned research and interaction/ collaboration with all concerned industry representatives. Fortunately, new materials are developed to facilitate IPM programs. These new products must be evaluated under California conditions. This development of new products appears to have slowed somewhat recently with the consolidation of the agrichemical industry and changes in ownership that have disrupted and delayed research plans. In the interim, available experimental products will

Continued on Page 44

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COTTON REVIEW

Continued from Page 42 be evaluated, registered products will be researched and evaluated for efficacy, and other IPM tactics will be studied and developed. This research has allowed and will continue to allow a thorough evaluation of the applicability of experimental materials for the California cotton system before they appear on the market. By examining the complete “big picture” of California cotton IPM, this project helps to determine the applicability and fit of these products. The pests of interest in this project include cotton aphids, spider mites, thrips, whiteflies, lepidopteran larvae, and lygus bugs. Emerging and invasive pests will also be addressed, as needed and relevant. The integration of insecticides and acaricides with other management approaches (biological control, etc.) will be emphasized.

Summary: Insecticide/ Acaricide Efficacy The research season in 2019 progressed well, despite some weather challenges early in the season that made research challenging when trying to get cotton planted, although this was something that commercial growers faced as well.

Late-season rains prevented us from getting out cotton planted “on time”, especially at the Shafter Research Station. Planting at West Side Rec was less affected. Whitefly populations were low but were relatively consistent over the course of the trial. Our aphid populations steadily declined after the first application, leading to very low populations after the second application. In the past year, we continued conducting the research trials at the locations (West Side REC and Shafter Research Station) where they have been conducted for the past several years. Field and laboratory work was split between both locations, with the lygus and mite trials conducted at West Side REC and the aphid/whitefly study at Shafter Research Station.

Lygus

Objective: To evaluate Lygus bug management tactics, including newly registered insecticides, combinations 44

Progressive Crop Consultant

of materials and varied timings, and industry standard (registered) insecticides, as well as the effect of treatments beneficial insects and secondary pest populations. ▶ Application dates: 2 applications, July 9 and July 14 ▶ Study location: West Side Research and Extension Center, Five Points, CA; Fresno County ▶ Application equipment: pull-behind tractor sprayer, CO2 propellant, Spraying Systems TX-VS10 nozzles (5 nozzles per row) ▶ Application parameters: 20 GPA, 40 PSI, 3.5 MPH ▶ Plot Size: 10 rows x 68' feet, 4 replications ▶ Plot design: randomized complete block ▶ Plot condition: irrigated Acala cotton (PhytoGen 764 WideStrike RF) planted on 38 in rows Insect sampling: Lygus: Adults and nymphs per 50 sweeps per plot at various days after treatment (DAT).

Secondary pests: 10 leaves/plot (5th main stem node leaf from top) were collected and aphids and spider mites counted in the lab 10 DAT1).

Natural enemies were assessed once at 7 DAT1 using the same sweep net sampling used for lygus sampling.

Later sampling using the same technique was not possible because of the growth habit of the cotton.

Yield: We picked the middle two rows with a commercial picker. We weighed seed cotton and calculated yield per acre, accounting for exact feet of row that were harvested.

Lygus nymphs: Pre-treatment populations of nymphs were 7.75 per 50 sweeps. At 2 DAT1, only Warrior and Vydate provided any level of control (70 and 76 percent). At 6 DAT1

March / April 2020

Vydate provided 80 percent control, while both Transform treatments, Carbine, and Diamond+Carbine all provided 70-80 percent control.

Differences were more pronounced 10 DAT1, with the same treatments (other than Transform-L) providing 80-90 percent control. Only Vydate had high levels of control 13 DAT1.

At 2 DAT2, a number of treatments had 80-90 percent control. At 6DAT2, Diamond+Carbine, Orthene, Transform (L and H) and Vydate all had 90-100 percent control. Diamond alone provided 80 percent. At 10 DAT2, only Orthene and Vydate had above 80 percent (83) control. The pattern was similar 13 DAT2 and at 21 DAT2, Diamond provided 90 percent control, Orthene 97 percent, and all remaining 51 percent and lower.

Lygus adults: At the first sampling (2 DAT1), Transform-L and Vydate provided a degree of control (70 and 80 percent). At 6 DAT2, only Transform-L provided any degree of control (75 percent). At 10 DAT2, many of the materials provided some degree of control in the 40-50 percent range, and Carbine, Diamond, Transform-H, and Warrior all provided 64 to 68 percent control. At 13 DAT1, Transform-H provided the best level of control (70 percent), with some control (54 and 59 percent) still offered

by Carbine and Diamond+Carbine.

2 DAT2 Orthene provided 86 percent control. At 6 DAT2, both Transform rates provide 88 percent control.

COTTON REVIEW At 10 DAT2, a number of materials provide 45-60 percent control.

Natural enemies: We have not yet attempted to analyze the natural enemy data using multivariate statistics, so we present analysis of summed counts of natural enemies. At 2 DAT1, there were significant differences among treatments based on the overall analysis, but none in pairwise comparisons (numerically lowest in Belay, highest in Diamond+Carbine). At 10 DAT1, natural enemies were least abundant in the Belay and Sivanto-High treatments and highest in the Brigade and Untreated.

At 13 DAT1, natural enemy populations had increased across most treatments, with the untreated having the most, followed by Brigade and Baythroid.

Orthene, Assail, and Belay all still had low natural enemy populations.

Secondary pests: Aphid and mite populations were low during this trial and none of the treatments led to very high levels. Populations of aphids did differ significantly between treatments (F14,42 = 2.67, P = 0.007).

At 10 DAT1 when they were assessed, aphid populations were highest in the Brigade plots (~1 per leaf), followed

by Baythroid, Vydate, and then the Untreated. The only significant differences were between Baythroid and Assail, the latter which had the fewest. Mites were extremely low overall, with no significant differences among treatments (F14,42 = 0.57, P = 0.87). After the second application (6 DAT2), the untreated had the most natural enemies, followed by Vydate.

Orthene, Transform-ow, and Assail all had few natural enemies. These patterns generally persisted through the end of the study. At 13 DAT2, the untreated had by far the most natural enemies, followed by Warrior and the Admire/Carbine treatment.

Yield: Yield was highest in the Vydate treatment with 3,254 pounds seed cotton per acre. This was followed by Diamond+Carbine with 3,152, Carbine with 3,093, Transform-H with 3,090.

Brigade had the lowest yield at 2,015, followed by Baythroid at 2,148.

Bioassays

Similar to previous years, we have continued to monitor insecticide resistance in lygus populations for key insecticides. This includes older materials like Vydate and Capture, and newer materials that have been increasingly relied upon for lygus management, Capture and Carbine.

For Vydate and Capture, these assays consisted of exposure of insects to the material in insecticide coated plastic bags. The Carbine method relies on

®

dipped green beans, while Transform uses floral foam soaked with a solution containing the insecticide.

The data are still being processed for these assays, but we can report on the number of assays that were completed.

To mirror prior years, we conducted both early and late season assays. For the early season assays, we had four locations, with insects collected between May 31 and June 13. For the late season

Continued on Page 46

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COTTON REVIEW

Continued from Page 45 assays, we again attempted assays at four locations, but lygus were no abundant enough for the full complement of assays. At two of the locations, we could run all four materials. At one site, we only had enough for two materials, so we focused on Carbine and Transform.

At the other, site, we were unable to collect enough lygus for assays.

Aphids and whiteflies

Objective: To compare the efficacy of selected registered insecticides and experimental materials against cotton aphids and whiteflies during the midand late-season period in Pima cotton. ▶ Application dates: 28 August and 11 September – Insecticides – 21 treatments ▶ Study location: Shafter Research Station near Shafter, CA; Kern County ▶ Application equipment: Highclearance trailer spryer pulled with a tractor, CO2 propellant, Spraying Systems TX-VS6 nozzles (5 nozzles per row) ▶ Application parameters: 30 GPA, 40 PSI, 3 MPH ▶ Plot size: 5 rows x ~55' feet, 4 replications, 38 in. rows ▶ Plot design: Randomized Complete Block ▶ Plot condition: irrigated Pima cotton (‘Phytogen 841 RF’) Insect sampling: All insect data were collected from 10-leaf samples (5th main stem node leaf down from terminal) per plot. Cotton aphids (Aphis gossypii) and whitefly nymphs Bemisia tabaci Biotype B, (formerly B. argentifolii): visually counted on leaves using a dissecting microscope.

Data on WF nymphs were collected per entire leaf as well as per “quarter-sized” disk (between the main leaf veins; not reported here). This is the area that the treatment threshold is 46

Progressive Crop Consultant

based upon. Whitefly adults: leaves were carefully examined and turned over in the field and adults counted.

Yield: We picked the middle two rows with a commercial picker. We weighed seed cotton and calculated yield per acre, accounting for exact feet of row that were harvested. We did not harvest any plots in the first block because vigor was extremely poor, and this would have not been useful yield data. Yield was very low overall.

For all results, see tables and figures for full analysis details and means.

Aphids: On the day of application, aphids averaged 116/leaf. At 2 DAT, The low rate of Transform was most effective (91 percent control), followed

by Lorsban+Dibrom and the high rate of transform. At 7 DAT1, both Transform rates performed well, with 98 and 97 percent control of the high and low rates respectively. Lorsban and Sefina-Low both provided 89 to 90-percent control. At 13 DAT1, many of the treatments provided excellent levels of control (many over 90 percent 80 percent). This included all of the newer materials (Sefina, Sivanto, Transform, PQZ, Carbine; all rates) as well as Assail, Lorsban+Dibrom, and Knack. Meanwhile, by this point, Vydate, Lorsban, and Courier had increased numbers of aphids relative to the control (numerically, not significantly different). Immediately after the 2nd application (2 DAT2), the Lorsban+Dibrom had the fewest aphids. At 7 DAT2, aphid populations in the untreated had started to crash and were only 9 per leaf. The following sampling dates were somewhat less useful because of the low untreated numbers, with one exception being that these patterns showed which treatments otherwise maintained aphid populations (see Vydate in particular).

provided the best at 83 percent, followed by Assail+Bifenture at 76 percent.

A number of other treatments provided 60 to 70 percent control. At 13 DAT1, the untreated had fairly low numbers, so percent control was poor across treatments (other than Courier). At 2 DAT2, Sivanto-High provided the best control (82 percent), followed by Assail and Sefina-High. Lorsban provided the least level of control at this time point. At 14 DAT2, Cormoran provided the most control, followed by Assail, Carbine (although this appears to aberrant), Sefina-Low and Assail+Bifenture.

Across dates, Vydate and Admire Pro performed poorly, several times having more nymphs than the untreated.

Whitefly adults: Whitefly adult counts typically ranged between 1 and 2 per leaf in the untreated over the course of the study. There were only significant differences among treatments for several of the assessment dates (7 DAT1, 2 DAT2, and 21 DAT-2 – at α = 0.10). Posthoc comparisons did not indicate any significant differences except on 7 DAT1 when the untreated was significantly different from over half of the treatments. No individual treatment appeared to stand out when viewed across dates.

Secondary pests: Spider mites were evaluated as a secondary pest that could be flared by treatments for aphids/whiteflies. Mite counts were very low over the course of the study. We therefore analyzed counts summed by plot across the entire study. There were not significant differences among treatments for these counts (F19,57 = 1.17, P = 0.31).

Yield: Measuring yield was not one of the key aspects of this study because we are focused on managing aphids and whiteflies because of the way they threaten quality of lint (via sticky cotton) rather than quantity of lint. We did not detect significant differences in yield quantity (F19,38 = 0.41, P = 0.97).

Whitefly nymphs: On the day of applications, whitefly nymph populations were low at 0.9/leaf. At 2 DAT1, only Knack provided >50 percent control at 56 percent. At 7 DAT1, a number of Comments about this article? We want the other treatments began to provide to hear from you. Feel free to email some level of control, with Sivanto-Low us at article@jcsmarketinginc.com

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47

COTTON REVIEW

By GREG PALLA | San Joaquin Valley Quality Cotton Growers Association

T

he purpose of this study was to evaluate the effectiveness of the Cotton Clean™ product when applied with various methods and at various rates. The results confirmed what our preliminary research indicated. Generally, the study indicates that Cotton Clean™ shows significant benefit in reducing stickiness on cotton that is at a level of moderate to heavy levels of stickiness. Where stickiness is light or nearly absent, Cotton Clean™ does not have any significant effect on reducing stickiness. From these findings, one may conclude that where stickiness levels are very low to begin with, there may be insufficient food source (deposited insect sugar) for enzymatic sugar reduction through the use of Cotton Clean™. Therefore, the stickiness of cotton with low levels of stickiness do not change with any degree of significance. This is true statistically, as well as economically, as extremely low levels of stickiness generally cause no detectible difference in textile processing or quality of output.

Also, we determined cotton ginned at commercial gins where Cotton Clean™ was applied at time of ginning was significantly less sticky than cotton from the same farm that was ginned at a facility where no Cotton Clean™ was applied at time of ginning.

48

Progressive Crop Consultant

Introduction

Aphid and whitefly pests are well distributed throughout the San Joaquin Valley and in many other irrigated upland and pima cotton producing regions, particularly where arid conditions exist. It is well documented that several species of these pests can deposit objectionable levels of sugars through their excreta which can make processing seed cotton (in ginning) and cotton lint (in carding and spinning) very difficult and time consuming if sugar deposits reach moderate to high levels. Growers have used many methods and approaches in keeping sticky cotton producing pests to a manageable level, but there are instances where their efforts are ineffective in the avoidance of problematic stickiness levels. When this occurs, gins and spinning mills have severe problems in handling cottons in this condition.

It is believed that if the deposited insect sugar was converted into a substance with little or no viscous properties at ginning or spinning operational temperatures, without harming the cotton fiber onto which it was deposited, then ginning and spinning processes would be improved and lint quality preserved.

In 2016 San Joaquin Valley Quality Cotton Growers Association began

March / April 2020

work to identify ways to combat the ill effects of sticky cotton beyond control of the insect source itself. A biological agent was introduced on problematic seed cotton that had been plugging up stands at a roller ginning facility. It was sprayed on seed cotton at the module feeder in an aqueous solution. Cotton so treated did not exhibit problems with plug ups at the stands. After that initial trial further study was conducted and it was determined that a more precise formulation could be developed to address Trehalulose and Melizitose even more effectively. In 2017 Cotton Clean™ was developed in conjunction with the manufacturer and their principal dealer. Cotton Clean was provided to 12 different growers for use in applying at harvest and 1 gin used the material applied at the module feeder.

Lint samples were collected from bales treated with Cotton Clean™ and those bales not treated with Cotton Clean™. Those lint samples were tested using Thermodetector, Mini card, and Mesdan ConTest stickiness testing methods. Most test data sets indicated reduced stickiness on samples treated with Cotton Clean™, while a few sets were more inconclusive. Whether or not influential factors not recognized had impacted the results was unclear.

Continued on Page 50

COTTON CLEAN

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COTTON REVIEW

A BIOLOGICAL QUALITY ENHANCER A special formulation designed to mitigate the effects of undesirable deposits of insect sugars.

• Cotton Clean applied in the Cotton Gin has shown significant reductions in stickiness according to published data. Cotton Clean may also be applied in the Cotton Picker moistener system to treat potential stickiness problems.

• Cotton Clean should be used at 2 to 6 packets in both applications depending on the severity of insect sugar suspected.

• Cotton Clean used at its lowest rate in both applications, is still less than $1.00 per bale.

• Cotton Clean has been shown to improve throughput in the gin.

• Cotton Clean is inexpensive insurance designed to reduce the level of stickiness in your cotton.

• Cotton Clean’s goal is to reduce the effects of stickiness in the ginning and milling of cotton. Our wish is nothing less than “Clean Comfortable California Cotton.”

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March / April 2020

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49

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COTTON REVIEW Chart 1

Chart 2

Continued from Page 48

iii. Woolf Farming – Huron Gin

Some of those factors are the subject of this project proposal, including rates of application and methods of application. What is known is that ginning personnel report anecdotally that there were no problems with gin stand plugging on cotton treated with Cotton Clean™, whereas, untreated cotton from the same field continued to exhibit plugging problems.

iv. Errotabere Ranches – West Island Gin

2. Seed cotton samples (both Upland and Pima) were collected from the fields prior to harvest, identified and segregated so as to preserve identity for both test and control sample sets.

A better understanding of the proper rate of use of Cotton Clean™ and most effective method for application will help growers and ginners make the most of this contamination mitigation tool.

3. Varying rates (25 to 90 bales per pound) of Cotton Clean™ were applied through picker moistener systems at time of harvest as well as varying rates applied at time of ginning.

Methods and Materials

4. Lint samples were collected at the gins and transported to secure storage until fiber testing is conducted.

Plan of work:

1. Identify sources of seed cotton to be included in the study. Growers and ginners in the San Joaquin Valley were contacted to participate as volunteers in the study. In addition to commercial locations, research plots were used as a source of seed cotton. a. Cotton was collected from and ginned at: i. The Shafter Research Station – Farmers Co-Op Gin ii. Armstead Ranch – Westhaven Cotton Gin 50

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v. J. Polder Co. – West Island Gin

5. Lint samples were tested for stickiness using Mesdan Contest instrumentation and recorded.

6. Randomly selected lint samples were procured for testing at USDA ARS New Orleans for additional confirmation of results.

7. Results were analyzed and reported.

Results

The results from this experiment generally support our hypothesis that Cotton Clean™ reduces the stickiness grades determined by the Mesdan

March / April 2020

Contest Cotton Quality Testing machine. The overall results from all stickiness levels of cotton in the experiment were slightly in favor of the sample group that had Cotton Clean™ applied. The average stickiness level of the fields without Cotton Clean™ applied during ginning was 102. The average stickiness level of the fields with Cotton Clean™ applied during ginning was 97. A difference of 5 points on the measurement system of the Mesdan Contest machine is insignificant. While it is noted that some field stickiness grade averages were higher with Cotton Clean™ applied than without, those only occurred in samples with low (<100 stickiness grade).

However, when fields with lower levels of stickiness (<100 stickiness grade) were removed from the averaging process, the result is dramatically different. When only those fields with medium to heavy stickiness were considered, Cotton Clean™ applied at ginning reduced measured stickiness significantly, from 147 down to 97, a reduction of 34%.

In order to confirm validity of results measured by the Contest instrument, a random selection of samples from each field was sent to USDA-ARS in New Orleans for blind testing using the standard minicard stickiness test. The minicard test uses a different method of measurement to gauge stickiness levels than the Contest instrument, but has shown relatively good correlation of stickiness between the two

COTTON REVIEW

measurement technologies. That being said, due to the variability of stickiness among samples within a field the results may also illustrate some degree of variation. The measurements reported

by USDA are None, Light, Medium, Heavy, and Very Heavy. In order to make relevant those designations to Contest values, we assigned values we believe to be consistent with similar levels of stickiness as measured by the Contest instrument. None = 10, Light = 75, Medium = 125, Heavy = 200 and Very Heavy = 375. We assigned a numeric value of 10 for None in order to present it graphically, but for all intents and purposes Contest levels of 0 and 10 are effectively indistinguishable.

The results by field for the samples without Cotton Clean™ applied during ginning were 4 fields were None, 10 fields were Light, and 1 field was Heavy.

The results by field for the samples with Cotton Clean™ applied during ginning Chart 3

were 1 field was None and 14 fields were Light. None of the samples treated with Cotton Clean™ measured above a Light designation. It should be noted that the minicard designations are subjective evaluations of the technician conducting the test. The difference between Light and None in some instances can be almost indistinguishable. Medium, Heavy, and Very Heavy designations tend to be much more pronounced. So as indicated by the Chart 3 below, one can see that only where stickiness is more than Light, (in this case Heavy in field 18), can we see significant improvement with Cotton Clean™. This is consistent with the results developed independently with the Contest instrument and so therefore, we conclude the independent results confirm one another.

large scale test from a farm producing > 10,000 bales indicated that stickiness grades were significantly reduced when Cotton Clean™ was applied at the time of ginning.

Since only one commercial gin applied Cotton Clean™ uniformly on cotton of a large scale (>10,000 bales) we were only able to evaluate stickiness grades of cotton ginned commercially at one rate (80 bales ginned per pound of Cotton Clean™ applied).

At this rate stickiness grades averaged 32 versus an average of 58 for those bales ginned from the same farm but ginned at a ginning facility that did not use Cotton Clean™. Even though all the stickiness levels in this instance were not considered heavily sticky, this

This study could not have been conducted without the assistance and cooperation of many individuals and organizations. We wish to thank all who contributed something to this effort, especially the following: Armstead Ranch, California Cotton Ginners and Growers Association, California State University, Bakersfield, Errotabere Ranches, J. Polder Co., Stone Land Co., USDA ARS New Orleans, Westhaven Cotton Co., and Woolf Farming Co.

Conclusion

Cotton Clean™ shows significant benefit in reducing measured stickiness in instances where stickiness levels in the field are expected to be medium or moderate levels and above. Even when cotton stickiness levels are below moderate, proper application of Cotton Clean™ at manufacturers suggested rates at time of ginning shows significant reduction in measured stickiness.

Acknowledgements

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COTTON REVIEW

UPLAND AND ACALA RESEARCH CENTER VARIETY TRIALS

By BOB HUTMACHER | UCCE Extension Cotton Specialist and UC AES

A

cala and Upland acreage continues to be far less than Pima plantings in this and recent years. There are tradeoffs in shifting to Pima (typically reductions in yields) and in shifts to non-Acala Uplands (typically lower price for lint), and growers need reliable, unbiased information regarding expected lint yields and fiber quality in order to make reasonable, lower-risk decisions. All of the entries in both types of trials were harvested in late October or in November by spindle picker (center two rows harvested out of four row wide plots). Subsamples from all field replications of the trials at both sites will be collected, and will be ginned starting in early December on a mini-gin, since the Shafter Research gin is no longer in operation due to budget restrictions. Subsamples from all plots will also be submitted for hvi analyses run through the USDA Classing office in Visalia, California.

2019 Trial Activities:

Entries included in the field trials included the following planted at West Side REC locations (CA Upland Advanced Strains trials) and at Shafter and West Side locations (UC Acala/Upland variety trials). Results of trials will be available at UC cotton web site at cotton info.ucdavis.edu.

Entries planted in 2019 UC / Cotton Inc. / CCGGA Research Funded Acala / Upland Variety Trials – West Side REC location only for 2019: FM 1830GLT, ST 4550GLTP, FM 2398GLTP, ST 5600B2XF, ST 5707B2XF, FM 2498GLT, ST 5471GLTP, FM 2574 GLT, PHY 764WRF, DP 1646B2XF, DP 1820 B3XF, and DP 1845B3XF. Entries Planted in 2019 CA Upland Advanced Strains Variety Evaluations – West Side location: Phy-764 WRF (check), DGX 19001 B3XF , DGX 19014 B3XF, DGX H929 B3XF, BX 2002 GL, BX 2005 GLT, BX 2037 GLT, BX 2016 GLTP, BX 2022 GLTP, BX 2076 GLTP, BX 2398 GLTP, FM 2498 GLT, ST 5600 B2XF, ST 5707 B2XF, FM 1621 GL, 18 R411 B3XF, 18 R421 B3XF, 18 R423 B3XF, 18 R438 B3XF, 18 R445 B3XF, 18 R448, and B3XF.

Continued on Page 54 52

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March / April 2020

COTTON REVIEW

Representing the Issues

For California Cotton Ginners and Growers

The California Cotton Ginners and Growers Association is a voluntary agricultural trade associations that proudly represents 100% of all cotton ginners and growers in the state. Our focus is solely on California cotton, which gives us the opportunity to specifically represent the interest of the California cotton industry. With numerous success stories under our belt and many more on the horizon, the association has gained a reputation for first class representation, both locally and statewide.

California Cotton Ginners & Growers Association (559) 252-0684

ccgga.org

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COTTON REVIEW

Continued from Page 52

or Shafter Research Station site in Kern County if possible, plus the University of CA West Side REC for these trials)

Entries Planted in 2019 Western and National Entries–NATIONAL STANDARDS TRIALS – West Side REC location: DP 1646 B2XF, NG 4545 B2XF, PHY 764 WRF, PHY 499 WRF, DAYTONA RF, DP 1549 B2XF , FM 1830 GLT , FM 2574 DP 1522 B2XF. Entries Planted in 2019 RBTN (Regional Breeder Testing Network) Program–West Side REC location LA16063019, LA16063033, LA16063054, 13AFX6-27-2, 13AFX13-12-5, Ark 1115-36, Ark 1102-55, Ark 1114-21, Ark 1117-60, Ark 1124-50, Ark 1112-59, TAM 13S-03, TAM 12J-39, TAMLBB15905, TAMLBB16507, GA2016024, GA 2016099, GA 2016103, MS 2010-8737, CSX 8308, DP 393 check, DP 493 check, FM 958 Check, UA 222 check.

All of the entries in these trials were included in our field Fusarium race 4 screening trials for 2019 at one location. Results from those trials were summarized and reported in our final screening information, with results on the University of CA cotton web site at http://cottoninfo.ucdavis.edu. The type of information provided in these field trials on variety performance in the CA Uplands Advanced Strains Trial and Acala/Upland West Side REC and Shafter (for primary Upland/Acala trial) for 2019 focused mostly on yield performance, gin turnout, and fiber quality components. This information will be available following the conclusion of the growing season, and data presentation will be via the UC cotton website, or paper copies can be provided on request. In addition to the yield data we also make available the summary fiber quality / hvi testing data from the samples submitted to the Visalia USDA classing office.

2018 Project Summary

The overall project supports in part conducting three types of variety trials: a. Testing of commercial non-Acala Upland varieties (and remaining Acala types if available), with a target of two sites (one on-farm site 54

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b. Small scale testing at the UC West Side REC of a range of Upland varieties that are either only available in small seed quantities or that are experimental or of limited current commercial interest for grower field trials (CA Upland Advanced Strains Trials) c. Small scale testing at the UC West Side REC of entries in the National Standards and Western Regional trials in a small plot, four replication trial at this one site.

For 2018, the set of trials planted were: d. Acala and non-Acala Upland varieties to bed grown in two sites including a plot trial at the University of CA West Side REC in Fresno County and the former UC/USDA field station site in Shafter, CA in Kern County. e. A small plot trial with limited seed availability CA Upland cultivars (or entries of limited or unknown commercial interest for the San Joaquin Valley), with the plots established at the West Side Research and Extension Center. f. Entries in the UPLAND COTTON Western Regional and National Standards trial coordinated by USDA-ARS, with entries supplied for western region by Alison Thompson, USDA-ARS, Maricopa, AZ on request of the national standards committee.

This project, with partial support from Cotton Incorporated plus added support from the CA Cotton Ginners and Growers Association Research Fund and from participating seed companies for the Advanced Strains trial, is now the only public variety testing program for Upland/Acala varieties of potential interest for San Joaquin Valley cotton production.

March / April 2020

The small plot trials have 4 replications, with plots 4 rows in width by 60 to 70 feet in length (depending upon seed availability and locations used for the trials). The test sites at the West Side Research and Extension Center in Fresno County were planted the third week of April this year, and the Shafter site was planted in the third week of April this year. The goals of the project are to provide trial sites for testing a large number of entries of potential interest to seed companies and growers, with entries chosen to assess relative performance in SJ Valley settings and areas where Uplands/Acalas have been of at least some continuing commercial interest.

Data Collection and Availability From Field Trials:

Summaries of prior year trial results are available at http://cottoninfo.ucdavis.edu).

In addition, results are presented at the Cotton Workgroup meetings and at winter and spring grower/PCA meetings of the University of California. Results of the trials will be reported in winter meetings of the UCCE Specialist and Farm Advisors, and will be available in a printable form (pdf or Word) as full tables on the University of California cotton web site: http://cottoninfo.ucdavis.edu

Field Work for 2018

Acala and Upland acreage continues to be far less than Pima plantings in this and recent years. There are tradeoffs in shifting to Pima (typically reductions in yields) and in shifts to non-Acala Uplands (typically lower price for lint), and growers need reliable, unbiased information regarding expected lint yields and fiber quality in order to make reasonable, lowerrisk decisions.

All of the entries in both types of trials were harvested in late October by spindle picker (center two rows harvested out of four row wide plots). Subsamples from all field replications of the trials at both sites were collected, and will be ginned starting in November on a mini-gin, since the Shafter Research gin is no longer in operation due to budget restrictions.

Subsamples from all plots will also be submitted for hvi analyses run through the USDA Classing office in Visalia, CA.

COTTON REVIEW *If the services are available, we may try to run two replication subsamples per variety through the Shafter Research Gin, if it is in operation this year, in order to provide more reasonable gin turnout estimates.

2018 Trial Activities:

Entries included in the field trials include the following planted at West Side REC locations (CA Upland Advanced Strains trials) and at Shafter and West Side locations (UC Acala/Upland variety trials). Results of trials will be available at the UC cotton web site mentioned for prior year results.

• All of the field plots at the West Side REC yielded and looked relatively good, despite heavy early- to mid-season lygus pressure and the hottest July on record in the Fresno County and San Joaquin Valley area (with over 30 consecutive days with high temperatures in excess of 100 degrees F). Some of the bottom crop was lost due to lygus pressure, with some losses also attributable to high nighttime temperatures • As with the past two years, we no longer have access to the Shafter Research Gin at the old Shafter Research Center, so the only gin turnout and lint percent data available are those derived using minigins, with no other cleaners other than hand removal of trash materials during the ginning process.

All of the entries in these trials were also included in our field Fusarium race 4 screening trials for 2018 at one location. Results from those trials were summarized and reported in our final screening information, with results on the University of CA cotton web site at http://cottoninfo.ucdavis.edu The type of information provided in these field trials on variety performance in the CA Uplands Advanced Strains Trial and Acala/Upland West Side REC and on-farm trials focuses mostly on yield performance, gin turnout, and fiber quality components. This information is available via the UC cotton website mentioned earlier, or paper copies can be provided on request. In addition to the yield data we also make available the summary fiber quality / hvi testing data from the samples submitted to the Visalia USDA classing office. Thank you for the past and current support of these trials. If you have questions, please direct them to Bob Hutmacher at (559) 260-8957 or rbhutmacher@ucdavis.edu.

Comments about this article? We want to hear from you.

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COTTON REVIEW

Pima On-Farm Variety Trials, Pima Research Center Variety Trials

By BOB HUTMACHER | UCCE Extension Cotton Specialist and UC AES

Project Summary ield evaluations of Pima cotton varieties will be conducted at a UCCE Research Center location (West Side Research and Extension Center) and at 3 grower field sites as follows:

Preliminary Summary of 2019 Year 2019 Trial Activities:

F

a. For 2019, we conducted trials at the UC West Side REC and 3 grower field farm sites. Sites are located in Kings County, Kern County, and Merced County) b. For 2018, we conducted Pima variety trials at the West Side REC, Fresno, Merced and Kings County grower sites. c. We offered the opportunity to conduct smaller-scale research plot variety trials of Pima varieties at the West Side REC, including any experimental varieties supplied by seed companies where seed quantity available for testing is limited.

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Progressive Crop Consultant

Research Center and Farm Trial Sites: West Side REC, Kern County – Bone Farms, Merced County – Bowles Farms, Entries included in the field trials for Kings County – Hansen Ranches. In 2019 included the following cultivars addition, all of the entries in these trials planted at West Side REC and Farm were included in our field Fusarium locations. Results of trials each year will race 4 screening trials for 2019 as in be available at the same UC cotton web all prior years. A selection of Pima site mentioned for prior year results. varieties from Egyptian sources were planted at a Merced County site for Entries Planted in 2019 Pima Variety evaluations in including yield potential, Trials – West Side REC: DP 341 RF, DP earliness and FOV-4 resistance, and 348 RF, Phy PX 8504RF, DP 359 RF, PHY if possible, fiber quality samples will 841 RF, PHY 881 RF, PHY 888 RF, HA be collected for hvi evaluations.

1432, PHY 802 RF, and PHY 805 RF. Results from those trials will be summaHA 1432 was also planted at a rized and reported in our final screening Merced Co site. Phy-802 RF and information after completion of field Phy-805RF were only at WSREC. data and analyses. The results will be available on the University of CA cotton Entries planted at the grower sites will web site at http://cottoninfo.ucdavis.edu be reported by individual sites. There were differences in the entry list due The 2019 field trials were still underway to expressed grower interest and at the time of this report, so there are willingness to have plantings, and no yield results or other hvi results some differences due to limited seed from 2019 trials available. The 2018 availability. Complete list of plot maps results from Pima variety trials are at each site can be available on request. available on the web site mentioned.

For the most part, the varieties planted were the same as at WSREC, except for some sites that did not want the Hazera Comments about this article? We want hybrid, which is non-transgenic and to hear from you. Feel free to email us not glyphosate herbicide resistant. at article@jcsmarketinginc.com

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COTTON REVIEW

September 17-18, 2020 Visalia Convention Center Visalia, California New This Year: Extended DPR and CCA Seminars

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COTTON REVIEW

Verticillium Wilt Resistance of Newer Germplasm in Pima, Acala and California Upland Varieties

By BOB HUTMACHER | UCCE Extension Cotton Specialist and UC AES

T

he overall objective of this research is to evaluate field screening location(s) with a moderate to high level of sustained Verticillium wilt inoculum to provide location(s) for field screening of cotton germplasm of interest in CA Cotton production. The aim of the work will be: (1) to sustain a relatively small location (approximately 0.5-1 acres) at the West Side REC where we can maintain a Verticillium wilt population for field screenings to identify relative susceptibility of newer commercial varieties of interest for California cotton production, and for screening of experimentals from both commercial breeders or seed companies and those from USDA-ARS or other public breeding programs; and (2) to support evaluation of relative verticillium wilt levels in cultivars being tested in the FOV race 4 screening location(s).

Some of the evaluations have either not been done (West Side REC) for 2019 or have not yet been summarized (Tulare County site) at the time of preparation of this report since the best time for evaluations of this type are generally mid- to late-summer. Results from the 2019 field evaluations will be summarized when data is available.

Summary From 2018

Tulare County Location All entries grown in the FOV race 4 screening trials were grown at a 58

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location with Verticillium present, which also turned out to be a location that had race 4 FOV present. The screening for verticillium was still done at this location since the plantings were in place and we considered it to be useful information, and the verticillium screening was done on a minimum of 5 plants per entry per replication, for a total of 15 plants per entry to rate for incidence (of plants with Verticillium evidence in the stem – vascular staining about 1/4 to 1/3 of the way up the stem, as compared to root vascular staining evaluations for FOV).

West Side REC Location: Evaluations were done at a site at the West Side REC of the University of CA where we planted small plots for evaluation. The screening for verticillium was done at this location on 7 plants per entry per replication, for a total of 21 plants per entry to rate for incidence (number of plants with Verticillium evidence in the stem – vascular staining about 1/4 of the way up the stem, as compared to root vascular staining evaluations for FOV).

The overall objective of this research is to evaluate field screening location(s) with a moderate to high level of sustained Verticillium wilt inoculum to provide a location for field screening of cotton germplasm of interest in CA

March / April 2020

Cotton production. The aim of the work will be: (1) to sustain a relatively small location (approximately 1 acre in multiple variety trials) at the West Side REC where we can maintain a Verticillium wilt population for field screenings to identify relative susceptibility of newer commercial varieties of interest for CA Cotton production, and for screening of experimentals from both commercial breeders or seed companies and those from USDA-ARS or other public breeding programs; and (2) to support evaluation of relative verticillium wilt levels in cultivars being tested in the FOV race 4 screening locations.

The intent of continuing this work on a relatively small scale, and with data reported from both West Side REC and field trial locations where we also are doing Fusarium race 4 field screening is to develop information on verticillium wilt incidence in currently-grown and possible future cultivars of interest for California cotton production. Verticillium wilt incidence was evaluated in 5 plants per field replication at each field site.

The intent is that UC and USDA-ARS investigators as well as seed company representatives and breeders could use this information in determining the relative need for follow-up evaluations and screening efforts for verticillium wilt susceptibility as they advance

COTTON REVIEW

of very low incidence, or even zero incidence cultivars in both Upland and Pima data particularly at the Univ CA West Side REC site, but in some cases also at this one Tulare County site. It was interesting that the experimental Egyptian Pima cultivars worked with in recent years and in crosses did not appear to be susceptible to Verticillium, at least at 2018 evaluation sites. Similar data will be collected from two sites in 2019 and made available after analysis

The intent of this work is to provide it to seed companies as a means of identifying materials that may require some additional evaluations for verticillium susceptibility as they move forward in their breeding programs.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

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Monitoring lures for conventional and organic California tree nuts!! cultivars through their selection processes. The charts attached to this brief report give an indication of the levels of verticillium seen during the current year evaluations for the broad mix of cultivars.

Verticillium wilt incidence evaluations were done on a large collection of experimental Pimas and Uplands that were included in our Uplands Advanced Strains trial, plus experimentals submitted by seed company representatives or breeders, plus public breeder entries in the RBTN (Regional Breeder Testing Network) evaluations coordinated by Ted Wallace of Mississippi State University in cooperation with the USDA-ARS. Figures 1 through 5 show Verticillium incidence in commercial Upland/Acala & advanced experimental Uplands at Tulare County site in 2018 field evaluations. The five graphs show data for over 100 entries plus three check varieties. The check varieties were evaluated for consistency of data across field replications, and generally incidence of verticillium was evident across all three field replications in most entries. Check varieties included were: DP-340 Pima, Phy-888RF Pima and Mon-109-C7 Experimental Pima.

Data for the Tulare County site and the West Side REC site for 2018, and similar results will be prepared when 2019 data is available on the UC Cotton Website.

Verticillium incidence is generally higher in Upland varieties than in Pima varieties. However, there are examples

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COTTON REVIEW

Identification and Development of Cotton Germplasm and Potential Breeding Lines with Improved Fusarium Wilt Resistance, Fiber Quality and Yield

By BOB HUTMACHER | UCCE Cotton Specialist and AES Agronomist Objectives of Research

for a number of generalizations: (1) most Pima cultivars show more severe symp1. Develop and expand the cotton progeny toms and suffer higher levels of stunting and breeding populations segregating and plant mortality from FOV4 than seen for Fusarium wilt race 4 (FOV4) resiswith most Uplands or non-Acala, and tance. (efforts are roughly split between Acala cotton; (2) some moderate to highUpland/Acala types of cotton and Pima ly-resistant commercial Pima cultivars germplasm). have been identified from several seed companies and private breeders; and (3) 2. Evaluate resulting progeny, breeding several experimental Pima germplasm lines, and germplasm for FOV resistance. or breeding lines with moderate to high resistance to FOV4 have been identified, 3. Utilizing selected materials, maintain developed, and publicly released (SJ-FR01 seed supplies through progeny propaga- to SJ-FR09) by the Univ. of California tion and breeding population increases and USDA-ARS. These germplasm lines at field location(s) in California and in have helped to increase the genetic base greenhouses as necessary for limited for FOV4 resistance in Pima Cotton. seed entries.

Since 2013, more than 4,000 entries and 4. As selected germplasm are advanced, developed progeny have been evaluated also conduct trials to evaluate growth in infested FOV4 fields and a portion characteristics and yield performance (1/4) in the greenhouse using artificial (growth habit, growing season length FOV4 inoculation. Our primary obrequirements and yield performance) at jectives have been to identify/develop West Side Research Center location additional Pima cultivars, and evaluate and develop the Upland gene pool for 5. Identify breeding lines and germplasm improved FOV4 tolerant germplasm. with improved combinations of FOV Efforts have included introducing a race 4 resistance, fiber quality, and yield known FOV4 dominant gene that has for release and availability to breeders shown resistance in Pima (e.g., Pima-S6) and seed companies as appropriate. into Upland cultivars, as well as, introducing tolerant gene(s) from identified Planting tolerant/resistant varieties is an Upland tolerant lines from our research effective strategy to manage FOV4 damage obtained from the USDA-ARS Cotton and losses in cotton. Progress has been Germplasm Collection and Universitymade by University of California and breeding programs into elite or improved USDA, ARS, and the private companies yield and fiber quality cotton lines. from information and results generated by this and other FOV4 research projects For the breeding efforts, entries and funded through California cotton growers/ progeny have been planted in naturalproducers. Research efforts have identified ly-infested FOV4 fields and seeded in and developed tolerant/resistant Pimas, as 5-by-1 meter plots and replicated three have made some progress in identifying im- times. During the growing season, proved FOV4 resistance in Upland cultivars. plant responses to inoculum pressure were assessed through evaluations of Field evaluations have provided information root and stem vascular staining levels, 60

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March / April 2020

plant mortality, foliar wilt symptoms and measures of relative plant vigor. Selected cotton entries used as parents to make crosses and progeny developed from these parental entries (F1 populations) were also inoculated with FOV4 and grown under greenhouse conditions for rating.

In addition, resistant/tolerant varieties or germplasm may not express similar modes of inheritance of resistance when they are derived from different genetic backgrounds or are challenged by different Fusarium types or races of different geographic origin.

The postulated pathogenicity or mode of infection mechanisms and the inheritance of Fusarium resistance significantly differ among races for cotton entries or lines.

Previous reports indicated FOV4 resistance is associated with a complex allelic-recombination and duplicated marker-genes between cotton chromosomes 14 and 17.

Genomic islands or regions on chromosomes 3, 6, 8, 11, and 25 have also been reported to be associated with allelic dosage for FOV4 tolerance. Additional analyses revealed that cotton lines and progeny share resistance genes for plant defense against Fusarium races (1, 4, and 7).

In Upland cotton, germplasm with improved levels of FOV4 tolerance have been identified, and new breeding lines are being developed by USDA-ARS and the University of California with the support of the CA Cotton Alliance and the CA Cotton Growers and Ginners Association. From 2019, more than 150 Upland breeding lines are being evaluated to validate their higher FOV4 levels of tolerance and to identify the best FOV4 tolerant lines for releasing to the public and private researchers and breeders. In Figure 1, the evaluation of FOV4 results and the progress of selection

Continued on Page 62

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COTTON REVIEW

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Figure 1. Average Root Vascular Wilt Staining values (VRS) of select germplasm. Examples shown are evaluations from 2016 to 2018 selections of selected entries or Parents (1-9) to be used in crosses to develop new progeny/breeding lines with improved Fusarium wilt race 4 (FOV4) tolerance (rating of vascular root staining (VRS) - scale 0 = no infection to 4 highly infected root with VRS or almost death).

2003, FOV in California was thought to be primarily caused by race 1. Race 1 of FOV is typically found in sandy soils, of a few breeding lines from 2016 to with the most severe, economic impacts 2018 are compared with check lines found when the disease organism is with known level of FOV4 resistance present in an interaction with root-knot (Shorty-Upland, Pimas: PS7 and P3-39 nematodes (Bell, 1984; Veech, 1984). susceptible and PS6 resistance).

Susceptibility to FOV, particularly race In Pima cotton, Egyptian and Peruvian 1 FOV is increased by the effect of the nematode’s wounds (Garber et al., 1979).

Pima or long staple cotton have been In 2003, UC Davis scientists (Kim et evaluated for relative levels of FOV4 al., 2005) identified a race 4 isolate of resistance. A half-dozen of these FOV in California soils. Race 4 of FOV lines were selected to make crosses was first identified in India on Asiatic and develop progeny that eventually cottons and was not previously identified will derive new and more diverse as a problem in the U.S. Recent field Pima germplasm resistance to FOV4. investigations (Kim et al., 2005; Ulloa et From 2019, more than 300 Pima al., 2006) have found race 4 FOV in clay variants (Gossypium barbadense loam and loam soils, in which root knot L.) from the country of Uzbekistan nematode populations and root damage are being evaluated to identify symptoms were largely absent. new sources of FOV4 resistance for developing novel germplasm.

The introduction of new genetic variabilSignificance of Research ity or genetic diversity into elite cotton Fusarium wilt [Fusarium oxysporum germplasm is difficult and the breeding f. sp. vasinfectum Atk. Syn & Hans process slow. When breeders use new (FOV)] of cotton (Gossypium spp.) in and exotic germplasm sources, which California has long been considered possess resistance disease genes, to introa serious fungal disease for cotton. duce genetic variability, large blocks of Some races of this disease were first undesirable genes are also introgressed noted in 1959 in California (Garber during the recombination between the and Paxman, 1963), and the number two parental lines (linkage drag). This of infested sites remained relatively linkage drag has limited the use of such limited until the mid-1970’s. Before germplasm. In terms of the maintenance

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of elite germplasm with elite genes/ traits, very high constraints are placed on today’s cotton breeders. However, the competitiveness of the cotton industry will be dependent upon continuing improvements of traits such disease resistance, fiber quality, and yield. We feel that improvements in host-plant resistance currently is the most economic and effective strategy for managing Fusarium Race 4 for continuing cotton production in the San Joaquin Valley region of California. Continuing the development of resistant cultivars or germplasm to FOV is important for reducing yield losses and reducing further expansion of the pathogen.

The primary areas of work in this project include the following: 1. Maintain and further develop access to one (preferably two) field test sites infested with race 4 FOV as well as greenhouse space to continue resistant germplasm testing in the San Joaquin Valley.

2. Using field and greenhouse screening sites available to us, test cotton progeny and breeding lines and continue making crosses with potential for improved FOV4 resistance. Collect seed from self and open pollinated

COTTON REVIEW cultivars of interest/improved FOV4 resistance or other traits, delint and prepare seed for plantings for further • FOV4 testing of segregating populations and for seed increases necessary to allow further agronomic testing for yield and quality, plus to provide seed for interested breeders for further development.

3. A link to ongoing plant genetics program in FOV resistance of Dr. Ulloa and his continuing molecular work is a vital part of this project plan.

Identification of developed breeding lines and germplasm with improved FOV resistance through molecular breeding increases the need for molecular markers because molecular markers facilitate selection of resistant cottons, and decrease cost, time, and the risk associated with subjective greenhouse or field phenotypic evaluations. Molecular markers can also help in the identification of the genes that provide host-plant resistance against FOV. 4. Under current arrangements with USDA-ARS cooperators, one additional major part of the project is to produce, maintain and expand seed supplies for advancing germplasm.

Work to be done includes seed preparation, progeny propagation • and breeding population increases at field and greenhouse location(s) in California.

Progress on Objectives • A series of 4 to 9 Pima lines were grown for seed increase with intention of release as improved “SJ” series lines from program efforts since 2014. These lines are meant to have superior FOV resistance with the capacity to be used as germplasm in breeding programs.

Bolls of each line were harvested and have been evaluated for fiber quality parameters.

• An additional 50+ lines were selected from other populations the past two years, as well as an additional dozen or more selections made from those with superior

FOV resistance and fiber quality.

During the 2017 and 2018 seasons, more than 160 additional Upland entries/germplasm were evaluated under a FOV race 4 infested field in California. These entries represent a wide range and diverse genetic backgrounds of germplasm material or cotton types. We continue to follow our established breeding scheme or strategy for identifying, selecting, and developing FOV race 4 resistant/ tolerant germplasm. Selected breeding lines from 2013-2014 and now re-selected in 2015 through 2018 have been examined and targeted for the introgression of FOV race 4 resistance/ tolerance genes from entries such as Pima-S6 (PS-6), Upland TM-1, and Acala FBCX2, an original pedigree-parental line of Acala NemX. So far from this set of derived progeny, around 20 breeding lines continue to show FOV race 4 resistance-improvement, and about 12 to 15 lines were re-selected in a seriously infested field this and last season. In addition, we continue to search for new sources of FOV race 4 resistance/tolerance within the Upland germplasm gene-pool by evaluation of around 150 added entries in each of the past several years.

In 2018, 2017 and 2016, as in prior years, over 100 newly tested genetic-diverse Upland and some Pima entries/germplasm were evaluated for FOV race 4 tolerance. These entries were also received from screening and selection efforts at the USDAARS, PSGD Laboratory, Lubbock, TX. From this set of entries, about two dozen additional cultivars were identified with good levels of FOV race 4 tolerance. Selected entries were self-pollinated for seed increase and further testing, and entries were evaluated in fields for FOV resistance and other desirable plant characteristics in field trial sites in 2018. Similar efforts are underway from 2019.

Evaluation of Inoculation and Screening Strategies in the Greenhouse and Field Grain carriers (wheat, rye ) were inoculated with FOV race 4 and

added to the soil in whole grain and ground form to the soil at both of our field FOV4 screening sites (Tulare County and Kern County) to supplement existing FOV4 inoculum and assess the feasibility of using with these substrates as potential methods of inoculation compared to the current standard of liquid conidial inoculation used in our greenhouse inoculation and screening trials. We utilized rye grain in 2017 and 2018 field trials due to what appeared to be superior inoculum development compared with other tested grains.

Dr. Maggie Ellis of CA State University Fresno has worked on some seed inoculation in growth chamber settings, with FOV-4 seedling evaluations done at intervals after pathogen exposure.

The approach could be helpful as an alternative quick-screening method alternative to the root dip method we have been using in the UC Kearney REC greenhouse. We have worked with her graduate student (Josue Diaz) and Dr. Ellis in field assessments and greenhouse assessments, and feel that there will be value in combining some of these early screening approaches with field assessments for more complete cultivar disease resistance evaluations. With that in mind, there is evidence to suggest that rolled towel methods may be useful as a reliable pre-screening test to identify materials that are so susceptible that field screens are unnecessary; and additional work is needed to identify a reliable severe test that could be replicated as a follow-up/ critical test to further verify the best-performing cultivars/germplasm identified in field screening tests (both could be very useful in breeding programs).

Developing a broad germplasm base of populations for future selection of material with advanced FOV resistance and good fiber quality As materials are developed for which we require seed production as well as more advanced agronomic testing for yield or fiber quality, fields have been set up at UC West Side REC for seed increase needs, and screen materials developed for larger scale self pollination needs. As

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being advanced in the testing program: •

Egyptian source Pima entries: Three entries selected for advancement based on very good FOV vascular stain ratings.

•

Crosses made in 2015 and 2016 (Pima x Upland crosses): 31 entries advanced in selection for seed increase based on very good FOV vascular stain ratings.

•

New Entries from Upland Program and Collection of Mauricio Ulloa for 2017: 17 entries advanced in selection for seed increase based on good to very good FOV stain ratings.

•

Experiment #9 (based on 2015 and 2016 Pima selections tested for FOV4 tolerance at Tulare County site): 10 entries advances in selection for seed increase and further testing based on good FOV stain ratings and agronomic characteristics – tested multiple years and sites.

•

Experiment #10 (based on 2015 Upland selections tested for FOV4 tolerance at Tulare County site): 5 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.

•

Experiment # 11 (F-2’s based on 2014 Crosses at Tulare Co. site (some Upland and Upland-by-Pima included) followed by reselections in Greenhouse evaluations: 22 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.

•

Experiment #12 (both Upland and Upland by Pima crosses at Tulare County site): 17 entries advanced for seed increase and further testing based on good FOV stain ratings and agronomic characteristic data.

"Bee-proof” netting used in the tenting and bags helps prevent insects from cross pollinating the cotton that researchers want to be self-pollinated for seed increase/production. (Photo courtesy of B. Hutmacher)

Continued from Page 63 needed, we will develop new crosses for promising materials, and continue to utilize lines developed based on crosses made in the past few years in order to provide not only resistant Pima materials but also develop some Upland / Acala FOV4 resistant/tolerant materials.

In all evaluations of responses of cultivars to FOV race 4 pressure, rating procedures are standardized across sites and experiments. Measured responses to FOV will include percent plant survival and standardized ratings of disease severity and vascular discoloration.

Vascular discoloration of the lower stem and upper tap root are observed by slicing the stem longitudinally, and rated according to the scale of 0) no symptoms, 1) light staining as spotty areas, 2) light colored staining, continuous and covering ¼–½ of the stem diameter, 3) moderate brown or black staining in a band encircling most of stem cross section, 4) brown or black staining across most vascular tissue in cross section, and 5) dark brown or black staining accompanied by plant death.

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acre of tented or bagged plants (to prevent bee pollination), with a much smaller (about 1/4 acre) similar tented planting for seed increases done also at West Side REC in 2019. The photos shown below were taken in August, 2018, and show an approximately two acre area with about 1 acre of planted rows (split into two fields) where we grew out some selections and crosses that we determined to have improved FOV4 resistance (as determined in multiple field disease resistance screenings). For 2018, there were about 600 bagged or “tented” plots in these two fields at the UC West Side REC, representing close to 400 different entries for which we grew out plants to be self-pollinated to increase seed amounts for continuing work, and in many cases, to provide seed for additional testing and release to breeders. The purpose of the "bee-proof” netting used in the tenting and bags is to prevent insects from cross pollinating the cotton that we want to be self-pollinated for seed increase/production.

As examples of the work being done on several fronts (Pima, Upland, crosses), in field trials done in heavily FOV4 infested fields, we evaluated lines, crosses and some reselections based on current and prior year screening efforts, with the following examples of some cultivars

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COTTON REVIEW

A ssessm ent o f F u s a r iu m in S J V C o tto n

F ie ld E v a lu a t io n S u p p o r t , Id e n t if i c a t io n a n d C o m m e r c ia l V a r ie t y S c r e e n in g E v a lu a t io n s

d. Entries from cotton breeders at a variety of locations, including those from the RBTN tests done nationwide, plus efforts will be made to solicit entries from private company breeders working with Pima or hybrids (we have some funding through Cotton Incorporated CORE that helps cover some of the costs for the other agronomic evaluations (yield, fiber quality) for the Regional Breeder entries from U.S. public breeders – but the costs of the FOV race 4 screening work are not provided by that funding).

Field Sample Evaluations Work

Some support has been utilized to facilitate travel to field sites and allow us to be in the fields to physically do the visual surveys and collect samples,

By BOB HUTMACHER | UCCE Cotton Specialist and AES Agronomist and to provide county and UC support for repeated trips to screening sites/ fields as well as to grower fields where disease impacts and survival under his project covers two the Principal Investigator for this moderate to severe FOV race 4 pressure, study gets requests for field evaluations primary purposes: 1) Conduct with focus on evaluations of newer germplasm screening trials of to assess presence of Fusarium race experimental and commerciallycommercially-available cultivars plus 4. Efforts beginning in 2002 and available cultivars. The two objectives evaluations of experimental cultivars continuing through current efforts mentioned above are at least somewhat seed companies submit to us for FOV have been in repeated field visits related, as we conduct field trials to resistance evaluations. In these evaluato grower field sites, collection and evaluate germplasm resistance to FOV, tions, all entries in all University of CA evaluation of stem and hypocotyl and we need to identify and access variety trials (Acala/Upland, Upland samples for evidence of vascular fields and cooperative growers if field Advanced Strains, Pima, Pima experstaining, and AgDia test evaluations screening trials are to be conducted. imental cultivars, National Standards when growers/consultants make the trials) are included, plus experimental request for Fusarium race identification. entries submitted by seed company Field evaluations in the resistance breeders. 2) Support field efforts to screening program each of the The varieties tested include all commercollect samples and evaluate fields to years of the trials have included: cial and public breeder entries in our determine and characterize the race variety trial program plus company/ of Fusarium (race 4 or others) in SJV a. Commercially-available germbreeder submitted experimental culticotton fields when growers, seed complasm of Pima varieties included vars. This screening effort is separate pany reps or consultants contact us for in our variety trials. from, and in addition to, the work assistance with plant evaluations and covered in a separate breeding profusarium race identification. b. Commercially available gergram effort supported through cotton mplasm of CA Upland and industry funding for a project entitled Prior and Current Work any remaining Acala varieties “FOV race 4 Germplasm Development” Resistance Screening Work – included in our variety trials. that in recent years has been jointly Commercially Released Cultivars funded by CA Cotton Alliance and and Company Experimentals. This c. Experimental germplasm CA Cotton Growers Association work has been directed toward from company commercial Research Funds. That project is a identification of relative levels of development and improvement cooperative project with Dr. Mauricio resistance/susceptibility to race 4 FOV, programs. including both indices of severity of Continued on Page 68

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Continued from Page 66 Ulloa of USDA-ARS in Lubbock, Texas. The cooperative work with Dr. Ulloa is somewhat different from the screening efforts supported by this proposal in that this project is more focused on maintaining: (a) support for FOV race 4 resistance screening for commercial entry commercial and experimental entries, plus entries from public breeders; and (b) some funds to continue support for field race 4 evaluations requested from growers, consultants and seed companies for which we need to purchase AgDia test kits and cover related other expenses.

Field Sample Evaluations

Since 2013, we have been using the AgDia company race 4 FOV quick test on root and lower stem samples in these field evaluations. For some FOV race identification pathology work for samples when we request additional evaluations over and above what can be done using the AgDia quick tests, we are working with Dr. Maggie Ellis at CSU Fresno to determine local capabilities for identification of other races of FOV if that becomes necessary and useful. The funds from this proposal/project help provide funds to purchase the FOV4 AgDia kits, which cost approximately $35 for each sample run (just for the supplies, not other lab costs or staff time).

Summary Report of 2018-19 Activities

For 2019, sites for field evaluations

and sampling were located in 4 cotton producing San Joaquin Valley counties (Fresno, Merced, Kings, Tulare Counties), with the most new confirmed sites located in Merced County. There were 27 fields visited and evaluated visually for FOV4 evaluation, and sampling for Fusarium race 4 done in 19 fields, and confirmations of FOV4 in 16 of the fields visited. Unless we see significant increases in different variants of FOV (race 4, others) in cotton, we expect a downward trend in requests for field visits to continue in the next years.

The number of requests for field evaluations compares with sampling in earlier years: (1) 2018—48 fields evaluated, with 37 confirmed as race 4 FOV; (2) 2017—66 fields evaluated; (3) 2016—89 fields evaluated; (4) 2015—89 fields were visited for in-field evaluations, with AgDia tests run on 47, and 21 positive determinations in tests for race 4. These numbers most likely do not represent the full number of additional fields that could have been identified as race 4 FOV, as some fields were visited where samples were not collected due to lack of grower desire or approval to collect samples needed to provide an assessment.

Results 2019 – Field Resistance Screening Evaluations

Field varietal screens were planted and completed at both field screening sites at the time of this report, both in fields confirmed to be infested with FOV race 4. The field tests were

done only in a part of the field where a prior cotton crop showed consistent, significant plant losses due to FOV race 4 (greater than 50 percent mortality in susceptible Pima entries). An initial plant population count was done within 2 weeks after planting in plots at both sites, followed by plant survival counts done a minimum of two times during an evaluation period of 7 to 8 weeks after emergence of cultivars being tested for resistance at the Tulare County site and a Dos Palos area (Merced County) site.

In addition to plant survival percentages, we evaluated plants for root vascular staining, foliar damage index rating, and plant size / height and node counts as a measure of vigor. At both sites, major hand weeding efforts were required to keep weeds under control in these sites due to restricted use of herbicides necessitated by working with conventional cotton varieties.

The commercial varieties and company and RBTN program breeder experimental materials evaluated in our Commercial Entry and Company/ RBTN Experimentals screening trials for 2019 are shown in the following figures in this report. Average root vascular stain values for the TULARE COUNTY SITE are the only 2019 date summaries available and ready to share at the time of preparation of this report.

Data analyses on the rest of the data sets are underway and will be made available to seed companies, breeders and industry partners in the fall.

Figure 1

Figure 2

Root Vascalar Stain rating averages Tulare County-FOV-4 screening site - 2019

Root Vascalar Stain rating averages Tulare County-FOV-4 screening site - 2019

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0

DGX DGX DGX BX 19001 19014 H929 2002 B3XF B3XF B3XF GL

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COTTON REVIEW Figure 3

Figure 4

Root Vascalar Stain rating averages Tulare County-FOV-4 screening site - 2019

Root Vascalar Stain rating averages Tulare County-FOV-4 screening site - 2019

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The following tables (Figures 1-4) show the average Root vascular stain index ratings for all of the Pima and Upland cotton entries in the commercial screening trial for FOV4 resistance conducted at the Tulare County site in 2019. As with prior years, check varieties are included in the screen: more susceptible varieties such as DP-340 and DP-744 Pima, and some more highly resistant commercial Pima varieties such as Phy 888RF, Phy 841 RF, DP 348 RF, DP 359 RF and others).

Also included in this screen are all varieties entered in the following variety trials for 2019: CA Uplands/Acala trial, CA Uplands Advanced Strains trial, National Standards Uplands trial, Pima variety trial, and RBTN (Regional Breeder Testing Network) entries.

Other than the previously mentioned Pima cultivars with higher levels of FOV4 resistance, there are a limited number of entries in this commercial screen that appear worth a follow-up evaluation as potential higher FOV4 resistance varieties, including: Group figure 1: FM 2398, ST 4550, PX 8504 Pima; Group figure 2: DGX 19014, BX 2037, FM 162; Group figure 3: Phy-60, Phy 64 through Phy 67; Group figure 4: Ark 1112-59, TAM LBB 15905, CSX 8308.

When data is compiled for the second trial location (which includes most commercial entries other than the RBTN program entries), there will also be an opportunity

38 55 21 60 -50 -59 -03 -39 905 507 024 099 103 -37 eck eck eck eck eck RF XF XF XF eck eck eck eck eck 2 h 2 2 2 5 4 1 5- 2- 4- 7h h h h h h h h h 7 15 16 016 016 016 0-8 3 c 3 c 3 c 8 c 2 c 9 W 9 B 2 B 5 B 7 c F c a c a c a c 11 110 111 111 112 111 13 12 k B B 2 2 2 8 39 49 95 22 R im im im 49 54 52 54 -C 01 A A Ar Ark Ark Ark Ark Ark TAM TAM LB LB A G G S 2 CSX DP DP FM UA G hy P 1 P 1 G 4 109 4 W 0 P 4 P F P M M P 4 4 D D N on M 7 1R 76 -3 TA TA M Phy DP DP 88 y Ph

to determine consistency of resistance screen results for two sites.

Data Summaries for 2018

As examples of the full data sets that are provided each year as a result of this project, this report show is the summary averages for the Tipton area site (Tulare County) in 2018. Similar data will be developed and posted when 2019 results are completed. These 2018 tables and those from prior year summaries are shown on the UC cotton web site at http://cottoninfo.ucdavis. edu . This information includes foliar Fusarium ratings, root vascular stain ratings, plant height and node number as indicators of vigor. In coming weeks as data is processed, we will add the plant survival percentage for each entry, but it is not included in this summary.

Data shown are determined from five plants evaluated in each of three field replications per entry. The tests include all entries in University of CA cotton variety trials, additional commercial germplasm (company selected varieties plus experimentals they submitted) plus entries from the Regional Public Breeders testing program (including check varieties, organized nationally by Dr. Ted Wallace of Mississippi).

summarized and available at this time).

“Check” varieties that are moderately to highly susceptible include: Phy-725RF, DP-340 (moderate), while a quite tolerant check variety would be Phy802RF. The scale for Foliar FOV index and root vascular stain index ratings is 0 to 5, with 0 being no symptoms, 5 being severe (usually reserved for dead, near-dead plants). Keep in mind that ratings are done at 7+ weeks post emergence, so they are done on plants surviving at the time of the rating, which in the most severely impacted entries can be some of the few survivor plants, with most others dead. It is recommended that the combination of lower vascular stain ratings as a relative indicator of disease severity in tested plants must be considered in combination with survival of the plants in order to assess relative levels of resistance.

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Information to focus on in reviewing the tables as best indicators of overall responses to FOV4 infection are: (a) root vascular stain index; and (b) survival percent at 7 weeks, since they indicate relative severity of infection and impacts on plant mortality (this data, as mentioned above, is not

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Characterization and Interaction of Fusarium Races and Rhizoctonia on Disease Development in Cotton

By MARGARET L. ELLIS | Plant Science Department, California State University, Fresno and ROBERT HUTMACHER | UCCE Cotton Specialist and Center Director Westside REC

Objectives of Proposed Research

were able to expand on our current proposed work and add the following objectives to the ARI proposal.

1. To survey and molecularly identify Fusarium oxysporum f. sp. vasinfectum (FOV) races and other seedling and 4. To use representative identified FOV wilt pathogens in commercial and races for phenotypic evaluation of grower cotton fields in California. selected Upland cotton germplasm 2. To further evaluate the seedling and wilt capabilities of FOV races with different inoculation methods using susceptible and resistant Pima and Upland germplasm.

5. To determine the effects of pH, temperature, and moisture on disease development in cotton when inoculated with FOV4.

3. To further evaluate the interactions of different FOV races and Rhizoctonia Objective 1: To survey solani and their impact on disease and molecularly identify development in cotton.

Fusarium oxysporum f. sp. vasinfectum Additional match funding has been (FOV) races and other approved from the California State seedling and wilt University Agricultural Research pathogens in commerInstitute (ARI) for both years of the cial and grower cotton project thanks to support letters fields in California. provided by CCGGA and Cotton Inc. With the additional funding, we Prior to this proposal, 70

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Fusarium isolates were collected in 2017 and 2018. Isolate information is provided in Table 1. All isolates were identified using two PCR assays and DNA sequencing of the translation elongation factor (EF-1α) gene. The first PCR assay produced a 208 bp amplicon unique to

Table 1: Isolates of Fusarium collected in locations in the San joaquin Valley of California in 2017 and 2018 Location

x

Year Collected FOV race Genotype x

Kings Co., CA (Site 1)

2017

Kings Co., CA (Site 2)

2017

Tulare Co., CA (Site 1)

2017

Kings Co., CA (Site 3)

2018

Merced Co., CA (Site 1)

2018

Merced Co., CA (Site 2)

2018

Merced Co., CA (Site 3)

2018

Fov race 3 Fov race 4 F. solani Fov race 3 Fov race 4 Fov race 4 Fov race 3 Fov race 4 Fov race 4 F. solani Fov race 4 Fov race 4 Fov race 4 Fov race 4 Fov race 4 Fov race 4

N T N N N T N N T N N T N T N T

Number of Isolates 3 13 1 4 1 19 1 2 24 1 37 16 1 7 4 6

Genotype based on absence (N type) or presence (T type) of the Tfol insertion

in the PHO gene unique to FOV race 4 (Ortiz et al., 2017)

COTTON REVIEW Table 2: Isolates of Fusarium spp. and Rhizoctonia solani collected in 2019 Location Kings Co., CA (Site 1) Merced Co., CA (Site 1) Kern Co., CA (Site 3) Merced Co., CA (Site 1) Merced Co., CA (Site 2) Merced Co., CA (Site 3) Merced Co., CA (Site 4) Merced Co., CA (Site 5) Merced Co., CA (Site 6) Kern Co., CA (Site 1) Kern Co., CA (Site 2) Kern Co., CA (Site 3) Kern Co., CA (Site 4) Kern Co., CA (Site 5) El Paso TX

Species Rhizoctonia solani Rhizoctonia solani Rhizoctonia solani Fusarium Fusarium Fusarium Fusarium Fusarium Fusarium Fusarium Fusarium Fusarium Fusarium Fusarium Fusarium

Number of isolates 14 2 2 16 7 6 5 3 3 24 1 4 10 7 24

similar to 2017 and 2018 isolates.

A preliminary baiting method using collected soil from a cotton field in Dos Palos, Calif. was completed. This assay was modified for the isolation of Pythium spp. from field soil using soybean as bait. From this assay isolates of what appear to be FOV, Pythium, and R. solani were all baited using the susceptible Pima cultivar DP-340. Soil has been collected from a number of FOV races 3, 4, and 7, while the second locations across the San Joaquin Valley locations across CA and will be used multiplex PCR assay genotyped FOV and six locations in the El Paso, Texas in the baiting method to isolate other isolates into two genotypes, N (396 region were sampled beginning in potential pathogens not isolated from bp), and T (583 bp). These genotypes mid-May 2019. To date, single spore collected plant material. Soil samples were identified based on the absence isolations for 110 Fusarium isolates have from some of the first locations where (N type) or presence (T type) of the been completed (Table 2). All isolates FOV race 4 was identified in CA but insertion of the transposable element were collected from symptomatic cotton are no longer in production for cotton Tfo1 in the phosphate permease (PHO) seedlings. Additionally, 18 isolates of were also collected. This assay might gene unique to FOV race 4. Although Rhizoctonia solani were also isolated allow us to determine if the pathogen not shown these isolates have been from symptomatic cotton seedlings FOV race 4 is still present in these genotyped with newly developed (Table 2). Other fungal species were locations, despite being out of producprimers. We are repeating the genotyp- isolated and are currently being identified tion for at least a decade in some cases. ing currently for verification of results. morphologically. It appears that there may be some additional Fusarium species that For the current proposed research, 11 are not FOV. Isolates will be genotyped Continued on Page 72

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Continued from Page 71

Objective 2: To further evaluate the seedling and wilt capabilities of FOV races with different inoculation methods using susceptible and resistant Pima and Upland germplasm.

Three assays will be compared to further evaluate seedling and wilt capabilities of FOV races/genotypes. A rolled towel assay was developed in our lab, and will be compared to the rootdip inoculation method and an infested-oat-seed method that was modified from a protocol by Beccera et al. (2012).

Protocols for these methods have all been established and tested in preliminary studies. A rolled towel assay using eight representative Fusarium isolates was completed to evaluate possible variation in aggressiveness towards cotton by different FOV4 genotypes and R. solani isolates. The assay was set up using Pima cultivar DP-340. The results from two runs of the assay are provided in Figures 1 and 2. There was a significant difference among isolate and experiment (P<0.0001), but there was not a significant difference for the interaction for isolate and experiment.

Additionally, these same isolates or a similar set will be used in the comparison of different greenhouse assays.

We plan to use varieties of both Pima and Upland cotton with varying levels of plant host resistance in the assays.

Finally, we have started to screen previous isolates collected from 2017 and 2018 using the root dip inoculation method. This will also be done for a majority of isolates collected in 2019.

Once pathogenicity for the majority of the isolates is tested using the root dip assay and genotyping is completed 72

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Figure 1: Rolled towel assay for 8 Fusarium isolates Disease Severity Index

100 90 80 70 60 50 40 30 20 10 0

A

A

A

A

A

AB BC

BC

C

T20

Tm2

FOV4(T)

Tx1

Tx2

FOV4(N)

1512JA

T11

FOV3

B22

CSU3 Control

F. solani

Fusarium isolates To calculate the disease severity index (DSI), lesion length and total plant length were measured with a ruler for each seedling and then the lesion length was divided by the total plant length and multiplied by 100. Seed that did not germinate and were colonized by FOV were given a 100% index rating (Ellis et al., 2011).

Figure 2: Rolled towel assay for 8 Fusarium isolates

5 4.5

Ordinal Rating

Two undergraduate students have been trained and have been conducting the work mentioned above under the guidance of Dr. Ellis and her previous graduate student. Another student has also started to isolate DNA from the single spore isolations for identification using new PCR primers. Additionally, DNA sequencing of isolates will be done using the translation elongation factor and internal transcribed spacer region.

A

4

A

A

A

A

3.5

AB

B

3

B

2.5

C

2 1.5 1 0.5 0

T20 FOV4(T)

Tm2

Tx1

Tx2

FOV4(N)

1512JA

T11

FOV3

B22

CSU3 Control

F. solani

Fusarium isolates For the ordinal scale a 1-to-5 scale was used, where 5 = no germination, complete colonization of the seed; 4 = germination, complete colonization of the seed, and 75% or more of the seedling root with lesions; 3 = germination, some colonization of seed, and 20 to 74% of the root with lesions; 2 = germination, little colonization of the root, and 1 to 19% of the root with lesions; 1 = germination, healthy seedling with no visible signs of colonization.

a representative set of isolates can be used in our screening efforts.

Objective 3: To further evaluate the interactions of different FOV races and Rhizoctonia solani and their impact on disease development in cotton.

The graduate student for this objective has been currently evaluating environmental parameters of our CA FOV and R. solani isolates such

March / April 2020

as pH and temperature. Infested-oat inoculum has been prepared to begin the interaction study with FOV race 4 and R. solani. Furthermore, we also plan to co-inoculate with different FOV race 4 genotypes and F. solani.

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COTTON REVIEW

Maintaining Fusarium Wilt Race 4 (FOV4) Resistance/ Tolerance of Cotton

By DR. MAURICIO ULLOA | USDA-ARS Plant Stress and Germplasm Development Research, Lubbock, TX

T

he funded amount for this project from CCGGA is devoted to support travel to California for Dr. Ulloa and to assist in evaluation, progeny development, breeding and coordination of seed increases of selected developed progeny and breeding lines of Pima and Upland cotton for future testing and germplasm public releases with improved resistance/tolerance to Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 (FOV4), a soil borne fungal pathogen. These FOV4 breeding research efforts and activities are coordinated and supported by the California team. In addition, funding partially pays for professional research/ services support needed to increase our understanding of plant FOV4 defense mechanisms.

Over the past 14 years, the fungus that causes FOV4 has impacted fields 74

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in California’s San Joaquin Valley.

This fungus is particularly difficult to control in cotton as the hyphae or fungus-overwintering structures reside in the woody vascular tissues, preventing the penetration of fungicides. These structures can survive in soils indefinitely. In the United States, FOV4 was first confirmed in California cotton fields in 2003, however, in 2017 it was also identified in far-west Texas and in 2019 in New Mexico.

Cultivars with relatively high levels of resistance to FOV4 were originally identified in commercial Pima cotton (Gossypium barbadense L.), ‘Phytogen 800’, and originated-pool germplasm, ‘Pima S-6’. Field evaluation of cotton cultivars in FOV4-infested fields have provided information to develop a number of generalizations: (1) most Pima cultivars show more severe

March / April 2020

symptoms and suffer higher levels of stunting and plant mortality from FOV4 than with most Upland and Acala cottons; (2) some moderate to highly-resistant commercial Pima cultivars have been developed from several seed companies and private breeders; and (3) several USDA-ARS experimental Pima germplasm or breeding lines with moderate to high resistance to FOV4 have been identified, developed, and publicly released (SJ-FR01 to SJ-FR09). These germplasm lines have helped to increase the genetic base for FOV4 resistance in Pima Cotton. Typical FOV4 symptoms are shown in Figure 1. Disease symptoms of this pathogen have been observed to differ between Pima and Upland cotton.

From 2006-18, we have been evaluating Pima germplasm from the USDA ARS and international breeding collections,

COTTON REVIEW

A

B

Figure 1. Foliar and root symptoms of Fusarium wilt (Fusarium oxysporum f. sp. vasinfectum) race 4 (FOV4). A) Foliar symptoms for Pima (Gossypium barbadense L.) cotton and B) Foliar with no visual symptoms and root with vascular root staining symptoms for Upland (G. hirsutum L.) cotton. (All photos courtesy of M. Ulloa.)

and Upland germplasm from the USDA ARS Cotton Germplasm Collection College Station, Texas or breeding lines from around 13 public (universities and USDA) cotton breeding programs across the Belt through the regional breeder testing network or RBTN sponsored by Cotton Inc. and have provided information about the level

of FOV4 tolerance of these breeding lines and germplasm. In addition, since 2013, more than 4,000 entries and developed progeny have been evaluated in infested FOV4 fields and a portion (1/4) in the greenhouse using artificial FOV4 inoculation.

responses to fungus-inoculum pressure were assessed through evaluations of root and stem vascular staining levels, plant mortality, foliar wilt symptoms and measures of relative plant vigor.

In Upland cotton, germplasm with good levels of tolerance have been

During the growing season, plant

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Continued on Page 76 www.progressivecrop.com

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COTTON REVIEW Highly Tolerant/Resistant Upland Line

Figure 2. Infested Fusarium wilt race 4 (FOV4) field site around Dos Palos, CA. planted with selected breeding lines to validate their tolerance level before public releases. Photos showing Dr. Ulloa next to one of the FOV4 highly resistant Upland lines surrounded by empty research plots from a susceptible FOV4 variety-check.

Continued from Page 75 identified, and new breeding lines are being developed by USDA-ARS and the University of California.

After FOV4 artificial-greenhouse and natural-infested FOV4 evaluations of these accessions, less than 0.1% were selected to develop highly resistant FOV4 progeny. Two sources (NM12Y1004 - NM12Y1005 and SA-3208) of Asiatic breeding origin

were identified with tolerance to FOV4 and used to introgress and increase resistance. Pedigree information from additional parental lines or breeding stocks used to develop progeny revealed their sources to be exotic and wild Upland germplasm triple/multiple crosses, deriving these SA-obsolete cultivars named ‘Auburn M’, ‘DES 920’, ‘MARSPD202085’, ‘S.N.0503-1’, PD 2165, and ‘Stoneville 14’, among others.

In 2019, around 130 selected breeding lines were ginned, acid delinted, and planted at two infested field sites in California [Los Palos (Figure 2) and Tipton Co. (Figure 3)] to validate their resistance/tolerance against FOV4.

These selected lines were also planted at the Tipton FOV4 infested site (Figure 3). In addition, evaluations were performed on more than 500

Figure 3. Infested Fusarium wilt race 4 (FOV4) field site around Tipton, CA. planted with selected breeding lines to validate their FOV4 resistance/ tolerance level before public releases, with an additional 500 Pima and Upland entries. Photos showing evaluation site and roots with no vascular root staining, a typical diagnostic infection sign of FOV4.

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COTTON REVIEW FOV4 INFESTED FIELD SITE VISITED 5/29/2019

FOV4 INFESTED FIELD SITE VISITED 7/08/2019

Figure 4. IInfested Fusarium wilt race 4 (FOV4) field site around El Paso, TX area planted with selected breeding lines to validate their tolerance level before public releases.

additional Pima and Upland cotton lines from progeny and breeding lines with different levels of FOV4 tolerance/ resistance. Most of these lines were derived from multi-cross-combinations between and within Pima and Upland cultivars or germplasm lines with known FOV4 resistance to develop progeny and new populations to assess FOV4 resistance.

In addition, a subset of these entries

was also planted in the El Paso, TX area in FOV4 infested field (Figure 4). Following are images from the FOV4 infested field site near El Paso, TX. We planted lines with known levels of FOV4 tolerance, and resistant and susceptible FOV4 check-cultivars using a RCBD with three replications (Figures 1-3 see pgs. 75-76).

Continuing with the breeding efforts of this cooperative project next year,

we anticipate additional visits to California by Dr. Ulloa to coordinate and support the selection, harvest, ginning of breeding lines with good to excellent FOV4 tolerance/resistance for the 2020 year’s season.

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77

COTTON REVIEW

S c r e e n in g o f 1 ,0 0 0 A c a la C o t to n L in e s

For Fusarium Race 4 Resistance Using O&A's Site-Specific Mass Screening Protocol in a High Spore Count "Hot" Field(s) B y D R J A M E S M . O L V E Y , P h .d | P r e s i d e n t , O & A E n t e r p r i s e s , I n c .

Photos taken right after planting and again at harvest time.

(Photos courtesy of J. Olvey.)

Work Completed • Selected 1,100 Acala Cotton Lines to be screened.

• Prepared seed (ginned, delinted, treated, and packaged) for planting.

• Planted seed in multiple testing locations.

• Took multiple stand evaluations to determine the degree of FOV4 damage.

Findings to Date • The year started off well with good stands on all Acala Lines.

Photos taken right after planting and again at harvest time.

• Upon the completion of stand evaluations, we eliminated over 800 Acala Lines as being susceptible to FOV4.

Work to Be Completed • Determine the degree of vascular staining in each Acala Line that has not already been eliminated from stand evaluations.

• Rate each Acala Line based on productivity.

• Assemble data and analysis throughout the year.

• Complete Final Report.

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Test plot with check rows on either side to make sure the FOV4 is hot in that particular spot.

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