Progressive Crop Consultant - May/June 2019

May/June 2019 Evaluation of Nitrogen Stabilizers to Improve Corn Yield and Plant Nitrogen Status Weed Identification: A Crucial Component of Weed Management Evaluation of Grafted Tomato Plants for California Fresh Market Producton Systems Walnut Husk Fly Management MAY/JUNE 2019

V I N E YA R D REVIEW

See Page 15

pages 36-50

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Volume 4 : Issue 3 May/June 2019

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IN THIS ISSUE 4

Evaluation of Nitrogen Stabilizers to Improve Corn Yield and Plant Nitrogen Status

CONTRIBUTING WRITERS & INDUSTRY SUPPORT

Weed Identification: A 12 Crucial Component of Weed Management Evaluation of Grafted Plants for 18 Tomato California Fresh Market Producton Systems

4

Whitney Brim-Deforest UCCE Rice Advisor Akif Eskalen Department of Plant Pathology - UC Davis

Husk Fly 26 Walnut Management

Michelle LeinfelderMiles Delta Farm Advisor, UC Cooperative Extension, San Joaquin County

ACP Control with Systemic

30 Insecticides

V I N E YA R D R E V I E W

Brenna Aegerter UCCE Farm Advisor for San Joaquin County

18

José Ramón ÚrbezTorres Agriculture and AgriFood Canada Stephen Vasquez Technical Viticulturist, Sun-Maid Growers George Zhuang UCCE Fresno County

UC COOPERATIVE EXTENSION ADVISORY BOARD

Grapevine Heat Stress and

36 Sunburn Management

Kevin Day

Emily J. Symmes

County Director and UCCE IPM Advisor, UCCE Pomology Farm Sacramento Valley Advisor, Tulare/Kings County

Grapevine Trunk Diseases: 42 Current Management Strategies Pierce’s Disease and Glassywinged Sharpshooter: Still 48 a Threat to California Viticulture

Emily J. Symmes Sacramento Valley Area IPM Advisor University of California Cooperative Extension and Statewide IPM Program

Steven T. Koike,

Kris Tollerup

Director, TriCal Diagnostics

V I N E YA R D REVIEW

36

UCCE Integrated Pest Management Advisor, Parlier, CA

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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Evaluation of Nitrogen Stabilizers to Improve Corn Yield and Plant Nitrogen Status

By MICHELLE LEINFELDER-MILES | Delta Farm Advisor, UC Cooperative Extension, San Joaquin County

N

Introduction

itrogen (N) is part of a balanced, natural cycle in the environment among the atmosphere, soil, plants, animals, and water. Nitrogen is the most important element needed by crops, and we often add nitrogen fertilizer to optimize crop productivity. Nitrogen use in agricultural systems must be reported for regulatory compliance under the Irrigated Lands Regulatory Program and the Dairy Order to help ensure that a greater fraction of the applied N is recovered in the harvested crop and not lost to the environment. Nitrogen management gives consideration to the four R’s: • Right source: selecting a fertilizer source that matches with crop need and minimizes losses.

• Right rate: applying the right amount based on crop need and nutrient availability through other sources.

• Right time: applying the nutrient when the crop can use it.

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• Right place: fertilizer placement that optimizes the crop’s ability to use it.

Tim Peltzer

The four R’s address management considerations (e.g. fertilizer program, irrigation), but site characteristics (e.g. soil, cropping system, weather conditions) also influence N recovery in the crop. Also important to improving crop N recovery is understanding barriers to adopting best management practices, such as costs or risks to crop quality or yield.

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While the four R’s articulate four principles for nitrogen management, the N cycle in cropping systems is complicated. Nitrogen can be introduced and lost by various paths.

We generally add N with fertilizer or

Continued on Page 6 4

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May/June 2019

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Continued from Page 4 organic matter amendments—such as crop residues, compost, or manure.

Fertilizers provide N in plant-available forms—ammonium (NH4+) and nitrate (NO3-). Organic matter amendments must be mineralized before the N is available for plant uptake.

Mineralization is a process that involves soil biology converting organic N to NH4+. The timeline of this conversion will depend on the properties of the amendment, environmental conditions—such as soil temperature and moisture, and the activity and abundance of soil microbes.

In the soil, NH4+ has different fates. It can be immobilized by microorganisms, taken up by plants, fixed to soil particles due to its positive charge, volatilized to ammonia gas (i.e. lost from the system), or converted to NO3-—a process known as nitrification. Nitrification is a two-step process. The first step is the conversion of NH4+ to nitrite (NO2-)

by Nitrosomonas bacteria. The second step is the conversion of NO2- to nitrate (NO3-) by Nitrobacter bacteria. These two steps generally occur in close succession to prevent the accumulation of NO2- in the soil. Conditions that affect nitrification include soil aeration, moisture, temperature, pH, clay and cation content, NH4+ concentration, among others. Just as NH4+ has different

THE FOUR R’s

R

ight source: selecting a fertilizer source that matches with crop need and minimizes losses

R

ight rate: applying the right amount based on crop need and nutrient availability through other sources,

Right time: applying the

nutrient when the crop can use it,

R

ight place: fertilizer placement that optimizes the crop’s ability to use it.

6

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fates in the soil, so too does NO3-. Plants preferentially take up NO3-, but if NO3is present when plants are not in need of it, then NO3- may be immobilized by microorganisms, volatilized to nitrogen gas (i.e. lost from the system), or leached out of the root zone (i.e. lost from the system).

Technologies have been developed to mitigate N losses from the system.

These technologies are collectively known as enhanced efficiency fertilizers (EFF) and include additives, physical barriers, and chemical formulations that stop, slow down, or decrease fertilizer losses. Nitrogen stabilizers, slow-release fertilizers, and polymerized fertilizers are examples of

May/June 2019

EEF. Nitrogen stabilizers are fertilizer additives intended to improve crop N use efficiency and reduce N losses to the environment by interrupting the microbial processes that change N to its plant-available forms. We developed a trial to evaluate two N stabilizer products with the objective of determining whether the treatments improved corn silage yield or plant N status compared to fertilizer alone.

We did not attempt to measure N losses from the system (e.g. leaching, denitrification), as these are very challenging to quantify.

The products in our trial were Vindicate (Corteva Agriscience) and Agrotain Plus (Koch Agronomic Services). Vindicate delays the nitrification process by inhibiting the Nitrosomonas bacteria that converts NH4+ to NO2-. Vindicate has bactericidal activity, and the active ingredient is nitrapyrin. Agrotain Plus has two modes of action—reducing ammonia volatilization and delaying nitrification. Ammonia volatilization is the conversion of NH4+ in the soil to ammonia gas (NH3) in the atmosphere, and it is reduced by inhibiting the urease enzyme. Ammonia volatilization is most problematic when the N source is urea-based and not incorporated or watered into the soil. The active ingredients of Agrotain Plus are Dicyandiamide (DCD), which delays nitrification, and N-(n-butyl)thiophosphoric triamide (NBPT), which reduces volatilization. DCD has bacteriostatic activity, which means it slows the metabolism of Nitrosomonas.

We hypothesized that N stabilizers would improve yield and N uptake over the fertilizer-only treatment, providing growers with a tool for nutrient stewardship.

Methods The trial took place in San Joaquin County on a DeVries sandy loam soil.

The field had a winter wheat crop that was cut for forage in the late spring. Dry manure was applied to the field between wheat harvest and corn planting, which occurred on May 24, 2018. The variety was Golden Acres 7718. At-planting fertilizer provided approximately 12 lb N per acre (4-10-10). Sidedress fertilizer application occurred on June 21st and provided approximately 105 lbs N per acre (UAN 32). Four treatments were

Continued on Page 8

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Figure 1. Nitrogen stabilizers applied at sidedress fertilizer application.

Continued from Page 6

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Vindicate at 35 fluid ounces per acre, 2) Agrotain Plus at 3 pounds per acre, 3) combination of Vindicate and Agrotain Plus at aforementioned rates, and 4) fertilizer-only, no stabilizer product (“untreated”). Plots were 35 feet across (i.e. fourteen 30-inch rows), in order to adapt to equipment of different widths, by 900 feet long.

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We evaluated soil N status, plant N status, and silage yield. Prior to planting, 20 soil cores were randomly collected from across the trial and aggregated by foot-increments, down to two feet.

Mid-season leaf and soil samples were collected

when the corn was in the R1 stage (i.e. silking). Soil was collected from 10 in-row locations in each treatment, and aggregated by foot-increments, down to two feet. Leaves were sampled from ten plants in each treatment, sampling the leaf one-below and opposite the earleaf.

Harvest occurred on September 20th.

All fourteen rows were harvested for weight, and samples were collected at the silage pit for aboveground biomass N analysis. The samples were dried at 60⁰C for 48 hours for calculating dry matter (DM). Post-harvest, 10 in-row soil cores were collected to one-foot depth and aggregated for each treatment. Laboratory analyses were conducted by Ward Laboratories (Kearney, NE; https://www.wardlab. com/). We used Analysis of Variance to detect differences in treatments and Tukey’s range test for means separation (JMP statistical software). Treatments were considered statistically different if the P value was less than 0.05.

“

Continued on Page 10

Technologies have been developed to mitigate N losses from the system. These technologies are collectively known as enhanced efficiency fertilizers...

“

applied at sidedress, when plants were at V3-4 stage of development (Figure.

1). The N stabilizers were applied at the label rates, and the treatments were: 1)

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Table 1. Plant N, yield, dry matter (DM), and N removed results for the 2018 N stabilizer efficacy trial. There were no significant differences among treatments.

TABLE 1 Treatment

Midseason (R1) Leaf Total N (%)

Aboveground Biomass Total N (%)

Yield at 30% DM (tons/acre)

DM (%)

Total N Removed at Harvest (lbs N/acre)

2.97 2.97

1.12 1.11

40.4 37.7

0.37 0.34

272 250

2.71

1.16

38.7

0.34

269

2.87 2.88 4 0.32

1.09 1.12 2 0.18

38.3 38.8 3 0.48

0.35 0.35 3 0.20

251

Vindicate Agrotain Plus Vindicate and Agrotain Plus Untreated Average CV (%) P value

Continued from Page 8

Results and Discussion There were no statistically significant differences among treatments for plant tissue N, yield, dry matter, or total N removed at harvest (Table 1). Midseason leaf N averaged 2.88 percent across treatments, and aboveground biomass N at harvest averaged 1.12 percent. At mid-season, leaf N from 2.7 to 3.5 percent indicates that the plants had sufficient N to carry the crop to harvest, and at harvest, whole plant N from 1.0 to 1.2 percent indicates that the N fertilization program was adequate for maximizing yield [1].

Calculated to 30 percent dry matter, average yield across treatments was 38.8 tons/acre, and dry matter was 35 percent. There was a trend for the two treatments with Vindicate to have a higher N removed than the two treatments without it, but the difference was not statistically significant. The low coefficient of variation (CV), which is a measure of variability in relation to the mean, indicates low variability among replicates for all of these parameters.

yield reductions [2]. There were no differences among treatments in soil N status at the mid-season sampling, but there were differences at the postharvest sampling (Table 2. See page, 11). Mid-season soil NO3-N averaged

The pre-plant (post-dry manure application) soil nitrogen status was 17 parts per million (ppm) NO3-N and 4 ppm NH4-N for the 0-12 inch depth, and 7 ppm NO3-N and 2 ppm NH4-N for the 12-24 inch depth. When soil NO3-N is below 25 ppm in the top foot of soil, it is recommended to apply N fertilizer in order to prevent 10

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261 5 0.39

32 ppm across treatments in the top foot of soil, and 10 ppm in the second foot of soil, which is an adequate concentration to carry the crop through to harvest. Soil NH4-N averaged 4 ppm and 2 ppm across treatments for the top

Table 2. Soil N status (as NO3-N and NH4-N) at mid-season and post-harvest samplings for the 2018 N stabilizer efficacy trial.

TABLE 2 Treatment Vindicate Agrotain Plus Vindicate and Agrotain Plus Untreated Average CV (%) P value

Mid-season NO3-N (ppm) 0-12 inches

Mid-season NO3-N (ppm) 12-24 inches

Mid-season NH4-N (ppm) 0-12 inches

Mid-season NH4-N (ppm) 12-24 inches

Post-harvest NO3-N (ppm) 0-12 inches

Post-harvest NH4-N (ppm) 0-12 inches

33 32

10 10

4 4

2 2

38 b 44 ab

2 2

32

9

3

2

57 a

2

31

12

4

2

43 ab

2

32 25 0.99

10 31 0.75

4 20 0.58

2 36 0.97

46 7 0.04

2 19 0.89

in the environment and is the most foot and second foot, respectively. The important nutrient in cropping CV was high for mid-season soil data, systems. Giving consideration to N which indicates high variability among management will help ensure that a replicates. Post-harvest soil NH4-N averaged 2 ppm across treatments in greater fraction of the applied N is the top foot of soil, but soil NO3-N recovered in the harvested crop and was higher than at any other time not lost to the environment, and keeps during the season, averaging 46 ppm growers in regulatory compliance. across treatments. These results may Enhanced Efficiency Fertilizers, such indicate that as N stabilizers, the dry manure have been shown mineralized to improve N is part of a balanced, later in the crop yield in natural cycle in the season, after the regions like the environment and is the most peak demand Midwest and important nutrient in cropping of the corn. the Northeast, systems.

Post-harvest and may help soil NO3-N to mitigate N above 20 ppm is losses from the considered high and indicates that this environment. In our trial, we evaluated crop was not deficient in N [2]. The low the efficacy of N stabilizer products for CV for NO3-N indicates low variability improvements in corn silage yield or among replicates. The significant plant N status compared to fertilizer differences among treatments are not alone. Under the management and well-understood, particularly as the environmental conditions of this trial, control (fertilizer-only) treatment had we found no differences in yield or plant soil NO3-N that was not different from N status; however, plant and soil tests any of the treatments. Interestingly, indicated that N was never limiting in Vindicate had the lowest post-harvest the trial. If N was lost from the system, soil NO3-N and a trend toward higher the loss was not large enough to result N removed (though not statistically in N limitation in the control. Future higher), which may indicate that study should test these products using product use made N available at a time different N sources and N rates (e.g. that optimized N uptake. grower rate and grower rate minus 50 lbs N/acre). It may be possible to reduce Summary the fertilizer N rate without sacrificing yield.

N is part of a balanced, natural cycle

“

“

References 1. Nutrient Management for Field Corn Silage and Grain in the Inland Pacific Northwest. https://www.cals.uidaho.edu/ edcomm/pdf/PNW/PNW0615.pdf.

2. Nutrient Management Guide – Silage Corn (Western Oregon). https://catalog. extension.oregonstate.edu/em8978.

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

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By WHITNEY BRIM-DEFOREST | UCCE Rice Advisor, Yuba/Sutter Counties

W

eed identification is the foundation for weed control. For both cultural controls (tillage, weed-whacking, etc.), and herbicides, misidentification can lead to wasted time, money, and resources.

But even for experienced weed scientists and botanists, weed identification can be difficult. Traditional keys, for example, primarily rely on our ability to distinguish between plants at flowering, and often require a fair amount of knowledge of botanic terms, and possibly even a microscope. Aside from the difficulty of using the keys, identification at flowering is usually too late for weed control, particularly for the use of many herbicides.

There are many tools available to use for weed identification, ranging from books to cards, to online databases, and even computer programs and smartphone apps. The resources found below are just a few of the plethora of weed identification resources, highlighting some of the most relevant for California, and many that are free or low-cost.

Print Printed materials may be a bit difficult to carry into the field, obviously, but they can be a good resource, especially 12

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for learning more about the biology and ecology of the weed species once it is identified.

1) Weeds of California and Other Western States (DiTomaso and Healy, 2007)

in California. It is available from the UCANR website. The weeds are divided into the following 8 plant groups, for easy searching:

This 2-volume set is available through the UCANR website (as well as many other websites), and contains many, many weeds found in California, as well as those that may be likely to move into California from surrounding states.

It includes over 700 weed species, in over 60 families. It also has tables to help distinguish between commonlyconfused weeds.

2) Weed Identification Cards (DiTomaso, 2013) This set of cards is adapted from the Weeds of California and Other Western States book listed above, and contains the 48 most widely distributed weed species

May/June 2019

1. Volumes 1-2 of Weeds of California and Other Western States (DiTomaso and Healy, 2007).

• Broadleaf annuals, erect • Broadleaf annuals, low growing • Broadleaf annuals, scrambling • Broadleaf perennials, not viney • Broadleaf perennials, viney • Grass annuals • Grass perennials • Sedges The cards are small and can be held in the hand while in the field.

They are laminated, so even if they get moist, they will not be ruined.

Computer Based There are a couple of resources available (one USB-loaded program and one web-based application) if you need some help identifying weeds, especially during early growth stages. While the USB can only be used on a computer, the web-based application can also be used on a smart-phone (in the field), although it does require connectivity to the web to be able to do so.

Continued on Page 14

2. Weed Identification Cards (DiTomaso, 2013).

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13

Continued from Page 13 1) Weed ID USB (DiTomaso, 2014).

The Weed ID USB contains identification information for 722 broadleaf species and 200 weedy grasses. Using the program, it is possible to identify weeds even at the seedling stage, using key characteristics visible to the naked eye, instead of requiring a microscope or hand lens. For example, key traits such as stem crosssection, leaf shape, hairs on the leaves, etc. It also allows the user to select the family, or genus, if known. After making selections, the program will, through process of elimination, show a list (with photos and descriptions) of all the weed species fitting those characteristics. Once down to a few species, the user can visually compare the photos of their specimen to the photos in the database.

The USB is available through the California Invasive Plant Council Website (www. cal-ipc.org), or by contacting Dr. DiTomaso directly (jmditomaso@ucdavis.edu).

2) Online Weed Identification Tool (University of Wisconsin-Madison): The University of Wisconsin-Madison hosts an online weed identification tool that is very similar to the USB drive (above). It is freely available at https://weedid. wisc.edu/weedid.php. Several states are available, so be sure to select California as the search location. There are far fewer species in this database in comparison to the USB drive, but the identification method is similar. The user has to select plant characteristics, and through a process of elimination, the possible weed species with those characteristics will remain. The user can then use the photos to identify their specimen.

Continued on Page 16 14

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Continued from Page 14

Mobile Apps Although there are several smartphone applications available for both Androids and IPhones, testing of several yielded only one with enough species to make it worthwhile to use in the field.

1) Pl@ntNet (www.plantnet.org) The Pl@ntNet app (available for both Android and IPhone) was created by a consortium of universities and public research institutions. It contains plant species from all over the world, so the user has to be careful to select the correct continent (North America). It does not cover only weeds, however, which is important to note. It also contains native and naturalized species.

The app works by matching key photo characteristics with identified photos already in the database. The user takes a photo, then specifies which characteristic to focus on (leaf, fruit, bark, flower, habit, or other), then the app matches the photo with potential specimens in the database. The user then selects the species that most closely matches, and submits it to the app, where it is reviewed (seemingly by experts). Upon testing it, it was able to accurately identify several grasses, broadleaves, and shrubs.

can assist in identification. Visit the herbarium website at https://herbarium. ucdavis.edu/services.html for collection and sample delivery protocols. The herbarium can identify up to five samples per person per year at no charge, and after that, an hourly rate for identification applies.

There are many more tools available for weed identification beyond the ones listed above, including many helpful keys and online resources. In order to identify a weed, it may be necessary to utilize many tools and second opinions, particularly if it is a less well-known species, or if it is new to a cropping or natural system. While identification can be time-consuming, especially when we are anxious to get rid of a weed, ensuring proper identification before deciding on a plan for control can save a lot of time, energy, and money over the long run.

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

In-Person Assistance When in doubt, ask another person to assist in identification. Fellow pest control advisors, growers, and other colleagues are great resources. However, if it appears to be a new or unknown weed species in a particular cropping or natural system, there are other resources available to help as well.

1) University of California Cooperative Extension advisors and specialists County-based advisors and campusbased specialists can be helpful in providing weed identification. Local offices are located in almost every county in California, and advisors there can tap into larger networks of weed scientists for help with identification, if they are unable to identify the weed themselves.

2) Weed identification at the UC Davis Herbarium For really tricky cases, the UC Davis Herbarium has botanists on staff that 16

Progressive Crop Consultant

May/June 2019

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17

Evaluation of Grafted Tomato Plants for California Fresh Market Production Systems

By BRENNA AEGERTER | UCCE Farm Advisor for San Joaquin County All photos courtesy of Brenna Aegerter

G

Why Graft?

rafting involves joining a fruit-producing shoot (called the 'scion') of a desirable cultivar onto the disease-resistant rootstock of another cultivar. For example, let’s say you normally grow the cultivar 'QualiT-47' for fruit production, but that cultivar is susceptible to a soilborne disease problem in your fields, then you could graft the top part of a 'QualiT-47' seedling onto the root-portion of a more disease-resistant cultivar. In the case of tomato rootstocks, the majority of the cultivars are interspecific hybrids

between cultivated tomato (Solanum lycopersicum) and wild tomato species (most commonly Solanum habrochaites, or less often S. peruvianum or S. cheesmaniae). Solanum habrochaites is known from other published research to be tolerant of salinity, drought, cold temperatures, and resistant to many soilborne diseases and many of these benefits have been demonstrated to be conferred to the grafted plant when an interspecific hybrid rootstock is used.

Most of us are familiar with grafting as a standard practice for California fruit and nut trees and grapevines, but it has experienced only limited commercial adoption among Beat the Heat & Care annual crops in for Your Crops with: California thus far.

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Progressive Crop Consultant

May/June 2019

For example, in Spain, 50 to 70 million grafted plants are grown annually for greenhouse production systems. There has also been some adoption of grafting by high-tunnel tomato growers in the eastern United States. In Southern California, the nursery Plug Connection is marketing grafted tomatoes to home gardeners, dubbing them as a “Mighty ‘Mato”. This allows a home gardener to grow an heirloom tomato variety, which often has little or no disease resistance, without worrying about rotation or other soilborne disease control measures.

Our goal was to evaluate the potential for grafting standard tomato cultivars onto rootstock cultivars that possess resistance to soilborne diseases and nematodes. Our primary objective was to evaluate the yield performance of grafted plants in replicated trials in commercial fresh market (“mature green”) production fields in the northern San Joaquin Valley. Our team consisted of myself, Scott Stoddard with University of California Cooperative Extension (UCCE) in Merced County, and Michael Grieneisen and Minghua Zhang in the Department of Land, Air and Water Resources at the University of California, Davis. This project produced the first publicly-available research results on grafted tomatoes for California production systems.

How is it Done?

For each tray of grafted tomatoes to be produced, two trays of seed are sown; one tray of the rootstock seed and another tray of the scion seed. At approximately one month after sowing, the young seedlings are grafted. Both seedlings are cut at the hypocotyl, and the scion shoot is spliced onto the

Continued on Page 20

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Production of splice-grafted tomato plants for our field trials.

Step 1. Scion and rootstock shoots, with stems of about the same diameter, are cut at 45° angles.

Step 1

Step 2

Step 3

Step 2. A soft silicone plastic clip is placed on the rootstock stump.

The scion cutting is placed into the clip, aligning the angled cuts.

Grafting success rates are highest when the diameters of the two stems to be joined are similar.

Step 3. The plants are then transferred to a healing chamber with high humidity, low light and moderate temperatures for about a week to allow the graft union to heal. The plants are then transferred back to finish growing in the greenhouse.

Continued from Page 18 rootstock stump. The method we used is a commonly used splice-graft with small, soft, silicone clips to hold the scion and rootstock together during healing. Grafted transplants cost more than non-grafted transplants due to increased seed costs and the labor required to do the grafting. Thus far, grafted tomato plants are only available from a few sources in California, and we won’t know what the cost for grafted tomato transplants will be until they are being produced in larger volumes here.

The use of fully- or semi-automated grafting robots is emerging as a way to reduce labor costs and improve the survival rate of grafted plants. This of course requires significant capital investment. About 20 seed companies offer tomato rootstock seeds (see list at http://www.vegetablegrafting.org/ tomato-rootstock-table/). However, for a nursery facility or grower considering doing their own grafting, building a 20 Progressive Crop Consultant

healing chamber may be a hurdle. There is research underway by others to look at conducting the one-week healing period inside the greenhouse. For more information on the logistics of grafting on a commercial scale, please see the Vegetable Grafting Manual, the link for which is provided at the end of this article under “More information”.

Field Trials in the Northern San Joaquin Valley The trials were conducted in commercial production fields at six locations over three years from 2016 to 2018; three locations in San Joaquin County and another three locations in Merced County. The treatments included all combinations of the scions and rootstocks listed in Table 2 (See page 22).

The plots were laid out in a randomized complete-block design with four replicate blocks, each block measuring

May/June 2019

approximately 80 by 40 feet. The cooperating growers managed the experimental plots similarly to the rest of their field with respect to pest control, fertilization, irrigation, and other management practices. Plants were mechanically transplanted into prepared beds at a 4- to 5-inch depth per normal practice; the graft union ended up well below the soil surface.

In staked or trellised production systems in other regions, the graft union is typically kept above ground to realize the full benefit of the rootstock pathogen resistance. With graft union buried below the soil surface, soilborne pathogens may attack the scion crown tissues or adventitious roots arising from the scion. Due to the lack of significant pathogen pressure in our fields, we believe this was not an issue for these trials.

In our trials, grafted plants were more vigorous and had better foliage cover of fruit at harvest than non-grafted plants of the same cultivar. We also measured NDVI (Normalized Difference Vegetation Index, a measure of the “greenness” or how much of the bed is covered with actively photosynthesizing foliage) and it was also slightly higher in grafted plots. Averaged across all six trials, marketable yield increased only 12 percent when grafting with ‘Maxifort’ or ‘DRO138TX’ as the rootstock, although the results were better in some individual trials. At the San Joaquin County sites, yields of non-grafted vines were similar to the statewide average yield and grafting increased yield significantly (25 to 40 percent depending on the year). Some scion-rootstock combinations were as much as 68 percent higher than the non-grafted plants of the same scion (e.g. ‘QualiT-27’ on ‘Maxifort’ at the San Joaquin site in 2018). At the Merced sites, yields of non-grafted vines were well above-average and grafting was much less beneficial. Many published field trials indicate that the yield advantages of grafted plants are greatest under sub-optimal growing conditions.

Field sites with heavy soilborne disease pressure, or abiotic stresses may be the best candidates to see improvements with grafting.

Fruit Size and Quality Many published studies have found that grafted plants produce a higher

Continued on Page 22

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Panel Discussion—Got Questions on Walnut and Almond Varieties—Get Them Answered Here

Pre- and post-Planting Nematode Management in Perennial Crops

8:00 AM

Cliff Beumel, Sierra Gold Nursery, Steve Rothenberg, Dave Wilson Nursery, and Tom Burchell Nursery, Speaker TBA

Caroline Eberlein, Postdoc, UC Riverside CE Credits: 30 Minutes; Other

8:30 AM

Research Updates on Almond Insect Pests: Navel Orangeworm, Leaffooted Bug, and Ants

Walnut Board

Jennifer Williams, Assistant Marketing Director, Walnut Board

Kris Tollerup, UCCE Area-wide IPM Advisor CE Credits: 30 Minutes; Other

An IPM Approach to Controlling Soilborne Diseases

9:00 AM

New Technologies for Irrigation Management

Phoebe Gordon, UCCE Farm Advisor, Madera CE Credits: 30 Minutes; Other

Spencer Cooper, Senior Manager, Field Outreach and Education

Break

9:30 AM

Trade Show CE Credits: 15 Minutes; Other

10:00 AM

10:30 AM

Research Updates on Walnut Insect Pests: Navel Orangeworm, Walnut Husk Fly, and Pacific Flatheaded Borer

11:00 AM

11:30 AM

Jhalendra Rijal, UCCE Area IPM Advisor, Merced, San Joaquin, and Stanislaus Counties CE Credits: 30 Minutes; Other

Spray Applications and Preharvest Intervals

Marline Azevedo, Deputy Ag Commissioner, Stanislaus Ag Department CE Credits: 30 Minutes; L & R

An Effective IPM Approach to Mite Control

Priscilla Rodriguez, Director of Food Safety for WAPA

Nutrition Management—Preharvest Preparation for Walnuts and Almonds Rich Kreps, CCA

Exploring Organics—What You Need to Know

David Havilland, UCCE Farm Advisor, Kern County CE Credits: 30 Minutes; Other

Nate Siemens, Organic Nut Grower

12:15 PM

Lunch NOW—Benefits of Mating Disruption for Almonds and Walnuts

1:00 PM

Adjourn

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What Almond Growers Need to Know About the Sterile Insect Program Houston Wilson, UC Riverside Cooperative Extension Specialist CE Credits: 30 Minutes; Other

The Ins & Outs of The Sustainable Groundwater Management Act (SGMA) Aaron Fukuda, Tulare Irrigation District, General Manager

8:40 AM

Best Strategies for Controlling Mites at Hull-Split Kris Tollerup, Kearney Agricultural Research Cooperative Extension Advisor, IPM CE Credits: 30 Minutes; Other

Root Health and Moisture Management for Pre-harvest Devin Clarke, Crop Manager, Tree Nuts, Yara North America Rich Kreps, CCA

9:20 AM

The Latest on Canker Diseases and New Management Practices Themis J Michailides Ph.D., Pathologist Mohammad Yaghmour AreaPlant Orchard SystemsUC KearneyCooperative AgriculturalExtension Research Kern Cooperative Advisor, County CE Credits: 30 Minutes; Other

Supplemental Pollination Elizabeth Fichtner, UC Farm Advisor Tulare County

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11:00 AM

11:30 AM

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Break Trade Show CE Credits: 30 Minutes; Other The Best Management Practices and Treatments for Hull Rot in Almonds Themis J Michailides Ph.D., Pathologist Mohammad Yaghmour AreaPlant Orchard SystemsUC KearneyCooperative AgriculturalExtension Research Kern Cooperative Advisor, County CE Credits: 30 Minutes; Other

What the Almond Industry Needs to Know About The Food Safety Modernization Act (FSMA) WAPA

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NOW-Benefits of Mating Disruption Brad Higbee, Field Research and Development Manager for Trécé Inc. CE Credits: 30 Minutes; Other Adjourn

May/June 2019

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21

Scion Cultivars (Trial Years)

Continued from Page 20 percentage of fruit in larger size classes than those produced by the nongrafted scion varieties. Averaged over all our trials, the differences in fruit size distribution between grafted and non-grafted were fairly small. In some trials, however, plants on vigorous rootstocks did have larger fruit. Some published studies provide measures of fruit quality, such as dissolved sugars, pH, total dissolved solids, vitamin C, lycopene, or even “taste-test” data.

Those studies indicate that the quality of fruit from grafted plants seems to be slightly inferior to fruit from the nongrafted plants, though still commercially acceptable. Our field trials focused on yields, and we did not measure any fruit quality data. However, we did not notice any fruit defect problems in grafted vines. Also, in 2018 we did cut open both red and mature green fruit at harvest to make sure that there were no problems inside the fruit.

‘Bobcat’ (2016)

‘DRO137TX’ (2016-18)

‘Dixie Red’ (2016)

‘Maxifort’ (2016-18)

*‘Galilea’ (2016)

‘Arnold’ (2018)

‘HM 1794’ (2016-18)

‘Guardior’ (2018)

‘Quali T 27’ (2017-18)

‘Estamino’ (2018)

‘Quali T 47’ (2017-18)

Non-grafted Control

‘Quali T 99’ (2017-18) Table 2. Scion and rootstock cultivars used in our field trials.

*Note: Galilea is a roma/saladette type, while the other seven cultivars are all round types; all but Dixie Red were developed for the Western U.S. mature green production system.

A study in Florida with determinant type cultivars has shown yield increases of 25 to 42 percent using certain rootstocks, but year-to-year variability also increased as compared to non-grafted plants. This variation underscores the importance of considering variable outcomes to determine the feasibility of grafted tomatoes here. Some fields will likely benefit more from grafting than others, and this may not always be predictable in advance.

Other research projects looking at grafting tomatoes are being conducted in California. A United States Department of Agriculture (USDA)-funded project with processing tomatoes is underway with collaboration of Gene Miyao, UCCE Yolo, Solano and Sacramento counties, Zheng Wang, UCCE Stanislaus County and myself, in addition to proprietary research being conducted by the industry. Rootstocks for heirloom tomato production are being evaluated

by Margaret Lloyd, small farms advisor with UCCE in Yolo, Solano and Sacramento counties.

Economics

Acknowledgements

Costs of field establishment are increased significantly with grafting.

Material costs for transplanting (seed plus nursery costs) alone might be $2,000 per acre or higher or more than with conventional transplants.

However, we don’t yet really know what the costs might be if this were adopted commercially in California, so our plant costs are based on small volume sales prices. If we assume a cost of $0.40 per grafted plant, then a yield increase of 19 percent at a market price of $6.55 per 25-pound box would pay for the increased plant cost.

The California Department of Pesticide Regulation provided partial funding for this project but does not necessarily agree with any opinions expressed, nor endorse any commercial product or trade name mentioned. In addition, this project was supported by the Specialty Crop Block Grant Program at the U.S. Department of Agriculture through Grant 14-SCBGP-CA-0006.

The contents of this report are solely the responsibility of the authors and do not necessarily represent the official views of the USDA. We also thank our grower-cooperators (Live Oak Farms and Pacific Triple E), Growers Transplanting Inc. for producing grafted

Variability From Trial to Trial or Field to Field

On-going and Future Work 22 Progressive Crop Consultant

Rootstock Cultivars (Trial Years)

May/June 2019

plants, and the following companies that supplied the seeds: Monsanto/De Ruiter Seeds, Gowan Seed Company, Harris Moran Seed Company, and Syngenta Vegetable Seeds.

For More Information Additional information on our field trials: https://ucanr.edu/sites/veg_crop_sjc/ Grafted_tomatoes/ Detailed information on how to undertake vegetable grafting is available at: http://www.vegetablegrafting.org/ resources/grafting-manual/ List of tomato rootstocks including disease resistances and where to order seed: http://www.vegetablegrafting.org/ resources/rootstock-tables/solanaceousrootstock-table/

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

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May/June 2019

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25

WALNUT HUSK FLY Management

By EMILY J. SYMMES| Sacramento Valley Area IPM Advisor University of California Cooperative Extension and Statewide IPM Program

W

alnut husk fly poses particular challenges for developing a truly integrated pest management (IPM) program due to the nature of its life cycle (one generation per year with a long emergence period) and lack of natural enemies. As a result, best practices for management rely heavily on monitoring and insecticide treatments. Precise timing based on monitoring method and rotation of chemistries to minimize resistance risk are keys to successful long-term control of this pest.

Susceptible Varieties Walnut husk fly (WHF) damage earlier in the season causes shriveled and darkened kernels, increased mold growth, and lower yields. Later season infestations result in little kernel damage, but may stain the shells and make husk removal difficult. All commercial English walnut cultivars are susceptible to WHF infestation, although they differ in their relative degrees of susceptibility and thus damage potential. In general, Hartley, Tulare, Franquette, Payne, and Serr are considered more susceptible, with Howard, Ashley, Chico, and Chandler exhibiting less susceptibility (in order as listed). However, even less susceptible varieties can be damaged by high populations of WHF. Black walnut is also a preferred host, therefore proximity to black walnut can significantly increase WHF pressure in commercial English walnut orchards.

The varietal differences in susceptibility have been correlated to fruit characteristics including husk color, husk hardness, fruit size, trichome 26 Progressive Crop Consultant

density, and plant volatile profiles, in addition to temporal factors (i.e., more severe earlier season damage may be more evident in earlier-leafing cultivars). Current research led by Dr. Steven Seybold (United States Department of Agriculture (USDA) Chemical Ecology Entomologist) is characterizing the plant volatile profiles associated with differences in varietal susceptibility, which may lead to improvements in monitoring and control products, as well as inform plant breeding approaches for genetic resistance or tolerance to WHF infestation.

WHF Life Cycle The life cycle and basic biology of walnut husk fly is fairly well understood (Figure 1. See page 27) There is a single generation per year, with adult emergence historically beginning in early to mid-June and lasting through September in the Central Valley. In coastal areas, and recently some inland valley locations, emergence can be detected earlier, in mid- to late-May. Peak emergence is generally observed July through mid-August in most locations. Females must mate and develop eggs prior to the initiation of oviposition into the walnut husk, a period which averages approximately two weeks after emergence. Once eggs are laid, maggots emerge within approximately four to seven days, and feed on the husk for a typical period of three to five weeks. After this period, mature maggots drop to the ground and pupate in the soil. Most adults emerge the following year, but a portion of the population may remain in the soil as pupae for two or more years before emerging as adults.

May/June 2019

Extended Emergence Period The extended emergence period of the single generation of WHF, and significant differences in the timing of initial emergence, peak emergence, and end of the flight based on location, year, and other factors, have been the subject of much research. As opposed to some other key pests (e.g., codling moth), there is not yet a validated phenology or degree-day model available for growers and pest control advisors (PCA) to readily adopt to predict key WHF development and adult activity timings. Two recent publications out of University of California (UC) Berkeley (Emery and Mills 2019a, 2019b) investigated the effects of temperature and other environmental parameters on walnut husk fly development and timing. One study evaluated 18 years of historical trap catch data from 49 walnut orchards spanning the Central Valley to determine which factors most influence emergence timing and thermal requirements for development (degree days to emergence), with the goal of developing a phenology model that can be used to predict initial and peak emergence. Some of the factors evaluated included latitude, walnut cultivar, orchard age, winter precipitation, winter chill, and

Figure 1. Life cycle of walnut husk fly.

Photo courtesy of University of California Statewide Integrated Pest Management Program

degree-day accumulation. While this model requires refinement for adoption by orchard practitioners (growers and PCAs), it represents a great step forward in improving our understanding of WHF developmental requirements to aid in our IPM program development.

Biological Control Agents Biological control agents for walnut husk fly in California walnuts are virtually non-existent. The pest in general appears to have few natural enemies. Some reports from the state of Washington indicate that a predatory mite and anthocorid bug species have been observed feeding on WHF eggs, and some spiders and ants may feed on larvae and adults. In addition, chickens and other birds are said to be among the natural enemies of WHF. However, any naturallyoccurring WHF biological control agents that may be found in walnut orchards are not known to provide any significant level of population reduction. Other mortality factors, particularly those that may impact the overwintering pupal stage in the soil (e.g., intentionally augmenting soil moisture, various cultivation practices, effects or augmentation of insect-parasitic nematodes or other microorganism populations, soil insecticide applications) have

been explored to some degree with no specific recommendations or guidelines emerging as a result.

WHF Management Guidelines In spite of some of these challenges for WHF management, guidelines regarding treatment timing and options are available, and when employed properly tend to provide adequate control of WHF in many situations (albeit with more insecticide intervention than may be desirable or sustainable in the long-term).

Because WHF activity and population abundance can vary significantly from orchard to orchard (even those in very close proximity), site-specific monitoring is necessary to get the most effective results from insecticide applications.

Monitoring Monitoring should begin earlier than the June 15 historical guideline (no later than June 1 in the Central Valley is the more recent recommendation).

Some reports of late May catches in 2016 further support the “earlier-isbetter” practice—there is little harm in counting zeroes for a few weeks.

Yellow sticky card traps baited with ammonium carbonate lures should be hung high in the canopy (minimum

2 per 10 acres) in dense foliage on the north side of trees and checked two to three times per week. Each orchard should be monitored individually for WHF activity to best determine if and when to treat. A summary article regarding the efficacy of available traps/ lures for WHF monitoring was published in 2014 (http://www.sacvalleyorchards. com/walnuts/insects-miteswalnuts/ walnut-husk-fly-trap-and-low-volumespray-study/).

Treatment Timing Treatment timing can be based on one of three monitoring methods (the first two have typically been most effective).

1. Detection of eggs in trapped females.

This is a simple process that requires slightly more time than counting overall trap catches and can increase the efficacy of treatments by timing applications to specifically target female oviposition activity. Females can be distinguished from males by the shape of the abdomen (pointier in females) and color of the front leg (female leg is entirely yellow, male leg is black close to the body, (Photo 1. See page 28). After females are identified, gently squishing the female abdomen will squeeze out eggs if they are present (Photo 2. See page 28).

May/June 2019

Continued on Page 28 www.progressivecrop.com

27

Continued from Page 27 Eggs resemble small grains of rice.

Previous guidelines indicated that the treatment window is one week after egg detection. However, recent modifications suggest that treatments should be considered as soon as the first female with eggs are found because in practice there is often a lag time in getting the treatments out, and trap checks (even two to three checks per week) may not be frequent enough to represent initial egg development in the female population. Therefore, planning to treat as soon as possible after eggs are detected may be the best option to minimize infestation and damage. [Note that this is the preferred method for timing treatments unless using GF-120® alone; see below].

2. Overall trap catches. For low to moderate populations, consider treatment when a sharp increase occurs in trap counts. In high pressure orchards or if using GF-120® alone, treatment should be considered when any flies are detected rather than waiting for a sharp increase in catches.

3. Stings on nuts. This is the least preferred method, as damage has already occurred. However, examining nuts for stings (Photo 3) can provide indication of efficacy of your management program when using one of the first two methods. If using this method to time treatments, consider treating when the first sting is observed using full cover neonicotinoid materials that have some ovicidal activity mixed with an adulticide.

Continued monitoring throughout the season is crucial. Short-residual insecticides plus bait will generally kill WHF for seven to ten days. Target subsequent applications at two- to fourweek intervals based on the efficacy of the previous spray and trap catches.

Clean traps the day after application and check three to four days later. If the number of flies drops to near zero, the spray was highly effective and a longer treatment interval may be used.

If post-treatment catches increase or eggs are detected in trapped females, and the residual period of the previous treatment has elapsed, additional treatments may be required if harvest is more than three weeks away.

28 Progressive Crop Consultant

There are several materials effective against WHF, both for conventional and organic orchards. All materials aside from GF-120® (which contains its own bait) should be applied with a bait (e.g., Nu-Lure®, molasses, etc.). However, very high population orchards with extensive previous damage may require full coverage sprays (no bait needed) to achieve adequate suppression. Keep in mind that rotation of chemistries (based on the Insecticide Resistance Action Committee (IRAC) mode of action classification) is critical to minimize resistance development for pests that are treated multiple times each season.

Proper aphid management can also help limit movement of WHF within and between orchards by reducing honeydew accumulation (a food source for adult WHF).

Photo 1. Male (left) and female (right) walnut husk fly adults.

The UC IPM Pest Management Guidelines (ipm.ucanr.edu/PMG/ r881301211.html) lists insecticides, baits, and rates for WHF. A summary of efficacy data for selected materials (updated September 2016) are summarized at (www.sacvalleyorchards. com/walnuts/insects-mites-walnuts/ walnut-husk-fly-biology-monitoringand-spray-timing/).

Referenced Articles Emery, S. A. and N. J. Mills. 2019a.

Effects of temperature and other environmental factors on the postdiapause development of walnut husk fly, Rhagoletis completa (Diptera: Tephritidae). Physiological Entomology 44: 33-42.

Photo 2. Female walnut husk fly with eggs.

Emery, S. A. and N. J. Mills. 2019b.

Sources of variation in the adult flight of walnut husk fly (Diptera: Tephritidae): a phenology model for California walnut orchards. Environmental Entomology 48: 234-244.

Photo 3. Walnut husk fly sting.

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

May/June 2019

All photos courtesy of University of California Statewide Integrated Pest Management Program

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ACP Control with Systemic Insecticides

By CECILIA PARSONS | Associate Editor All photos courtesy of Citrus Disease and Pest Prevention Program.

L

ast summer’s long hot spell may have contributed to the low trap counts of Asian Citrus Psyllid (ACP) in the Central Valley, but researchers remain adamant that keeping the numbers low is the best defense the state’s citrus belt has to keep out Huanglongbing (HLB).

Meanwhile, detection of HLB infected trees in residential areas of the southern California counties of Orange, Los Angeles and San Bernardino, continues to expand.

At the Kern County Spring Citrus meeting, Dr. Beth Grafton-Cardwell, director of the University of California (UC) Lindcove Research and Extension, said the threat to commercial citrus is real.

Best Techniques for Reducing Spread of ACP Newly hatched ACP nymphs feeding on an infected tree quickly pick up the bacterium that causes the disease, and move on to infect other citrus trees.

Removal of infected trees can help slow the spread, but detecting an HLBinfected tree can take time. GraftonCardwell said trees may initially only be infected on one quadrant and can be missed in a survey. It may take a year or two before the entire tree is infected, diagnosed and removed.

Coordinated spray treatments by growers when warranted by trap finds, treating with insecticides that have an extended residual and being vigilant about cultural practices are the important steps in keeping the state’s citrus industry viable in the face of HLB. Movement of stem and leaf material, 30 Progressive Crop Consultant

Tamarixia radiate male cisr. whether by harvest crews, hedging and topping equipment or on spray rigs can help prevent ACP from hitchhiking to new territory.

Although ACP finds in the San Joaquin Valley have been spotty, Grafton-Cardwell said the coordinated treatments are a tremendous tool.

“We are still in the eradicative mode here,” she stressed.

Besides the San Joaquin Valley, growers in the desert and Coachella areas have also been keeping the lid on ACP populations with coordinated treatments. The Ventura coastal growing region and Riverside-San Bernardino citrus have more ACP pressure. A summary of 224 scouted sites in California from June 2017 to September 2018 showed that at Ventura’s 47 sites, 87 percent had ACP nymphs present.

In the Riverside San Bernardino region of the 47 sites, 88 percent were infested.

The 50 sites in the San Joaquin Valley had zero percent while Coachella’s 45 sites had 8 percent.

Samples The hot, dry weather in the desert and San Joaquin Valley growing areas help harden new flush depriving ACP as they need soft flush to lay eggs and as food for the nymphs. Growers or farm managers are asked to sample for ACP whenever young flush is present. The

May/June 2019

protocol is to sample one flush on ten trees on each border of a block. If ACP is found, the grower liaison should be notified to confirm a find and make plans for a coordinated treatment.

Grafton-Cardwell said not to rely on empty yellow sticky traps to determine if ACP has invaded an orchard, as they prefer the new flush.

Workshops on sampling for ACP will be held again this year, Grafton-Cardwell said.

When growers are asked to participate in a coordinated treatment they should respond quickly and use the most effective product possible. These treatments are another reason why ACP levels have been lower in the San Joaquin Valley, plus growers are also using pyrethroids to control glassy winged sharpshooter.

It is important to note that ACP tend to be found on the border trees of the blocks. For all insecticide applications, the borders should be treated before treating the interior. Research has shown, Grafton-Cardwell said, that 80 percent of the ACP in a block are on the border trees. This does not hold true for young citrus.

Residual Toxicity In addition to the coordinated treatments, the residual toxicity of

Continued on Page 32

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Learn more at SivantoInsecticide.com. © 2019 Bayer CropScience LP, 800 North Lindbergh Boulevard, St. Louis, MO 63167. Always read and follow label instructions. Bayer, the Bayer Cross, and Sivanto are registered trademarks of Bayer. Sivanto is not registered for use in all states. For additional product information, call toll-free 1-866-99-BAYER (1-866-992-2937) or visit our website at www.CropScience.Bayer.us.

May/June 2019

www.progressivecrop.com

31

“

“

In southern California a total of 1,127 HLB positive trees have been removed. Last year at this time the number was 501 trees. This shows the disease is spreading...

ACP tamarixia emergence holes.

Continued from Page 30 the pesticide used is important. Broad spectrum products that have a four plus week residual include Baythroid, Danitol, Actara, Admire, Leverage and Agri-flex.

These products come with a warning that use may cause flare ups of scale or mites. Insecticides that are selective with a two to four week residual are Delegate, Exirel, Fujimite, Movento and Surround.

Materials allowed in organic production have a residual of less than two weeks.

They include Pyganic, Entrust, oils and Celite. These need to make direct contact to be effective and Grafton-Cardwell recommends two spray applications to increase chances of control.

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The longer the residual, the more effective the product will be in controlling ACP as eggs and nymphs are difficult to reach with a spray and adult ACP can fly in from untreated areas and not be affected. The goal is to keep ACP nymphs below 0.5 per flush. Admire and Platinum gave the best results.

Biological Control

Navel Orangeworm, Amyelois transitella

Biological control, release of the parasite Tamarixia by California Department of Food and Agriculture (CDFA) throughout ACP infested residential sites in southern California, will continue, Grafton-Cardwell said. Releases in commercial citrus are not feasible due to use of spray applications for other insect pests and timing.

Tamarixia populations build and move into citrus October-November, after fall flush.

Control measures buy time for research and horticultural advances including early detection, using genetic engineering 32 Progressive Crop Consultant

May/June 2019

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Bio control

Foliar application

to create a protected tree, and HLB resistance. Other strategies include higher density orchards planned for shorter tree life span, using interference RNAs to prevent ACP from picking up the disease and growing citrus under protective cover.

Pest Control Districts Judy Zaninovich, Kern County ACP/ HLB grower liaison said residential finds of ACP were very high 2015-16.

The county pest control district’s pilot program for residential citrus has taken out 2,000 trees near sites where

Inspecting leaves

ACP was detected. There are similar pilot programs in southern California counties.

In southern California a total of 1,127 HLB positive trees have been removed.

Last year at this time the number was 501 trees. This shows the disease is spreading, but also that CDFA is improving their detection.

Last year, Zaninovich said, the potential for a late summer spike in ACP populations was recognized and coordinated treatments were done.

Knowing there is the potential for an

upswing in ACP at that time, she said the plan would be repeated this year.

She said there is also evidence that nighttime applications may be more effective.

Irrigation Injection Best practices for application of systemic pesticide imidacloprid delivered via irrigation was discussed by both Sarge Green, director of Center for Irrigation Technology at Fresno State and Rick Leonard of Bayer.

Continued on Page 34

Control Pocket Gophers in Tree Fruit & Nuts

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Lab Research

Foliar application

Tamarixia

Continued from Page 33

®

Distribution optimization is the key.

The goal there is to make sure the water is in the right place at the right time. Green said the soil type controls movement of the material and pore size dictates movement. Matching water delivery to the soil type will improve efficacy of the material applied. Green noted that regular maintenance and auditing of the water delivery system is important in micro and drip systems.

Leonard supplied some of the basics for efficient use of imidacloprid delivered via irrigation. Admire systemic can be tank mixed with fertilizer, but needs agitation. In a 12 hour set, the product should be injected in a one to two hours period after the first three to four hours of the set to achieve the best distribution.

It will take two to three weeks for the material to move up from the roots into the trees. The cooler the weather during that time, the longer it will take to move throughout the tree. The best strategy of use is to target the fall flush.

Ventura coastal area growers have a more difficult time achieving success with this systemic application, Leonard said, due to the high clay and organic matter soils. If the material only reaches the sub lethal levels for ACP, it invites resistance.

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V I N E YA R D R E V I E W

In This Issue Grapevine Heat Stress and Sunburn

36 Management

Grapevine Trunk Diseases: Current

42 Management Strategies

48 Pierce’s Disease and Glassy-winged

Sharpshooter: Still a Threat to California Viticulture

May/June 2019

www.progressivecrop.com

35

Grapevine Heat Stress and Sunburn Management

By GEORGE ZHUANG | UCCE Fresno County

H

eat waves with extreme daily temperatures are becoming more and more common in the San Joaquin Valley (SJV) during the middle of growing season, e.g., July and August. In 2017, grape growers in the SJV experienced two to three weeks with maximum daily temperature ≥ 110 °F. Sunburn with the associated severe water stress have resulted in significant yield loss and poor berry quality at harvest. Berry sugar, organic acids, anthocyanins, and phenolics

36 Progressive Crop Consultant

all can be impacted by extreme daily temperatures. Sugar accumulation can be significantly affected since the leaf photosynthetic rate starts to decrease when the canopy temperature passes 30 °C. Under high berry temperature (≥ 30 °C), the degradation of organic acids start to accelerate as well as anthocyanins and phenolics.

Water Stress When the heat wave occurs, it usually

May/June 2019

also causes grapevine water stress due to the need of evaporative cooling in order to lower the canopy temperature. High daily temperature coupled with severe water stress will eventually reduce the berry size and ultimately make the berry shrivel and raisin (Figure 1. See page 38). Several vineyard practices can be adopted by growers to alleviate the potential damage from the heat wave and reduce the yield loss as well as the degradation of berry composition:

Continued on Page 38

May/June 2019

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37

Continued from Page 36

1

Row Orientation

1) Row orientation

The optimum row orientation in the SJV is southwest to northeast with approximately 45° angle to have the equal sunlight exposure on both sides of the canopy. The traditional row orientation of raisin vineyard in the SJV of east to west is still good to minimize the direct light exposure on fruit-zone.

North to south row orientation should be avoided for sunburn susceptible varieties, e.g., Muscat of Alexandria and Chardonnay.

2) Trellis selection 3) Variety selection 4) Canopy management 5) Irrigation scheduling 6) Canopy shading

2

7) Canopy cooling

Trellis Selection Trellis selection is as important as row orientation. Vertical shoot positioning trellis is usually not suitable in the SJV due to the excessive light exposure on fruit-zone. Two-wire vertical trellis, or “California Sprawl”, is the most common and yet suitable for the SJV. Any trellis with a sprawling system is preferred under the hot climate.

3

Varieties

Figure 1. Berry shrivel, raisining, and sunburn of Syrah during the heat wave.

All photos courtesy of George Zhuang.

Variety evaluation has been on-going in University of California (UC) Kearney REC for a couple of years and the initial data has confirmed that certain varieties from southern Mediterranean regions can tolerate the heat and produce the decent yield and berry composition.

Some varieties, e.g., Fiano, are under commercial test to further prove their suitability under the SJV’s hot climate.

However, the adoption of alternative varieties might largely depend on marketing and consumers’ acceptance.

Continued on Page 40 38 Progressive Crop Consultant

May/June 2019

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May/June 2019

www.progressivecrop.com

39

Continued from Page 38

6

4

Canopy Shading

Canopy Management Canopy management, e.g., shoot thinning and leafing, is applied to provide enough light exposure and air circulation on fruit-zone without exposing the clusters to too much direct sunlight. Hand or mechanical leafing (Figure 2) can be applied only on the “morning” side of the canopy to avoid the afternoon sunlight exposure on fruit-zone.

Canopy shading including shade cloth (Figure 3) and sun protectant, e.g., Kaolin and CaCO3 (Figure 4), can be used to shade the canopy and fruit to avoid excessive light exposure and sunburn. Cost and timing might be the most important factors when growers decide to use shade cloth and sun protectant. Generally, the optimum timing to apply canopy shading is after berry set or several days before the heat wave.

5

7

Irrigation Management

Canopy Cooling

Irrigation management might be the most critical and powerful tool for growers and the appropriate irrigation scheduling can be applied to avoid excessive heat damage/water stress as well as berry sunburn. Severe deficit irrigation should be avoided before the heat wave occurs to make sure vines have no or minimal water stress under the extreme daily temperature. Soil moisture sensor, pressure chamber, or basically by feel and appearance can help growers to assess soil moisture and vine water status, or growers can simply follow the grape evapotranspiration (ET) report (https://ucanr.edu/ sites/viticulture-fresno/Irrigation_ Scheduling/) to decide the amount of irrigation per week to avoid severe grapevine water stress during the heat wave.

Canopy cooling can also be applied by in-canopy misting. Studies in Australia have found by in-canopy misting it can cool canopy and clusters by several degrees, and ultimately improve yield and berry composition during the heat wave (https://www.wineaustralia.com/ research/search/completed-projects/ ua-1502).

Integrated Approach Finally, it might require an integrated approach by using more than one of the mentioned strategies to maximize the production and berry quality during the heat wave. Growers should consult local farm advisors and conduct the small trials to evaluate the effectiveness of different approaches under the local condition.

Figure 3. Shade cloth on fruit-zone at “afternoon” side of the canopy.

40 Progressive Crop Consultant

May/June 2019

Figure 2. Mechanical leafing at “morning” side of the canopy during bloom.

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Figure 4. Sun protectant of CaCO3 foliar spray during veraison.

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41

Grapevine Trunk Diseases: Current Management Strategies

By AKIF ESKALEN | Department of Plant Pathology-UC Davis and JOSÉ RAMÓN ÚRBEZ-TORRES | Agriculture and Agri-Food Canada Background

G

rapevine trunk diseases (GTD) are currently considered one of the most important challenges for viticulture worldwide. These destructive diseases are caused by a broad range of wood-colonizing fungal pathogens, which primarily infect grapevines through pruning wounds. In most occasions, a single vine can be infected by more than one of these pathogens. The economic impact of GTD can be significant in both young and mature vineyards. Characteristic symptoms include poor vigor, distorted leaves and shoots, shoot and tendril dieback and berry specks caused by fungal toxins produced by some of these pathogens. Perennial cankers produced by canker-causing fungi on grapevine cause spur, cordon and trunk dieback and the eventual death of the entire vine.

Epidemiology

Most of the fungal pathogens responsible for GTD produce overwintering fruiting structures containing the spores of the fungus. When environmental conditions are favorable, these fruiting bodies release the spores into the environment. Spores will land on susceptible pruning wounds and will initiate infection completing their life cycle. In California, research suggests that the majority of GTD spores are released during winter (December to February) following primarily though not always precipitation events.

GTD fungal pathogens have a broad host range and in California are known to cause dieback in many different native or introduced tree species and also in other woody perennial crops, including tree fruits and nut trees. Therefore, the source of GTD inoculum (spores) can come into a vineyard from multiple sources.

Continued on Page 44 42 Progressive Crop Consultant

May/June 2019

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Continued from Page 42

Figure 1

B

A

C

D

Figure 1. Leaf (tiger stripes) (A), fruit (black measles) (B) and vascular (C) symptoms caused by esca disease complex. Esca (black measles) and petri disease are primarily caused by the vascular pathogens Phaeomoniella chlamydospora and Phaeoacremonium minimum, which are also involved in Petri disease in young plants (D).

Figure 2.

In mature plants, several basidiomycetes fungi (primarily in the genera Fomitiporia, Fomitiporella, Inocutis, Inonotus, and Phellinus) play also a role in disease and symptoms development.

Characteristic symptoms are a white rot in the vascular system in many occasions observed as a yellowishspongy wood.

Figure 2 Treat pruning wounds on mother plants to prevent new infections

Management in Nursery:

Sanitation in mother fields and during the entire nursery process Disinfect grafting machines regularly Reduction of the cutting hydration period Apply control products (chemicals or biologicals) as a dip after grafting, before storage and/or before dispatch Hot water treatment of dormant nursery plants prior to dispatch Continued on Page 46

44 Progressive Crop Consultant

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Figure 3

Continued from Page 44

Management A in VINEYARDS: Use the cleanest plant material available when establishing new vineyards.

Minimize stress conditions on young vines after planting.

In California, delayed pruning has been shown to minimize infection of pruning wounds as wounds are past the high disease pressure period of winter months In vertical shoot position (VSP) systems, double pruning has shown to facilitate late pruning of large acreage vineyards and thus, reduce infection.

Prune dead shoots, spurs and cordons below the symptomatic tissue (at least a few inches past the last symptomatic wood).

A Figure 4

Protection of pruning wounds with effective registered chemicals and/or biological control agents is the most effective way to prevent new infections from airborne spores of GTD fungal pathogens. More than one application may be necessary to protect the pruning wound during its susceptible time period.

Remedial surgery, where visible infected parts of the vine (spurs, cordons and/or trunk) are removed, can be an effective strategy to eradicate the pathogen from the vine (primarily when cuts are done lower down on the trunk about 20 to 30 cm above ground) and thus, prolong the lifespan of vineyards.

46 Progressive Crop Consultant

C

Figure 3. Botryosphaeria dieback, commonly known in California as ‘Bot canker’ is caused by multiple species in the Botryosphaeriaceae family.

Characteristic symptoms are the lack of spring growth of infected areas, including cordons (A) or spurs (B). Cross sections of infected parts reveal a wedge-shape canker (C). The GTD disease known as Phomopsis dieback and primarily caused by the fungus Phomopsis viticola shows very similar symptoms as Botryosphaeria dieback.

Make a clean and smooth pruning cut to speed up the callusing process at the pruning wound.

Sanitation is very important in the vineyard. Remove pruned and infected plant materials to prevent the development and increase of GTD fungi overwintering structures in the vineyard.

B

May/June 2019

Figure 4.

Symptoms of Eutypa dieback, caused by the fungal pathogen Eutypa lata and several other Diatrypaceae species, are characterized by distorted and chlorotic leaves and short internodes (A) and by wedgeshape cankers (B).

B

Free Access Literature:

Gramaje, D., Úrbez-Torres, J. R., and Sosnowski, M. R. 2018.

Managing grapevine trunk diseases with respect to etiology and epidemiology: current strategies and future prospects.

Plant Disease 102:12-39. https://doi.org/10.1094/PDIS-04-17-0512-FE https://ucanr.edu/sites/eskalenlab/ Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

Do you know if your foliar nutrients are getting in?

the form of foliar nutrients do matter!

The 5 R’s of foliar nutrition are - apply the Right nutrients, in Right form, at the Right time, in the Right mix and in the Right place. Applying effective nutrients based on a “Science Driven™” approach that DO penetrate leaf tissue ensures your crop is getting the nutrients it needs at the right time.

The form of foliar nutrients DO matter. Many foliar nutrient formulations are built on large chain molecules or unreacted oxides or carbonates that are not in-solution. These types of foliar nutrients and others have limited uptake on most leaf surfaces.

Agro-K has three main foliar lines – one based on phosphite (Sysstem®) another based on dextrose/lactose (Dextro-Lac®) and a third for organic growers (CLEAN™). They are true 100% nutrient solutions based on low pH small molecular formulations that penetrate leaf tissue rapidly and completely.

Rapid and complete uptake of foliar applied nutrients gives growers the ability to effectively meet “peak nutrient demand” timing. Whether you’re applying zinc for rapid leafout to maximize leaf size, or magnesium and iron to ensure maximum chlorophyll development or potassium for fruit bulking, if nutrients do not go in quickly and fully then your foliar dollars are less effective and yield and quality suffers.

Make sure you know how well your foliar nutrients penetrate.

Ask for SAP analysis comparisons.

The chart shows three Agro-K zinc formulations, Sysstem-ZN, Zinc Dextro-Lac and CLEAN Zinc were applied to Viognier grapes on August 8th, along with a commonly available competing zinc amino acid product. Leaves were pulled prior to application and eight days after treatment. SAP analysis, which measures only the free-nutrients available within the leave sap,

Science-Driven Nutrition SM

Viognier Wine Grapes

Zinc levels (ppm) via SAP Analysis 100 96 83

75

68

50

49

25 4

0

5

4

3

5

5

8 Days After Treatment Pre-treatment n UTC n Sysstem ZN n Zinc DL n Clean Zinc n Competing Zinc Amino Acid

showed that zinc levels prior to zinc applications were the same for all treatments in this fully replicated trial. SAP analysis eight days later shows all three Agro-K foliar products were far more effective than the competing amino acid product in delivering zinc into the leaf tissue where it matters.

This year make sure you know the efficacy of your foliar fertilizers before you spray! Talk to an Agro-K representative or your authorized Agro-K distributor and/or PCA for more information on foliar nutrients that truly WORK!. Call 800-3282418, visit www.agro-k.com, or email info@agro-k.com.

AGRO-K CORpORAtiOn 8030 Main Street, NE • Minneapolis, MN 55432 800-328-2418 • www.agro-k.com

May/June 2019

www.progressivecrop.com © 2019 Agro-K Corporation.

47

Pierce’s Disease and Glassy-winged Sharpshooter: Still a Threat to California Viticulture

By STEPHEN VASQUEZ | Technical Viticulturist, Sun-Maid Growers

F

irst known as Anaheim grapevine disease or California vine disease, Pierce’s disease (PD) has impacted California’s grape production since the late 1880’s. Grape growers had been losing vineyards to an unidentifiable disease, which prompted the US Government to hire Newton B. Pierce, the first United States Department of Agriculture (USDA) plant pathologist and namesake of the disease. Pierce had spent considerable time walking vineyards in Los Angeles, San Bernardino and Orange Counties where Muscat of Alexandria used for raisins and Mission and other wine grape varieties were dying at alarming rates (2). At the time, approximately 25,000 acres had been infected and or lost to an unknown “malady”. Pierce also spent time traveling to France, Italy and other Mediterranean grape growing regions studying plant disease symptom expression and declining grapevines to compare with those found in California. After researching all aspects of California viticulture production, including pests, diseases and associated symptoms, Pierce could never correctly identify the cause of California vine disease. For many years, a plant virus was

48 Progressive Crop Consultant

thought to be the culprit of PD. It wasn’t until the mid-1970’s when University of California (UC) researchers isolated a bacterium from diseased vines. Once isolated, the bacteria were reintroduced to healthy grapevine plants that developed Pierce’s disease symptoms within two to four months (1). The bacterium is known to move from vine to vine with the help of insect vectors representing the sharpshooter (Cicadellidae) and spittlebug (Cercopidae) families.

Infected insects ease of movement into a vineyard can be devastating in a few seasons when a PD susceptible grape variety is planted.

Although Pierce’s disease outbreaks occurred in California vineyards from time to time since being ID’d it was not a primary issue for the grape industry.

Major raisin, table and wine grape growing regions had moved north into the San Joaquin and Sacramento Valleys and the central and north coast. The mild, southern California weather was the perfect environment for the pathogen, vectors and disease development. In contrast, the seasonality of the interior valleys and coastal grape growing regions seemed

May/June 2019

to result in a lower PD incidence year to year. However, there were PD “hot spots” located near riparian areas (i.e. Napa and Kings Rivers) or alfalfa planting that experienced significant vine deaths. Those hot spots were costly to individual farming operations but was not a concern for the industry.

That changed when the disease/vector dynamics shifted.

In 1999, the nonnative PD vector, glassy-winged sharpshooter (GWSS), arrived in Temecula Valley. At that time a once thriving southern California wine industry was experiencing rapid vine death. GWSS turned out to be an effective vector and superior flyer when compared to native sharpshooters.

Additionally, vineyards planted next to citrus proved to be a deadly combination. GWSS used citrus groves to feed, breed and for protection from potential predators from late fall to early spring. California grape growers were concerned about their future as they watched Temecula Valley vineyards die. As GWSS spread to other parts of California, PD became a much greater concern and problem. According to K.P. Tumber et. al (3) California growers are

paying $56+ million in lost production and vine replacement annually.

Pierce’s Disease: Cause, Symptoms and Management Cause of Pierce’s Disease A gram-negative bacterium was found to be the causal organism of Pierce’s Disease in 1975 (1). Prior to Xylella fastidiosa being identified, it was thought that a virus was responsible for the demise of southern California vineyards. Newton B. Pierce, the diseases namesake, began researching the cause in the late 1880’s but never properly identified it as a bacterium.

Living in the xylem of grapevines, X. fastidiosa blocks the movement of water and nutrients throughout the plant. Once infected, the bacterium moves systemically from the point of infection to other parts of the plant. Early season symptoms can be confused with nutrient deficiencies (i.e. Zinc), displaying interveinal leaf chlorosis and stunted growth. Late season symptoms have a scorched

foliage appearance resulting from the plants inability to move water through the xylem vessels. Young vines are more susceptible than older vines to infection and may die by the end of the season, while older plants may display symptoms over several seasons. However, when bacteria populations increase to a level that restricts significant sap movement, foliage and fruit will dehydrate and die.

Geographical location, time of year and variety (Table 1. See page 50.) will determine how severe the symptoms

become. As temperatures increase, fruit will shrivel, and green shoots mature poorly and never cure prior to winter. At this point, financial losses are expected to impact vineyard viability.

Pierce’s Disease Symptoms • Springtime symptoms consist of grapevine leaves displaying interveinal chlorosis • Late-summer or fall symptoms consist of grapevine leaves displaying concentric rings of drying from the leaf margin towards the center. Leaf margins of red or black grape varieties turn red and then brown • Leaves that have turned brown will detach, leaving only the petioles attached to canes • A unique disease symptom is the irregular, patchy bark maturity, leaving half the shoot brown and half green, displayed as islands of green and mature brown coloration • Berries on clusters will shrivel and/ or raisin Pierce’s disease symptoms can often be

Photo courtesy of University of CA.

Continued on Page 50

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49

Table 1. Variety Susceptibility to X. fastidiosa** Highly susceptible

Moderately susceptible

PD resistant*

• Chardonnay

• Riesling

• 07355-075 (50% Petite Sirah, 25 % Cabernet Sauvignon)

• Redglobe

• Chenin blanc

• 09331-047 (50 % Zinfandel, 25 % Petite Sirah, 12.5 %

• Fiesta

• Cabernet Sauvignon • Ruby Cabernet • Muscat of Alexandria • Thompson Seedless

Cabernet Sauvignon)

• 09356-235 (50 % Sylvaner, 12.5 % Cabernet Sauvignon, 12.5 % Carignane, 12.5 % Chardonnay)

• 09314-102 (62.5 % Cabernet Sauvignon, 12.5 % Carignane, 12.5 % Chardonnay)

• 09338-016 (62.5 % Cabernet Sauvignon, 12.5 % Chardonnay, 12.5 % Carignane)

*UC Davis PD resistant wine grape varieties released in 2017 from Dr. A. Walker. ** This is a partial list of susceptible PD varieties. Contact your local UC farm advisor for a complete list.

Continued from Page 49 confused with nutritional deficiencies, water related issues or other diseases.

Multiple tissue samples should be shared with your pest control advisor (PCA), certified crop advisor (CCA), local farm advisor or university plant pathologist to correctly ID the symptoms. Once properly identified, a treatment plan can be devised to improve the vineyard’s health.

Management Management strategies will depend on several factors. Insect vector, grape variety and location will have a significant impact on the success of managing PD. The four main insects that transmit PD are the bluegreen sharpshooter (Graphocephala atropunctata), native to coastal regions near riparian areas; the green sharpshooter (Draeculacephala minerva) and red-headed sharpshooter (Xyphon fulgida), native to interior valleys; and the glassy-winged sharpshooter (Homalodisca vitripennis), a non-native species to California and the most dominate vector of X. fastidiosa. It is important to monitor for sharpshooter insects if PD is to be managed. Sticky cards, sweep nets and visual observations of the vineyard and nearby properties will help in determining the population size and what control measures will be needed.

Once identified, properly timed insecticide applications will help reduce 50 Progressive Crop Consultant

the population. Vineyards located in areas where the PD bacterium is common, and temperatures are mild will be a challenge at keeping PD under control. In this case, identifying and managing the insect vector will be most important. If GWSS is the primary vector, insecticide applications will need to be timely to keep insects from moving into the vineyard. Citrus planted next to a vineyard will have to be sprayed as well to keep populations in check. Citrus should be visually checked for adults, nymphs and eggs. Visit the UC Pest Management Guidelines online for the most current insecticide management strategies (4,5).

Locations that have a history of PD should not be planted to highly susceptible varieties like Chardonnay if possible. Finding a more tolerant PD variety will improve the health of the vineyard. Newly developed PD resistant varieties have been released from UC Davis. These numbered wine grape selections (Table 1.) can be planted in areas with a high incidence of PD and used for blending with traditional varieties. Unfortunately, there are not any PD resistant varieties for raisin or table grape production, but research is ongoing.

Grapevines showing unusual foliar symptoms should be taken to your local UC Cooperative Extension office for identification. Plant tissue suspected of having Pierce’s disease can be sent to a diagnostics lab for

May/June 2019

positive identification using molecular tools. Leaf blades and petioles sampled from green portions of the cane in the late summer to early fall will give the best results. Vineyard insects should be caught and identified, too. A sweep net or sticky cards strategically placed in the vineyard can be used to survey insect populations in areas displaying foliar symptoms. Unique insects can be taken to your local Agriculture Commissioners office or the California Department of Food and Agriculture— Plant Health and Pest Prevention Services Division for identification.

These first steps are paramount for developing a management plan.

References 1. Davis, MJ, Purcell, AH, Thomson, SH, 1977.

Pierce’s Disease of Grapevines: Isolation of the Causal Bacterium.

2. Pierce, NB. 1892. The California vine disease: a preliminary report of investigations. U.S Dep. Agric. Div. Veg. Pathol. Bull. 2, 222.

3. Tumber K, Alston J, Fuller K. 2014. Pierce’s disease costs California $104 million per year.

Calif Agr 68(1):20-29. https://doi.org/10.3733/ ca.v068n01p20 4. UC Pest Management Guidelines – Pierce’s Disease: Xylella fastidiosa http://ipm.ucanr.edu/ PMG/r302101211.html 5. UC Pest Management guidelines – Sharpshooters http://ipm.ucanr.edu/PMG/ r302301711.html

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

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52 Progressive Crop Consultant

May/June 2019