Progressive Crop Consultant - January/February 2019

January/February 2019 Clonal Paradox Rootstocks Hold Their own in Tehama County Howard Trial A Nitrogen Fertilization Tool for Drip Irrigated Processing Tomatoes 2018 Armyworm Season in Rice California Citrus Network:

An Online Forum to Facilitate Communication and Information Exchange Regarding California Citrus JANUARY/FEBRUARY 2019

V I N E YA R D REVIEW pages 21-42

PUBLICATION

Volume 4 : Issue 1 January/February 2019

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PUBLISHER: Jason Scott Email: jason@jcsmarketinginc.com EDITOR: Kathy Coatney 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

Clonal Paradox Rootstocks Hold their own in Tehama County Howard Trial

10

A Nitrogen Fertilization Tool for Drip Irrigated Processing Tomatoes

16

2018 Armyworm Season in Rice

CONTRIBUTING WRITERS & INDUSTRY SUPPORT

10

Luis Espino Rice Farming Systems Advisor, University of California Cooperative Extension

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

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Habitat Diversification for Pest Management in Vineyards—More Complicated Than It Seems

28

Improving Grape Coloration and Ripening Using the Plant Hormone Ethylene

34 38

44

The Impacts of Smoke to Vineyards

16

Counties), Richard Buchner, UCCE Farm Advisor Emeritus and Allan Fulton UCCE Irrigation and Water Resources Advisor Tehama, Colusa, Glenn, and Shasta Counties

Houston Wilson Asst. Cooperative Extension Specialist Daniel Geisseler Kearney Agricultural Associate UCCE Specialist, Research and Extension UC Davis and Kelley Liang, Center Dept.

Junior Specialist UC Davis Entomology, UC Riverside County George Zhuang Glenn McGourty and Matthew Fidelibus Winegrower and Plant University of California Science Advisor, UCCE Cooperative Extension, Mendocino and Lake Fresno County, counties Department of Viticulture and Enology, University of Luke Milliron California (UC) Davis UCCE Farm Advisor (Butte, Tehama, and Glenn

UC COOPERATIVE EXTENSION ADVISORY BOARD Kevin Day

Emily J. Symmes

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

Field Evaluation of Seven Rootstocks Under Saline Condition California Citrus Network: An Online Forum to Facilitate Communication and Information Exchange Regarding California Citrus

Dr. Greg W. Douhan University of California Cooperative Extension, UCCE Citrus Advisor, Tulare, CA

Kris Tollerup

Dr. Brent Holtz

County Director and UCCE Pomology Farm Advisor, San Joaquin County

UCCE Integrated Pest Management Advisor, Parlier, CA

Steven T. Koike,

V I N E YA R D REVIEW

21

Director, TriCal Diagnostics 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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sites. Second, because they are clonally propagated, they will impart less genetic variability and be more predictable in the orchard. Disadvantages include the loss of genetic diversity in orchard plantings and that additional expertise is required to micropropagate, nursery culture and graft to produce a commercially viable product.

Clonal Paradox Rootstocks Hold their own in Tehama County Howard Trial By: Luke Milliron UCCE Farm Advisor (Butte, Tehama, and Glenn Counties), Richard Buchner, UCCE Farm Advisor Emeritus and Allan Fulton UCCE Irrigation and Water Resources Advisor Tehama, Colusa, Glenn, and Shasta Counties All photos courtesy of Luke Milliron

L

and available for perennial orchard crops is limited in the Central Valley, which often results in farmers either planting on less productive and more challenging soils or removing existing non-productive orchards and replanting them.

Non-traditional orchard soils present challenges because they may have poorer nutrient availability or water quality. Replanting after an existing orchard puts a farmer at risk of a replant problem, when soil pathogens and nematodes from the first orchard inhibit performance of the replant orchard.

One solution for managing replant problems is to replant with a different species (e.g. walnuts to almonds). Another possibility is to develop rootstock genetics to manage the replant problem. The California walnut industry traditionally utilizes two rootstocks for commercial production. Northern California Black (Juglans hindsii) or Paradox hybrid seedling (Juglans hindsii x Juglans regia). Both rootstocks are open pollinated resulting in genetic variability. Due to superior vigor, better adaptability to marginal soils and lower susceptibility to Phytophthora and crown and root rots, Paradox is the preferred rootstock for Northern California. Recent technology has resulted in micropropagation and commercial availability of three new clonal Paradox walnut rootstocks, VX211, RX1, and Vlach. These rootstocks are clones of seedling Paradox judged by researchers and breeders to offer superior traits.

Clonal rootstocks may have several horticultural advantages. First, they can be selected for desirable attributes such as disease resistance, nematode tolerance, and vigor, giving farmers the opportunity to match rootstock selection with planting

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University of California (UC) and United States Department of Agriculture (USDA) researchers have been trialing the three new clonal Paradox rootstocks in experiments across the California walnut growing region. Work in controlled greenhouse studies, as well as field trials have shown that the clonal Paradox rootstock VX211 offers lesion nematode tolerance, and that RX1 offers moderate resistance to Phytophthora crown and root rot.

Their research has also suggested that all three commercially available clonal Paradox rootstocks (VX211, RX1, and Vlach) generally have lower incidence of crown gall compared to the standard seedling Paradox. RX1 generally has the lowest crown gall incidence and may have low to moderate resistance.

Recent History of Clonally Propagated Paradox Clonally propagated Paradox rootstocks have been available since 1999 with the release of Vlach, which originated from a vigorous Paradox tree in Stanislaus County. In 2007 RX1 and VX211 were released by the University of California and USDA, after being vetted for several years. The three clonal Paradox rootstocks are sold as potted rootstock, or they are June-budded or grafted to the walnut variety of choice at the nursery and sold as bare root trees. The three rootstocks are now planted across thousands of acres in California.

For more information on the terminology, propagation, availability and pest interactions of walnut trees in the nursey trade, please see: sacvalleyorchards.com/walnuts/ orchard-development/walnut-trees-inthe-nursery-trade/

Tehama County ‘Howard’ Clonal Rootstock Trial One of the trials underway to evaluate the commercially available clonal Paradox rootstocks is located in a Continued on Page 6

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Continued from Page 4 Howard orchard in Los Molinos, California (Tehama County). The objective of this plot is to evaluate and compare the clonal rootstocks RX1, VX211 and Vlach to seedling Paradox and nursery budded June-bud Vlach trees. To evaluate these rootstock treatments against each other we measured trunk cross sectional area (TCSA), dry in shell yield, edible yield, percent jumbo walnuts, percent light kernels and percent mold.

The clonal rootstock experiment in Tehama County was planted in March of 2009 as part of a large commercial Howard walnut orchard planted in a north/south orientation, at a 14-foot by 26-foot hedgerow configuration.

The Tehama Soil Survey lists the soil as class one Columbia loam. The previous planting was Hartley walnut and the site was pre-plant fumigated with 400 pounds of methyl bromide per-acre.

The rootstock treatments were planted as three adjacent rows of six trees and replicated in five randomized plots.

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Trees are micro sprinkler irrigated and managed as part of the larger orchard.

Planting and Establishment RX1, VX211 and Vlach were micropropagated by North American Plant Lab, Lafayette Oregon and grown for one year in a conventional walnut nursery, machine harvested and planted as soon as possible following digging.

Seedling Paradox from the same nursery was planted as a control or reference rootstock to compare to the clonal Paradox treatments. June-budded Vlach, nursery grafted to Howard was included as the grower standard, since it is the rootstock and nursery product utilized in the orchard outside the plot. RX1, VX211, Vlach and the seedling Paradox were planted in March 2009 as ungrafted trees and patch budded to Howard in September 2009.

Unfortunately, freezing temperatures in December of 2009 resulted in very poor bud take.

To ensure that all trees were treated

January/February 2019

equally, RX1, VX211, Vlach and the seedling Paradox were all re-grafted in May 2010 using whip grafts. Not all of the 2010 whip grafts took and the remaining trees were again whip grafted in May of 2011. Finally, all May 2011 grafts were successful, and all trees had Howard scions in 2011. Note that the June-budded Vlach, propagated by the Bonilla nursey, were already grafted to Howard when planted in March 2009. Consequently, those trees have an advantage of over two years of uninterrupted growth compared to the other rootstocks, which is reflected in growth and yield measurements.

Tracking Growth and Yield In each three adjacent row plot the center six trees are the measured trees with six guard trees to the east and six guard trees to the west. Tree and crop measurements include trunk cross sectional area, calculated using trunk circumference 12 inches above the graft union. Dry in-shell yield is calculated using the total field green weight

(measured by load cell at harvest) multiplied by a green field weight to dry in-shell weight conversion, calculated from subsamples.

Subsamples were also used to commercially evaluate nut quality. Due to tree mortality, not every plot had the original six trees, consequently total plot weight is divided by the number of harvested trees per plot and reported as weight per tree. Edible yield, percent jumbo walnuts, percent light kernels and percent mold were taken directly from the commercial grade sheets.

for Biological Controls N .O . W., , ia r a n r e lt A , se o Anthracn and more .. .

Field grafting was a tremendous challenge in this experiment, and points to the benefit of selecting nursery grafted trees if available. For this experiment, nursery grafted trees on clonal rootstocks were not available and field grafting was the only option.

The key consequence of the grafting challenges were graft age differences throughout the plot. Assuming graft differences would decrease with time as trees matured, full plot yield measurements were delayed until 2017 to minimize to the greatest extent possible any graft date differences.

Recall the June-budded Vlach were planted already nursery grafted so they had an age advantage which is probably responsible for their superior performance through 2018. Again, tree age may minimize or reduce that effect, so additional years of yield measurement may show a decline in the competitive growth and yield advantage of June-budded Vlach.

Resulting Growth The key comparisons are the micropropagated RX1, VX211, Vlach and the industry standard seedling Paradox. Interestingly, 2016 TCSA

Continued on Page 8

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Table 1. 2017 Tehama County Clonal Paradox Rootstock Comparisons 2016 % TCSA Dry In shell Edible Rootstock cm2 Yield lbs/tree Yield RX1 233 a 52.96 a 48.49 a Paradox seedling 234 a 59.20 ab 48.87 ab VX211 235 a 63.90 ab 51.11 ab Vlach 253 a 68.60 b 50.80 ab June-budded Vlach 315 b 69.50 b 51.60 b

% Jumbo 64.4 a 65.6 a 66.6 a 71.0 a 70.2 a

% Light Kernel 76.0 a 79.8 ab 84.0 bc 84.8 bc 86.0 c

% Mold 9.0 b 8.0 b 4.6 ab 5.6 ab 3.0 a

% Jumbo 73.4 a 66.8 a 66.0 a 70.8 a 64.4 a

% Light Kernel 76.4 a 80.2 a 79.2 a 82.6 a 83.2 a

% Mold 5.2 a 3.4 a 3.0 a 3.0 a 3.2 a

Table 2. 2018 Tehama County Clonal Paradox Rootstock Comparisons Dry In shell Yield lbs/tree 38.86 a 42.77 ab 43.52 ab 46.75 ab 52.42 b

Rootstock

RX1 Paradox seedling VX211 Vlach June-budded Vlach

% Edible Yield 43.66 a 43.08 a 43.74 a 43.71 a 44.68 a

Table 1 & 2 . Treatment means for tree size (trunk cross section area, TCSA cm2), dry in shell yield (lbs/tree) and quality comparisos for clonal Paradox rootstocks in Tehama County. If the rootstock treatments do not share a common letter in the column to the right of the averages, they are statistically different from one-another.

Continued from Page 7 measurements were not significantly different (Table 1) for those four rootstocks. Notice that only Junebudded Vlach trees were statistically significantly greater for TCSA in 2016.

2017 and 2018 Harvest Findings In 2017 dry in-shell yield generally favored June-budded Vlach and Vlach, with RX1 imparting statistically lower yields and VX211 and Paradox seedling falling in-between (Table 1) statistical differences are signified by not sharing a common letter). The following year yields were significantly lower overall, and the June-budded Vlach again imparted statistically higher yield than the RX1, with the other rootstock treatments falling in-between (Table 2).

Through these two harvests, the Junebudded Vlach trees with the growth advantage from not being field grafted, have been amongst the most productive trees in the plot. The trunk crosssectional area, or TCSA of June-budded Vlach was greater than the other rootstocks in 2016. Trees with larger trunks and presumably conferring larger canopies would be expected to produce more crop.

The nut samples gathered for Junebudded Vlach were wetter (i.e. greater percent of moisture loss during drying) 8

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January/February 2019

than RX1 or Paradox seedling in 2017 and wetter than all other rootstock treatments in 2018. Wetter Junebudded Vlach might indicate they were harvested a little early being larger more robust trees, again due to their advantageous early start.

Edible yield measurements favored June-budded Vlach, compared to RX1 in 2017, with the other rootstocks falling in-between. In 2018 edible yields were lower overall and not significantly different across rootstocks. Nut size characterized as percent jumbo walnuts did not statistically differ between the five rootstocks in either year. Looking at the kernel quality attributes (percent light kernels and percent mold), values favored June-budded Vlach, Vlach, and VX211 in 2017. RX1 and seedling Paradox seedling tended to impart fewer light kernels in 2017. They also had more kernel mold compared to June-budded Vlach in 2017. More refined canopy measurements might confirm the possibility that RX1 and seedling Paradox trees featured a more open canopy with walnuts more vulnerable to heat/sun damage from the unusually hot 2017 growing season in Tehama County. There were no light kernel and mold differences between rootstocks in 2018. Despite the lack of statistical differences in 2018, RX1 again had numerically fewer light kernels

and higher percent mold. Percent mold was lower in 2018, possibly due to the smoky summer in the Sacramento Valley that provided some protection from sunburn related mold, compared to the previous summer of recordbreaking temperatures.

Nursery Product and the Importance of a Good Early Start This plot serves as an important lesson in the lingering ill effects of setbacks due to in-field grafting and budding problems. Vlach, already a vigorous rootstock was allowed to get a twoseason head-start on the rest of the field when planted as a June-bud. Many growers have had positive experiences with planting clonal rootstock and subsequently fall budding or spring grafting in the field with very high percentage take. However, unforeseen setbacks like the December frost in 2009 that killed the new chip buds and the 50 percent take of the subsequent April’s bark grafts are also experienced by growers. As in the case of this trial, June-budded clonal rootstocks are not always available, and their higher price tag when they are available discourages some growers from planting them.

At this orchard, the growth and yield advantage of the June-budded trees may fade in future years. However, for this site, the June-budded trees have been a solid investment.

For more information on the various walnut nursery products available and how to handle them, please see: sacvalleyorchards.com/walnuts/ horticulture-walnuts/walnut-treetraining-different-nursery-products/

What Have We Learned About These Clonal Paradox Rootstocks?

At the Howard orchard trial site in Tehama, the clonally propagated Vlach, VX211, and RX1 Paradox rootstocks have all performed competitively against the Paradox seedling rootstock that is standard in the region. The differences between the clonal rootstocks have been relatively subtle.

The standard Paradox seedling has been in the middle of the pack across yield and quality attributes. Although not separating out statistically, VX211 and Vlach have so far been numerically higher yielding and offered good quality

(high percent light kernels and low percent mold). In a Solano county trial, cumulative yield from the 4th through 8th leaf has also resulted in no yield differences between the three clonal rootstocks and Paradox seedling. At the Solano site Paradox seedling also falls numerically in the middle of the pack, with VX211 and Vlach in-front. UC and USDA researchers regard RX1 as moderately vigorous, Vlach as vigorous, and VX211 as highly vigorous.

The class one Columbia loam and preplant fumigation with methyl bromide at the Tehama county trial site may mean that attributes like VX211’s tolerance of some nematodes and RX1’s moderate to high resistance to some Phytophthora species, have not had the opportunity to shine. Thus far, the nursery product choice of a Junebudded tree has been the big advantage at the site. At the site of your next walnut orchard, availability, cost, and the subsequent required handling of the various nursery products will all have to be judged. In addition, consider the attributes conferred by clonal rootstocks for vigor, crown gall, nematodes, and Phytophthora/wet feet when choosing a rootstock. Researchers will continue to test these rootstocks, as well as an even newer generation of clonally propagated rootstocks, across the California walnut growing region.

For more information on selecting the right clonal rootstock for managing your soil and pest problems please see: sacvalleyorchards.com/blog/ walnuts-blog/selecting-the-right-clonalrootstock-for-managing-soil-and-pestproblems/

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We want to sincerely thank an amazing team of UC and USDA researchers who have worked tirelessly on developing and testing new rootstocks for California walnut production. They include Janine Hasey, Chuck Leslie, Wesley Hackett, Pat J. Brown, Andreas Westphal, Michael McKenry, Greg Browne, Bruce Lampinen, Katherine Jarvis-Shean, Dani Lightle and Dan Kluepfel. This work is made possible by the funding support of the California Walnut Board.

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

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A Nitrogen Fertilization Tool for Drip Irrigated Processing Tomatoes By: Daniel Geisseler | Associate UCCE Specialist, UC Davis and Kelley Liang, Junior Specialist | UC Davis County

T

he processing tomato industry has seen a dramatic shift in production practices over the last 20 years, caused mainly by a wide adoption of drip irrigation. While less than 10 percent of the acreage was drip irrigated in 1999, this number reached 85 percent in 2012. The shift from predominantly furrow irrigation to drip irrigation has contributed to strong yield increases. It has also changed fertilization management, with fertigation through the drip system now being common. Subsurface drip irrigation allows application of water and nitrogen (N) fertilizer close to the roots throughout the season to match crop requirements. Fertigation can increase the N use efficiency considerably, minimizing N losses to the environment.

Applying the right amount at the right time requires knowledge about the N demand of the crop, the seasonal uptake pattern and the availability of other

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sources of N. Many factors that affect the balance between N availability and crop N demand are site specific, including yield potential, residual soil nitrate levels, nitrate in the irrigation water and N mineralized from organic matter during the growing season. This is especially true with residual soil nitrate levels at transplanting, which can vary considerably from one field to another and across years, as they depend on weather conditions, the previous crop and its management.

Three years ago, we started a project with the goal to develop a user-friendly N fertilization tool for processing tomato producers and consultants. To achieve this goal, we first monitored N uptake in commercial fields. We then developed a template for a N budget, which takes into account crop N

January/February 2019

The in the field trial four weeks before harvest.

Photo courtesy of Daniel Geisseler.

requirement, availability of non-fertilizer N and efficiency of N fertilizer use. Finally, we tested the budget in a replicated field trial.

Nitrogen Uptake Plant samples were collected throughout the season at 3-week intervals in 11 commercial fields located in Yolo, San Joaquin and Fresno counties. Plants were cut at the base and fruits picked and weighed. Fruits and vines were then dried separately and analyzed for total N content.

The results from these fields revealed that little N was taken up during the first month after transplanting (Figure 1, see page 12). On average, less than 15 percent of the total aboveground N

Continued on Page 12

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Es�mated N uptake (lbs/acre)

300 250 200 150 100 50 0

0

20

40

60

80

100

120

Days a�er transplan�ng

Figure 1. Nitrogen accumulation in the vines and fruits of a processing tomato crop with an expected yield of 55 tons/ac. The curve is based on results from 11 commercial fields.

Continued from Page 10 was taken up during this period, which in most fields was less than 50 lb/ac. A moderate starter fertilizer application can therefore supply enough N during the initial 3-4 weeks after transplanting.

The initial period of slow N uptake was followed by 8-10 weeks of rapid uptake, with daily uptake rates reaching 7 lb/ac in some fields. On average, more than 80 percent of the total N in the aboveground biomass had been taken up by the time the plants reached the early red fruit stage. An adequate N supply is crucial during this period of high N demand, and N fertigation should be timed to avoid temporary N limitations.

During the last month before harvest, N uptake was low and in some cases a decrease in the total biomass N was observed. After the crop reaches the early red fruit stage, N applications are generally no longer needed. Late applications may not be taken up by the plants, and will be at risk of being leached during the winter.

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Creating an N Budget Template restricting root activity and nutrient Across all commercial fields, the tomato fruits contained 3 lb N/ton of fresh weight at harvest. The N in the fruits accounted for two thirds of the total N in the aboveground biomass. These values were used to determine total N requirement for the budget. As an example, the average N requirement of a 55-ton crop is 246 lb/ac. In most fields the plants were well supplied with N, and a value of 3 lb/ton for the fruits likely includes some luxury consumption.

The N demand of a crop can be covered with fertilizer, residual soil mineral N, nitrate in the irrigation water and N mineralized from soil organic matter during the growing season. These sources need to be taken into account when determining the need for fertilizer N. With subsurface drip irrigation, the surface layer of the soil profile remains dry throughout the season, potentially

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uptake. For the N budget, we assumed that only 50 percent of the pre-plant soil nitrate in the top foot can be accessed by roots. This assumption is a rough estimate which needs to be further investigated. This is especially important for the San Joaquin Valley where soil nitrate levels can be quite high and supply a significant portion of the N needed by the crop. For the residual soil nitrate in the second foot of the profile and for fertilizer N, we assumed that 80 percent is taken up by the plants.

Field Trial The budget calculations were validated in a replicated field trial at UC Davis in 2017 and 2018. The soil at the site was classified as a Yolo silt loam with a soil organic matter content of 1.8 percent and a pH of 7.4. Tomatoes were transplanted onto 60-inch beds in early May both years. Twenty-five gal/ac of a

Table 1. Nitrogen budget examples. Example 1 corresponds to the situation in the replicated field trial in 2018. Example 2 assumes the same yield, but larger credits for residual soil nitrate and nitrate in the irrigation water. Credits were calculated based on the description in the text.

Example 1 lb N/ac Expected yield Expected N in fruits Expected N in vines Expected N uptake

58 tons/ac 3 lb/ton 33 percent of total

58

tons/ac

25 15 10

ppm N ppm N

174 87

261

Residual soil nitrate N Irriga�on water N Soil N mineraliza�on Non-fer�lizer credits

174 87

Example 2 lb N/ac

1st � 2nd � 22 ac-in

12 ppm N 11 ppm N

24 39

0 ppm N

0 40

Difference (uptake - non fer�lizer N) Starter applica�on In-season N(assumed efficiency:80 percent)

liquid starter fertilizer (8-24-6, 0.5 percent Zn) was applied to all treatments.

During the growing season, UAN 32 was supplied via drip tape in 5 weekly applications starting one month after transplanting. Three application rates were compared in the trial. The intermediate or optimal rate corresponded to the amount calculated in the budget.

This application rate was reduced or increased by 50 lb/ac for the low and high rate, respectively. All other management practices followed common practices for conventional processing tomatoes.

261

ppm N

49 53 45 40 187

102 159 25 167

The trial was machine harvested in late August both years. We expected a yield of 55 and 58 tons/ac in 2017 and 2018, respectively.

Pre-transplant nitrate-N in the top and second foot of the soil profile ranged from 8 to 13 ppm (parts per million).

Taking into account limited root access in the dry top soil, the available residual soil nitrate was about 50 lb/ac both years. The irrigation water did not contain any nitrate. Based on results from a different study which included

74 25 93

the field trial site, N mineralization was assumed to be 40 lb/ac. Subtracting these N credits and the starter N application from the expected amount of N required, the N fertigation requirements were estimated to be 165-190 lb/ac in the two years of the study. The detailed budget for the second year is shown in Table 1.

Average yields were higher than expected, reaching 58 tons/ac in 2017 and 63 tons/ac in 2018 (Figure 2).

Nitrogen application rate had no signif-

Continued on Page 14

Yield (tons/ac)

2018

2017

80

60

40

20

0 Low N

Intermediate N

High N

Low N

Intermediate N

High N

Figure 2. Yield in the replicated field trial. The N treatments had no statistically significant effect on yield. Each treatment was replicated five times. The tomatoes were machine harvested. Error bars indicate standard error.

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Continued from Page 13 icant effect on yield. It may appear that the yield in the high treatment in 2018 was greater than the other treatments.

However, due to some pest issues, variability across the plots was quite high.

Therefore, the statistical analysis concluded that it is likely that the observed difference is simply due to chance and not because of the higher N rate.

Discussion of the Budget Approach Even though the measured yield exceeded the expected yield in both years, reducing the optimal N application rate by 50 lb/ac had no effect on yield.

This was mainly due to the fact that the plants adjusted N uptake based on N availability. From the low N to the high N treatment, the N application rate was increased by 100 lb/ac, while the N in the aboveground biomass increased by 87 lb/ac across both years.

Our results suggest that using a value of 3 lb/ton may overestimate N requirements and that a fruit N concentration above 2.7 lb/ac is likely the result of luxury consumption. However, the N budget is based on marketable yield and not total yield. Therefore, the use of the higher value represents an adjustment for N in non-marketable fruits.

While fertilizer N use efficiency decreased only slightly with increasing N application rate within the range of our study, the amount of N removed from the field with the harvested tomatoes only increased by 46 lb/ac when the N rate was increased by 100 lb/ac. Close to half of the increased N uptake was due to higher N contents in the vines, which were left in the field and later incorporated. The decomposition of the vines will release part of this N resulting in higher nitrate levels in the soil, increasing the risk of nitrate leaching with winter rains. While the increasing N uptake with increasing N application rates suggests that the optimal N rate can be considered a range rather than an exact number, it is still important to accurately estimate fertilizer N requirements in order to minimize the risk of nitrate leaching and to keep production costs low.

Conclusions The results of this study were incorporated into a simple processing tomato N calculator, which is freely available online at http://geisseler.ucdavis.edu/ Tomato_N_Calculator.html. The calculator is easy to use and requires few readily available input variables.

However, such a simple tool cannot

capture all the factors that affect growth and yield of the crop in individual fields. Factors such as: differences in soil properties, crop management, disease pressure or weather conditions. While the assumptions used in the budget presented here provide a margin of safety for commercial producers, it is crucial to monitor the fields during the growing season in order to make adjustments if needed. Soil nitrate testing and leaf analyses are valuable tools to determine N availability and N status of the crop during the season. These tools allow for adjustments when the calculated N application rates do not match the plants’ demand.

This project was a collaboration between the authors and Gene Miyao, UCCE Farm Advisor, Yolo, Solano & Sacramento counties; Brenna Aegerter, UCCE Farm Advisor San Joaquin County; and Tom Turini, UCCE Farm Advisor Fresno County. Funding was provided by the CDFA Fertilizer Research and Education Program (FREP).

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

Photo courtesy of Daniel Geisseler.

14

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January/February 2019

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“Herbicides are important in almond orchards,” says Pest Control Advisor/ “Alion does a really good job, “I continue to use Alion in a pre-emergent Certified Crop Advisor (PCA/CCA) has long residual weed control rotation because it’s a good product and David Vermeulen, Modesto, California. and it takes care of a lot of it works really well. We can see Alion “Weeds compete for nutrients. They broad-spectrum weeds…” reducing the weed population overall as compete for water. Those are probably soon as we start using it,” Garcia states. your bigger two issues in the almond “I think it’s one of the top – if not the top – pre-emergent product orchard, especially early on, so by keeping them down you have out in the market right now. Alion does a really good job, has long more water and more nutrients getting to the plant to get a better residual weed control and it takes care of a lot of broad-spectrum crop. Weeds also harbor insects – take morning glory, when you weeds that are giving us issues here in the Central Valley.” control it, you have a little less mite pressure in the orchard.”

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January/February 2019

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15

2018 Armyworm Season in Rice

By: Luis Espino | Rice Farming Systems Advisor, University of California Cooperative Extension

Figure 1. This picture was taken in 2015 in a Glenn County field. The field had already been treated twice, but worms kept feeding on foliage. All photos courtesy of Luis Espino.

F

or many years, armyworms have been considered a secondary pest in rice fields. Treatments were sometimes needed, but for the most part, most growers could get by without spraying an insecticide. That changed in 2015, when a severe armyworm outbreak occurred throughout the Sacramento Valley. Infestations were worst in Butte, Glenn and Sutter counties. Severe defoliation was observed in some fields, where plants were eaten to the water level (Figure 1). That year, growers and pest control advisors realized that pyrethroids, a common insecticide group used on rice, do not do a good job controlling armyworms. The industry was able to obtain a Section 18 Emergency 16

Progressive Crop Consultant

Registration for the insecticide Intrepid (methoxyfenozide), an insect growth regulator, but the registration came a bit too late, when the outbreak had passed.

The next two years saw variable infestation levels, with 2016 being less problematic than 2017. Again, a Section 18 registration was obtained for Intrepid at the end of June both years.

In 2018, armyworm levels were variable, with high levels in some fields, and average levels in others. Intrepid was available from mid June until the end of the season. Severe defoliation as seen in 2015 did not happen; however, this year growers and PCAs were on their toes, monitoring fields closely.

January/February 2019

Armyworm Cycle in Rice Two species of armyworms can be found in rice fields, the true armyworm (Mythimna unipuncta) and the western yellowstriped armyworm (Spodoptera praefica). In the past few years, the true armyworm has been the dominant species; however, there is evidence that in some years the western yellowstriped armyworm can be dominant. Adults of both species are nocturnal moths that most of us will not get to see during the day. These moths lay their egg masses in vegetation surrounding rice fields beginning in late May and through June.

Their eggs are difficult to find Continued on Page 18

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17

Figure 3. Armyworms usually pupate in the soil. In rice, however, they can find hiding place between tillers and pupate there.

Continued from Page 16 (I haven’t been able to find them in or near rice fields). The small larvae emerging from the eggs are very difficult to find also, hiding under clods and at the base of plants in levees and around rice fields. Their feeding is almost unnoticeable. As they grow, the larvae spread to other plants and their feeding increases. When they reach the fifth instar, larvae become voracious eaters that can defoliate plants quickly (Figure 2). In rice, this typically occurs in late June and early July. The last stage lasts six days, and during this time the larvae eat the most. Usually, growers and PCAs don’t notice the damage and worms in the field until they have reached the fifth instar.

After the sixth instar the larvae pupate. In other crops, larvae drop to the soil, hide and pupate. In rice, larvae find hiding spots between tillers above the water

and pupate there (Figure 3). Some of the pupae may drop to the water and drown, but some likely survive.

Armyworm numbers climb up again during rice heading. There is so much foliage at this point that armyworm foliar feeding is not an issue. However, worms can feed on the panicles.

Typically, larvae will chew on green panicle branches, causing blanking of the kernels on that branch (Figure 4, see page 20). In some cases, panicle injury can be severe.

Monitoring One of the factors that make armyworm outbreaks a challenge to manage is that most of the time, defoliation is not noticeable until the worms are large.

Large worms feed quickly, eat large amounts of foliage, and are difficult to control with any insecticide.

Figure 2. Armyworms go through six instars during their development. The blue bars represent the duration, in days, of each instar. The red line represents how much foliage they can eat during each instar. For reference, 200 cm2 is equivalent to a third of a 8x11 inch paper sheet.

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January/February 2019

Currently, the best guideline we have is to rely on percent defoliation or panicle injury. Once the defoliation reaches close to 25 percent of the foliage, a treatment is recommended. If 10 percent of panicles show armyworm injury, a treatment is recommended. In order to time the treatments properly, growers and PCAs have to be “on top” of the field. I have heard many stories of fields that looked fine before the weekend or vacation, only to be found severely defoliated after only a few days.

Pheromone Trapping I started monitoring the flight of armyworm moths in 2016 using pheromone traps. Monitoring moths does not predict if armyworms will be a problem in a particular field, but it lets us know when the peak of armyworm activity is happening, and therefore when we should expect armyworms in the field and step up the monitoring. Models that predict armyworm development based on temperature are available, and used together with moth flight monitoring, can help in estimating when larvae should reach the fifth instar in the field.

In 2016, seven sites were monitored with pheromone traps. In 2017, 16 sites were monitored and the numbers e-mailed weekly to growers and PCAs.

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On average, the number of moths trapped per day at the peak of the early infestation was similar in 2017 and 2018 (Figure 5, see page 20). However, the peak in 2017 was 10 days earlier than in 2018. It is possible that earlier infestations resulted in more injury because of defoliation of smaller plants.

Additionally, 2017 was a late planted year because of late spring rains, meaning the crop was delayed. During heading, peak moth flight was much lower in 2017 than in 2018. In both years, panicle injury was not as common as foliage injury and rarely a problem.

In general, traps in areas where a diversity of crops are grown had higher number of moths than areas where rice is the dominant crop. This is probably because armyworms are poliphagous, with other crops providing habitat and perhaps overwintering sites. Foliage treatments went out in locations where traps had peak catches of over 20 moths per trap per day; however, in some cases, higher catches did not result in worm populations that needed a treatment.

Insecticides As mentioned before, pyrethroids do not do a good job controlling armyworms in rice. Grower and PCAs’ field experiences during the outbreak years confirm this.

This year, field trials also confirmed these observations. Intrepid does a good job and affects worms quickly. Dimilin (diflubenzuron), another insect growth

Continued on Page 20

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Figure 5. Average number of moths trapped in 16 rice fields across the Sacramento Valley during 2018. This year, the first peak was similar to 2017, but it happened 10 days later.

Even though a second peak was detected in mid August, injury to panicles was not widespread.

Continued from Page 19 regulator, also controls armyworm.

However, the pre-harvest interval is 80 days, allowing for its use only during the late June, early July infestation. Since this is the time when armyworms can be a critical problem, Dimilin can be a viable alternative.

Conversations with growers and PCAs revealed an interesting trend. Since Intrepid was available early in 2018, before infestations started, growers and PCAs were more willing to scout their fields and wait to see if populations reached damaging levels. They knew that if they needed to treat, they could used Intrepid and achieve good control.

Before 2018, a preventive approach was being tried by some, using insecticides before armyworms reached treatment levels, with the hope of catching them small and therefore improving control. In many cases, this resulted in more than one insecticide application targeting armyworms.

Effect on Yield

Figure 4. Armyworm can feed on the rachis of panicle branches, causing blanking in those branches.

20 Progressive Crop Consultant

Research has shown that armyworms can reduce yield by defoliating rice or blanking kernels when feeding on panicles. A survey conducted early this year documented that average yield loses due to armyworm, after using an insecticide, ranged from 1.25 to 8 percent. In 2015, growers sprayed on

January/February 2019

average two times to try to control armyworms. Treatments reported consisted mostly of pyrethroids and/ or carbaryl. Yield losses averaged from 4 to 12 percent, but losses as high as 24 percent were reported. In 2016 and 2017 survey respondents reported higher yield losses due to armyworm infestations when they used pyrethroids than when using methoxyfenozide, indicating better armyworm control with methoxyfenozide. Yield losses from methoxyfenozide treated fields were 29 to 64 percent lower than from pyrethroid treated fields.

Concluding Remarks It is impossible to predict how the 2019 armyworm season will be. Hopefully, Intrepid will be available for use, but that is not a given. While Dimilin is a good option, remember the pre-harvest interval limitation. The armyworm trapping network will continue next year, so that growers and PCAs can increase their monitoring when moth populations start increasing and large larvae are predicted. The rice industry will continue to work to ensure control tools are available to growers and PCAs on a timely manner.

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

JANUARY/FEBRUARY 2019

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

In This Issue 22 Habitat Diversification for Pest

Management in Vineyards—More Complicated Than It Seems

28 Improving Grape Coloration and Ripening Using the Plant Hormone Ethylene

34 The Impacts of Smoke to Vineyards

38 Field Evaluation of Seven Rootstocks Under Saline Condition

January/February 2019

www.progressivecrop.com

21

VINEYARD REVIEW

Habitat Diversification for Pest Management in Vineyards— More Complicated Than It Seems By: Houston Wilson | Asst. Cooperative Extension Specialist Kearney Agricultural Research and Extension Center Dept. Entomology, UC Riverside Ammi majus blooming in a Sonoma County vineyard.

All photos courtesy of Houston Wilson.

C

Vineyard Habitat Diversification

over crops, hedgerows and other‌ on-farm habitat plantings can potentially attract and support beneficial insects that can then potentially increase biological control of pests—the key word here being potentially. The diversity and abundance of beneficial insects that can be found on a wide variety of non-crop plants, many of them flowering, has been very well documented over the past several decades. These data have subsequently been used to advocate for the establishment of on-farm habitat plantings, with the assumption that adding in non-crop plants that attract beneficials will (1) lead to more beneficial insects on your farm, (2) those beneficials will go on to attack the key pests that you’re concerned about and (3) they will do so in a manner that lowers pest populations below economic thresholds.

This logic is embodied in a number of public and private programs as well as publications that promote on-farm habitat diversification. While this logic is not entirely off-base, the development of specific on-farm habitat strategies that can reliably and economically control arthropod pests in agriculture has

22 Progressive Crop Consultant

remained fairly limited. This is primarily because such practices are very ecologically specific and must be tailored to the target pest and its key natural enemies, as well as the agronomic and economic requirements of the cropping system itself. As such, habitat diversification practices that work for a specific pest in a specific crop are not typically transferable to other crop-pest systems.

Moreover, practices that may work for a given crop-pest system may not be readily transferable to the same croppest combination in another region or climate. This is not to say that on-farm habitat plantings have no potential, but rather that the development of practices that can produce consistent and economically relevant outcomes require research and development on a pest-bypest and crop-by-crop basis.

Leafhoppers and Anagrus Parasitoids in California Vineyards Leafhopper pests in California vineyards include the Western grape leafhopper (Erythroneura elegantula), which is native to the state, along with two invasive species that arrived in the 1980s, the variegated leafhopper (E. variabilis) and Virginia creeper leafhopper (E. ziczac). These closely related leafhopper

January/February 2019

species all feed on grape leaves, which can reduce vine productivity, crop yield/quality, and the adults can be a nuisance at harvest. These leafhoppers are primarily controlled by a suite of parasitoids that attack their eggs, this includes Anagrus erythroneurae, A. daanei and A. tretiakovae. These Anagrus parasitoids are unique in that they seasonally move between vineyards and natural areas, such as riparian and oak woodland habitats.

During the growing season, Anagrus parasitoids will regularly attack and reproduce on the eggs of Erythroneura leafhoppers in vineyards, but when vines senesce in the fall these leafhoppers enter a reproductive diapause and overwinter as adults in and around the vineyard, typically taking shelter in leaf litter or nearby vegetation. In the absence of Erythroneura eggs, the Anagrus parasitoids must seek out an alternate leafhopper species that continues to produce eggs over the winter, and these alternate hosts are typically located on plants outside of vineyards. When grape vines begin to develop again in the spring, the Erythroneura leafhoppers move onto the vines where they begin to feed and soon after start to lay eggs into the new leaf tissue. It is at this point that

Continued on Page 24

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VINEYARD REVIEW Continued from Page 22 the Anagrus parasitoids will leave their alternate hosts and then move back into the vineyard and resume attacking the new Erythroneura leafhopper eggs on grape leaves.

Overwintering Habitat for Leafhopper Parasitoids

is this plant abundant in the landscape, it’s drought tolerant, grows in very disturbed conditions, harbors Anagrus parasitoids year-round, and is a California native plant. Thus, in combination blackberry and coyote brush are likely responsible for supporting regional populations of these Anagrus parasitoids near vineyards.

crop but this effect was actually due to changes in vine vigor—competition from the cover crop led to reduced petiole nitrate levels which had a negative impact on leafhoppers. Additional studies have demonstrated that leafhoppers prefer more vigorous vines as well as vines with greater levels of irrigation (Daane and Williams 2003).

Summer Cover Crops

Another series of experiments explored the use of summer flowering cover crops in North Coast vineyards. One set of trials evaluated spring-sown species that required supplemental irrigation, this included buckwheat (Fagopyrum esculentum), sweet alyssum (Lobularia maritima), and sunflower (Helianthus annus) (Nicholls et al. 2000). Another set of trials used fall-sown species that relied on winter rains alone, these species were purple tansy (Phacelia tanacetifolia), bishop’s flower (Ammi majus) and wild carrot (Daucus carota) (Wilson et al. 2017). In both of these studies, the flowering cover crops attracted a lot of beneficial insects but this never translated to increased biological control of leafhoppers in the vine canopy itself.

Previous University of California (UC) Cover crops are incredibly useful for research demonstrated that blackberry (Rubus spp.) and French prunes (Prunus soil quality maintenance, as they can contribute to erosion control, improved domestica) were the primary plants that water penetration, reduced compaction, harbored the alternate insect hosts that and restoration of soil fertility—but can the Anagrus utilized during the winter they also contribute to biological con(Doutt and Nakata 1965, Kido et al. trol of pests? In California, the use of 1984, Wilson et al. 1989). Follow-up studies demonstrated that Anagrus populations were higher and arrived earlier in vineyards that Anagrus daanei parasitizes a leafhopper egg were closer to riparian areas where blackberry was abundant (Doutt et al. 1966, Doutt and Nakata 1973). Unfortunately, efforts to establish blackberry plantings in vineyards outside of riparian areas largely failed and any further desire to propagate this plant near vineyards was snuffed out when it was revealed that blackberry was a reservoir for Xyllela fastidiosa, the bacterium that causes Pierce’s Disease as well as a host plant for glassy-wing sharpshooters (Homalodisca vitripennis), which can transmit this pathogen to grape vines. That leaves cover crops to attract beneficial insects to increase biological control of vineus with the French prunes, which of yard leafhoppers was first explored in course aren’t naturally occurring in the the 1990s by various UC researchers. landscape like blackberry and thus provide a relatively limited overwintering One series of trials evaluated fall-sown resource for the Anagrus parasitoids. legume/grass cover crop blends that While some growers have attempted to consisted of vetch (Vicia spp.), oats establish French prunes in and around (Avena spp.) and/or barley (Hordeum their vineyards, these overwintering sp.) in Central Valley vineyards (Daane refugia are dwarfed by the sheer quanand Costello 1998, Roltsch et al. 1998, tity of vineyard acreage that needs to be Costello and Daane 2003, Hanna et al. colonized by these parasitoids.

2003). Rather than mow and plow these More recently, surveys conducted in the down in the spring, as is typical when they are used for soil management, the North Coast region identified a number cover crops were left in place until they of previously unknown overwintering dried out in the early summer. In some host plants utilized by the Anagrus— cases, leafhopper densities were indeed most notably coyote brush (Baccharis reduced in the presence of the cover pilularis) (Wilson et al. 2016). Not only

Finally, a study in the Lodi area assessed the influence of a perennial native grass cover crop that consisted of blue wildrye (Elymus glaucus), meadow barley (Hordeum brachyantherum) and California brome (Bromus carinatus) (Daane et al. 2018).

Leafhopper populations were reduced in the presence of the cover crop but again the effect was due to changes in vine vigor—the cover crops reduced petiole nitrate levels which led to lower leafhopper densities. Furthermore, the deep-rooted perennial grasses also improved water infiltration which led to increased soil moisture and reduced vine water stress, which can also lead to lower leafhopper densities.

Taken as a whole, these studies demonstrate that the effect of cover crops on

Continued on Page 26 24 Progressive Crop Consultant

January/February 2019

NORTH VALLEY

Nut Conference Jan 30, 2019 SAVE THE DATE!

NEW LOCATION! GLENN COUNTY FAIRGROUNDS 221 E Yolo St, Orland, CA 95963

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Laws and Regulations Update Marcie Skelton, Glenn County Agricultural Commissioner

8:30am

Mite Control in Almonds David Haviland, UCCE IPM Advisor, Kern County

9:00am

Walnut Husk Fly Management Dr. Bob VanSteenwyk, Entomology Specialist Emeritus, UC Berkeley

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Preventing and Managing Walnut Crown Gall Dr. Dan Kleupfel, Plant Pathologist, USDA ARS, Davis

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Break; Trade Show Open

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Butte-Yuba-Sutter Water Quality Coalition Update Rachel Castanon, Program Coordinator, Butte County Farm Bureau

11:00am

Navel Orangeworm Research Updates Dr. Emily Symmes, UCCE IPM Advisor, Sacramento Valley

11:30

Early Season Irrigation: Do We Know When to Start?

Dr. Ken Shackel, Department of Plant Sciences, UC Davis

12:00pm

Lunch

1:00pm

Botryosphaeria and Band Canker update Dr. Themis Michailides, UCCE Plant Pathology Specialist, Kearney Agricultural Research and Education Center

1:30pm

Weed Management in Young Orchards Dr. Brad Hanson, UCCE Weed Specialist, UC Davis

2:00pm

Adjourn

In Conjunction with the UCCE Butte/Glenn/Tehama Counties Almond & Walnut Day

January/February 2019

www.progressivecrop.com

25

VINEYARD REVIEW Continued from Page 24 leafhoppers is primarily due to changes in vine vigor rather than any increase in biological control. While cover crops are in some cases used to moderate vine vigor, in many situations this can be achieved much more economically by adjusting irrigation regimes, soil amendments and pruning practices.

Landscape Diversity Given the importance of overwintering habitat to Anagrus parasitoids and the dismal performance of cover crops, researchers have more recently started to focus on the relationship between landscape diversity and biological control of vineyard leafhoppers. Landscape diversity can be defined in many nuanced ways, but generally refers to the quantity of natural habitat that falls within a larger radius surrounding the vineyard (for example, the total area of all riparian habitat within two miles of a vineyard).

Recent studies in the North Coast evaluated biological control of leafhoppers in multiple vineyards located in contrasting low and high diversity landscapes.

Vineyards in high diversity landscapes, with lots of natural habitat within one third mile of the vineyard, tended to have more Anagrus parasitoids earlier in the season, which then led to increased leafhopper parasitism rates and lower late-season leafhopper densities (Wilson

et al. 2015a, Wilson et al. 2017). While not all natural habitats necessarily harbor Anagrus overwintering habitat (i.e. coyotebrush and blackberry), these plants are more likely to be present in a high diversity landscape given that there is more natural habitat overall.

In a related study, biological control of leafhoppers was evaluated in vineyard blocks that were close to (30 feet) and far away from (500 feet) riparian habitats. Since these areas harbor a lot of blackberry, it could be that Anagrus populations and leafhopper parasitism is greater on vines closer to the riparian area. Leafhopper densities were indeed lower on vines closer to the riparian areas, but this was once again due to changes in vine status rather than increased parasitism (Wilson et al.

2015b). Similar to the cover crop studies, vines that were close to the riparian area tended to be less vigorous, most likely due to changes in microclimate and soil conditions associated with vine shading from the tall riparian vegetation and compacted dirt roads along the riparian border of vineyard blocks.

Conclusion As you can see, almost all the vineyard habitat research to date has focused on leafhoppers, whereas growers are of course managing for a much wider

range of pests, including mealybugs/ ants, sharpshooters, mites and thrips.

Impacts of habitat diversification on these other pest species has simply not taken place yet. Very early research on Willamette mites (Eotetranychus willamettei) did find that Johnson grass (Sorghum halepense) could harbor alternate prey that supported Western predatory mites (Galendromus occidentalis) and led to lower Willamette mite densities on vines—but no economic program was ever developed for this pest. Beyond that, not much else is known about how habitat diversification influences other key grape pests.

Research on habitat diversification to control vineyard leafhoppers has demonstrated the importance of overwintering habitat for Anagrus parasitoids and moderation of vine vigor. Alternately, cover crops do not appear to be a viable way of increasing biological control of leafhoppers. While their ability to reduce vine vigor can translate to some changes in leafhopper populations, there are other ways to moderate vigor that are more practical and cost-effective. Furthermore, vigor moderation in the absence of Anagrus overwintering habitat may still result in increased leafhopper densities, as it is a combination of early-season parasitism and moderate vine vigor that regulates leafhopper populations.

Phacelia tanacetifolia blooming in a Napa County vineyard.

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January/February 2019

VINEYARD REVIEW

A common legume/grass winter cover crop blend in a Napa County vineyard.

Even with all the emphasis on leafhoppers, habitat diversification strategies that can produce consistent results for this pest remain elusive, and many key questions remain. How much Anagrus overwintering habitat is adequate? How far can these parasitoids migrate into vineyards? Does overwintering habitat need to be directly adjacent to the vineyard? And so on…

Doutt, R. L., and J. Nakata. 1965.

Overwintering refuge of Anagrus epos (Hymenoptera: Mymaridae). J. Econ.

Entomol. 58: 586-586.

In summary, specific habitat diversification practices that can produce consistent and economically relevant impacts on vineyards pests remain elusive. While in theory this is not entirely impossible to achieve, the reality is that a lot of additional research is certainly still needed at this point in time.

Doutt, R. L., J. Nakata, and F. Skinner.

1966. Dispersal of grape leafhopper parasites from a blackberry refuge.

Calif. Agric. 20: 14-15.

References Costello, M. J., and K. M. Daane. 2003.

Spider and leafhopper (Erythroneura spp.) response to vineyard ground cover. Environ. Entomol. 32: 1085-1098.

Daane, K. M., and M. J. Costello. 1998.

Can cover crops reduce leafhopper abundance in vineyards? Calif. Agric.

52: 27-33.

Daane, K. M., and L. E. Williams.

2003. Manipulating vineyard irrigation amounts to reduce insect pest damage.

Ecol. Appl. 13: 1650-1666.

Daane, K. M., B. N. Hogg, H. Wilson, and G. Y. Yokota. 2018. Native grass ground covers provide multiple ecosystem services in Californian vineyards. J. Appl. Ecol.

Doutt, R. L., and J. Nakata. 1973. The Rubus leafhopper and its egg parasitoid: an endemic biotic system useful in grape pest management. Environ.

Entomol. 2: 381-386.

Hanna, R., F. G. Zalom, and W. J. Roltsch. 2003. Relative impact of spider predation and cover crop on population dynamics of Erythroneura variabilis in a raisin grape vineyard. Entomol. Exp. Appl. 107: 177-191.

Kido, H., D. Flaherty, D. Bosch, and K. Valero. 1984. French prune trees as overwintering sites for the grape leafhopper egg parasite. Am. J. Enol. Vit. 35: 156-160.

Nicholls, C. I., M. P. Parrella, and M. A. Altieri. 2000. Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer cover crops.

Agric. For. Entomol. 2: 107-113.

Roltsch, W., R. Hanna, H. Shorey, M. Mayse, and F. Zalom. 1998. Spiders and Vineyard Habitat Relationships in Central California, pp. 311-338. In

C. H. Pickett and R. L. Bugg (eds.), Enhancing Biological Control: Habitat Management to Promote Natural Enemies of Agricultural Pests. University of California Press, Berkeley, California.

Wilson, H., A. F. Miles, K. M. Daane, and M. A. Altieri. 2015a. Landscape diversity and crop vigor influence biological control of the western grape leafhopper (E. elegantula Osborn) in vineyards. PLoS ONE 10: e0141752.

Wilson, H., A. F. Miles, K. M. Daane, and M. A. Altieri. 2015b. Vineyard proximity to riparian habitat influences western grape leafhopper (Erythroneura elegantula Osborn) populations. Agric., Ecosyst. Environ. 211: 43-50.

Wilson, H., A. F. Miles, K. M. Daane, and M. A. Altieri. 2016. Host plant associations of Anagrus spp. (Hymenoptera: Mymaridae) and Erythroneura elegantula (Hemiptera: Cicadellidae) in northern California. Environ. Entomol.

45: 602–615.

Wilson, H., A. F. Miles, K. M. Daane, and M. A. Altieri. 2017. Landscape diversity and crop vigor outweigh influence of local diversification on biological control of a vineyard pest.

Ecosphere 8.

Wilson, L. T., C. H. Pickett, D. Flaherty, and T. Bates. 1989. French prune trees: refuge for grape leafhopper parasite. Calif. Agric. 43: 7-8.Laborupt Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

January/February 2019

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VINEYARD REVIEW

All photos courtesy of Cecilia Parsons.

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Improving Grape Coloration and Ripening Using the Plant Hormone Ethylene By: Cecilia Parsons |Associate Editor

28 Progressive Crop Consultant

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VINEYARD REVIEW

V

alue of red table grape varieties is dependent upon berry color. Achieving the desired red hues at harvest is the goal for growers seeking premium prices for their crop.

Numerous Factors Affect Coloration

University of California Cooperative Extension viticulture advisor Ashraf El-Kereamy in Kern County said there are many factors that can affect coloration and are used on red seedless table grape varieties.

Red table grape varieties such as Crimson Seedless and Flame Seedless, under certain conditions, may require help in coloring while some new varieties of red table grapes develop color without assistance. Flame and Crimson are popular varieties, El-Kereamy said, and still in favor with growers due to their harvesting time—the varieties need a little more attention to bring out the color.

The red, purple and black colors in table grapes are due to the plant pigments, anthocyanins. These pigments are derived from the basic products of photosynthesis and are converted by enzymes to flavonoids and coupled to sugar molecules by other enzymes yield the final anthocyanin pigments.

Deficit Irrigation El-Kereamy said deficit irrigation at the proper time can assist in bringing on berry color.

A study funded by the California Table Grape Commission found total berry skin anthocyanin contents and individual pigment compounds increased with deficit irrigation at two experimental sites in Coachella and San Joaquin valleys.

Deficit irrigation induced expression of several genes involved in anthocyanin accumulation.

Other Cultural Practices There are some other cultural practices growers can use to improve berry color. Large, dense canopies that prevent light from reaching the developing fruit can stall berry coloration. The cultural practice of shoot and leaf removal to allow more light to reach the fruit can help with coloring.

Vine nutrition and rootstock selection also effect canopy size, contributing to color determination.

Plastic covers on grapevines are used to protect them from rain events and extend harvest. Transparent or green plastic

Continued on Page 30

Disruption in any of the enzyme mechanisms by genetic, environmental or cultural practices could alter anthocyanin production and affect berry coloration.

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Lack of Color at Harvest What causes disruption and subsequent lack of grape color at harvest is complicated. El-Kereamy said red coloration is under hormonal control that is influenced by several factors. Some can contribute to optimal berry coloration, other factors, which may be out of the control of the grower can contribute to lack of color.

Use of nutrients or supplements as a part of a vineyard management plan can effect color due to composition or mode of action if they are applied at the critical stage for anthocyanin induction and development.

Nitrogen and Potassium Nitrogen (N) and potassium can influence grape color and must be managed. Moderate nitrogen supply before bloom and moderate potassium during veraison can help in optimizing anthocyanins. However, excessive N can have a negative effect on color. Fruit ripening and coloration can be delayed by too much applied nitrogen. Determining the optimal amount of N for vine growth without over application is essential. Foliar potassium application can boost grape anthocyanin accumulation and coloration, but it can reduce berry size in some cases.

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VINEYARD REVIEW Continued from Page 29 covers are used with red varieties to let in light and assist with coloration.

Red table grapes grown on sandier soils will color more than the same varieties grown on heavier soils, El-Kereamy said.

Temperatures have a significant effect on anthocyanin biosynthesis and accumulation. Anthocyanin biosynthesis increases with temperature until the maximum of 95 degrees F. Temperatures above 95 reduces anthocyanin biosynthesis and degradation is increased causing poor red coloration.

Water management and building a good early season canopy can help overcome the negative effect of high temperatures.

Grape anthocyanin biosynthesis and accumulation are best when nighttime temperatures are below 73 degrees F. This presents a problem for growers in the Coachella Valley and some southern parts of the San Joaquin Valley.

Ethylene El-Kereamy’s studies on anthocyanin in grapes demonstrated that grapes produce a small amount of the ethylene at veraison which induces expression of genes and starts anthocyanin accumulation in red grapes. Internal ethylene concentration in grapes affects anthocyanin and color. An external source of ethylene releasing compounds applied to grapes causes an increase in internal ethylene and also activates anthocyanin. According to El-Kereamy the high temperatures inhibit the coloration due to hormonal changes that act against activation of anthocyanin biosynthesis genes.

Abscisic acid Another plant hormone known for its role in anthocyanin biosynthesis is abscisic acid or ABA. An increase in the ABA content of berries coincides with veraison and red color initiation in grapes. The application of ABA at

Continued on Page 32 30 Progressive Crop Consultant

January/February 2019

RE

L IA

ERED MATE ST R GI

For Use In Organic Agriculture

Washington State Dept. of Agriculture

31

VINEYARD REVIEW Continued from Page 30 veraison also stimulates anthocyanin biosynthesis. Commercial products that contain an ethylene releasing compound or ABA as the active ingredient are commonly used in vineyards to improve color. El-Kereamy said that attention should be given to varietal differences, timing of the application and other cultural practices during the application. Practices or conditions that suppress the internal concentration of ethylene will result in poor coloration.

It does not have an effect on berry size, El-Kereamy said. ProTone is the commercial product with ABA and it can be mixed with Ethephon and used as a spray application for color. Both of these products are plant growth regulators. Other plant growth regulators gibberellic acid and cytokinins are known for their effects on ethylene and ABA and have a negative role in coloring grapes.

Ethephon is listed as a pesticide, El-Kereamy said, and must be used according to the label. There is a re-entry period and Ethephon Pre-harvest interval period. That requirement makes timing an application tricky. The spray is applied at color break stage, not beThe commercial product Ethephon is standard practice for fore. You want to be ‘pushing the color,” El-Kereamy said. Quality table grape growers who need help with color. Ethephon of the fruit can be affected if applied too close to harvest. is a plant growth regulator used to promote fruit ripening, abscission, flower induction, and other responses. It Comments about this article? We want to hear from you. is applied as a tank spray. It moves inside the berries and releases ethylene and activates anthocyanins biosynthesis. Feel free to email us at article@jcsmarketinginc.com

32 Progressive Crop Consultant

January/February 2019

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VINEYARD REVIEW

View of the Ranch Fire on the first day where many vineyards were damaged. All photos courtesy of Glenn McGourty.

The Impacts of Smoke to Vineyards By: Glenn McGourty | Winegrower and Plant Science Advisor, UCCE Mendocino and Lake Counties 34 Progressive Crop Consultant

January/February 2019

VINEYARD REVIEW Smoke Damage in Vineyards

C

alifornia and the Pacific Northwest have endured one of the worst fire seasons on record in 2018. The huge areas burned, loss of buildings and life have been horrific. A combination of tinder dry vegetation, a prolonged dry season and lack of rain that would normally be expected in autumn have created “perfect storm” conditions that have scorched over a million acres, left communities completely destroyed, numerous lives lost and displaced thousands of people.

Impacts are being felt far beyond the fire zone as smoke creates the most unhealthy air quality conditions across the state ever measured.

The smoke from fires can also greatly affect wine grape and wine quality in close proximity to burn areas (which seems trivial compared to the loss of property and life).

Direct Impacts of Fire on Vineyards Forest and brush fires have the potential to harm vineyards, wine grapes and

wine in several different ways. The most damaging event is when vineyards actually catch fire and burn. This happens mostly to small vineyards surrounded by brush and forest. If you are concerned about fires in this situation, it is a good idea to minimize the vegetation on the vineyard floor either by cultivating the vineyard so that the soil is bare, or mowing very close to the ground early in the growing season to reduce any dry material. Removing brush, mowing and managing the landscape to risk damaging fires close to the vineyard is advisable. Cal Fire has recommendations to make your area reasonably fire safe that centers on eliminating low growing brush and vegetation to prevent the fire from climbing into the crown of trees if you live in a forested area. Increasingly, control burns during low danger fire conditions are being discussed and implemented, but for now it is just beginning to be used as a fire prevention tool.

The next most devastating problem is when the edges of the vineyard either burn or are exposed to superheated air from the flames that essentially

cook the vascular system of the vines and wilt the fruit. Wine grapes are not adapted to fire having originated from riparian areas (unlike so many of our California natives, which depend on fire for propagation and renewal). The bark is very thin, and provides no insulation from heat. The overall mass of the wood in the vine is relatively small, so even internal cells found in the woody xylem are likely to die from heated sap that might actually boil when exposed to hot air accompanying a fire. Vines damaged by fire or heat rarely recover—if the vines are either charred or the leaves are completely desiccated, odds are the vines have been severely damaged and are not going to return to healthy growth. You may see some buds push, but often the vascular system of the vines is seriously compromised in the woody portions, and there is likely to be irreversible damage. Check the vines by cutting into the cambium, and inspect the health of the xylem and phloem.

Using a hand lens or microscope, you can detect damage by obvious discoloration (grey or brown instead of green) and wilting in the cambium.

Cut into lateral buds to see if they are still green and viable. You can wait and

Continued on Page 36

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VINEYARD REVIEW

A damaged vineyard from the Valley Fire in Lake County. The vineyard actually burned and melted the drip line, but one month later, the vines are resprouting.

Continued from Page 35 see how the vines push the following growing season, and retrain vines if needed. If damage appears minimal, you can prune during the following winter and see how the vines push the following growing season, retraining vines if required by removing damaged parts.

Smoke and Vineyards During a forest fire, large volumes of smoke are produced that can travel many miles and inundate valleys, especially at night when cold air settles into low lying areas. Smoke contains visible airborne byproducts of combustion, made up of water vapor, particulates (including tar, ash, carbon and partially burnt fuel fragments), and many gases (CO2, CO, N2O, S2O, NH3, CH4, NOx, ozone, and other nonmethane hydrocarbons.) Smoke makes up about 1.5-2 percent of the material that has burned.

Smoke flavors in wine result from smoke following the combustion of lignin in wood, resulting in phenolic compounds released into the air. Wood is composed of about 20-30 percent lignin, which gives wood strength and lines water conductive tissues. Guaiacol 36 Progressive Crop Consultant

and 4-methylguaiacol are compounds associated with smoke. Both are chemicals that we can taste in smoked food flavoring. These compounds can be found in oak barrels during the toasting process. On their own, these two chemicals have flavor profiles described as “bacon, burnt bacon, smoky, leather, spicy, phenolic, and spicy, salami, and smoked salmon” which doesn’t sound so bad (isn’t everything better with bacon!) The problem is that there are more than 70 other compounds in forest fire smoke known as glycosides that produce very undesirable flavors and odors that are described as, “like licking an ash tray, burnt garbage, a burnt potato, a campfire that has been drenched with water.”

When grape vines are exposed to fresh smoke, the phenolic compounds concentrate in the skins of the fruit, more than in the pulp and the juice, and also in the leaves. They conjugate with sugars, and are released during fermentation. Both guaiacol and 4-methylguaiacol can be detected in the fruit by gas chromatography, so it is possible to sample fruit before harvest to make picking decisions. While these compounds aren’t necessarily the sole cause of smoke flavors, they are highly

January/February 2019

correlated to many other compounds (the glycosides) that cause the wine to taste bad. Glycosides are not easy to test for as a group, and at this time, no commercial lab in the US is able to test for these smoke compounds likely to be in the fruit and wine. There are protocols in place to test fruit before picking, and anything found to have more than 0.5 parts per billion (ppb) guaiacol is considered likely to have smoke flavor problems. Sampling whole berries is recommended, as the skins of the berries have the highest concentration of guaiacol and 4-methylguaiacol compared to juice.

Whole berry test results indicate that levels between 0.5 ppb to 2.0 ppb are moderately affected, and will require special handling and treatment in the winery. Levels above that are almost certainly going to have major problems with smoke flavors, and may be cause for rejection by the winery, especially for red fruit. During fermentation, the glycosides are released when yeasts metabolize the sugars leaving the smoke compounds behind. This may increase their concentration 6 to 10 times.

No doubt the intensity and duration of smoke plays a factor. We noted locally that not all vineyards were equally affected, and why this occurred, and

VINEYARD REVIEW the pattern of smoke affected vineyards remains a bit of a mystery.

Wine grapes are most likely to be affected if your vineyard is close to a large fire and is inundated with intense smoke. Many of the smoke flavor compounds are volatile, and are most likely to affect fruit for a relatively short period of time, as little as two hours after combustion. However, these compounds move readily with wind, and can travel some distance from the source of the fire, as much as four or five miles. Australian researchers have shown that there is little guaiacol or 4-methyl guaiacol in ash that might settle on your fruit. Researchers were unable to remove guaiacol from the fruit by washing or rinsing with any solvents. However, removing the leaves from around the fruit, high volume and high pressure washing with water before harvest did seem to help reduce smoke flavors in the wine. By contrast, if you are in a confined valley, and smoke settles as an inversion layer for a day or two from a distant fire, it is less likely that you will have issues with off flavored fruit. At that point, the smoke is composed mostly of very small particulate matter, less than 10 microns in size.

Varieties also differ as to how much smoke that they will absorb and the extent of off flavors that result.

Experiences in California, Canada and Australia suggest that the most affected varieties in decreasing order are Sangiovese> Pinot noir> Cabernet sauvignon> Chardonnay > Sauvignon blanc> Syrah >Merlot> Petite Sirah.

Conclusion Off flavors to wine grapes and wine are part of the collateral damage from large wild fires. Research is underway to better understand the dynamics of how smoke flavors are acquired by fruit.

Maybe even more important is research into techniques that can fix off flavors caused by smoke when the fruit is made into wine. A certainty is that in the changing climates of our wine growing regions, more fire and smoke will occur.

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

A month after these vines were burned in the Valley Fire in Lake County and they are most likely dead.

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VINEYARD REVIEW

All photos courtesy of George Zhuang.

Field Evaluation of Seven Rootstocks Under Saline Condition By: George Zhuang and Matthew Fidelibus | University of California Cooperative Extension, Fresno County | Department of Viticulture and Enology, University of California (UC) Davis

T

Background

he San Joaquin Valley (SJV including crush district 11, 12, 13, and 14) contains 40 percent of the wine grape acreage and crushes 70 percent of California wine grapes (California Grape Acreage Report and Grape Crush Report 2016). Due to the pest threats from nematodes and phylloxera, grapes planted in the SJV are usually grafted on nematodes or phylloxera resistant or tolerant rootstocks. The commercial standard rootstocks for the SJV winegrowers are Freedom and 1103P. Freedom rootstock has high root knot nematode and medium phylloxera resistance. High scion capacity makes it a popular rootstock for the high per acre yield in the SJV. However, vines on Freedom tend to accumulate high levels of potassium (K) in their fruit, which can in turn lead to undesirably high juice pH. Further, it has relatively low salt tolerance compared to other rootstocks, and is thus not the best choice for some SJV vineyards (Christensen 2003).

1103P rootstock has both high phylloxera and root knot nematode resistance with the medium salt tolerance. These characteristics make it good rootstock for sites with moderately saline soil and irrigation water (Christensen 2003).

38 Progressive Crop Consultant

Other common rootstocks have been used in SJV vineyards are Ramsey (Salt Creek), 140Ruggeri, and Schwarzmann.

Ramsey has high phylloxera and root knot nematode resistance and high salt tolerance. However, Ramsey is difficult to propagate (Christensen 2003). 140Ru has high phylloxera resistance and high salt tolerance with low root knot nematode resistance and low K uptake (Christensen 2003). As a comparison, Schwarzmann has high phylloxera and medium root knot nematode resistance with medium salt tolerance (Christensen 2003).

as Freedom and 1103P rootstocks with adequate harvest juice Brix (personal communication from Dr. Andy Walker). Grapevines generally show reduced vigor and yield when the soil electrical conductivity (EC) is above 2.5 dS/m (Christensen 2000). Specific salts, like sodium (Na), chloride (Cl) and boron (B), causing toxicity of grapevines. High Na (>690 ppm), Cl (>350 ppm), and B (>1 ppm) levels in soil start to cause the significant toxicity and ultimate damage on the grapevines (Figure 1, see page 40) (Christensen 2000).

GRN rootstocks have been bred by Dr. Andy Walker in UC Davis and were under field evaluation at different locations around California to quantify the nematode resistance and viticultural performance of scion variety. There are currently five GRN rootstocks: GRN-1, GRN-2, GRN-3, GRN-4, and GRN-5. Previous field trials of GRN rootstocks have focused on nematode resistance and viticultural performance of scion variety. However, there is a lack of information on their salt tolerance under the field condition. The preliminary research results from a field trial in the northern SJV showed that the GRN-1, -2 and -3 yielded similarly

Although it has been widely recognized that high soil salinity can significantly impact the vine growth and per acre yield, there is limited information on fruit quality and wine chemistry as well as wine sensory traits. Loryn, et al. 2014 indicates that NaCl accumulated in berries can have a negative impact on juice and wine sensory characteristics with the detection threshold value of NaCl in wine as low as 0.31 g/L in Australia.

January/February 2019

Pinot gris on seven rootstocks were compared in a commercial vineyard

Continued on Page 40

39

VINEYARD REVIEW Continued from Page 38 with saline water and soil near Cantua Creek in Fresno County during 2017 and 2018. Rootstocks were planted in 2015 with field grafting during the dormant season. Data collection started with the first harvest season of 2017 and continued in 2018. Five vines were flagged in the field and labeled as one data point. As for each data point, leaf nutrients, yield components and juice chemistry were measured for both years as well as pruning weight during the dormant season. Three data points per rootstock were randomly selected and results were presented as the average.

The salt/drought tolerance information of selected rootstocks included in this study was described in the Table 1.

Figure 1. Boron toxicity on Pinot gris with leaf margin necrosis.

Results Petioles and leaf blades were sampled at veraison in 2017, and bloom, veraison and harvest in 2018. Large variation has been observed for petiole NO3-N across two years (Figure 2, see page 41), and petiole NO3-N can be affected by various factors, e.g., fertilizer application, timing of sample collection, and weather on the particular day of collection. Therefore it is difficult to draw the conclusion on

one year’s data. However, the difference of petiole NO3-N by rootstocks was still consistent with higher petiole NO3-N from 140Ru and Ramsey in both 2017 and 2018. High petiole NO3-N is usually associated with high shoot vigor. Results of petiole K were similar to the results of petiole NO3-N. Petiole Cl was tested in 2018 only and 1103P, 140Ru and Schwarzmann showed lower Cl (Figure 3, see page 41). Lower

Table 1. Salt/drought info included of rootstocks included Table 1. Salt/drought tolerance tolerance info of rootstocks in this study.

Rootstock 1616C Schwarzmann 140Ruggeri Ramsey (Salt Creek) 1103Paulsen

Parentage V. longii V. riparia V. berlandieri

in this study.

Drought tolerance1

Salt tolerance

V. riparia

Low

Medium

V. rupestris

Medium

Medium

High

Medium-High

Medium-High

High

Medium-high

Medium

V. rupestris

V. champinii V.berlandieri

petiole Cl is regarded as beneficial for grapevine’s growth and yield, since higher Cl reduces leaf stomatal conductance, and therefore decrease photosynthesis, yield and berry sugar accumulation. Certain rootstocks, e.g., 1103P, 140Ru, Schwarzmann and Ramsey, have been recommended as salt-tolerant rootstocks due to the lower Cl uptake (Christensen 2003; Cox, 2009). Our results were largely

V. rupestris

GRN-1

V. rupestris V. rotundifolia ‘Cowart’

?

?

GRN-2

((V. rufotomentosa x (Dog Ridge x Riparia Gloire)) x Riparia Gloire

?

?

GRN-3

((V. rufotomentosa x (Dog Ridge x Riparia Gloire)) x V. champinii c9038

?

?

GRN-4

((V. rufotomentosa x (Dog Ridge x Riparia Gloire)) x V. champinii c9038

?

?

1

drought tolerance and salt tolerance are cited from Christensen 2003.

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VINEYARD REVIEW in line with those studies. Boron was one of the targets in our study, since the experimental site has relatively high soil and water boron content (soil boron of 0.5-0.7 ppm in 2018). Less difference of petiole B was found by rootstocks (Figure 4), and currently less information was available in terms of B tolerant rootstocks.

However, 1103P and GRN3 rootstocks had relatively lower petiole B as well as blade B (data not shown), and there was an increase of petiole B from 2017 to 2018, and it might be largely due to less leaching water available from the dry winter of 2017. Similar yield was found across rootstocks at the first harvest of 2017, with the exception of 1103P. Yield was generally higher in 2018 than it in 2017 with more mature vines, however, GRN2 and GRN3 yielded the most across rootstocks (Figure 5). Higher vigor and canopy size might contribute to the higher yields.

Rootstocks did not affect Brix, pH or titratable acidity (TA), however, we did find a large variation from season to season with higher Brix and TA, lower pH in 2018 than these in 2017 (Figure 6, see page 42). Surprisingly, there was a stronger correlation between Na and pH in juice, with higher Na associated with higher pH (Figure 7, see page 42) than there was for petiole K, juice K or juice pH (Figure 8, see page 42). More data are needed to determine if Na-excluding stocks can consistently maintain lower fruit juice pH on salty sites. Boron is unique among the micronutrients because of the narrow acceptable range of soil B levels that fall between deficiency and excess (toxicity) (Christensen 2000). In our study, petiole B across rootstocks is around the critical value of 80 ppm, and good correlation has been found between petiole B and berry weight as well as the total yield (Figure 9, see page 42). This result evidently indicates petiole B exceeding critical value might result in smaller berry and ultimately, the yield loss.

2500

0.6

Veraison

2017 2018

Petiole Cl (%)

Petiole NO3-N (ppm)

2000

1500

1000

500

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1103P 140R 16-16 GRN2 GRN3 RamsSchwarz

Acknowledgment

0.2

Study in 2018 was funded through California Grape Rootstock Improvement Commission and supported by industry collaborators.

0.0 1103P 140R 16-16 GRN2 GRN3 RamsSchwarz

Rootstock

Rootstock

Figure 2. Petiole NO3-N by Figure 2. Petiole NO3-N by rootstocks (2017/2018) Figure rootstocks (2017/2018)

Figure Cl 3. by Petiole Cl by (2017) rootstocks Figure Figure 3. Petiole rootstocks (2017) 10

110

2017 2018 8

90

Yield (t/acre)

Petiole B (ppm)

Veraison

2017 2018

80

6

4

2

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50

0 1103P 140R 16-16 GRN2 GRN3 RamsSchwarz

1103P 140R 16-16 GRN2 GRN3 RamsSchwarz

Rootstock

Rootstock

Figure 4. Petiole B by rootstocks (2017/2018) Figure 4.

Figure 4. Petiole B by rootstocks

Reference California Grape Acreage Report. 2016. https://www.nass. usda.gov/Statistics_by_State/ California/Publications/Specialty_ and_Other_Releases/Grapes/ Acreage/2017/201704gabtb00.pdf California Grape Crush Report.

2016. https://www.nass.usda.gov/ Statistics_by_State/California/ Publications/Specialty_and_ Other_Releases/Grapes/Crush/ Final/2016/201603gcbtb00.pdf

70

(2017/2018)

Seven rootstocks have been compared in 2017 and 2018 for plant nutrition, yield and harvest fruit chemistry. Previously regarded salt-tolerant rootstocks, e.g., 1103P, 140Ru, Ramsey, perform as expected with lower petiole Cl content and our data was largely in line with previous results. So far, rootstocks in our study had significant impact on plant nutrition, yield and canopy size, measured as pruning weight, however, less impact on harvest fruit chemistry. Interestingly, GRN 2 and 3 rootstocks which accumulated the most petiole Cl, had the highest yields and pruning weight (data not shown), and more years’ data are needed to confirm the long-term impact. In terms of Boron, none of those rootstocks had significant impact on B uptake and higher petiole B has caused smaller berry and ultimately, yield loss in our study. This rootstock trial is still on-going and GRN 1 and GRN 4 rootstocks will be included in the following years’ study.

0.3

0.1

0

100

Veraison

2018 0.5

Summary

Figure 5. Yield (tons/acre) by(tons/acre) rootstocks (2017/2018) Figure Figure 5. Yield by rootstocks (2017/2018)

Christensen, P., Dokoozlian, N., Walker, A., and Wolpert, J. 2003.

Wine Grape Varieties in California.

University of California Agriculture

January/February 2019

Continued on Page 42 www.progressivecrop.com

41

VINEYARD REVIEW Continued from Page 41 and Natural Resources Publication 3419.

4.2

30

2017 and 2018, r=0.89

2017 2018

28

4.0

24

Juice pH

TSS (Brix)

26

22

Christensen, P. 2000. Raisin Production Manual. University of California Agriculture and Natural Resources Publication 3393.

3.8

3.6

20 18

3.4

16

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1103P 140R 16-16 GRN2 GRN3 RamsSchwarz

0

10

20

Rootstock

Figure 6. TSS (Brix) rootstocks (2017/2018) Figure Figure 6.by TSS (Brix) by rootstocks (2017/2018)

40

50

60

Figure 7. Juice pH and juice Na (2017/2018) Figure Figure 7. Juice pHcontent and juice Na content (2017/2018) 1.2

8000 2018, r=0.55

7000

Cox, C. 2009. Rootstocks as a management strategy for adverse vineyard conditions. The Grape and Wine Research and Development Corporation: Water & Vine – Managing the challenge. Fact sheet No. 14.

(The Grape and Wine Research and Development Corporation: Adelaide, Australia).

1.1

6000

Berry weight (g)

Harvest juice K (mg/L)

30

Juice Na (mg/L)

Loryn, L.C., Petrie, P.R., Hasted, A.M., Johnson, T.E., Collins, C., and Bastian, S.E.P. 2014. Evaluation of sensory thresholds and perception of sodium chloride in grape juice and wine. American journal of Enology and Viticulture. 65:1.

5000 4000 3000

1.0

0.9

0.8

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0 0.8

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1.4

1.6

1.8

2.0

2.2

50

60

70

80

90

100

Harvest petiole K (%)

Veraison petiole B (ppm)

Figure 8. Petiole K and juice K (2018) Figure Figure 8.

8. Petiole K and juice K (2018)

Figure 9. Petiole B and berry weight (2018) Figure Figure 9.

9. Petiole B and berry weight (2018)

42 Progressive Crop Consultant

January/February 2019

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

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California Citrus Network: An Online Forum to Facilitate Communication and Information Exchange Regarding California Citrus

By: Dr. Greg W. Douhan | University of California Cooperative Extension, UCCE Citrus Advisor, Tulare, CA

T

he University of California Cooperative Extension office in Tulare California is launching a new website (cacitrusnetwork.com) to facilitate exchange of information among individuals involved in citrus production in California from growers to academics. The ideology within this forum is to allow people within the field to exchange information in real time. It has been my personal observation, for example, that many pest control advisors (PCAs) have their own small network of individuals that they confide in regarding specific issues and often talk amongst themselves.

It is my belief that having an internet-based forum would allow individuals to broaden this ‘in house group’ to all individuals involved in the industry to better communicate ideas, information, and concerns regarding various aspects of citrus production. The forum site is set up to deal with the various citrus regions;

Continued on Page 46 44 Progressive Crop Consultant

January/February 2019

Figure 1. Screen shot of the main forum page on the cacitrusnetwork.com.

All photos and graphs courtesy of Greg Douhan.

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Photo 1—Shows damage is caused by Colletotrichum species—a disease called twig and shoot dieback of citrus.

Figure 2. Example posting of citrusguy1 including text and a picture of the issue he is observing in the field. Other users can then respond to this post to start a thread on the potential problem to try and solve the issue.

Continued from Page 44 San Joaquin Valley (SJV), Desert, Coastal, Southern Interior, and Sacramento Valley. The specific areas set up thus far are; Pests, Diseases, Irrigation, Fertility, Weeds, Harvesting Issues, and Postharvest Issues (Figure 1, see page 44). Two additional sections have also been set up for discussions: a general citrus area and posting dealing with all issues related to Asian Citrus Psyllid (ACP)/ Huanglongbing (HLB). Users will also be able to upload pictures taken from the field when posting a question (Figure 2).

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The utility of this forum is that a person has the ability to make an observation in the field, snap a couple of pictures of what he/she saw, and easily post this information to the forum where the citrus community at large could view and respond to start a thread on the topic. This could be done out in the field using a smart phone or tablet or from an office computer at the user’s leisure. The success of this network will rely on individuals in the citrus industry to utilize this new important tool. The site is up and running but is certainly in the beta-testing phase. Therefore, having individuals using the site and reporting any problems or making suggestions on making it better is highly desirable; this can be done by emailing or calling Dr. Greg W. Douhan who is the administrator of the forum (contact information on the website). The site has also been set up with security in mind so it will take a new user around a working day to receive an email to join because initially this was not done and the website was hacked with random postings that had nothing to do with citrus. Users can also set up their accounts to remain anonymous if they choose via a random username or they can inform who they are with contact information when a posting is made. If the forum is successful, support will be sought to produce an app for smart phones to make the process easier than a web-based forum.

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

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