Progressive Crop Consultant - July/August 2018

July/August 2018 New Pest of Almond: The Knowns and Unknowns of Brown Marmorated Stink Bug in California Evaluation of Some Rootstocks for 'Scarlet Royal' Table Grape Fusarium Wilt of Tomato: A Growing Concern in California Automated Technology Has the Potential to Improve Weed Control Systems in Vegetable Crops

PUBLICATION

Volume 3 : Issue 4

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

CONTRIBUTING WRITERS & INDUSTRY SUPPORT Michael Cahn Matthew Fidelibus UC Cooperative Extension, Department of Viticulture & Enology, University of Monterey County California, Davis Ashraf El-Kereamy University of California Gene Miyao Cooperative Extension, UCCE Vegetable Crops Advisor, Sacramento, Kern County Solano & Yolo Counties Steve Fennimore Jhalendra Rijal University of California, Ph.D, Area IPM Farm Davis Advisor San Joaquin Valley, UC Cooperative Extension & Statewide IPM Program

UC Cooperative Extension Advisory Board Kevin Day

Steven Koike

David Doll

Emily J. Symmes

Dr. Brent Holtz

Kris Tollerup

County Director and UCCE Pomology Farm Advisor, Tulare/Kings County UCCE Farm Advisor, Merced County County Director and UCCE Pomology Farm Advisor, San Joaquin County

UCCE Plant Pathology Farm Advisor, Monterey & Santa Cruz Counties

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Automated Technology Has the Potential to Improve Weed Control Systems in Vegetable Crops

New Pest of Almond: the Knowns and Unknowns of Brown Marmorated Stink Bug in California

14

Evaluation of Some Rootstocks for 'Scarlet Royal' Table Grape

20

Fusarium Wilt of Tomato: A Growing Concern in California

26

Attention to Water Management can Improve Nutrient use in Organic Vegetables

UCCE IPM Advisor, Sacramento Valley UCCE Integrated Pest Management Advisor, Parlier, CA

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

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IN THIS ISSUE

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July/August 2018

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20 UPCOMING EVENTS: South Valley Nut Conference October 26, 2018 | 7:00AM - 1:30PM - wcngg.com Tulare County Fairgrounds 215 Martin Luther King, Jr., Tulare, CA 93274

Mid-Valley Nut Conference November 2, 2018 | 7:00AM - 1:30PM - wcngg.com Modesto Jr. College Ag Pavilion 2201 Blue Gum Ave. Modesto, CA 95358

Kern County Ag Day

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November 28, 2018 | 7:00AM - 1:30PM - wcngg.com Kern County Fairgrounds 1142 S P St. Bakersfield, CA 93307 July/August 2018

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AUTOMATED TECHNOLOGY Has the Potential to Improve Weed

Control Systems in Vegetable Crops

M

ost herbicides used in vegetable crops were registered 40 to 50 years ago. For example, the primary herbicides used in lettuce are benefin (Balan registered 1970), bensulide (Prefar registered 1964) and pronamide (Kerb registered 1972). In California, Kerb, Balan, and Prefar were applied to 53, 6, and 15 percent of head lettuce, respectively, in 2015 (CADPR 2017, NASS 2017). Processing tomatoes in California has more herbicides registered than lettuce, but the top 5 products used and year of registration are trifluralin (1963), glyphosate (1974), S-metolachlor (1976), rimsulfuron (2001) and oxyfluorfen (1979). Because of the small acreages, fragmented markets and high potential liability, development of new herbicides for vegetables is not a market sector that is attractive to pesticide registrants. Additionally, many vegetable markets have few or no herbicides such as herbs, leafy greens, and all vegetables produced organically. Today all organic-compliant herbicides on the market are contact herbicides, and none has soil or systemic activity. Bottom line; there are many unmet needs in vegetable weed control programs.

Heavy regulation increases the cost of herbicide development, paying for these

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high regulatory costs forces registrants to focus on broad acre crops—a barrier to development of herbicides for vegetable crops. If the high regulatory barriers prevent development of new vegetable herbicides, are there other technologies with lower barriers that can help control weeds in vegetable crops? Pest control devices, like cultivators are farm equipment, and not regulated like pesticides.

A pesticide device as defined by the U.S. Environmental Protection Agency (US EPA) is “an instrument or contrivance (other than a firearm) that is used to destroy, repel, trap or lessen the severity of any pest such as insects, weeds, rodents, certain other animals, birds, mold/ mildew, bacteria and viruses (USEPA).

“A pesticide device—works by physical means …” which is what cultivators do.

Pesticide devices may provide a more direct path to develop new tools for vegetable crops by combining devices with computer processors and robotic technology, i.e., automated weeders.

Automated Weeders Automation of weed control has two components, detection and actuation.

Automatic detection involves machine recognition of key features of the plant

July/August 2018

Robocrop intra-row cultivator being used to weed tomatoes. All photos courtesy of Steve Fennimore

By: Steve Fennimore, University of California, Davis and differentiation between the crop and weed, as discussed below. Actuation, or the action of killing the weed, can take two approaches; one approach is to spray the weed with an herbicide and the other mechanical such as a cultivator knife. Here we will explore examples of both of these approaches using automated lettuce thinners as an example of chemical application automation and a robotic intra-row weed hoeing as an example of mechanical weed control automation.

Detection

To date the only commercially utilized method of sensing in existing robotic weed control machines uses traditional two-dimensional machine vision techniques. More commonly, two-dimensional image processing differentiates the plant from soil by color or light reflectance, and crop recognition (from weeds) by size differences and crop row pattern. These techniques are most effective during the early portion of the growing season, when weed control is most critical, before canopy closure has occurred and the crop plants have not yet overlapped. For best per-

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Figure 1 Robocrop intra-row cultivator used to weed lettuce.

Continued from Page 4 formance, they require a uniform crop stand, and a relatively low weed density.

These devices work best in transplanted crops where the crop plants are larger than the weeds. The technique is better suited for the control of a robotic hoe than a sprayer, where the need to accurately recognize or map weeds growing in close proximity to the crop is not necessary.

Weed Control Actuators These are devices, such as cultivators that kill weeds by uprooting, thermal weeders like flame or steam that kill the weeds by destroying leaves and growing points, and abrasives that shred weed foliage. The context here is that devices controlled by weed detection systems selectively kill the weed but not the crop.

Physical weed removal There are three methods of physical weed control compatible with automation:

11. Mechanical intra-row cultivation 22. Thermal weed control 33. Abrasion—sand blasting 6

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All of these methods have the advantage of being pest control devices. Weed control devices also have the advantage of utility in both conventional and organic fields. With the exception of abrasion, all of these physical methods for weed removal have been in use for decades. Automation is a means to take a proven weed control device and combine it with ® automation technology.

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July/August 2018

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intra-row space without damaging the crop.

Two designs for intelligent intra-row cultivators are currently on the market: the rotating disc design from Tillett and Hague Technology Ltd. in the UK and is marketed as the Robocrop “In Row” cultivator (Figure 1, page 6) and reciprocating knives that reach in and out of the crop row using machine vision guidance (Figure 2, below). Both systems essentially do the same thing, but by different mechanisms. The Robocrop cultivator has a rotating disc controlled by a vision system to detect the crop plant and align the disc cut away section with the crop plant. The disc rotational phase is altered as needed by changing the speed of the hydraulic drive to align the cut away section with the crop plant to allow for variation in crop spacing. In transplanted vegetable crops the Robocrop rotating cultivator provided effective weed control and was safe to the crop—yields were not reduced relative to the standard cultivator treatment.

In my program at Salinas, California, we evaluated the Robovator intelligent

cultivator in broccoli and lettuce in comparison to a conventional inter-row cultivator. The Robovator removed 27 to 41 percent more weeds than the standard cultivator and reduced hand weeding times by 29 to 45 percent compared to the standard cultivator. We also found that the Robovator did not reduce broccoli and lettuce yields.

Summary

will likely persist, and there is need to improve labor use efficiency where we can. The first generation automated weeders demonstrate the feasibility of weed removal technology and suggest that weed removal systems in the future will be better, and cheaper.

Because automated weeders utilize devices rather than pesticides, they can be used in a variety of crops with Robocrop intra-row cultivator being fewer barriers used to weed lettuce. than herbicides.

Automated weeding technology may be the best current option to improve weed control in vegetable crops. At present these weeders are made in small shops in limited quantities, and are likely more expensive than if they were manufactured in larger quantities. Barring a legislative breakthrough on immigration and guest worker programs, farm labor shortages

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

Figure 2 Robovator intra-row cultivator equipped with reciprocating knives weeding tomatoes.

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New Pest of Almond: The Knowns and Unknowns of Brown Marmorated Stink Bug in California By: Jhalendra Rijal, Ph.D. | Area IPM Farm Advisor-Northern San Joaquin Valley, UC Cooperative Extension & Statewide IPM Program Background

Figure 1

B

rown marmorated stink bug (BMSB), Halyomorpha halys, is a new invasive insect, and potentially the most destructive stink bug species out there. BMSB caused a serious crop loss in 2010 to mainly tree fruits, peaches and apples in the Mid-Atlantic region of the U.S. Since then, it has become a major pest that requires a scheduled spray program throughout the crop growing season. BMSB attacks a wide host range (more than 170 plant species listed in www.stopbmsb.org) that includes crops, ornamental and landscape trees. The major host crops reported include apples, peaches, nectarines, pears, cherries, grapes, peppers, tomatoes, sweet corn, beans, soybean, and more. Both immatures and adults feed by inserting their straw-like (piercing-sucking) mouthparts into fruits, seeds, seed pods, buds, leaves, and stems, causing direct economic damage.

Although reported in the early 2000s in California (Los Angeles area), a large population of BMSB was found in the mid-town and downtown areas of Sacramento in the Fall-2013. In the

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July/August 2018

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Continued from Page 8 past few years, it has been a nuisance problem in the area during the winter, with homeowners, and gardeners losing backyard trees. Community gardens in urban areas have also been affected by BMSB. Currently, there are 16 counties (Figure 1, page 8) with an established BMSB population in residential areas.

We reported the finds of BMSB in crops (peaches 2016, and almonds in 2017) as the first reports in California, more than 30 BMSB adults were captured in BMSB pheromone-baited traps from a peach orchard near Modesto, Stanislaus County. The orchard had peaches, cherries, and nut crop (e.g., almonds, walnuts), where we observed BMSB activities in the trap in 2017. Additionally, we reported the first evidence of BMSB infestation in a new host almond crop from an orchard located within one to two miles from the first detection site (peach). In 2018 season, we are capturing BMSB in traps in several locations, with significant damage to the nuts in orchards in the northern San Joaquin Valley.

Identification BMSB adults are approximately 5/8-inch-long and with shades of brown color on both the upper and lower body surfaces. They are the typical “shield” shape stink bugs, almost as wide as they are long. To distinguish them from other stink bugs, look for two white bands on the antennae. There are other four stink bug species (Consperse stink bug, brown stink bug, rough stink bug, spined soldier bug) that resembles with the BMSB, but none of them has ‘white bands’ on the antennae. Nymphs also have white bands on their antennae. Adults and nymphs (2nd-5th instar) actively feed on fruits. It takes about 45 days from egg to adult stage, and adults live an additional 45 days.

Damage

Figure 2 BMSB feeding damage appeared in the harvested nuts. The typical necrotic spots on hull and shell including damage to nut meats.

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BMSB adults overwinter in human-made structures such as houses, barns, shops, and even in dry and dead trees during the fall and early winter.

Therefore, BMSB is also considered a significant nuisance pest in residential areas. With the warming of the season in the Spring, the overwintering adults migrate to the crops. BMSB may move and feed alternatively among different

July/August 2018

wild and cultivated host plant species, if available.

We are still in the early stages of knowing the extent of economic damage that BMSB can cause in almonds in California. However, based on our observations in a number of orchards in 2017 and 2018, BMSB moving into the orchard early in the season (March-May) seems to cause a substantial injury to developing nuts, ranging from aborted and dropped nuts, gummy nuts, to the blank, shriveled and ‘dimpled’ kernels at the harvest (Figure 2).

Feeding on developing almonds leads to the gummy nuts with multiple feeding spots. Damaged nuts show feeding signs externally (multiple gumming, light brown speckles, yellowing) as well as internally (pinhole, water-soaked lesion, cork tissue, internal gumming).

BMSB releases a salivary enzyme to dissolve the fruit tissue for the easy uptake of their food, which leaves a characteristic necrotic lesion in the fruit (Figure 3, page 11).

Some of these feeding signs match with that from the leaffooted bug and native stink bug feeding damage, although necrotic spots on the harvested shell and hull are uniquely associated with the BMSB feeding. BMSB can attack the crops throughout the season beginning mid-March, although the susceptibility of the crop to BMSB in a different time of the year has yet to be evaluated. The leaffooted bug is a major issue in April, the native stink bug is in May-June, while BMSB can be an issue during their emergence (mid-March to May, based on 2017 observation) from the overwintering shelters to the crop.

Also, once established, the population of BMSB moving to the orchard tends to be much bigger compared to the native stink bugs.

In three almond orchards, with BMSB population this year, we observed significant nut drops beginning midApril, and the majority of those nuts had gummings (external exudation) on them. Based on field observations, Fritz variety seems to be more susceptible than the Nonpareil variety. We observed substantial damage to Carmel variety as well. The presence of adults and the damage have been noticeably higher in the border rows, mostly in a side of the orchard next to the open field. Our ongoing work focuses on determining the extent of the damage by BMSB in

Figure 3 BMSB adults and newly hatched nymphs and feeding damage in developing almonds. Pictures were taken from commercial almond orchards (2017-2018)

different times of the year in almonds to determine the window of vulnerability.

Monitoring Although there are commercial BMSB lures available to use, not all lures

are equally effective. Consulting your local Farm Advisor or other sources will help to figure out which lure to use.

There are two types of traps that can be used in orchards. 1) Black pyramid trap (Figure 4a) has been the standard BMSB trap, but this trap is expensive and more cumbersome for field use. So, in 2017,

along with other researchers in the East Coast, we tested the new trap type ‘sticky panel trap’ (Figure 4b). Both trap types had the same lure which attracts both adults and nymphs. Although an overall number of adult capture was numeri-

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A

B

Figure 4 BMSB Traps. A. left, Pyramid Trap and B. Right, Sticky Panel Trap.

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Phenology of BMSB in northern San Joaquin Valley (Modesto area)

Figure 5

Continued from Page 11 cally higher in pyramid compared to the sticky panel trap in a few locations, both trap types caught BMSB adults from all locations. Based on those results, we

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recommend that the sticky panel trap which is much more user-friendly to BMSB monitoring in orchards. The traps should be placed in a border-tree row adjacent to the open fields, houses or any other potential overwintering sources.

July/August 2018

The first BMSB was captured in midMarch in 2017 season, while around the first week of April this year. In 2017, the peak BMSB adult activity was in early May, early July, and much bigger counts in the fall (early October) (Figure 5,

page 12).

BMSB captures in the traps may not represent the BMSB population and infestation in the orchard since the performance can vary with the crop monitored. In some cases, we noticed the BMSB adults and the feeding activities in the tree, but no capture in the trap.

Therefore, it is important to scout BMSB activities regularly in the orchard. Visual observations of the insect (egg mass, nymphs, adults) and damaged fruits (deformed fruits, exuded fruits) and beat tray sampling (shaking branches/ twigs to dislodge insects) are early BMSB detection methods. Visual observation of the border trees for the presence of insect and the gumming fruits is highly recommended. Based on observations, nuts that are closer together in a group showed intense feeding damage.

Management Because the brown marmorated stink bug is a newly established pest in California, a management program for California crops is still being developed.

At this point, use of insecticides targeting the leaf-footed bug and other native stink bug species in almonds may be the option to use. In general, pyrethroid insecticides are considered to be effective against native stink bugs. However, the residual control is not very long, and they are a poor fit in integrated management program (IPM) program because of their negative impact to beneficial arthropods. For example, use of pyrethroids in the spring can flare up mite population in almonds. Always read, understand, and follow the label directions before using any pesticide. Future work should focus on evaluating insecticides against BMSB in crops in California. Interested to learn more about the BMSB, use this website, StopBMSB.org.

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G

rapevine roots are vulnerable to numerous soil pests, including plant-parasitic nematodes and phylloxera. In the warm regions of central and southern California, areas most suitable for growing table grapes, nematodes are the most important soil pests. Numerous species of nematodes, including citrus (Tylenchulus semipenetrans), dagger (Xiphinema index and Xiphinema americanum), ring (Mesocriconema xenoplax), root-lesion (Pratylenchus vulnus), and root-knot (Meloidogyne spp.) nematodes along with other less common species, may feed on grapevine roots, and thus cause severe damage.

New Rootstocks The uncertain future availability of effective fumigants and post-plant nematicides coupled with inadequate resistance mechanisms of commonly used rootstocks to some species of root-knot nematode has driven plant breeders and nematologists to redouble their efforts to develop new rootstocks with broad and durable pest resistance. Rootstock breeding programs have released many new stocks, including 10-17A, 10-23B, RS-3, RS-9. These rootstocks are expected to have broader nematode resistance.

Table Grape Breeding Programs Scarlet Royal Table Grape.

All photos & charts courtesy of Ashraf El-Kereamy

Evaluation of Some Rootstocks for

‘Scarlet Royal’ Table Grape

By: Ashraf El-kereamy | University of California Cooperative Extension, Kern County Matthew Fidelibus | Department of Viticulture and Enology, University of California, Davis 14

Table grape breeding programs have also recently released several varieties, including ‘Scarlet Royal’ Scarlet Royal (US Plant Patent 16,229*) is a mid-season red seedless table grape developed

by David Ramming and Ronald Tarailo of the United States Department of Agriculture (USDA)/Agricultural Research Service (ARS) in Parlier, California. Scarlet Royal produces large, conical-shaped clusters that are medium to well filled. Berries are large in size and oval in shape. The flesh is firm and meaty, and the skin is medium to thick.

The flavor is described as sweet and neutral. Scarlet Royal ripens mid-to-late August, filling a desirable harvest window between Flame Seedless and Crimson Seedless. Scarlet Royal has become the most widely planted red table grape variety in California. However, there is no information on the most suitable rootstocks for Scarlet Royal with respect to vine growth, yield and quality. In 2008, a rootstock trial was established within

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Table 1. Summary of rootstocks being evaluated in a ‘Scarlet Royal’ vineyard in Goshen, California. The grafted vines were planted in 2008.

Rootstock

Origin

Parentage

Freedom

USDA, Fresno

V champinii x 1613C

1103 P

Sicily, Italy

V. berlandieri x V. rupestris

Kober 5BB

Austria

V. berlandieri x V. riparia

Teleki 5C

Hungary

V. berlandieri x V. riparia

RS-3

KAC, Parlier

(V. candicans x V. rupestris)x(V. riparia x V .rupestris)

RS-9

KAC, Parlier

(V. candicans x V. rupestris) x (V. riparia x V. rupestris)

USDA 10-23B

UDSA, Fresno

V. doaniana

10-17A

UDSA, Fresno

V. simpsoni x Edna ((V. lincecumii x V. rupestris) x V. vinifera))

RSD-34

KAC, Parlier

((V. candicans x V. rupestris) x (V. riparia x V. rupestris)) x V.doaniana

are presented in (Table 1, above).

Continued from Page 14 a commercial table grape vineyard at Goshen for Scarlet Royal by the former University of California Cooperative Extension (UCCE) viticulture advisor Jennifer Hashim-Maguire. The vines are spaced seven feet between vines and 10 feet between rows. Vines are quadrilateral cordon trained, spur pruned and trellised to an open-gable system. The plot consists of nine rootstocks and own-rooted controls with five replications of nine vines per replicate.

The objective was to determine the effect of a range of rootstocks, including traditional and recently released stocks on the yield, quality and vine growth of Scarlet Royal table grape in California.

Origin and the parentage of each rootstock

Yields During the three bearing years of the study, we harvested the trial at the same time as the grower; the total amount of the marketable fruits of the multiple picks is presented in (Figure 1). In 2013,

vines on all rootstocks produced similar yields, however, in the following year, vines on 1103 P rootstock produced more crop than vines on Freedom or RSD-34. In the third year, vines on 1103 P again showed a higher yield compared to those on Freedom or RSD-34, and they also out-performed own-rooted vines, and vines on Teleki 5C, and Kober 5BB. Berry weight showed a

Figure 1 Marketable yield of the Scarlet Royal table grape grafted on different rootstocks

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July/August 2018

similar trend as marketable yield (Figure 2), with vines on 1103 Paulsen (1103 P), 10-17A, RS-3, and RS-3 rootstocks had a higher berry weight compared to the others.

Despite the variation of the berry Brix and acidity from year to year, no significant differences were observed among berries from vines on the different rootstocks. Petiole analyses were made each year to determine whether or not rootstocks affected uptake of Figure 2 Berry weight of the Scarlet Royal table grape grafted on different rootstocks. macro and micronutrients and salts. ride than own-rooted vines, whereas ride content in the own-rooted Scarlet The three years chloride accumulation in vines on the Royal progressively increased over the of data showed a significant difference other rootstocks including 1103 P, Kober course of the three-year study. in the sodium and chloride uptake 5BB, Teleki 5C, RS-9, USDA 10-23B by the own-rooted vines and all rootand RSD-34 was nine-times less than stocks. It seems that own-rooted vines own-rooted vines (Figure 4, page 18). accumulated a considerable amount of Continued on Page 18 Similarly to the sodium content, chlosodium in their petioles reaching five times more than that of vines grafted on any of the rootstocks; no significant difference was observed among the different rootstocks (Figure 3). Interestingly, the percentage of sodium in the own-rooted vines increased progressively from 2013 to 2015 raising a question about the production sustainability and longevity of own-rooted vines at that site. Chloride content also increased in the own-rooted vines.

However, there was also variation among rootstocks concerning chloride uptake.

Vines on Freedom, RS-3, and 10-17A accumulated two to three-times less chloFigure 3 Sodium content of the Scarlet Royal table grape grafted on different rootstocks.

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Continued from Page 17

ISOMATE

Pruning Weights End of season pruning weights were generally similar among vines on all rootstocks except for those on RSD-34 which had lower pruning weights compared to vines on all other rootstocks. A higher pruning weight was observed in the Scarlet Royal grafted on 1103 P in the third year compared to own-rooted vines. There were few consistent rootstock effects on uptake of nitrogen, potassium, and phosphorus. In the first year of the study, vines on Freedom accumulate more nitrogen than those on own-rooted vines, but not more than those on 1103 P or RSD-34. In the third year of the study, vines on Freedom, Kober 5BB, and RSD-34 had significantly higher petiole nitrogen levels than vines on the other rootstocks. Phosphorus content showed a significantly high level in the Scarlet Royal scion grafted on Teleki 5C, Kober 5BB, 1103 P, and RSD34 during the second and third year of the study. Potassium content of the first year showed a similar trend across all rootstocks including own rooted vine.

In the second year, only RSD-34 was lower than all other stocks. In the third year, 1103 P showed higher potassium content, and RSD-34 showed a significantly lower content compared to the own-rooted vines.

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Figure 4 Chloride content of the Scarlet Royal table grape grafted on different rootstocks.

18

Progressive Crop Consultant

July/August 2018

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Fusarium Wilt of Tomato: A Growing Concern in California

By: Gene Miyao, UCCE Vegetable Crops Advisor, Sacramento, Solano and Yolo Counties Intro paragraph from a 2004 local newsletter, Tomato Info, UC Cooperative Extension, Yolo County.

F

usarium wilt, presumably race 3, of tomato is showing in more local fields. Yields losses from Fusarium wilt can be substantial (Figure 1). While race 3 resistant varieties are available, the choices are currently limited. Identification of Fusarium wilt is an important first step. The UC IPM manual describes and illustrates the disease well. Branches and leaves turn bright yellow, usually beginning with one or two branches. The growth stage when this is the most distinct is when vines are nearly full-grown. At this point, the contrast is extreme from the lush green vegetative stage and the yellowing symptoms caused by Fusarium (Figure 2, page 22).

Other characteristic symptoms include dark brown discoloration of the vascu-

Figure 1 Field loss from susceptible (right) vs resistant cultivar (far left). All photos courtesy of Gene Miyao

20

lar system of the stem (Figure 3, page 23). Although less common when leaf yellowing is one-sided, that is distinct to this disease (Figure 4, page 23). I believe a one to two percent incidence of Fusarium wilt might well be sufficient to set the stage for escalating losses when tomatoes are rotated back into the field. While it is hard to predict the rate of increase for our area, a couple of fields have reached over 10 percent levels in some hot spots.

From my limited visits to the Sutter Basin where race 3 has been present for many years (first discovered by a local grower in 1987 and confirmed), race 3 has not progressed as rapidly as race 2 in that production area. However, do not be lulled into believing race 3 is a ‘wimpy’ pathogen. What should you do once it

is discovered? Since this is a soilborne pathogen, avoid contaminating clean fields with soil transported on equipment from infested fields. This Fusarium is very crop-host specific. It can survive long periods. Therefore, the level of benefits achieved by rotating out of tomatoes is unclear at this point. Pay special attention to the race 3 resistant varieties at the seed company field days.

Potential of mechanical spread of Fusarium wilt, race 3: To evaluate the potential of Fusarium oxysporum f. sp. lycopersici to be spread from infested to non-infested fields from diseased toma-

Continued on Page 22

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Table 1. Evaluation of spread of Fusarium wilt from November 2010 field introduction, UC Davis Fusarium wilt infected plants* Year # % 2010 0 0 2011 12 1% 2012 34 2% 2013 287 19% *with lab confirmation

Continued from Page 20

tomato harvesters and vine diverters, should be cleaned and inspected before moving into new fields. Vigilance in equipment cleaning may reduce the introduction of Fusarium wilt from infested fields.

are included in this discussion. In the combined analysis of the three sites with moderately high Fusarium incidence, the top yielding varieties were HM 3887 and N 6428 (Table 2, page 24). H 8504 was in the lowest yielding group. Brix performance varied across locations.

Discussion: The performance of HM 3887 under our moderately high incidence of race 3 was impressive. Should a successive-year, repeated test in the same site be conducted, I suspect a tolerant variety might be overrun. Under higher disease pressure, risk of catastrophic disease impact escalates when relying on a tolerant compared to a resistant cultivar.

Thus, from a management perspective, a tolerant variety might be a candidate for fields with historically moderately low Fusarium incidence combined with rotation out of tomatoes for a few years.

Without a reliable soil sampling system to directly measure Fusarium wilt pathogen populations, risk assessment relies on monitoring disease level in the

to plant debris, University of California Davis (UCD) emeritus plant pathologist Mike Davis and I collaborated on a UC Davis, campus-based field test. The study began by collecting stems from FusariWhile our study only involved hanum wilt, race 3 infected plants from two dling of diseased plant tissue, infested local, commercial fields. Stems were then soil may also be tied to the movement of dried, cut into about 1 inch-long pieces Fusarium wilt. and buried in the center of pre-made beds in the fall of 2010.

Fusarium Wilt Race 3 Variety Over the subsequent Evaluations, 2016 Figure 2 Yellowing of leaves three years, from and branches 2011-2013, In response to increased tomatoes were incidence cropped each of Fusaryear to evalium wilt, uate the esBeat the Heat & Care race 3, a tablishment for Your Crops with: team of and spread five UC of this longfarm adlived soilvisors conborne patho® ducted tests gen. Tillage in commercial management was fields across the no-till, season-long High Temperatures & Extreme Heat Central Valley with Additional Environmental Stress Conditions that the product is useful for: including the time a history of race 3. between introduction of the infected Frost & Freeze • Drought Conditions A uniform set of 15 stems and the 2011 crop planting. In all Transplanting • Drying Winds varieties included a subsequent years, tillage was restricted susceptible (H 8504) A foliar spray that creates a to flail mowing and roto-tilling in-line What is semi-permeable membrane and two tolerant culwith the beds.

Anti-Stress 550®? over the plant surface. tivars (HM 3887 and DRI 319). Incidence Our field study indicated that Optimal application period is of Fusarium with When to apply Fusarium wilt could establish quickly one to two weeks prior to the Anti-Stress 550®?

H 8504 averaged 24 threat of high heat. in a new soil environment to infect the percent, 20 percent following crop season (Table 1). In each subsequent season, the percent infection and 29 percent in the The coating of Anti-Stress When is Anti-Stress 550® three northern sites level continued to increase. By the end becomes effective when the most effective?

(Robbins, Woodproduct has dried on the plant. of the third tomato crop year, the level The drying time of Anti-Stress is land and Stockton, approached 20 percent. While our test the same as water in the same respectively) and with plot dimensions were small (16, 5-ft. weather conditions. low (two percent) or wide beds x 90 ft.), the results were clear: no Fusarium detected *One application of Anti-Stress 550® will remain effective 30 Fusarium could establish quickly and to 45 days, dependent on the rate of plant growth, in the southern sites once introduced, would progressively application rate of product and weather conditions.

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Progressive Crop Consultant

July/August 2018

SAVE THE DATE Figure 3 Internal discoloration of stem

recent tomato crop to guide subsequent varietal decisions. Several Fusarium wilt, race 3 resistant varieties are available that provide high yield performance. The resistant varieties are the clear choice where race 3 is problematic (Figure 5, page 24).

We especially thank all our grower cooperators. In some cases, harvest was by the Morning Star Company.

Ag Seeds and T, S & L provided variety consultation, collection of seed and greenhouse support, particularly from Lance Stevens.

The Processing Tomato Advisory Board analyzed our fruit quality. Advisor Brenna Aegerter compiled the data and ran the combined and many individual statistical analysis of variance tests. Finally, we are thankful for the funding support from the California Tomato Research Institute and its contributing growers. The UC team included: Amber Vinchesi (Colusa/Sutter-Yuba), Brenna Aegerter (San Joaquin), Scott Stoddard (Merced/Madera), Tom Turini (Fresno) and myself and research assistant Ben Leacox along with other assistants.

is actively seeking management strategies for the industry. Those include rapid diagnostic tools to differentiate between several pathogenic species of Fusarium of tomato.

Additionally, she is testing many common weed species and alternate

Continued on Page 24

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November 28, 2018 Figure 4 less frequent occurrence of one-sided leaf yellowing

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July/August 2018

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23

Table 2. Yield and fruit quality from high Fusarium wilt incidence trials (20 to 29%), combined from Sutter, Yolo and San Joaquin counties 2016.

Marketable

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Variety HM 3887 N 6428 BP 2 HM 58801 BQ 141 N 6429 SVS 8232 SVS 2493 H 1310 DRI 319 H 1539 BP 16 BQ 406 H 8504 BQ 142

Disease Resistance VFFNsw VFFF3Nsw VFFF3NPsw VFFF3Nsw VFFF3NPsw VFFF3NswLv VFFF3NPsw VFFF3NPsW VFFF3NPsw VFFNPsw VFFF3Nsw VFFF3NPsw VFFF3NPsw VFFNP VFFF3NPsw

Yield Tons/A 57.6 55.0 52.8 52.5 52.5 51.4 51.0 50.8 50.3 48.7 47.8 47.6 47.4 46.0 42.7

a ab bc bc bc bcd bcd bcd cde cde de de de ef f

Color 24.9 23.3 22.5 23.9 21.8 23.4 21.5 22.4 22.7 23.1 21.0 23.3 21.9 23.4 22.3

PTAB pH 4.42 4.41 4.53 4.42 4.43 4.47 4.39 4.47 4.43 4.39 4.45 4.42 4.47 4.36 4.46

LCD 5%

4.39

0.77

0.04

%CV

11

4

1

Brix 5.09 4.96 4.98 5.45 4.80 4.99 5.28 4.89 4.93 5.58 4.87 5.17 5.23 4.70 5.09 o

5

FF= race 1 and 2 resistance to Fusarium wilt FFF3= race 1, 2 and 3 resistance to Fusarium wilt

Continued from Page 23 crops which might serve to host the pathogen. The long-held tenet was this pathogen could survive over many years.

Also, the teaching was that only tomato was the host for the pathogen of tomato Fusarium wilt. Some earlier work by UCD grad student Hung Doan indicated that our Fusarium pathogen could grow on the surface of weed seedlings. Of course, the weeds survived. The upshot

is that some plant species may act as a mechanism to help in the survival and perhaps even increase the population in the absence of tomato. Dr. Swett’s investigation aims to identify which crops and weeds to avoid; and conversely, to show which crops might serve as better rotational choices.

The Swett lab is also examining the influence of soil moisture level and salinized water on Fusarium as an in-season

Figure 5 Variety trial with differential damage

24

Progressive Crop Consultant

July/August 2018

management guide.

Although a tall order, another field management tool Swett is exploring is the use of soil sampling to test for the presence of the Fusarium pathogen while developing a threshold level to gauge disease risk.

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

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b

7 DAT (8/31/17) n Untreated n Zinc + 4 DL 2qt + Top Set 1pt + Agrobest 0-20-26 1 gal

7 DAT (8/31/17) n Untreated n Zinc + 4 DL 2qt + Top Set 1pt + Agrobest 0-20-26 1 gal

Potassium

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450

10150

300

9800

b

Baseline

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Late season NOW sprays provide a great opportunity with foliar nutrition to increase 2018 nut size, splits and yield and set the stage for higher 2019 yields. However – many conventional foliar formulations do not penetrate well, especially from mid-summer onward after the pistachio leaf has hardened off and developed a thick waxy cuticle, making them ineffective. But Agro-K’s Sysstem® and Dextro-Lac® foliar product lines are designed to rapidly and completely move through even the toughest, hardened off, waxy pistachio leaf – even in late summer, making them extremely effective nutrient delivery tools.

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50

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acre returns. In addition, foliar nutrient programs added to late season NOW sprays will also increase the 2019 crop. Even though this year’s crop has not yet been harvested, by mid-season the tree is already building next season’s crop. Take advantage of the free ride to influence it!

In an August trial a mix of Agro-K nutrients, both micro and macro, were applied to pistachio trees. Utilizing SAP testing methodology over standard tissue testing allowed for analysis of “free nutrients” only; meaning those nutrients currently mobile within the plant’s sap and immediately available for plant use. Conventional tissue testing measures what is already bound within the leaf structure and mostly immobile. Measuring sap nutrient levels effectively detects recent nutrient changes. The charts above show statistically significant changes in six different nutrients 7 days after application. Zinc, manganese, copper, molybdenum, potassium and phosphorus levels all increased statistically vs. the control in the week after application of AgroBest 0-20-26, Top Set DL and Zinc +4 DL. This year, take advantage of your summer NOW application to feed your pistachio trees the key nutrients they need to maximize 2018 yield and set the stage for 2019 yields.

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Attention to

WATER MANAGEMENT can Improve Nutrient use in Organic Vegetables Michael Cahn | UC Cooperative Extension Monterey County

SUPPLYING NUTRIENTS

S

upplying nutrients in organic systems to meet the high uptake rates of vegetables such as broccoli, celery, lettuce, and spinach can be challenging. Lettuce often takes up more than four pounds of nitrogen (N) per acre per day during the rapid phase of growth that begins four to five weeks before harvest. Spinach can take up more than six pounds of nitrogen per acre per day during its rapid growth phase. Similar to nitrogen, vegetables also take up potassium at high rates. Unlike chemical fertilizers that can quickly supply mineral forms of N, P, and K to crops, organic amendments and fertilizers and cover crop residues require time to release nutrients so that they are available for plant uptake. Depending on the nitrogen content of organic fertilizers, only a portion of the total nitrogen will mineralize during the first weeks after application and subsequently nitrogen will continue mineralizing at slower rates.

Nitrogen mineralization from organic amendments can also be slow and amendments with low N content may temporarily immobilize nitrogen.

Because nutrient availability from organic fertilizers and amendments is less predictable than from chemical fertilizers growers need to plan ahead in managing nutrients in organic systems. Organic fertilizers, amendments, and plant residues often need to be added early in the crop cycle to mineralize a sufficient supply of nutrients to support the nutrient demands of a vegetable crop. Although nutrients can be challenging to manage in organic systems, optimal water management can help improve nutrient utilization of vegetables.

26

Progressive Crop Consultant

July/August 2018

HERBICIDE EC

FORORGANICPROD Organic fertilizers applied to the soil surface are susceptible to washing away during sprinkler irrigation and rain events. Photo courtesy of M. Cahn.

WATER MANAGEMENT

HERBICIDE EC

Water management influences chemical and physical processes that affect nutrient availability.

Mineralization rates of organic fertilizers and amendments are dependent on the moisture content of soil, mineralizing slower in dry compared to moist soils. Waterlogged soils can cause nitrate to be lost by denitrifying bacteria, and over applying water in well-drained soils will leach nitrate beyond the reach of crop roots.

Moisture is also needed to utilize nutrients from dry fertilizers. A recent study in the Salinas Valley showed that the release of nitrogen and phosphorus from organic fertilizer pellets applied to bed tops was significantly less than when incorporated into the soil.

Presumably the drier conditions on the soil surface compared to a few inches below would limit the mineralization of nutrients contained in the pellets.

In addition, organic fertilizer pellets applied to the soil surface can wash away when irrigated with overhead sprinklers or during heavy rain events.

Nutrients carried in agricultural run-off can pollute downstream lakes, rivers, and estuaries.

The efficiency of vegetables to take up nutrients is also affected by water management. Maintaining ideal moisture in soil helps roots maximize nutrient uptake. Though one might think that roots uptake nutrients directly from the soil colloids, they actually absorb minerals from water retained in the soil pores. As roots soak up water from the soil they also

Continued on Page 28

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Continued from Page 27 pull in nutrients. Calcium deficiency in tomatoes, which can manifest as blossom end rot on fruits, often occurs when a crop has been water stressed for a prolonged period. In drip irrigated vegetables dry soil along the shoulders of beds can confine plant uptake of nutrients to the moist soil surrounding the drip tape. Water stress can also slow crop growth and reduce the utilization

of applied nutrients. A recent field trial conducted in lettuce showed that N fertilizer recovery was less when the crop was under irrigated compared to when irrigated with the full water requirement.

BUILDING ORGANIC MATTER Building up the soil organic matter is not only important for increasing

Liquid organic fertilizers should be injected before a filter to prevent clogging of the drip emitters. Photo courtesy of Michael Cahn.

28

Progressive Crop Consultant

July/August 2018

the supply of nutrients and microbial activity in organic vegetable systems but can also help with water management.

Even a small increase in organic matter in the topsoil can help improve soil structure and water holding capacity.

A recent survey of more than 60 research studies found that a one percent increase in organic carbon was correlated with a two to four percent increase in water holding capacity

depending on the soil texture. Organic carbon had the largest effect on water holding capacity in sandy textured soils. Not only does increasing organic carbon in the soil help with water holding capacity but it can also reduce crusting of the soil surface which may reduce infiltration and accelerate runoff and erosion.

Continued on Page 30

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Continued from Page 29

LIQUID ORGANIC FERTILIZERS Water management is also important for supplying liquid organic fertilizers to vegetables. Although many organic fertilizers can be injected into drip and sprinkler systems, poor distribution uniformity can limit how evenly nutrients are applied across a field. Many commercial drip systems have distribution uniformities of less than 70 percent, meaning the driest zone receives 70 percent of the average amount of water applied to the entire field. These drier zones also receive less nutrients when fertigating. In addition, many organic fertilizers are not completely soluble and can clog drip emitters if injected without filtration, further reducing the application uniformity. It is usually safer to side dress liquid organic fertilizers that contain a significant portion of suspended solids than to inject into a drip system and risk clogging the emitters.

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

Baby spinach and other leafy greens have a high demand for nitrogen and potassium.

Photo courtesy of Michael Cahn.

30

Progressive Crop Consultant

KEY WATER MANAGEMENT POINTS Here are some key points about water management of vegetables to consider during the season that can help organically grown vegetables maximize the use of nutrients:

1 2 3

July/August 2018

Preplant and crop establishment: Apply an

appropriate amount of water to moisten soil for bed preparation and for crop establishment. The first irrigation after seeding or transplanting is usually sufficient to wet the soil to a significant depth; subsequent irrigations during crop establishment need only keep the surface soil moist to prevent soil crusting or drying of seeds before germination.

Over-applying water during this early phase when crop water use is low can leach nitrate-nitrogen that has built up in the top soil from mineralization of previous crop residues or incorporated cover crops, amendments, and fertilizers.

Post-establishment: Most vegetable crops

continue to have low water requirements after establishment because the canopy cover is still small.

Irrigations do not usually need to be very long to re-saturate the soil profile at this early stage and may be spaced more than a week apart depending on weather conditions. Careful monitoring of soil moisture in the root zone can determine the appropriate irrigation interval.

Use evapotranspiration data to determine the amount of water to apply.

Mid to late season: Avoid stressing the crop by applying sufficient water to meet its evapotranspiration requirement. Crop water requirements quickly increase in the second half of the season as the canopy rapidly expands and reaches maximum coverage. Under irrigating with drip may result in dry soil along the edges of beds which can be difficult to remoisten.

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© 2018, Trécé Inc., Adair, OK USA • TRECE, PHEROCON and CIDETRAK are registered trademarks of Trece, Inc., Adair, OK USA • TRE-1255, 05/18

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©2018 Compass Minerals. All Rights Reserved. Protassium+ and Design are registered trademarks of Compass Minerals International, Inc. or its subsidiaries in the U.S. and other countries.

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July/August 2018

Protassium+® sulfate of potash (0-0-50-17S) has less than 1% chloride and the lowest salt index per unit of K2O of all major potassium sources. This ensures efficient water and nutrient uptake. The result is healthier plants and higher yields — whether conventionally or organically farmed. What is scientifically better for your crop is also better for your business. So, if plants were rockets ... well then, we might just be NASA. To review field trials, plot studies and research, visit ProtassiumPlus.com.