PCC JanFeb 2021

January / February 2021 

Managing Soil Structure and Quality 

Soil Application of Fungicides in Strawberry 

Alternative Nematicides for Root-Knot Nematodes in Melons 

Weather Station Use in Vineyards 

Volume 6: Issue 1

4 

10 

16 

IN THIS ISSUE 

Managing Soil Structure 

and Quality 

Soil Application of 

Fungicides in Strawberry 

Alternative Nematicides 

for Root-Knot Nematodes 

in Melons 

VINEYARD REVIEW 

4 

PUBLISHER: Jason Scott 

Email: jason@jcsmarketinginc.com 

EDITOR: Marni Katz 

ASSOCIATE EDITOR: Cecilia Parsons 

Email: article@jcsmarketinginc.com 

PRODUCTION: design@jcsmarketinginc.com 

Phone: 559.352.4456 

Fax: 559.472.3113 

Web: www.progressivecrop.com 

CONTRIBUTING WRITERS & INDUSTRY SUPPORT 

Kris Beal 

Vineyard Team 

Surendra Dara 

UCCE Entomology and 

Biologicals Advisor 

Matthew Fidelibus 

UCCE Viticulture Specialist 

Karl T. Lund 

UCCE Area Viticulture Advisor 

Craig Macmillan 

Ph.D., Macmillan Ag 

Consulting 

Jaspreet Sidhu 

UCCE Vegetable Crops Farm 

Advisor, Kern County 

Gabriel Torres 

UCCE Viticulture Farm 

Advisor 

Stephen Vasquez 

Technical Viticulturist, Sun- 

Maid Growers 

Dr. Karl Wyant 

Vice President of Ag Science, 

Heliae Agriculture, 

Board of Directors, Western 

Region Certified Crop 

Advisers 

George Zhuang 

UCCE Viticulture Farm 

Advisor, Fresno County 

20 

Weather Station Use in 

Vineyards 

UC COOPERATIVE EXTENSION 

ADVISORY BOARD 

28 

34 

38 

Dormant Season 

Yield and Disease 

Management 

Making Nitrogen and 

Potassium Fertilizer 

Decisions in Vineyards 

Pierce’s Disease in 

Grapevine 

20 

38 

Surendra Dara 

UCCE Entomology and 

Biologicals Advisor, San Luis 

Obispo and Santa Barbara 

Counties 

Kevin Day 

UCCE Pomology Farm Advisor, 

Tulare and Kings Counties 

Elizabeth Fichtner 

UCCE Farm Advisor, 

Tulare County 

Katherine Jarvis-Shean 

UCCE Orchard Systems Advisor, 

Sacramento, Solano and 

Yolo Counties 

Steven Koike 

Tri-Cal Diagnostics 

Jhalendra Rijal 

UCCE Integrated Pest 

Management Advisor, 

Stanislaus County 

Kris Tollerup 

UCCE Integrated Pest Management 

Advisor, Fresno, CA 

Mohammad Yaghmour 

UCCE Area Orchard Systems 

Advisor, Kern County 

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. 

January / February 2021 www.progressivecrop.com 3

MANAGING SOIL 

STRUCTURE 

AND 

QUALITY 

Physical & Chemical Management 

Practices to Maximize Soil Quality 

By DR. KARL WYANT, Vice President of Ag Science, Heliae Agriculture, 

Board of Directors, Western Region Certified Crop Advisers 

You may have heard or read about improving 

your soil health or soil quality over the 

last year as this area of field management 

gains more attention. But what exactly do the terms 

mean and how can you incorporate the concepts in 

your day-to-day soil management practices? In Part 

1 of this article series, the physical and chemical 

connection to optimizing soil quality by focusing 

on the structure of your soil will be explored. 

Soil Quality and Health 

Soil quality has broad application to your farm. 

It refers to how well a soil functions physically, 

chemically and biologically and how well it does its 

“job” (Fig. 1, page 6). For example, a forest soil has 

a different job than a farm soil, and soil properties 

can be measured on how well the soil is performing 

(e.g. soil structure). 

Figure 3: The soil on the left has poor soil structure while the soil on the 

right has excellent aggregation and structure. As a result, the two fields 

have substantial differences in soil quality and their ability to support 

optimized crop growth (photo courtesy K. Wyant.) 

Many factors influence the soil quality on a farm 

and are summed up in Figure 2, on page 7. In 

this article, the focus will be on the physical and 

chemical management practices that maximize soil 

quality, expressed here as soil structure (Fig. 3). 

Continued on Page 6 

4 Progressive Crop Consultant January/February 2021

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soil structure and soil quality; however, 

pulling it off can be tricky. It is worth 

noting that some tillage can be beneficial 

(e.g. deep ripping of hard pans) 

but should be employed only when 

necessary to help avoid impacts on soil 

structure. 

Figure 1: Holistic management tools that help improve soil structure and soil quality includes 

physical and chemical controls (Part I in this article series) and biological controls (Part 2). 

Continued from Page 4 

Soil health refers to the interaction 

between organisms and their environment 

in a soil ecosystem concept 

and the properties provided by such 

interactions (e.g. ecosystem stability). 

When you think of soil health, think of 

the biological integrity of your field (e.g. 

microbial population and diversity) and 

a focus on supporting plant growth. 

This will be the focus of Part 2 of this 

article series. 

Poor soil structure and the resulting 

decrease in soil quality continues to 

impact yields in many farming areas. 

This is because many factors can negatively 

impact soil structure, including 

soil compaction from field equipment, 

poor salinity management, rainfall and 

irrigation droplets, excessive tillage, etc. 

Fortunately, fields that have poor structure 

(see Fig. 3 for a visual reference) 

can be fixed once you determine what 

is causing the issue. I strongly recommend 

that you put your field detective 

hat on and work with your favorite 

Certified Crop Adviser (CCA) to diagnose 

why your field is not performing 

as expected. 

Physical Controls 

Physical and chemical management 

strategies are important to help reverse 

poor soil structure and thus improve 

the overall soil quality of your field. 

The physical controls on soil structure 

generally relate to reducing disturbance 

to the soil and protecting the soil from 

future disturbance. With this broad 

mandate, there are a variety of techniques 

out there to accomplish this 

goal and help restore soil structure, 

but reducing tillage and incorporating 

cover crops into the growing operation 

are the most important. 

Tillage Practices and Soil Structure 

Field activities like tillage are crucial for 

any successful growing season, whether 

in the short term or long term. However, 

excessive tillage can be hard on your 

soil structure as common implements 

can slice, compact or crush soil aggregates 

and quickly change a soil from 

having excellent tilth (see right side of 

Fig. 3) to one that lacks those properties 

(see left side of Fig. 3). The physical 

destruction of aggregates can have an 

immediate impact on your soil quality 

and can impact your operation’s bottom 

line. Fortunately, there are many 

modern options for avoiding excessive 

tillage, including conservation tillage 

and residue management, strip tillage 

and even a complete elimination of the 

practice (no-till). Every operation is 

different, and changes in tillage need 

to take local growing practices into 

account before moving forward. Reducing 

tillage has been shown to improve 

Cover Crops 

This concept is related to keeping the 

soil covered and physically protected 

from disturbance into the future after 

the crop is planted. The cover crop, 

usually grown in between the rows of 

permanent crops (e.g. trees and vines) 

or in the ‘off-season’ for annual crops, 

can be used to shield the soil from wind 

and water erosion and also help open 

up soils that have a history of poor soil 

structure. Briefly, the canopy of a cover 

crop can intercept and slow the velocity 

of raindrops and break up wind gusts, 

which helps keep soil on the field. 

Belowground, the root systems of cover 

crops can poke through clods and 

hard pans and help open up channels 

in the soil profile to help move water 

downward into the profile. Fine root 

hairs can also tie soil particles together, 

improving soil structure and quality. 

Please contact your preferred CCA for 

more advice on tillage practices and 

cover crop selection and to see if it fits 

into your farming operation. 

Chemical Controls 

A common issue in fields that have poor 

soil structure and soil quality is related 

to a chemical relationship in the soil. A 

loss of soil structure due to a mismatch 

between soil structure, calcium and 

other elements is called deflocculation. 

Under normal conditions, soil particles 

with ample calcium naturally come 

together to form aggregates, which 

improves soil structure. When the 

calcium is displaced by other ions (e.g. 

sodium), the soil structure collapses, 

and soil quality can quickly deteriorate. 

One of the main goals of a chemical remediation 

program is to provide more 

calcium to the soil, thus reversing the 


Figure 2: Crop productivity is influenced by 

several interrelated concepts, which have an 

impact on the soil quality of a field 

(courtesy K. Wyant.) 

collapse in soil structure and driving 

an improvement in soil quality. The 

question is, “Which calcium amendment 

do I use?” 

I cannot stress enough the need to start 

your program with a soil sample and 

to utilize the experienced advice from 

a CCA. Taking a soil sample will help 

you figure out the following important 

parameters critical to your chemical 

program: 1) Which amendment to use 

(e.g. gypsum, lime, sulfur product); and 

2) Dosage of correct amendment to 

apply. 

Critical parameters on the soil report 

worth looking at are soil pH, fizz test 

results, EC (dS/m), SAR, sodium and 

chloride results. For example, the fizz 


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test measures the amount of free lime 

in a soil (CaCO 3 ), and this is either 

expressed qualitatively (low, high, etc.) 

or quantitatively (%). There are a few 

major bulk calcium amendments that 

are available to help restore your soil 

structure: lime, gypsum and sulfur 

products. 

Lime 

Lime (CaCO 3 ) is commonly used in 

soils that are acidic with soil structural 

issues and should not be confused 

with ‘free lime’ that shows up on a 

soil test report. Lime can provide a 

calcium source while also neutralizing 

acidic soil pH. Thus, soil quality can 

be improved on two separate fronts 

(soil structure and soil pH) with one 

program. Calculating the liming rate 

for a field (lbs/acre) can be tricky since 

you have to factor in both the amount 

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of calcium needed to fix your soil structure 

problem and the amount needed to 

adjust the pH. A good soil sample and 

an experienced CCA can help determine 

the optimum rate for your field. 

Gypsum 

Gypsum (CaSO 4 ) is a calcium amendment 

when one has low or very low 

fizz test readings. This is one reason 

why I recommend that you start your 

program with a soil test. When gypsum 

dissolves, it can supply calcium 

directly to the soil, which improves 

soil structure and allows excess salts 

(e.g. sodium) to drain. However, unlike 

lime and sulfur products, gypsum 

will have little impact on soil pH and 

should only be used to provide calcium 

to help restore soil structure and soil 

quality. An experienced CCA can help 

interpret your soil test and provide a 

reasonable gypsum 

recommendation 

(lbs/acre) to fix the 

issue. 

Sulfur Products 

Sulfur products, 

such as sulfuric 

acid and elemental 

sulfur, require the 

presence of free 

lime in the soil 

(CaCO 3 ). As such, 

soils that have medium 

to very high 

fizz test ratings are 

a great candidate 

for the use of sulfur 

products in your 

chemical reclamation 

program. Briefly, 

sulfur products 

react with the free 

lime in the soil to 

create gypsum as 

a by-product. The 

calcium in the 

gypsum is then able 

to go to work to improve 

soil structure. One advantage of 

using sulfur products is that you generally 

do not need as much material to get 

the job done as you do with gypsum (1 

ton gypsum = 0.57 tons sulfuric acid = 

0.19 tons elemental sulfur), which can 

impact field logistics and application 

costs. 

Also, repeated applications of sulfur 

products can reduce problematic soil 

pH areas by moving the soil pH from 

alkaline to neutral. One disadvantage 

to using sulfur products is that they 

have several reaction steps that can 

slow the reclamation speed of the field 

relative to lime and gypsum. Also, sulfuric 

acid products present some safety 

concerns that must be considered from 

a worker safety and transport level. 

Like lime and gypsum, an experienced 

CCA can help interpret your soil test 

and provide a reasonable recommendation 

(lbs/acre) to fix the issue. 

Conclusion 

Physical and chemical factors can have 

a profound impact on your overall soil 

structure and, thus, the soil quality of 

your field. Generally, poorly structured 

soils have a difficult time supporting 

optimized crop growth due to the severe 

reduction in water storage capacity, 

low oxygen, surface crusting and seed 

bed issues, accumulation of salinity, etc. 

If your soil looks like the example on 

the left side of Figure 3, it may be well 

worth your time and money to start implementing 

soil improvement practices 

as outlined in this article. You have a 

variety of management options, including 

the implementation of practices 

that improve the physical components 

of soil quality (e.g. tillage reduction 

and use of cover crops) or the chemical 

components such as adding bulk 

calcium amendments to your program. 

A bit of detective work beforehand 

determining why your field is having 

a soil structure problem can pay off in 

turning your field around and using 


your input dollars most effectively. 

In Part 2 of this article series, we 

explore the biological components 

that influence soil structure and soil 

health. We will define soil health and 

go through plenty of examples on how 

the living component of a soil can impact 

your soil structure and overall soil 

quality. Furthermore, we will discuss 

how to test for soil health in the field. 

Suggested Reading 

1. Soil Health Partnership Blog - 

https://www.soilhealthpartnership. 

org/shp-blog/ 

2. Soil Health Institute Blog - https:// 

soilhealthinstitute.org/resources/ 

3. PhycoTerra® Blog - phycoterra.com/ 

blog/ 

Dr. Karl Wyant currently serves as 

the Vice President of Ag Science at 

Heliae© Agriculture where he oversees 

the internal and external PhycoTerra® 

trials, assists with building regenerative 

agriculture implementation and 

oversees agronomy training. Prior to 

Heliae Agriculture, Dr. Wyant worked 

as a field agronomist for a major ag 

retailer serving the California and 

Arizona growing regions. To learn 

more about the future of soil health 

and regenerative agriculture, you can 

follow his webinar and blog series at 

PhycoTerra.com. 

Comments about this article? We want 

to hear from you. Feel free to email us at 

article@jcsmarketinginc.com 

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January/February 2021 www.progressivecrop.com 9

Botrytis gray mold in trials at the UC Shafter 

Research Station (all photos by S. Dara.) 

Soil Application of Fungicides in 

STRAWBERRY 

Study Looks at Drip Applications and 

Potential Impact on Crop Health and Yields 

By SURENDRA DARA, UCCE Entomology and Biologicals Advisor 


Propagules of gray mold fungus survive in 

the soil and infect flowers and fruits. 

Strawberry is a high-value specialty 

crop in California and is 

susceptible to multiple pathogens 

that infect roots, crowns, foliage, flowers 

and fruits. Verticillium wilt caused 

by Verticillium dahliae, Fusarium wilt 

caused by Fusarium oxysporum f. sp. 

fragariae and Macrophomina crown rot 

or charcoal rot caused by Macrophomina 

phaseolina are major soilborne 

diseases that cause significant losses 

if they were not controlled effectively. 

Chemical fumigation, crop rotation 

with broccoli, nutrient and irrigation 

management to minimize plant stress 

and non-chemical soil disinfestation 

are usual control strategies for these 

diseases. Botrytis fruit rot or gray mold 

caused by Botrytis cineaea is a common 

flower and fruit disease requiring 

frequent fungicidal applications. 

Propagules of gray mold fungus survive 

in the soil and infect flowers and fruits. 

A study was conducted to evaluate the 

impact of drip application of various 

fungicides on improving strawberry 

health and enhancing fruit yields. 

Methodology 

This study was conducted in an experimental 

strawberry field at the Shafter 

Research Station in fall-planted strawberry 

during 2019-2020. Cultivar San 

Andreas was planted on October 28, 

2019. No pre-plant fertilizer application 

was made in this non-fumigated field 

which had Fusarium wilt, Macrophomina 

crown rot and Botrytis fruit rot in 

the previous year’s strawberry planting. 

Both soilborne diseases were present 

throughout the field during late spring 


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1. Fruit yield per plant from 11 

weekly harvests between March 

11, 2020 and May 14, 2020. 

Fruit yield per plant from 11 weekly harvests between March 11, 2020 and May 14, 2020. 

Leaf chlorophyll and nitrogen content between February 4, 2020 and May, 15 2020. 

Marketable fruit yield on various harvest dates. Marketable yield was 4% to 28% 

higher where fungicides were applied to the soil with the exception of Abound dip, 

which resulted in 16% less marketable yield. 

2019 with symptoms of wilt or crown 

rot appearing in many plants. In the 

current study, each treatment was applied 

to a 300-foot-long bed with single 

drip tape in the center and two rows of 

strawberry plants. Sprinkler irrigation 

was provided immediately after planting 

along with drip irrigation, which 

was provided one or more times weekly 

as needed for the rest of the experimental 

period. 

Each bed was divided into six 30-footlong 

plots, representing replications, 

with an 18-foot buffer in between. 

Between November 6, 2019 and May 9, 

2020, 1.88 qt of 20-10-0 (a combination 

of 32-0-0 urea ammonium nitrate and 

10-34-0 ammonium phosphate) and 

1.32 qt of potassium thiosulfate w ere 

applied 20 times at weekly intervals 

through fertigation. Treatments were 

applied either as a transplant dip or 

through the drip system using a Dosatron 

fertilizer injector (model number 

D14MZ2). The following treatments 

were evaluated in this study: 

1. Untreated control: Neither transplants 

nor the planted crop was 

treated with any fungicides. 

2. Abound transplant dip: Transplants 

were dipped in 7 fl oz of 

Abound (azoxystrobin) fungicide 

in 100 gal of water for four minutes 

immediately prior to planting. 

Transplant dip in a fungicide is 

practiced by several growers to protect 

the crop from fungal diseases. 

3. Rhyme: Applied Rhyme (flutriafol) 

at 7 fl oz/ac immediately after and 

30, 60 and 90 days after planting 

through the drip system. 

4. Velum Prime with Switch: Applied 

Velum Prime (fluopyram) at 6.5 fl 

oz/ac 14 and 28 days after planting 

followed by Switch 62.5 WG 

(cyprodinil + fludioxinil) at 14 oz/ 

ac 42 days after planting through 

the drip system. 

5. Rhyme with Switch: Four applications 

of Rhyme at 7 fl oz/ac were 

made 14, 28, 56, and 70 days after 

planting with a single application 

of Switch 62.5 WG 42 days after 

planting through the drip system. 

12 Progressive Crop Consultant January / February 2021

NAVEL ORANGEWORM MANAGEMENT 

Parameters observed during the study 

included leaf chlorophyll and leaf 

nitrogen (with chlorophyll meter) in 

February and May; fruit sugar (with 

refractometer) in May; fruit firmness 

(with penetrometer) in April and May; 

severity of gray mold twice in March 

and once in May; other fruit diseases 

(mucor fruit rot caused by Mucor 

spp. and Rhizopus fruit rot caused by 

Rhizopus spp.) once in May, three and 

five days after harvest (on a scale of 0 

to 4 where 0=no infection; 1=1-25%, 

2=26-50%, 3=51-75% and 4=76-100% 

fungal growth); and fruit yield per 

plant from 11 weekly harvests between 

March 11, 2020 and May 14, 2020. Leaf 

chlorophyll and nitrogen data for the 

Abound dip treatment were not collected 

in February. Data were analyzed 

using analysis of variance in Statistix 

software and significant means were 

separated using the Least Significant 

Difference test. 

Results and Discussion 

Leaf chlorophyll content was significantly 

higher in plants that received 

drip application of fungicides compared 

to untreated plants in February 

while leaf nitrogen content was significantly 

higher in the same treatments 

during the May observation. There 

were no differences in fruit sugar or 

average fruit firmness among the treatments. 

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The average gray mold severity from 

three harvest dates was low and did not 

statistically differ among the treatments. 

However, the severity of other 

diseases was significantly different 

among various treatments with the 

lowest rating in Abound transplant dip 

on both three and five days after harvest 

and only three days after harvest in 

plants that received four applications of 

Rhyme. Unlike the previous year, visible 

symptoms of the soilborne diseases 

were not seen during the study period 

to evaluate the impact of the treatments. 

However, there were significant 

differences among treatments for the 

marketable fruit yield. 

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The highest marketable yield was 

observed in the treatment that received 

Rhyme and Switch followed by Velum 

Prime and Switch and Rhyme alone. 

The lowest fruit yield was observed in 

Abound dip treatment. Unmarketable 

fruit (deformed or diseased) yield was 

similar among the treatments. Compared 

to the untreated control, Abound 

dip resulted in 16% less marketable 

yield and such a negative impact from 

transplant dip in fungicides has been 

seen in other studies (Dara and Peck, 

2017 and 2018; Dara, 2020). Marketable 

fruit yield was 4% to 28% higher where 

fungicides were applied to the soil. 

Although visible symptoms of soilborne 

diseases were absent during the study, 

periodic drip application of the fungicides 

probably suppressed the fungal 

inocula and associated stress and 

might have contributed to increased 

yields. The direct impact of fungicide 

treatments on soilborne pathogens was, 

however, not clear in this study due to 

the lack of disease symptoms. 

Considering the cost of chemical 

fumigation or soil disinfestation and 

the environmental impact of chemical 

fumigation, treating the soil with 

fungicides can be an economical 

option if they are effective. While this 

study presents some preliminary data, 

additional studies in non-fumigated 

fields in the presence of pathogens are 

necessary to consider soil fungicide 

treatment as a control option. 

Acknowledgments 

Thanks to FMC for funding this study 

and Marjan Heidarian Dehkordi and 

Tamas Zold for their technical assistance. 

References 

Dara, S. K. 2020. Improving strawberry 

yields with biostimulants and nutrient 

supplements: a 2019-2020 study. UCANR 

eJournal of Entomology and Biologicals. 

https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=43631. 

Dara, S. K. and D. Peck. 2017. Evaluating 

beneficial microbe-based products for 

their impact on strawberry plant growth, 

health, and fruit yield. UCANR eJournal 

of Entomology and Biologicals. https:// 

ucanr.edu/blogs/blogcore/postdetail. 

cfm?postnum=25122. 

Dara, S. K. and D. Peck. 2018. Evaluation 

of additive, soil amendment, and biostimulant 

products in Santa Maria strawberry. 

CAPCA Adviser, 21 (5): 44-50. 





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ALTERNATIVE NEMATICIDES 

FOR ROOT-KNOT NEMATODES IN 

MELONS 

By JASPREET SIDHU, UCCE Vegetable Crops Farm Advisor, Kern County 

California is one the largest 

producers of melons in the U.S., 

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grown in California are cantaloupes 

and honeydew types. Although some 

acreage is reported throughout the 

state, most are grown in the Southern 

desert valleys and San Joaquin Valley. 

Root-knot nematodes (RKN), Meloidogyne 

spp., are the most significant 

plant parasitic nematodes affecting 

melon production in California, 

especially in light-texture soils. The 

nematodes are widespread in Central 

and Southern California. 

Damage results from feeding of second 

stage juveniles (J2) inside melon roots, 

and the roots respond to nematode 

invasion by formation of root galls. 

Nematode-infested plants become 

stunted and less vigorous with severe 

galling of roots. Deformed roots due 

to galls are unable to sustain the water 

and nutrient needs of the plant in hot 

weather, leading to wilting and poor 

growth of plants, reduced yield and 

poor fruit quality. Nematode-infested 

plants may also become more vulnerable 

to other soilborne pathogens. 

Currently, there are no resistant cultivars 

in melons, and RKN management 

has mainly relied on the use of preplant 

soil fumigants and soil-applied nematicides. 

Management with these prod- 

ucts is expensive and involves safety 

and environmental risks. New fumigant 

regulations by the Department of 

Pesticide Regulations (DPR) have been 

put in place to restrict the emissions of 

volatile organic compounds from the 

use of soil fumigants. These regulations 

include limits on the amount of soil 

fumigants a grower is allowed to use 

in a year, caps on the amounts allowed 

within a township and new expanded 

buffer zones, meaning large parts of a 

field may not be treated all. These new 

regulations by DPR may mean that 

there will be some fields not treated for 

nematodes because of caps placed on 

the amount a grower is allowed to use 

or caps on the amount of fumigants 

allowed in a township. 

Alternative control options that have 

high efficacy, are economically viable 

and environmentally safe need to be 

evaluated under field situations. The 

goal of this project was to evaluate the 

efficacy of Salibro, an organic product 

and a developmental product (DP1) in 

comparison to Nimitz (fluensulfone) in 

melons applied through deep-buried 

drip tube. Nimitz is registered on melons 

in California. 

2020 Field Trial 

This study was conducted as a small 

plot field trial on our RKN-infested site 

at the Shafter research farm. A western 

shipper-type melon variety, ‘Durango’, 

was hand transplanted onto 60-inch 

beds on June 30, 2020. There were four 

replications and five treatments in this 

trial arranged in a randomized block 

design. Rates, timings and method of 

application for each treatment is listed 

in Table 1, on page 18. Each plot was 

20 feet in length with a five-foot buffer 

between plots along the bed. Treatments 

were applied either as a pre-plant 

or post-plant application through 

buried drip. Before chemigation, water 

was run for ten minutes to ensure all 

treatment tubing was filled, and after, 

chemigation water was run for about 

20 minutes to flush the lines. The plots 

were irrigated using a surface drip and 

maintained using standard agronomic 

practices. 

Before applying the treatments, soil 

samples were collected from all plots 

using a sampling tube at a depth of 

eight to 10 inches and submitted for 

analysis to determine the RKN count. 

Soil samples were collected and analyzed 

for nematodes again at harvest. 

Melon roots were evaluated for galling 

at mid-season and at harvest. Data on 

nematode counts and root galling was 

analyzed using SAS (statistical analysis 

software). 





Table 1: Treatments, rate/A, application schedule and timings. 

Table 2: Mid-season average plant vigor of melon plots in five treatments during the 

2020 growing season. Vigor on a scale of 1-5, with 1=worse and 5=best plants. 

Table 3: Average plant weight (g±SE) of melon vines in five treatments during 

the 2020 growing season. 

Table 4: Average root galling of melon plots in five treatments during the 2020 growing 

season. Galling on a scale of 0-10 (0=no galls, 10=completely galled roots). 

Data and Results 

Plant vigor for each plot was rated 

visually on August 11, 2020 on a scale 

of 1-5, with 1=worse and 5=best plants. 

Vigor included the size of the vines and 

general appearance or health of plants. 

On the same day, five plants from 

each plot were randomly selected and 

visually rated for severity of root galling 

on a scale of 0-10; (0=no galls, 10=completely 

galled roots). The average galling 

on these five plants was used to give a 

galling index for each plot. The fresh 

shoot weights of these plants (without 

fruits) were determined. 

At harvest on September 22, 2020, soil 

samples were collected from each plot 

for RKN count. All plants in each plot 

were dug and the severity of root galls 

on these plants was visually rated on a 

scale of 0-10 (0=no galls, 10=completely 

galled roots). The average of the galling 

on these plants in each plot was used to 

give a galling index for each plot. 

Plant Vigor 

No obvious differences were observed 

in plant vigor among treatments (Table 

2). Some plots were a little more vigorous 

than others, but these differences 

were not attributed to treatment effect. 

There were no significant differences 

observed in fresh shoot weight of melon 

plants during mid-season evaluation on 

August 11 (Table 3). However, Nimitz 

resulted in higher shoot weights than 

the other treatments. 

Root Galling 

The severity of root galling was assessed 

at mid-season and at harvest. At 

mid-season evaluations, root galling 

was moderate and ranged between 

2.4 in the Nimitz treatment and 4.6 in 

the untreated control (Table 4). Root 

galling in Nimitz and Gropro treatments 

was significantly lower than the 

other treatments. At harvest, there was 

a little increment in root galling across 

all treatments, however there were no 


Figure 5. Root galling at harvest. 1) Untreated control 2) Nimitz 3) Gropro 4) Salibro 5) DP1 

significant differences among treatments. 

Surprisingly, Salibro and the 

developmental product was not beneficial 

in the trial and had higher root gall 

ratings than the non-treated control 

plots at harvest. 

Conclusion 

In our 2020 trial, there were some treatment 

effects on mid-season root galling 

with Nimitz and the organic product 

Gropro having statistically lower root 

galling index compared to other products. 

However, none of the treatments 

were significantly different at harvest, 

and the results indicate that none of 

the treatments had a long-lasting effect 

on RKN levels in the soil. Therefore, 

further evaluations are needed to better 

determine the efficacy of these products 

as sole treatments and in combination 

with other products and their potential 

and continued use by the melon 

industry. 

This project was funded by the California 

Melon Research Board. 

Fruit Growers Laboratory, Inc. 

Precision Analyses for Improved Crop Quality & Yield 

www.fglinc.com 

SOIL 

FOOD 

SAFETY 

DISEASE 

I.D. 

LEAF 

TISSUE 

PARASITIC 

NEMATODE 

WATER 

ORGANIC 

AMENDMENTS 

Contact One of Our Convenient Locations for Assistance 




Corporate Offices & Lab 

Santa Paula, CA 

(805) 392-2000 

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Stockton, CA 

(209) 942-0182 

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Chico, CA 

(530) 343-5818 

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San Luis Obispo, CA 

(805) 783-2940 

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Visalia, CA 

(559) 734-9473 


VINEYARD REVIEW 

Weather Station use in 

VINEYARDS 

Newly Developed Weather Technologies Provide 

Multiple Beneficial Insights to Growers 

BY GABRIEL TORRES, UCCE Viticulture Farm Advisor 

and STEPHEN VASQUEZ, Technical Viticulturist, Sun-Maid Growers 

An anemometer, found at the top of the weather station, measures 

wind speed and direction and can be placed in or near the vineyard. 

(all photos courtesy S. Vasquez.) 

Talk to a farmer; at some point, 

the discussion will focus on the 

weather. It is the number-one topic 

discussed amongst farmers because 

weather can impact farming in significant 

ways. A rain event in June may 

benefit one crop but negatively impact 

another. Weather forecasts are important 

for scheduling farm activities, 

and for many years, farmers relied on 

the Farmer’s Almanac for long-range 

forecast. 

Fortunately, today’s California farmers 

have multiple options to obtain weather 

forecasts and real-time data to make 

farming decisions. One of California’s 

oldest publicly accessible weather networks 

is the California Irrigation Management 

Information System (CIMIS). 

Built to improve irrigation efficacy, UC 

Davis and the California Department 

of Water Resources (DWR) established 

CIMIS in 1982. CIMIS has provided 

California growers with weather data 

accessed via the internet at cimis. 

water.ca.gov/. Growers can select one 

of the 145 stations near their property, 

download the data to a computer and 

manipulate it for their use (e.g. calculating 

ET). However, todays farmers are 

busier than ever, and having to rely on 

downloading climate data throughout 

the season can be challenging, especially 

when data from multiple locations 

are needed or when there are not any 

CIMIS stations nearby. 

The CIMIS weather station network has 

been, and continues to be, a valuable 

tool for agriculture. But growers and 

researchers need weather data that 

better represents their farm or research 

location. Some of California’s first “local 

weather stations” used in vineyards 

were hygrothermographs that recorded 

temperature and humidity. Several 

UC grapevine pest and disease models 

were developed and tested in the late 

70s and early 80s using hygrothermo- 



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graphs placed throughout California’s 

vineyards. However, in the late 80s, 

hygrothermographs were replaced with 

weather stations equipped with radio 

telemetry and controlled by a data-collecting 

base station. Since then, as 

technology improved, weather stations 

have become more sophisticated and 

provide real-time, on-demand data, 24 

hours/day. 

Growers can log onto CIMIS once an account has been setup 

General and detailed weather station information from an app. 

Disease model (left) and degree days threshold option (right). 

Some of the first weather stations recorded 

temperature, humidity, precipitation 

and wind speed and direction, 

displaying the data as graphs that needed 

some interpretation. Today’s grape 

growers have access to the same data, 

but data presentation is clearer with 

user-friendly web portals and phone 

and tablet apps. Additionally, climate, 

environmental and irrigation sensors 

have been improved or newly developed 

to generate data that can be used 

to make farming decisions (e.g. solar 

radiation, atmospheric pressure, leaf 

wetness, plant and fruit growth, plant 

health, soil moisture, electrical conductivity, 

pH, nitrogen, phosphorus, potassium, 

microbial activity, water pressure 

and usage, and more). Having access to 

numerous types of data allows growers 

to manage their vineyards in a much 

different manner than just a decade ago. 

However, access to that much data can 

be overwhelming if it is not understood 

or managed properly. Growers should 

be trained or have dedicated personnel 

to help interpret the information and 

share it with colleagues that will be 

making farm management decisions. 

Some Practical Uses of Vineyard 

Weather Station Data 

Advanced sensor technology has 

made it easier for growers to install, 

build, maintain and expand a reliable 

in-house network of stations collecting 

different information. Access to 

local data helps decision-making that 

impacts crop yield and quality. For 

example, in addition to knowing how 

much precipitation a vineyard experienced 

during a rain event, information 

such as leaf wetness, relative humidity, 


soil moisture and wetting depth can 

help forecast diseases (i.e. bunch rot), 

future fertilizer and irrigation applications 

and general vineyard activity that 

involves tractor work. Combine that information 

with vineyard characteristics 

(i.e. variety, soil type, etc.) and suddenly 

growers can evaluate more acres with 

fewer vineyard visits that save them 

time and money. The improved collection 

and transmission of data from 

base (aka weather) stations equipped 

with unique sensors have become 

valuable tools for managing vineyards. 

Base stations now incorporate weather, 

phenological, pest and disease models 

developed by university researchers to 

enhance their offerings via portals and 

apps. The following are some additional 

applications that can benefit grape 

growers interested in designing their 

own network of sensors. 

Pesticide Applications 

Pesticide applications must follow 

California’s laws and regulations. Prior 

to any application, climatic conditions 

must be checked so pesticide applications 

are optimized. Having a base 

station within a vineyard can improve 

pesticide application efficiency and efficacy. 

An anemometer, which measures 

wind speed and direction, can help pesticide 

applicators decide if wind conditions 

will permit a pesticide application. 

Wind speeds need to be between 2 to 10 

mph to make a legal application. Knowing 

the wind direction can help decide 

the potential movement of a pesticide 

to an undesirable target (i.e. organic 

field). Tracking vineyard temperature 

can help determine if temperatures are 

hot enough to cause spray mist evaporation 

or phytotoxicity. In that situation, 

waiting for daytime temperatures 

to cool or spraying at night could help 

solve the issue. Being able to check a 

vineyard’s temperature prior to sending 

a crew to apply pesticides will save time, 

money and improve pesticide planning. 

Temperature sensors can also be 

used to detect inversion layers that can 

contribute to pesticide drift. Placing 

temperature sensors at multiple heights 

(e.g. 5 feet and 30 feet) will determine if 

the lower layer is cooler than the upper 

layer. When this happens, pesticides 

can move horizontally from thousands 

of feet to miles from the original point 

of application. When a vineyard experiences 

inversion layers, temperature 

sensors and a base station can detect 

the scenario and send an alarm to the 

person planning pesticide applications. 

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Degree Days and 

Temperature Modeling 

Temperature, measured in degree-days 

(DD), influences grapevine growth 

throughout the season. From grapevine 

bud dormancy to fruit maturity, 

temperature regulates vine and fruit 

development. DD model predictions 

can help growers prepare for seasonal 

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cultural practices (i.e. bloom sprays). 

For grapes, temperatures greater than 

50 degrees F have been determined as 

the developmental DD threshold. In 

California, Thompson Seedless development 

as a function of DD has been 

determined. Approximately 50% bud 

break for this cultivar is observed when 

155 DD are obtained with a February 

20th start date. To reach 50% bloom, 

an additional 741 DD are needed, with 

® 

maturity reached between 2880-3240 

DD. A grower can use this information 

to track and identify DD specific to the 

varieties that they grow that have similar 

growth characteristics to Thompson 

Seedless. UC has also developed DD 

models for western grape leafhopper, 

omnivorous leafroller, powdery mildew 

and other pests and diseases to help 

grape growers make management 

decisions. 

The Grower’s Advantage 

Since 1982 

© 

Chilling Hours 

Grapes require a specific number of 

chill hours to complete dormancy, 

break bud and begin a new season. The 

minimum number of chill hours required 

for grapes to produce a commercially 

viable crop averages approximately 

150 hours, which is low compared 

to stone fruit (i.e. cherries, peaches, 

etc.) that need ≥800 hours. Without 

adequate chill hour accumulation, 

bud break and yield become erratic, 

increasing farming costs significantly. 

Knowing when chill hour requirements 

are not being met can help a grower 

decide when to apply chemicals that 

improve bud break. A local weather 

station can better define chill hour accumulation 

than regional weather data 

(i.e. CIMIS). Most weather stations can 

automatically calculate the chill hours 

and portions. The chill portions algorithm 

accounts for warmer times of the 

day and presents a clearer forecast for 

predicting cold temperature needed for 

uniform bud break. More information 

about chill hour accumulation can be 

found here: fruitsandnuts.ucdavis.edu/ 

Weather_Services/chilling_accumulation_models/about_chilling_units/. 

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Worker Protection 

Worker protection is undoubtedly one 

of the most important responsibilities a 

grower has when people are working in 

the vineyard. Excessive UV or heat exposure 

can result in chronic and acute 

health issues. Weather stations not only 

track and monitor adverse weather conditions, 

but can also be programmed 

to send warning emails prior to critical 

UV or heat events. Since growers must 

record these events, weather station 

data is an easy way obtain documentation. 

Weather stations have many uses in 

the vineyard beyond temperature 

and precipitation. The complexity of 

the station will depend on a grower’s 

need. They can generate an enormous 

amount of data that will need to be 

interpreted correctly so good decisions 

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Table 1: Types of sensors needed to make management decisions. 


can be made. Table 1 shows what types 

of information can be determined from 

the different kinds of sensors. 

Selecting a Weather Station 

that Makes Sense 

Purchasing the right weather station 

will depend on the type of data needed 

to meet your needs. With multiple 

weather station options, growers can 

design a simple or complex weather station 

network that best suits their farm 

operation. Working with a weather tech 

company will help a grower determine 

their specific needs. After an initial 

needs assessment, a few follow-up 

meetings with a vendor will help finetune 

a weather network design. A 40- 

acre vineyard might easily be covered 

by a single station, especially when site 

characteristics are similar (i.e. climate, 

soil). However, using a single station to 

cover a 400-acre vineyard could result 

in misinterpreted climate data that may 

vary over a large property. Advancements 

in communication and sensor 

technologies now make it possible to 

have multiple sensors communicate 

remotely with a base station and have 

the information organized into an easyto-read 

format. 

Hardwired vs Solar Panel 

The decision to use hardwired or solar 

power will depend on where the station 

will be located. Easy access to electricity 

and/or communication lines is 

usually the determining factor. Open 

space near buildings or rooftops are 

sometimes preferred because electricity 

is in close proximity. If in-field hardwired 

installation is preferred, wires 

placed in conduit to the correct depth 

and properly wired will be needed to 

avoid damage or interference with 

data collection. Solar-powered stations 

have become more affordable and are 

also easy to install. Solar panels and 

batteries will need to be checked and 

maintained biannually to avoid data 

collection interruptions. Whichever 

type you choose, it’s important to avoid 

installing stations near tall objects (e.g. 

trees, utility poles, buildings), paved 

roads or bodies of water because they 

will interfere with data collection. Poor 

site selection can result in poor data 

collection. 

Number of Soil Moisture 

Sensors Per Acre 

Temperature, humidity and wind 

speed and direction are less variable 

than soil moisture and can be located 

in one or two areas that represent the 

property (e.g. pump station). However, 

the number of soil moisture sensors 

required per block will depend on how 

variable the soil texture is. If soil and 

topography are homogeneous (i.e. uniform), 

and several blocks have similar 

characteristics (e.g. cultivar, rootstock, 

age, irrigation and management), two 

or three sampling points should be 

sufficient. Soil moisture measurements 

should be set at a minimum of one, 

three and five-foot depths to determine 

water movement. However, soil moisture 

sensors can take measurements 

every foot, which may be needed for 

certain situations. Additionally, if a 

vineyard has different types of soils 

that represent different blocks, multiple 

soils moisture sensors may be needed 

to collect accurate data for irrigation 

scheduling. 

Basic vs High-End Stations 

All weather stations will provide some 

type of climate data, but vineyard size 

(acres), one’s knowledge and confidence 

in interpreting the data and data access 

frequency will help you identify they 

type of weather station that’s right 

for your operation. A basic station 

will offer traditional climate data like 

temperature, humidity and, in some 

cases, rainfall amounts. In addition 

to traditional climate information, 

more sophisticated weather stations 

will include wind speed, soil moisture, 

water pressure and amounts, etc. that 

will result in a lot of data that someone 

will need to track if weekly decisions 

are going to be made. It’s important to 

evaluate the presentation of the data 

that weather station vendors offer. Portals 

and apps have simplified the way 


that growers see and use large amounts 

of data, which makes it easier for vineyard 

decisions to be made. If you have a 

larger operation or want to have a more 

automated system, a station that is connected 

to the internet can be a better 

option. With this station, you will be 

able to collect the data in real time in 

the field or remotely. General and more 

detailed data can be accessed from your 

computer or phone app. Some manufacturers 

offer services to set alarms 

for pest and diseases based on models, 

degree days and chilling days. The 

alarms can be sent to your phone via 

text, email or automated call. Services 

varies from providers. 

No matter what type of base station 

and sensor configuration you choose to 

purchase, it is important that you first 

identify what information will help you 

make better management decisions. 

Additionally, you should identify someone 

that will be tasked with monitoring 

the system and sharing information 

with farm personnel. This person 

should be involved in the discussions 

with the vendor(s) since they will also 

be in constant contact with the vendor’s 

customer service representative. 

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HAVE BECOME 

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VINEYARDS.’ 

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Dormant Season 

Yield & Disease 

MANAGEMENT 

Winter Pruning Improves Yield, Quality and Lifespan of Vineyards 

By GEORGE ZHUANG, UCCE Viticulture Farm Advisor, Fresno County 

and MATTHEW FIDELIBUS, UCCE Viticulture Specialist 

Pruning and disease management 

are important vineyard practices 

that need attention in the dormant 

season. Pruning directly affects the 

upcoming season’s potential yield and 

quality and can directly and indirectly 

affect the vineyard’s long-term productivity. 

Pruning practices, and the care of 

pruning wounds, can also help manage 

trunk diseases. Pruning practices 

that optimize productivity and quality, 

and protect against trunk disease, will 

help extend the productive lifespan of 

vineyards. 

Dormant Pruning and 

Yield Management 

Grapevines are pruned for three main 

reasons: 

Figure 1: Bud fruitfulness from different nod positions on 15-node and 20-node canes of 

common raisin varieties in California. Figure is elaborated from Cathline et al. 2020. Catalyst: 

Discovery into Practice. 4: 53-62. 

1. To keep the vine in a shape that 

conforms to the trellis system and 

facilitates vineyard operations. 

2. To remove old wood and retain 

fruiting canes or spurs for the 

current season crop, plus spurs for 

future wood placement. 

3. To select a quantity and quality of 

fruiting wood that is in balance 

with vine growth and capacity. 



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Bloom diseases are opponents that are constantly 

evolving. They are more prevalent than ever in California, 

where increasingly erratic weather is a consistent threat, 

creating prime conditions for diseases to thrive and 

have a significant effect on almond yield potential. As a 

result, growers need a strategic game plan to make the 

best countermove against bloom diseases while also 

managing resistance. 

Scala, ® Luna Experience ® and Luna Sensation ® from 

Bayer are the recommended fungicide treatments to 

counteract these challenges. Growers can’t out-spray 

bloom diseases, but they can outsmart them through 

a combination of knowledge, application timing 

and by using products that demonstrate consistently 

high performance, overcome weather challenges 

and manage resistance. 

“We always like to recommend that our fungicides 

are used in a preventive manner prior to there being 

disease issues. So proper timing is very important,” 

says Matthew Wilson, field sales representative 

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Scala fungicide is notable for its control of Brown rot 

blossom blight at pink bud as an early-season spray 

option. It also offers both preventive and curative 

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the bud and blossom. It is crop safe, mixes well with 

IPM programs and other products, and is effective 

across a wide range of temperatures and weather 

conditions, with minimal adverse effects on beneficial 

insect species. 

PCA Ryan Garcia of Salida Ag Chem in Modesto, 

California, uses Scala. “I’ll use it in the early stages 

of bloom for Brown rot blossom blight. I think it’s a 

great material.” 

Application Timing 

“We’re kicking off with Scala,” notes grower Scott Long, 

general manager for Superior Fruit Ranch in Ceres, 

California. “We’ll come back with Luna ® and that 

gives us full coverage, plus it really helps us cover 

all aspects and concerns in the early spring period.” 

Luna Experience and Luna Sensation are strong 

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Diseases to Watch 

/// Brown Rot Blossom Blight – Thrives in humid temperatures 

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/// Anthracnose – Originates in warm, rainy weather. 

/// Jacket Rot – Rare, but, under cool and wet conditions at 

bloom, can cause devastating loss. 

/// Scab – Favors wet weather and spreads to new sites by 

wind or rain. 

/// Shot Hole – Requires prolonged periods of moisture, 

and water moves spores to new sites. 

/// Alternaria – Develops with high humidity where dew forms 

and air is stagnant. 

/// Rust – Favors humid conditions, worsens in rainy weather 

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Hull Rot 

ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. 

Not all products are approved and registered in all states and may be subject to use restrictions. The distribution, sale, or use of an unregistered pesticide is a violation of federal and/or state 

law and is strictly prohibited. Check with your local product dealer or representative or U.S. EPA and your state pesticide regulatory agency for the product registration status in your state. 

Bayer, Bayer Cross, Luna, ® Luna Experience, ® Luna Sensation, ® and Scala ® are registered trademarks of Bayer Group. For additional product information, call toll-free 1-866-99-BAYER 

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The choice of pruning method is largely 

influenced by fruitfulness characteristic 

of vine variety. For instance, most raisin 

varieties are cane pruned because 

their basal buds produce shoots with 

fewer and smaller clusters than apical 

buds (Fig. 1, page 28). In contrast, most 

wine varieties are spur pruned, since 

most wine varieties have adequate basal 

bud fruitfulness and spur pruning is 

less laborious and costly than cane 

pruning. However, cane pruning is 

sometimes preferred for certain wine 

varieties, like Carmenere, which have 

low basal bud fertility, or in cool climate 

regions where cool spring weather 

might reduce basal bud fruitfulness in 

other varieties. Understanding the factors 

determining the bud fruitfulness 

provides insight as to the best pruning 

practice for a given vineyard. 

Figure 2: Timing of cluster differentiation in the primary bud along one 15-node cane of 

Thompson Seedless. Figure is elaborated from Williams 2000, Raisin Production Manual 

(UC ANR Publication 3393). 

Figure 3: Bud fruitfulness generally correlates with the light exposure. Note different 

varieties respond to light exposure differently. Figure is elaborated from Sanchez and 

Dokoozlian 2005, American Journal of Enology and Viticulture. 56: 319-329. 

Grapevine yield is formed over a 

two-year cycle that begins with the 

initiation of cluster primordia within 

compound buds. Cluster primordia 

are initiated in basal buds first, around 

bloom time, with more apical buds 

forming cluster primordia in succession, 

and most buds having formed 

whatever cluster primordia they will 

have by veraison (Fig. 2). Sunlight 

promotes cluster initiation, so sunny, 

warm weather between bloom 

and veraison helps maximize cluster 

primordia formation, whereas cool and 

cloudy weather can lead to less fruitful 

buds (Fig. 3). Because basal buds tend 

to form cluster primordia earlier than 

the apical buds, spring weather can 

have a greater impact on the fruitfulness 

of some varieties than others. For 

example, cane-pruned varieties initiate 

cluster primordia over a longer time 

period than spur-pruned varieties. 

Raisin growers have long been advised 

to retain “sun” canes, which generally 

have more fruitful buds than “shade” 

canes. Cane and spur morphology 

can also indicate potential fruitfulness. 

Mature, round canes and spurs 

having moderate thickness and internode 

length are often the most fruitful. 

Narrow canes and spurs often indicate 

weak growth with inadequate starch 


content to support cluster primordia 

formation. In contrast, exceptionally 

thick canes with long internodes and a 

flattened shape, commonly referred to 

as “bull” canes, may also be expected to 

have poor fruitfulness. Stressed vines 

may have insufficient carbohydrate 

content to support maximum bud 

fruitfulness. Insufficient water, inadequate 

nutrition and poorly managed 

pest or disease issues (e.g. nematodes 

and powdery mildew) can all stress the 

vines and reduce bud fruitfulness. As 

previously mentioned, node position 

also affects fruitfulness, cluster size and 

fruit quality of cane-pruned varieties. 

Leaving longer canes could increase 

yields if the vines do not become overcropped. 

Cluster initiation is generally completed 

by veraison, so, by late summer, the 

number of clusters a designated bud 

may have in the following season has 

already been determined. Therefore, 

before pruning, growers can collect and 

dissect representative buds from a vineyard 

and observe and count the cluster 

primordia with the aid of a dissecting 

microscope. This information may be 

used to help predict yield potential and 

adjust their pruning severity to help 

achieve a desired number of clusters 

per vine. As growers gain experience 

with this method, it might also help 

them adjust their canopy or irrigation 

management practices to help improve 

fruitfulness, since shoot exposure to 

light improves bud fruitfulness. 

After a pruning strategy has been 

decided on, and the vines were pruned, 

the maximum potential number of 

clusters per vine has been fixed. One of 

the main goals of pruning is to retain 

the optimal number of buds per vine 

to regulate the crop size. If too many 

buds are retained after pruning, the 

vines may become overcropped, leading 

to poor canopy growth, unripe fruit 

and possible carry-over effects on the 

following year, resulting in erratic and 

delayed budbreak, slow canopy growth 

and poor yield and fruit quality. In con- 

Top left: Dead arms/cordons on vines with trunk disease. Top right: Botryosphaeria canker 

on trunk cross section. Bottom left: Esca symptoms on grape leaf. Bottom right: Eutypa 

dieback symptoms on grape (photos courtesy G. Zhuang.) 

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trast, if too few buds are retained, the 

vines may be undercropped, resulting 

in suboptimal yield and excessive canopy 

growth, which can cause self-shading, 

reducing fruit quality. Therefore, 

understanding bud fertility and potential 

crop load can help inform pruning 

decisions and thereby optimize yield 

and quality. 

Double pruning on wine grape with long spurs retained after the first pass. A second pass 

with a field crew will prune the spurs back to two buds (photo courtesy G. Zhuang.) 

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Disease Management 

Pruning practices also have implications 

for grapevine trunk diseases, 

which can seriously reduce vineyard 

productivity. Trunk diseases are caused 

by different fungi including Esca or 

black measles, Botryosphaeria (Botryosphaeria 

canker), Eutypa lata (Eutypa 

dieback) and Phomopsis viticola 

(Phomopsis cane and leaf spot). All of 

these fungi can enter the vines through 

pruning wounds, especially after 

precipitation. After a fungal infection 

has been initiated, it grows toward the 

roots, slowly killing the vascular tissue, 

decaying the wood and eventually 

killing the vines. The typical symptoms 

from trunk-diseased vines are cankers, 

dead arms and cordons, and trunks, 

with vines collapsing in a few years. 

The economic loss can be dramatic, and 

trunk diseases may significantly reduce 

the productive life of vineyards. 

Pruning methods can affect the 

potential disease risk. Cane pruning 

typically has less trunk disease risk 

than spur pruning systems since cane 

pruning leaves fewer pruning wounds 

than spur pruning. The best mitigation 

strategy for trunk disease is prevention. 

Selective pruning, sometime referred to 

as “vine surgery”, can remove infected 

wood, sometimes resolving an established 

infection. However, vine surgery 

is laborious and will not be effective 

unless all the diseased wood is removed. 

Retraining may be needed to replace 

arms or cordons removed in surgery, 

and the surgery will result in large, 

open pruning wounds that could easily 

become infected if not protected with 

pruning protectants. The labor cost to 

renew the cordon or trunk is typically 

economically prohibitive in the San 


Joaquin Valley, and it also does not 

offer the long-term solution, since those 

fungi can slowly reinfect the vine if 

complete elimination of diseased wood 

was not achieved by the vine surgery. 

The current preventative measures include 

double pruning or delay pruning, 

pruning wound protection and vineyard 

sanitation. 

Double pruning or delayed pruning 

helps prevent the exposure of final 

pruning wounds until February or 

March when most rain events finish 

and weather is warming. Less rain 

with warm weather helps the vines seal 

the pruning wounds and prevent the 

fungi entering through pruning cuts. 

However, double pruning or delayed 

pruning does have some barriers for 

some growers to adopt (e.g. pre-pruner 

and labor availability). For growers who 

can adopt it, double pruning or delayed 

pruning offers an effective way to minimize 

trunk disease. 

Pruning wound protectants (mostly 

fungicides) are another option when 

double pruning or delayed pruning 

is impractical. Dr. Akif Eskalen, UC 

Davis, has been evaluating different 

pruning wound protectants in California 

since 2019, and the results from 

those trials can be found here: ucanr. 

edu/sites/eskalenlab/Fruit_Crop_Fungicide_Trials/. 

Fungicide efficacy is 

variable, but the application of pruning 

wound protectants before the rain event 

can help prevent the fungal infections. 

However, pruning wound protectants 

cannot provide complete protection, 

and we still do not know how long the 

protection lasts after the spray. More 

than one spray might be needed if rain 

events occur more frequently after 

pruning. 

Vineyard sanitation should be also integrated 

into the trunk disease management 

plan. Because numerous fruiting 

bodies can be found on pruning debris 

left in the vineyard, complete destruction 

is desirable to reduce the source 

of inoculum and avoid new infections. 

An extensive sanitation of the vineyard 

should be practiced, keeping the 

inoculum level as low as possible. This 

can be accomplished by pruning out all 

diseased wood, removing it from the 

vineyard and destroying it by burning 

or burying. 

Recently, mechanical pruning has 

become more popular due to the increased 

cost and declining availability 

of farm labor. However, mechanical 

pruning may leave more than double 

the number of spurs per vine compared 

to traditional hand pruning. Delayed 

pruning or pruning wound protectants 

should be applied after pruning to 

reduce the risk of trunk disease. In all, 

trunk disease does not only affect this 

year or next year’s yield and general 

vine health, but also reduces the longevity 

of vineyard production life. 




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The What, When and How Much for Applying Key Nutrients 

By CRAIG MACMILLAN, Ph.D., Macmillan Ag Consulting and KRIS BEAL, Vineyard Team 

The goal of fertilization for any 

crop is to ensure the optimum levels 

of nutrients are available to the 

plant at key stages in the growth cycle. 

Balancing these factors is an art as well 

as a science. The first step is identifying 

what nutrients to apply. The second step 

is deciding how much fertilizer to apply. 

The third step is choosing the best time 

to make the application. 

Tissue Analysis 

In an ideal world, all of the plant’s 

needs would be met by nutrients available 

from the soil. In wine grapes, however, 

soil tests are not a useful predictor 

of fertilizer needs as the vine’s uptake 

of nutrients is affected by soil chemistry 

such as pH and the dynamics of different 

soil types. Therefore, tissue analysis 

in the forms of leaf blade and petiole 

analysis are required. Tissue should be 

sampled twice per year. Bloom time 

petiole analysis describes the vine’s nutritional 

needs during the growing season. 

Tissue sampling at early veraison 

is useful for making decisions about 

macronutrient adjustments postharvest 

as nitrogen, phosphorus and potassium 

are all mobile in the vine between 

harvest and leaf fall. 

Bloom time tissue analysis provides a 

good picture of shortages in micronutrients 

such as zinc, magnesium and 

boron. Leaf blades and petioles are 

separated and analyzed separately. For 

bloom time sampling, leaves should 

be selected opposite the first cluster, 

ideally at 50% bloom. When sampling 

at veraison, select the most recently 

matured leaf — usually the fifth or so 

leaf from the tip. The most important 

things to consider are sampling at the 

same time each year and accurately 

reflecting variation within the block. 

Tissue analysis results need to be interpreted 

in the context of other information. 

Are vines exhibiting symptoms of 

a nutrient deficiency or excess? What 

is the overall vegetative growth of the 

vine? Is fruit set less than desired or uneven? 

Nutrient deficiencies are relatively 

easy to spot, but not always easy to 

diagnose. Tissue analysis will identify 

or confirm what those deficiencies are. 

Assessing vegetative growth is relatively 

easy. These data are only meaningful 

when compared year to year, so several 

years of data collection may need to 

be conducted before the relationship 

between fertilizers applied and their 

effects can be identified. 

Therefore, record keeping is an important 

part of making fertilizer decisions. 

Information including tissue analysis 

and fertilizer applications from previous 

years provide insight into how 

in-season and post-season fertilizer 

applications affected nutrient status 

over time. Data on pruning weights 

and estimates of canopy growth at 

bloom can also show trends suggesting 

whether too much or too little nitrogen 

is being supplied. 

Fertilizer Rates 

As every vineyard and every block 

within a vineyard is different, the only 

way to accurately (i.e. efficiently) determine 

amounts of nutrients to apply is 

to adjust published ranges for the deficiency 

or excess of nutrients based on 

personal experience. Translating tissue 

analysis results into specific amounts 

of fertilizer to apply is not an exact 

science. Differences in soil can have 

a sizable impact on nutrient uptake 

and, therefore, fertilizer requirements 

between areas. Consider flagging rows 

or using GPS coordinates to sample the 

same areas. Year to year comparisons 

will tell you if your fertilizer decisions 

are accurate and effective. 

Nitrogen and potassium are the primary 

nutrients that need to be supplied 

with fertilizers, although phosphorus 

and calcium are also important. Both 

have downsides if oversupplied, however. 

Excess N results in excessive growth 

and overcropping while excess K yields 

an unacceptably high pH in the juice 

at harvest. Replacing minerals is very 

important as they are transported 

off-site in the crop and not recycled 

back into the soil like leaves or canes. 

Every situation is different, but believable 

ranges are 3 to 5 pounds N, 5 to 

8 pounds K, and 1 to 2 pounds Ca are 

removed from the vineyard each year. 

Most of these nutrients are taken up by 

the vine during the postharvest period 

if they are available. 

Grapevines are composed of 1 to 2% 

N. 30% of N that the vine uses is taken 

up during the period between harvest 

and leaf fall. The same is true for 

K, although the rate of uptake drops 



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off dramatically about a month after 

harvest. N is an important requirement 

for the production and function of 

proteins and is a major component of 

chlorophyll. Wine grapes will consume 

40 to 50 pounds N per acre during 

the growing season. Much of this will 

be returned to the soil in the form of 

prunings and leaves, but the breakdown 

of pruning wood into bioavailable 

forms of N takes years, and much 

may be lost as nitrous oxide during the 

process. N is released from soil organic 

matter at the rate of approximately 20 

lbs/acre/percent organic matter. Therefore, 

on soils with less than 2% organic 

matter, the rate of N provided through 

fertilization should be increase by 10 

to 20%. On soils with greater than 3% 

organic matter, consider reducing the 

amount of N delivered. Nitrate levels 

in irrigation water can be meaningful 

contributors to total N supplied to 

the vine. In some areas of California, 

nitrate levels are high enough that they 

could be considered fertilizers. 

Rates of N application in wine grapes 

vary from 0 to as much as 60 pounds 

per acre per year. Making decisions 

about the rate of nitrogen fertilizer to 

apply is complicated as excessive applications 

can result in nitrates leaching 

into groundwater and/or the generation 

of the greenhouse gas nitrous oxide. In 

leaf blades at bloom time, less than ~2% 

total N is considered deficient. N deficiency 

is expected with levels less than 

~1.5% in leaf blades at veraison. 

K uptake is negatively affected by high 

magnesium in the soil. Therefore, even 

if K is plentiful in the soil, additional 

K may need to be provided to avoid 

deficiency. K levels are deficient below 

1% in both petiole and leaf blades 

during the spring and ~0.7% in the fall. 

A reasonable target is 2 to 3%. 

Timing Application 

N may be applied in a split application, 

with half being applied just after 

berry set and the other half being 

applied postharvest. In-season applications 

of N may not be necessary at 

all depending on the results of tissue 

analysis. This is an especially important 

consideration given that too much N 

in the vine during the growing season 

can result in excessive growth, shading 

inside the canopy and higher disease 

incidence. To avoid this, spoon feeding 

vines during the growing season can 

afford more control. 

The goal of postharvest fertilization 

is to deliver N, K and Ca to the root 

zone during a time when the vines will 

take up the nutrient and store them 

in the trunk so that they are available 

when the vine breaks dormancy and 

the demand for these nutrients is the 

highest. For example, one study found 

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Fertilizer label on a storage tank (photo courtesy Jacob Hernandez, 

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that 50% of N in the canopy comes 

from N which had been stored in the 

trunk and roots of the vine. Timing 

is critical. Too soon and N may kick 

off a new flush of growth and delay 

dormancy. Too late and the vine is no 

longer moving water into the trunk. 

The canopy needs to be healthy and 

functional. Hitting this window with 

late ripening varieties may be difficult, 

especially if a frost knocks the leaves 

off. Also, care must be exercised in cold 

areas because excessive N postharvest 

can cause hardiness issues. Fertigation 

is the preferred method of delivering N 

and K fertilizers as foliar applications 

can result in an overly rapid uptake. 

Also, there needs to be sufficient soil 

moisture for vine roots to take up the 

elements. 

The amount of time required for vines 

to restore their carbohydrate and mineral 

reserves varies by crop load. Vineyards 

with a crop load of 2 to 4 tons per 

acre need very little time to recover and 

restore after being harvested. Vineyards 

in the 4 to 8 tons per acre range 

require about a month for restoration. 

Vineyards cropped above eight tons 

per acre need between 4 and 8 weeks to 

build their reserves back up. 

A Note on Compost 

A grower may want to apply compost to 

their vines for multiple reasons, including 

delivering nutrients, inoculating 

the soil with microbes, increasing soil 

organic matter and improving soil 

structure. When using compost as a 

fertilizer, one must know the chemical 

analysis of the material and take into 

account the range of nutrients compost 

will contribute to the vine, including 

but not limited to P and K. Good 

quality, finished compost will have a 

C:N ratio of less than 20:1. Of the total 

N per ton in the compost, about 30% is 

available to the vine. Of that, approximately 

half is available the first year 

after application, with the remaining N 

becoming available over the next three 

to four years. 

Although grapevines can survive in depleted 

soils, maintaining adequate crop 

loads and vine health requires replacing 

the elemental nutrients removed 

in fruit and to account for the long 

time required to recycle N and K from 

prunings and leaves back into the soil. 

A successful fertilization program provides 

enough of the required elements 

without producing excessive growth, 

high juice pH or generating pollution. 

Scientific data and historical records 

combined with experience can achieve 

the goals of the fertilizer program. 

Thanks to Dan Rodrigues of Vina Quest 

LLC for his contribution to this article. 




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Pierce’s Disease 

in 

GRAPEVINE 

Identification and Control of Insect Vectors is Crucial to Control 

By KARL T. LUND, UCCE Area Viticulture Advisor 

Pierce’s disease is caused by the 

bacterium Xylella fastidiosa. These 

bacteria live within xylem, the vascular 

tissue through which water travels 

in a plant. As the bacteria population 

grows, it stimulates the plant to produce 

tyloses. The combination of bacteria 

and tyloses cause vessel plugging, which 

restricts water movement in the plant, 

thus causing many of the disease symptoms. 

These blockages will eventually 

lead to the vine’s death. It is estimated 

that Pierce’s disease costs the California 

grape industry $56.1 million a year in 

lost productivity (Tumber et al., 2014). 

To minimize losses, it is important to 

understand the biology of the disease, 

including the bacteria’s host range, how 

the bacteria moves from plant to plant, 

and how to identify infected plants will 

help growers prevent losses and control 

the disease. 

About the Bacterium 

The bacterium X. fastidiosa has a large 

known host range. The European Food 

Safety Authority maintains a database 

of known hosts for X. fastidiosa 

(their updated list approved in April 

2020 can be found at doi.org/10.2903/j. 

efsa.2020.6114.) Research done 

throughout California has identified 

many hosts, including weeds such as 

shepherd’s purse (Capsella bursa-pastoris), 

filaree (Erodium spp.), cheeseweed 

(Malva parvifolia), burclover (Medicago 

polymorpha) and annual bluegrass 

(Poa annua) among many others 

(Shepland et al., 2006 and Costa et al., 

2004). Overall, at least 350 host plants 

have been identified from over 75 plant 

families as hosts for X. fastidiosa. From 

a control standpoint, once X. fastidiosa 

has been introduced to a geographic 

area, it will be virtually impossible to 

eliminate it from that location with 

such a wide variety of possible hosts. 

X. fastidiosa does have another level of 

complexity. To date, four distinct subspecies 

of X. fastidiosa have been identified. 

X. fastidiosa ssp. fastidiosa is the 

subspecies that causes Pierce’s disease 

in grapevine, while X. fastidiosa ssp. 

multiplex is the subspecies that causes 

almond leaf scorch (Rapicavoli et al., 

2018). This does mean that almond 

trees with almond leaf scorch would be 

unable to be the source of Pierce’s disease 

in a vineyard. To narrow down the 

definitive host range, grape-specific PD 

(X. fastidiosa ssp. fastidiosa) was inoculated 

into a range of possible host plants 

using glassy-winged sharpshooters as 

a vector. After an incubation period, 

multiple positive ELISA results were 

obtained for several plants including 

black mustard (Brassica nigra), black 

sage (Salvia mellifera), mirror plant 

(Coprosma repens), Spanish broom 

(Spartium junceum), Mexican elderberry 

(Sambucus mexicana), almond 

(Butte) (Prunus dulcis), white sage 

(Salvia apiana), sycamore (Platunus 

racemose) and coast live oak (Quercus 

agrifolia), confirming that they could 

host the bacteria (Costa et al., 2004). 

This does ultimately lower the number 

of possible plant hosts for X. fastidiosa 

ssp. fastidiosa; however, it still includes 

a long list of common plants found in 

and around vineyards, enough that 

even including this reduced host list, 

managing only these species, and other 

hosts yet to be identified, is still outside 

the ability in most growing regions. 

Insect Vectors 

Bacteria within the xylem tissue of one 

plant may be spread to another plant 

through the feeding activities of certain 

xylem-feeding insects. In vineyards, 

two groups of insects have been identified 

as possible vectors: sharpshooters 

and spittlebugs. Spittlebugs have been 

shown to vector X. fastidiosa in controlled 

settings, but their importance 

as a Pierce’s disease vector in vineyards 

is unclear. Sharpshooters, on the other 

hand, are known to be effective vectors 

of Pierce’s disease in vineyards. 

There are several different sharpshooters 

in California that vector X. fastidiosa. 

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From left to right: green, red-headed and glassy-winged sharpshooters. Size comparison 

measurements are in the bottom right of each individual image (photos by Jack K. Clark, 

Regents of the University of California.) 

Images of glassy-winged sharpshooter. A. Top view of adult glassy-winged sharpshooter. B. Side 

view of adult glassy-winged sharpshooter. C. Top view of young nymph glassy-winged sharpshooter. 

D. Side view of late-stage glassy-winged sharpshooter (photos by K.T. Lund, UCCE.) 


the coastal portions of California is the 

blue-green sharpshooter. This sharpshooter 

is not adapted to the hotter 

climate of the San Joaquin Valley (SJV). 

In the SJV, there are three other sharpshooters: 

the green sharpshooter (Draeculacephala 

minerva), the red-headed 

sharpshooter (Xyphon fulgida) and the 

glassy-winged sharpshooter (Homalodisca 

vitripennis). 

Green and Red-Headed Sharpshooter 

The green sharpshooter and the 

red-headed sharpshooter are both 

small and prefer to feed on grasses. The 

red-headed sharpshooter is specifically 

drawn to and reproduces on Bermudagrass. 

Both the green and red-headed 

sharpshooter can be found in irrigated 

pastures and along waterways such as 

streams, creeks, canals and ditches. 

Neither of these sharpshooters prefers 

to feed on grapevines, however they 

may do so under certain conditions and 

thus transmit Pierce’s disease. Since 

they don’t prefer grapevines, they tend 

not to spread deeply into vineyards; 

thus, when these vectors transmit 

Xylella, it is usually only to grapevines 

along the edges of a vineyard, whereas 

vines in the middle or the sides away 

from the green or red-headed sharpshooters’ 

preferred habitat are not 

affected. 

Glassy-Winged Sharpshooter 

The glassy-winged sharpshooter is 

twice the size of either of the other two 

sharpshooters. Their large size makes 

them more effective as a vector for 

Pierce’s disease because they can travel 

further than smaller sharpshooters and 

feed more effectively on a wider variety 

of plants, including woody plants such 

as grapes. To date, over 350 plants 

have been identified as hosts of glassywinged 

sharp shooter (cdfa.ca.gov/ 

pdcp/Documents/HostListCommon. 

pdf). Many of the hosts for glassywinged 

sharpshooters are also hosts for 

X. fastidiosa. One of the key hosts for 

both glassy-winged sharpshooters and 

X. fastidiosa in the SJV, and for local 

control of Pierce’s disease, is citrus. 

The large feeding range of the glassywinged 

sharpshooter also means that it 

can spread the disease throughout the 

vineyard instead of just to the edges. 

The glassy-winged sharpshooter is not 

a native California insect, only arriving 

in California in the late 1980s (first 

recorded in 1989). As this non-native 

pest is such a dangerous vector, the 

CDFA tracks their distribution. Most 

of Kern county, parts of Tulare and 

Fresno counties, and a very small sliver 

of Madera county just over the San 

Joaquin River are all hosts to naturalized 

populations of glassy-winged 

sharpshooters within the SJV. In SoCal, 

Ventura, Los Angeles, Orange, San 

Bernardino, Riverside and San Diego 

counties as well as portions of Santa 

Barbara county and a small section of 

Imperial county all play host to endemic 

populations. 

Identification of glassy-winged sharpshooters 

within and near these areas is 

important for controlling their spread 

as well as the spread of Pierce’s disease. 

At the top, the insect has a deep brown 

color with creamy white dots on the 

head and thorax. These colors and dots 

continue onto the abdomen; however, 

here they are covered with transparent 

wings (the source of their glassy name). 

Highlighting the glassy wings are red 

lines and patches which can be seen 

from both the top and side. 


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CDFA map for April 2020 of glassy-winged 

sharpshooter distribution in California (photo 

courtesy CDFA.) 

The other main identifying mark is the 

flat white marking along the side of 

the of the abdomen. When sitting on a 

stem, this white mark stands out under 

and through the wings of this sharpshooter. 

Younger nymph glassy-winger 

sharpshooters have yet to develop their 

namesake wings. Their bodies are a 

lighter grayish-brown with very small 

white dots. In this stage, the standout 

feature is their red eyes. The red is the 

same color that will soon highlight the 

parent’s wings. 

Later-stage nymphs have started to 

transition to the adult body color, and 

the red color in the eye is mostly lost. 

However, the red color has transitioned 

onto the wing pads in a pattern that 

has started to develop the adult wing’s 

patterning. 

Vector Monitoring and Treatment 

Monitoring for glassy-winged sharpshooters 

can be done using yellow 

sticky cards. It is recommended to 

use cards that are at least 5.5” x 9” in 

size. One card should be placed for 

every 10 acres and checked weekly for 

recent activity. Monitoring should be 

done from budbreak through November. 

If a glassy-winged sharpshooter is 

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found, and you are outside of a known population 

center, please contact your local agriculture 

commissioner’s office or cooperative extension 

office. Green and red-headed sharpshooters are 

not attracted to yellow sticky cards, so to monitor 

their populations you will need to use a sweep 

net. Sweep lush green grasses near and within 

your vineyard in April and May to assess population 

size. 

Pierce’s disease leaf symptoms. Leaf margins turn yellow (or red in red varieties) 

then burn back from the margins to center in patches (photo by K.T. Lund, UCCE.) 

For both green and red-headed sharpshooters, 

finding two adults in 50 sweeps warrants a 

response. Unfortunately, as both sharpshooters 

are only incidentally on grapevines, treating 

the grapevines will not help the situation. The 

preferred habitat (lush grassy areas) will need to 

be addressed. Due to the overlapping generations 

seen in these sharpshooters, insecticide treatments 

are often ineffective. Removal of preferred 

habitat is a more effective treatment option for 

these sharpshooters. 

For glassy-winged sharpshooters, a single find 

warrants a response. A list of treatment options 

for glassy-winged sharpshooters can be found 

on the UC IPM webpage at ipm.ucanr.edu/PMG/ 

r302301711.html. The most common insecticides 

used for glassy-winged sharpshooter control 

contain the active ingredient imidacloprid. As 

with all chemical control, it is important to rotate 

active ingredients regularly. 

Pierce’s disease symptom on shoots. Patchy bark maturation on current year’s 

shoots leaving green islands (photo by K.T. Lund, UCCE.) 

Research conducted in 2017 showed that several 

other insecticides had long-term control 

of glassy-wing sharpshooters. These included 

Sivanto (a.i. Flupyradifurone) and Assail (a.i. Acetamiprid), 

which still showed greater than 90% 

mortality 7 weeks after application; Actara (a.i. 

Thiamethoxam), which still showed greater than 

90% mortality 5 weeks after application; Harvanta 

(a.i. Cyclaniliprole), which still showed greater 

Table 1: California Laboratories that offer Pierce’s disease testing. 


than 90% mortality 4 weeks after 

application; and Sequoia (a.i. Sulfoxaflor), 

which still showed greater than 

90% mortality 3 weeks after application 

(Haviland and Rill 2019). This research 

was conducted in citrus because relying 

on vineyard-only management is not 

enough for glassy-winged sharpshooters. 

With the larger range of the glassywinged 

sharpshooter, it is important to 

focus on an area-wide approach. A pilot 

program with cooperation between 

grape and citrus growers has shown 

great promise in Kern county. Citrus 

groves are a primary overwintering 

spot for glassy-winged sharpshooters. 

When treatments can be applied to 

these locations, it can lower the number 

of glassy-winged sharpshooters and, 

thus, the presence of PD in the area. 

References 

Costa, H. S., Raetz, E., Pinckard, T. R., 

Gispert, C., Hernandez-Martinez, R., 

Dumenyo, C. K., and Cooksey, D. A. 

2004. Plant hosts of Xylella fastidiosa in 

and near southern California vineyards. 

Plant Dis. 88:1255-1261. 

Haviland, D. and Rill, S. 2019 Evaluation 

of glassy-winged sharpshooter 

mortality following exposure to aged 

insecticide residues, 2017. Arthropod 

Management Tests, 44(1), 1–1. doi: 

10.1093/amt/tsz075 

Rapicavoli, J., Ingel, B., Blanco-Ulate, B. 

Cantu, D. and Roper, C. 2018. Xylella 

fastidiosa: an examination of a 

re-emerging plant pathogen. Mol. Plant 

Pathol., 19(4), 786–800 

Shapland, E. B., Daane, K. M., Yokota, 

G. Y., Wistrom, C., Connell, J. H., 

Duncan, R. A., and Viveros, M. A. 2006. 

Ground vegetation survey for Xylella fastidiosa 

in California almond or orchards. 

Plant Dis. 90:905-909. 

Tumber, K. P, Alston, J. M, & Fuller, K. 

2014. Pierce’s disease costs California 

$104 million per year. California Agriculture, 

68(1-2) 




Vine Infections 

Early identification of infected vines 

is the final step in preventing a larger 

problem from Pierce’s disease. Infected 

vines can be a source of the disease for 

vectors to spread to neighboring vines. 

They are also a strong indicator that 

the bacteria and a vector are present in 

your location. 

The leaves of infected vines will turn 

yellow (for green varieties) or red (for 

red varieties) along the margins. This 

discoloration will then work inwards 

from the margin, with the discoloration 

quickly turning to brown/dried dead 

tissue. This often happens unevenly or 

in sections. Shoot tissue also shows an 

uneven maturation process, leaving 

green islands within lignified brown 

tissue. 

Affected leaves eventually fall off, but 

will sometimes leave the petiole still attached 

to the shoot. Not all these symptoms 

will be found on every infected 

vine. If you suspect a vine is infected 

with Pierce’s disease, you can contact 

your county’s viticulture advisor for 

corroboration. Ultimately, a diagnostic 

analysis is required to confirm the presence 

of X. fastidiosa in the suspected 

vine. Table 1 lists laboratories 

within California that offer Pierce’s 

disease testing. 

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©2020 Kim-C1, LLC. All rights reserved. MOCKSI and Kim-C1, LLC logo are registered trademarks of Kim-C1, LLC. Always read and follow label directions. 559-228-3311 


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