Progressive Crop Consultant - November - December 2016 by JCS Marketing, Inc.

Progressive

Crop Consultant The Leading Magazine For Ag Professionals

November - December 2016 Dormant Monitoring CAPCA Meeting Includes Message of Advocating, Communication New Bot Management Techniques in Walnut are Finding Success Vine Mealybug Controls

PUBLICATION

Volume 1 : Issue 5

January 6, 2017 7:30am- 1:00pm

Yuba-Sutter Fairgrounds

442 Franklin Ave., Yuba City, CA 95991

ANNUAL

WALNUT TRADE SHOW

SAVE THE DATE Pre-Register to Attend

at wcngg.com and be eligible to win a John Deere Gun Safe at the show.

3 PCA/4.5 CCA CE Credits will be available Free to attend

Free tri-tip lunch

Free coffee and donuts in the morning Network with trade show and equipment vendors who offer products for the nut industry Win a hotel stay in Monterey

Y E L L A V H T NOR nce e r e f n o C Nut

Hosted By:

WEST COAST NUT

In conjunction with UC Cooperative Extension’s Butte/Glenn Walnut & Almond Day

JANUARY 19, 2017 Silver Dollar Fairground 7:30am - 1:00pm

2357 Fair St, Chico, CA 95928

CE Credits will be available Free to attend Free coffee and donuts in the morning Free tri-tip lunch November/December 2016

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DATE! www.progressivecrop.com

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Publisher: Jason Scott Email: jason@jcsmarketinginc.com Editor: Kathy Coatney Email: kathy@jcsmarketinginc.com Production: Logan Willems Email: logan@jcsmarketinginc.com Phone: 559.352.4456 Fax: 559.472.3113 Web: www.progressivecrop.com

Change of Address? Visit our website to complete the change of address form under the subscriptions tab.

In This Issue Monitoring 6 Dormant Almond and Walnut Pests

Contributing Writers & Industry Support J. E. Adaskaveg Dani Lightle Professor and Plant Patholo- UC Cooperative Extension gist Orchard Systems Advisor, Glenn/Butte/Tehama Kent M. Daane Counties Department of Environmental Science, Policy and Dave Mengel Management, University of Professor Emeritus, Kansas California Berkeley State University H. Forster Project Scientist Department of Plant Pathology and Microbiology, University of California, Riverside Janine Hasey University of California Cooperative Extension, Yuba/ Sutter/Colusa Counties.

Themis J. Michailides Plant Pathologist, University of California Davis & Kearney Agricultural Research and Extension Center Emily Symmes UC IPM Advisor, Sacramento Valley

Sabrina Hill Contributing Writer

Testing and Plant Analysis 10 Soil Key Tools in Nutrient Management for Corn and Wheat CAPCA Meeting Includes Message of

14 Advocating, Communication

New Bot Management Techniques in

18 Walnut are Finding Success 22

Vine Mealybug Controls

Using “HPLC” to Follow the Movement of an Insecticide Through the Vine to Optimize Application Methods

28 New Bio-Fungicides for Sweet Cherry

UC Cooperative Extension Advisory Board Kevin Day

County Director and Pomology Advisor, Tulare/Kings County

David Doll

UC Farm Advisor, Merced County

Dr. Brent Holtz

County Director and Pomology Farm Advisor, San Joaquin County

Steven Koike

Plant Pathology Farm Advisor

Emily Symmes

IPM Advisor, Sacramento Valley

Kris Tollerup

IPM Advisor, Fresno/Madera Counties, UC Statewide IPM Program and Cooperative Extension, Kearney Ag Research and Extension Center

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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14 November/December 2016

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TREE NUTS

Dormant Monitoring Almond and Walnut Pests Dani Lightle UC Cooperative Extension Orchard Systems Advisor, Glenn/Butte/Tehama Counties Emily Symmes UC IPM Advisor, Sacramento Valley

ormant monitoring is an important activity that can help you decide whether to pursue treatments of some pests (primarily scales and mites) in the dormant or delayed dormant period. A visit to the orchard during the dormant season can also provide information as to the level of pressure that might be expected from certain pests going into the following growing season. Pesticide applications during the dormant and delayed-dormant periods can be quite effective. Coverage tends to be very good since there are no leaves in the way of the application. Most natural enemies are not active during these times. Consequently, pest numbers can be reduced without simultaneously harming natural enemies – leaving those ‘good bugs’ to continue suppressing pests during the growing season and further enhancing your overall IPM program. Obviously, dormant season treatments are not a panacea for all orchard pests and come with risks. Runoff can be a big problem during the dormant season – especially when rain is in the forecast or soils are already saturated. Aside from common-sense principles governing dormant applications based on environmental conditions, there may be locally-based regulations limiting dormant treatments. Consult with your local Agricultural Commissioner to ensure your recommendations are in compliance. Additionally, costs associated with dormant applications may be higher than in-season applications, and orchard access can be a limiting factor. While dormant oil applications provide excellent control of brown mite and European red mite, they do not control webspinning spider mites, which are usually the most problematic mite Page 6

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during the growing season. To add insult to injury, using a dormant spray on low populations of brown mite or European red mite can suppress these populations enough that predator mites, which feed on brown mites/European red mites early in the season, will starve before the spider mites make their unwelcome appearance. Dormant monitoring can be done anytime between late November and January; although for almonds, January is on the late side if you determine that a dormant treatment is warranted. For both almonds and walnuts, the basics of monitoring are the same: examine spurs or branches for the presence of target pests and evidence of biological control, determine whether they are abundant enough to merit treatment, and make an informed decision on treatment type and timing. When dormant sampling, you will be monitoring for a wide range of pests. In almonds: • • • • •

Mummy nuts & stick-tights Brown mite eggs & European red mite eggs San Jose scale & European fruit lecanium Peach twig borer hibernacula (1st dormant season) Scab lesions

In walnuts: • • • • •

Mummy nuts & stick-tights European red mite eggs Walnut scale Frosted scale & European fruit lecanium San Jose scale

Monitoring in almonds involves collecting 100 spurs (or twig samples, in the case of 1st leaf trees). Aim to survey 35 to 50 trees across the orchard. From each tree, collect 2 to 3 spurs by clipping at the base of the spur, including some old spur wood. Be sure to select spurs from different locations in the canopy (inte-

November/December 2016

rior and exterior). Begin by examining the first 20 spurs and record presence/ absence of each pest. Continue examining up to 100 spurs (in batches of 20), and consider treatment if the following thresholds are met: • • •

Mites: treat if eggs are detected on 20 percent or more spurs. Scales: follow the decision tree for almonds. Scab: treat if lesions are detected on 10 percent or more spurs.

Additionally, survey for peach twig borer hibernacula on the crotches of trees entering their 1st dormant season. If a significant number of hibernacula are observed, consider treating during the dormant season to prevent damage to tree architecture from larval feeding on shoots in the spring. Minimizing the number of mummy nuts and stick-tights reduces overwintering sites for navel orangeworm. A generally accepted threshold is an average of two mummy nuts per tree in the Sacramento Valley; less in the southern portions of the Central Valley. If you exceed the threshold, implement winter sanitation practices and destroy the mummy nuts by March 1st. To monitor your walnuts, examine scaffolds and branches throughout the orchard. To better evaluate what is occurring at the top of the canopy, consider following after a pruning tower or hedger and looking at pruned branches for the various pests. There is no recommended number of branches to survey for walnut dormant monitoring. A safe bet would be to examine 100 branches (the recommended number for almond surveying) distributed from around the orchard; additionally, look at scaffolds from several trees. Treatment thresholds are as follows: •

Mites: no threshold established; avoid treating low populations that Continued on Page 8

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•

maintain mite predators early in the growing season. Scales: follow the decision tree for walnuts.

Mummy nut thresholds for walnut are not established, but they carry the same risk of overwintering sites for navel orangeworm. Minimizing the numbers of mummy nuts in trees, as well as destroying nuts on the orchard floor and any other debris areas in and around the orchard, will help reduce navel orangeworm pressure next season. Treatment decisions should be based on the level of infestation observed. In almonds, the most common dormant treatment is oil, which works by suppressing the respiration of scales or mite eggs. Infestation levels of San Jose Scale greater than 60 percent may require the addition of an insect growth regulator (such as Seize® and Centaur®) for better control. Other contact materials, such as carbaryl, carry the risk of toxicity to bees, especially if they are applied too close to bloom, and organophosphate use during the dormant period poses a serious threat to water quality. If scab is of concern in the orchard, a dormant or delayed dormant application of copper/oil or chlorothalonil/ oil, followed by a fungicide treatment at petal fall will help manage disease. When using chlorothalonil, be sure to get it on prior to bud swell to reduce the risk of burning the buds. If you missed the window for chlorothalonil, switch to copper/oil treatments to reduce the risk of phytotoxicity. Oils are not recommended for use during the dormant season in walnuts because of phytotoxicity concerns. Delayed-dormant treatments of insect growth regulators are highly effective for scale insects in walnuts. For more information on pest identification, monitoring, and treatment options, see the Almond Sampling and Treatment Guidelines at ipm.ucanr.edu/ PMG/r3900211.html and the Walnut Dormant Monitoring Guidelines at ipm. ucanr.edu/PMG/r881900311.html.

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November/December 2016

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Soil Testing and Plant Analysis

Key Tools in Nutrient Management for Corn and Wheat Dave Mengel Professor Emeritus, Kansas State University

or most people the objective of a nutrient management program for most crops is to provide adequate nutrients to support the growth and development of a high yielding crop, as simply and as cheaply as possible. That is a reasonable objective for many farmers, but like everything else in crop production, the devil is in the details. For example in growing wheat, where does quality come in? Many markets demand or pay premiums for high grain protein. Will the easiest and cheapest plan give the yield and quality needed to maximize returns? And what about issues such as environmental quality? Let’s take a systematic look at how tools such as soil testing and plant analysis, including new tools for assessing plant nutrient status such as active crop sensors, can be used to assist in efficient nutrient management of corn and wheat. Pre-plant Soil Testing Soil testing to determine the nutrients currently available in the soil is the first step in developing an efficient fertilizaPage 10

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tion program for any crop. It also is an important tool for determining the soil pH and organic matter content, and to monitor soil salinity issues, particularly when irrigating with marginal quality water. Of the 14 essential mineral elements required by plants, some such as P and K, are immobile in soils and accumulate in the soil surface. Others, such as nitrate-N and chloride are mobile and move into and may accumulate in the subsoil with leaching. So a quality soil testing program for corn and wheat may need to include both surface soil samples for immobile nutrients and subsoil or profile samples, for mobile nutrients. Surface sampling for immobile nutrients. A surface soil sample is normally collected to a sampling depth of 6 to 8 inches, following the instructions provided by the lab doing the testing, or the organizations providing the recommendations based on the test. Sampling deeper will generally result in lower test values while sampling shallower will give higher values, especially with no-till and mulch till systems commonly used for corn and wheat production today. Surface soil samples are commonly used to make pre-plant fertilizer applications for immobile nutrients which

November/December 2016

accumulate in the top few inches of soil. They are commonly analyzed for soil organic matter (SOM), soil pH and nutrients such as extractable phosphorus, and exchangeable potassium. Other immobile nutrients which naturally accumulate in the surface of soils are calcium (Ca), magnesium (Mg) and micronutrients such as iron (Fe), zinc (Zn), manganese (Mn) and copper (Cu). Soil testing is used to monitor these nutrients in areas where specific problems exist. For example copper in some parts of the Southeast, organic soils in the Great lakes region, magnesium in the Ohio River Valley and zinc in the Great Plains. Surface samples are generally taken as a guide for making pre-plant fertilizer recommendations for nutrients such as P and K and for lime applications on acid soils. Timing of when the samples are taken is generally not critical, though it can impact the values obtained in some cases, particularly soil pH and K levels. Samples for soil pH and liming on low CEC, poorly buffered soils can be influenced by salt accumulations due to evaporation during dry weather. This tends to result in lower pH at times and can impact liming decisions. Similarly, some higher clay soils have the capacity to

Photo Credit: Dave Mengel

CORN/WHEAT

Nutrient

Units

Crop Corn

Wheat

Whole Plant Less than 12” Tall

Ear Leaf at Green Silk

Whole Plant Tillering to Jointing

Flag Leaf Heading to Flowering

Nitrogen

3.5-5.0

2.75-3.50

3.5-4.5

Phosphorus

0.3-0.5

0.25-0.45

0.3-0.5

Potassium

2.5-4.0

1.75-2.25

2.5-4.0

2.0-3.0

Calcium

0.3-0.7

0.25-0.50

0.2-0.5

0.3-0.5

Magnesium

0.15-0.45

0.16-0.60

0.15-0.5

0.2-0.6

Sulfur

0.20-0.50

0.15-0.50

0.19-0.55

0.15-0.55

Chloride

Copper

ppm

5-20

5-25

Iron

ppm

50-250

30-200

Manganese

ppm

20-150

Zinc

ppm

20-60

15-70

Boron

ppm

5-25

4.0-25

1.5-4.0

1.5-40

Molybdenum

ppm

0.1-10

0.1-3.0

Aluminum

ppm

<400

<200

temporarily fix K within the clay mineral lattice during dry periods giving lower soil test values and reduced K availability to crops. This can be important on some soils particularly for high K demanding crops like corn or cotton. Regardless of the soils, Crop Advisors should strive to take soil samples far enough in front of the fertilizer season to have adequate time to process the data obtained, to get the full value from a soil testing program, particularly when developing site-specific or precision recommendations. Profile samples for mobile nutrients. Some nutrients are very mobile in soils and tend to move below the surface few inches of soil. These nutrients can accumulate in the subsoil, especially in drier regions, and a profile or subsoil sample is used to measure the availability of these nutrients to crops. Profile samples can vary from 24 to 60 inches in depth, depending on the rooting depth

0.18-0.60

of the crop, the properties of the soil, and the research base used to make recommendations for the specific nutrient. Examples of mobile nutrients commonly managed for wheat and corn using a profile sample are nitrogen (N), sulfur (S) and chloride (Cl). Profile sampling is most common in the drier regions of the country, especially for N, such as the western Corn Belt or wheat growing regions of the Great Plains. However the use of this tool is spreading as its use is being tested in other areas. One particular area where it’s use is increasing is where organic nutrient sources such as compost, animal manure or biosolids are being applied. Nutrients such as nitrogen and sulfur are primarily provided through the breakdown and mineralization of organic compounds in these products. This has the advantage that these are slow release products, reducing the potential for leaching from the root zone in some cases, but it also

is a biological process which is slow and can occur over multiple years. So residual effects from these products are common, and the management of these sources is more complex. Profile sampling can prove valuable to identify places where nutrients may have accumulated from previous years applications of these organic products, allowing fine-tuning of the recommendations. This has proven to be very helpful in areas where high N animal wastes such chicken litter are commonly used as fertilizer sources to avoid excess N application on wheat, minimizing lodging and dense canopies which favor foliar disease development. In-season soil testing for N: a special case One special case which can have value for in-season soil testing is using

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Continued from Page 11 the Pre-Sidedress Nitrate Soil Test for corn where organic nutrient sources are applied, or on fields with a history of manure, compost or biosolid applications. This test has been used successfully by many corn producers who routinely apply nitrogen at the 5 to 7 leaf stage on corn to estimate the rate at which N is being mineralized from current or previous applications of organic materials. In most places the test is used, a 12 inch soil sample is taken when the corn is at the 5-6 leaf stage, to determine the nitrate-N levels present in the soil. Based on this “snap shot” of nitrate mineralization, the side-dress N rate can be adjusted. Plant Analysis Routine monitoring programs. While specific soil tests are available for most nutrients, the availability of some nutrients to crops is often influenced by more than just the amounts present in the soil. Things like soil pH, soil drainage and oxygen levels in soils, and SOM content can influence the availability Page 12

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of micronutrient metals such as iron, zinc, copper and manganese and other micronutrients such as molybdenum. Other nutrients like N and S are found in large quantities in SOM and are released through mineralization during the growing season. But the rate of mineralization is influenced by soil temperature, pH and moisture and can be unpredictable. For this reason, soil tests alone are often not used for making routine fertilizer application of these nutrients to corn and wheat, but plant analysis may also be used. The development of a plant analysis program to provide an early warning system for nutrient depletion and deficiency should be considered by most corn and wheat growers. There are two primary ways plant analysis can be used: as a routine monitoring tool to ensure nutrient levels are adequate in the plant, and as a diagnostic tool to help explain some of the variability in growth and appearance we see in fields. Keep in mind however that any plant stress (drought, soil compaction, pest damage to roots, etc) can have a serious impact on nutrient uptake and the nutrient concentrations found in

November/December 2016

crops. Sampling under stress conditions for monitoring purposes can give misleading results, and is not recommended. Plant samples for monitoring crop growth and nutrient concentration in corn and wheat are best taken as the plant completes its vegetative growth and shifts into reproduction. For corn that is normally considered at early silking, and in wheat when the flag leaf has emerged at or before the pollination process has begun. In both crops, nutrients are rapidly moved from the leaves and stems to the developing grain once pollination is complete. So later sampling will normally result in lower nutrient values found in the leaf, a potential false test for a deficiency. For corn. 15-20 ear leaves, (the leaf is where the top ear is formed and emerges between the leaf and the stalk) should be collected at random from the field when silks are emerging and are still green. Sampling latter, once the silks have turned brown indicating pollination is complete, will give lower nutrient contents as the plant begins to move nutrients from the leaves to the developing seed.

Photo Credit: Dave Mengel

For wheat, 40-50 flag leaves, ( the top leaf on the plant), should be collected at random from the sampling area, after the head has emerged, but before pollination begins. Again sampling later will result in lower nutrient values as nutrients move from the leaves into the developing seed. The data returned from the lab will be reported as the concentration of nutrient elements, or potentially toxic elements in the plants. Units reported will normally be in percent for the primary and secondary nutrients (N, P, K, Ca, Mg, and S) and ppm or parts per million, for the micronutrients (Zn, Cu, Fe, Mn, B, Mo, and Al). Most labs/ agronomists compare plant nutrient concentrations to published sufficiency ranges. A sufficiency range is simply the range of concentrations normally found in healthy, productive plants during surveys. It can be thought of as the range of values optimum for plant growth. The medical profession uses a similar range of normal values to evaluate blood work. The sufficiency ranges change with plant age (generally being higher in young plants), vary between plant parts, and can differ between cultivars. So a value slightly below the sufficiency range does not always mean the plant is deficient in that nutrient, but just is an indication that the nutrient is relatively low. Values on the low end of the sufficient range are common in extremely high yielding crops, often because high yields are a reflection of efficient growth and production. However, if that nutrient is significantly below the sufficiency range, then one should ask some serious questions about the availability and supply of that nutrient.

Levels above the sufficiency range can also indicate problems. High values might indicate over fertilization and luxury consumption of nutrients. Plants will also sometimes try to compensate for a shortage of one nutrient by loading up on another. This especially occurs with nutrients such as iron, zinc and manganese. In some situations very high levels of a required nutrient can lead to toxicity. Manganese is an example of an essential nutrient which can be toxic when present in excess. One problem with using plant analysis only for monitoring is that in most cases the results are obtained too late to make significant corrections for that crop. It is a quality assurance tool. But it is an excellent companion to soil testing and field scouting to ensure the efficiency and effectiveness of your nutrient management program. Diagnostic samples. Plant analysis is also an excellent diagnostic tool to help understand some of the variation seen in the fields when scouting. When using plant analysis to diagnose field problems don’t wait for the ideal monitoring times, take samples immediately and record the current growth stage. Also try to take comparison samples from both good/ normal areas of the field, and problem spots. Collect soil samples from the same good and bad areas. If problems develop early in the season when corn plants are in the 5 to 6 leaf stage, collect whole plants from 15 to 20 different places in your sampling areas. Later in the season, collect 20-30 top, fully developed leaves with visible leaf collars. In wheat, before jointing or stem elongation collect 20-30 whole plants, or after stem elongation, collect 40-50 top fully

developed leaves with visible leaf collars. In all cases get plant samples to the lab as soon as possible for analysis. If shipping through the mail, allow the samples to wilt to remove excess moisture and ship in mailing envelopes or in paper bags in a card board box. Do not use sealed plastic bags as this will encourage decomposition. Interpretation. The table on page 8 gives the range of nutrient content commonly found in corn considered to be “normal” or “sufficient” in young plants < 12 inches tall and in earleaves at green silk. It also has the values for young wheat plants at tillering to jointing and for wheat flag leaves at heading to flowering. Keep in mind that these are the ranges normally found in healthy, productive corn and wheat. Crop Sensors for in-Season evaluation of N needs. One new technology which has entered the commercial market in recent years for use with corn and wheat to make in-season N need determinations is the crop sensor. Currently several companies are offering sensors which can be used to make over the top determinations of the N status of a crop, removing the need for collecting samples of soil or plant tissue and sending it to a lab for analysis. These new technologies are currently being used in the Corn Belt and Great Plains for topdressing wheat and sidedressing corn. A number of types of vehicles are being used from ATV’s to self propelled sprayers to drones to carry the sensors. So this is a rapidly developing area to keep an eye on.

November/December 2016

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Photo Credit: Sabrina Hill

CAPCA

CAPCA Meeting Includes Message of Advocating, Communication Sabrina Hill Contributing Writer

ore than a thousand pest control advisors from around California gathered at the Disneyland Convention Center October 10 through 12 for the 42nd annual California Association of Pest Control Advisors (CAPCA) annual meeting. The 2016 meeting theme was Feeding a Nation, Fighting the Fear. It is a theme opening speaker Rajan Gajaria, of Dow AgroSciences, called “intriguing”. Page 14

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“From my perspective, that’s essentially what we want to be talking about,” he said in an interview. Gajaria’s title with Dow AgroSciences is Global Leader, Latin and North America, and his talk focused on a global perspective, rather than just the nation. “Ag is really a global business. It’s a global supply chain. You might be growing products in California, but they find themselves all over the world.” The key focus of his talk was the second part of the talk - fighting the fear.

November/December 2016

“How do we use science, information, data, social media whatever is the mechanism to basically fight the fear. And, I would qualify that as the fear of the unknown,” he explained. “People don’t know what they don’t know. So, how are we going to be able to dispel some of the myths and fight the fear? That, I think, is at the heart of the conference.” He broke his talk into three main subjects and started with the concept of pride. “The first thing we talk about is pride. Do we really take pride in what

we do? That is essentially going to be infectious, whether it is PCAs in California, or reporters who work in ag, or people like me who work in the industry,” he said. “We might take it for granted in places like the U.S., but you just have to go across the pond to Europe and you start seeing people who are not even sure if this is the right thing to do within our industry. So, we’ve got to be able to kindle that fire up. We need to take pride (in the industry).” The second part of his talk focused on passion. “I think even when we talk pride, many times we do not take the time to show our passion,” he said. “It does not show up in dinner conversations or Thanksgiving, where your not-so-favorite aunt talks about how she and her family are all only eating organic. Do we really step up and show the pas-

sion to have those conversations?” Gajaria said his third topic, power and the power of information, was the one he was most excited about. “We don’t always have the right information,” he explained. “So, how do we use humor? How do we use information? How do we make it easy for people to access data and information which is real? As simple as it seems, people just don’t have access to it.” Gajaria encouraged the attendees to arm themselves with accurate and current information. As part of his presentation, he gave the PCAs access to a webpage that has links to several trusted sources of information on things like GMOs and agricultural principles. The address for the website is http://client.dow.com/CAPCA. “I can’t tell you the number of times I’ve had the chance to talk to audiences, whether it’s students or it could be

fraternities like (agricultural fraternity) AGR, where somebody would stand up and say ‘this is great, but can you point me to where this information is easily available’.” Gajaria also believes it is important for those in agriculture to help spread factual information to non-agricultural communities. He said that is a key part of Dow AgroScience’s Grow the Conversation movement. He pointed out, the movement is not about forcing an opinion, but rather engaging in a conversation. He also said that conversation needs to have a broad scope of engagement. “It has to be consumers at-large. It’s one thing for people in Fresno to believe, but what are you going to do to make San Jose, San Francisco, and LA believe?” he asked. “That’s the battle in

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Continued from Page 15 my mind for the PCAs. It’s easy to stay in our world in ag where everybody understands. We’re planting the seeds that they need to reach out and make sure that their audience is the consumers of the product we generate, the food we make.” Another featured at the CAPCA meeting was David Hollinrake, Bayer CropScience Vice President of Marketing. His message to the PCAs was also one of spreading the truth about modern agriculture. “The main message was the powerful voice that farmers have,” he said. “Yes, we’ve got some daunting challenges in front of us, relative to regulations. That’s largely built off the fact that even when I was growing up on a farm, there were a lot more people in the community who understood agriculture. As an example, when my grandfather was on the farm, some forty percent of the American population was connected to agriculture. Today, there’s one percent. The fact that we have so many people who aren’t in Page 16

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and around what we do, they form misconceptions. With misconceptions comes mistrust. So, the opportunity that we have in front of us is to educate and engage the general populations such that they better understand the technologies that we employ to feed a growing, hungry population.” Hollinrake said while social media has helped with the spread of information about agriculture, it is also a hindrance due to the spread of misinformation. However, he said the agriculture community has the ability to counter that. “The message that I really tried to convey is that farmers are the most trusted voice in food safety. So our job, and what we’re trying to do with our “Agvocate” platform is to enable farmers to be proud of what they do and to represent that in social communities so that others can have a better appreciation for the benefits of agriculture and the benefits of what farmers do.” Hollinrake added that is an important goal at Bayer CropScience. “Prop up the farmer in a way that enables them to showcase the great things that they

November/December 2016

do to feed that growing, hungry population.” On a more local level, Kern County Agriculture Commissioner/Sealer Ruben Arroyo spoke about the county’s pilot program involving pesticides around school. He explained the Kern County program was born out of some of the hearings on the proposed state regulation. The Kern High School District maintenance and operation had some concerns that they took to the Kern County Farm Bureau. The Farm Bureau and school district representatives then went to Arroyo and asked him if they could all work together to “make something happen.” “And that is how we started the pilot project. We tried to mirror close to what we knew the potential was in the regulation,” Arroyo said. The county started a program that requires growers notify schools of any pesticide spraying from 6 a.m. to 8 p.m., Monday through Friday, while the state regulations only run from 6 a.m. to 6 p.m. The Kern County program started with just the Kern High School District, as it was the

Nature’s Energy Powering Soils for Enhanced:

Photo Credit: Sabrina Hill

• Biodiversity • Fertility • Fertilizer efficiency • Nutrient Uptake • Sustainability

only district interested at that time. The district has six schools that are adjacent to farming. It was decided to keep the program focused on those adjacent schools, rather than going out a quarter mile as the other program does. This narrow focus provides more targeted data for the pilot program, which can be used to determine how well it is working. “We got the growers on board because they were already communicating with the schools,” Arroyo said. “This wasn’t anything new to them. What was new to them was that we were going to put it officially online. Some of them thought there may be some problems there, but we figured it out. We got them logged in and showed them how to use (the system).” He said other than the online aspect and the change of hours, growers in Kern County won’t notice much of a difference. “Most of them aren’t applying during school hours anyway. This is kind of our point and wanting to gather this data, to find out what the parents’ concerns are, what the schools’

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concerns are. And most importantly, to log what we already know is happening,” he said. “We already know the communication is happening. We’re doing it officially now, through the computer.” He said it is important to gather the data, because he believes it will show that pesticides are not being sprayed near schools in the manner that some say it is. “We’re not saying that this is wrong or it shouldn’t happen,” he said. “If there’s going to be a regulation that comes out, why not make it something that the growers can work with the people we’re trying to enforce this with? And that’s the schools.” He said the schools have some concerns of their own. “The Department of Pesticide Regulation has no authority to tell the schools what to do with this notification. They don’t necessarily have to notify parents,” he explained. “And so the schools are like ‘if we don’t notify the parents, we could face some liability. Rueben help me out with this.’ So, this is where I inserted myself into this line

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of communication. We have staff that know about pesticides. We have staff that know about the regulation. We have staff that interpret laws and regulation. So, I put myself out there and said we’re going to take all those calls for you, especially as part of this pilot project. But even more importantly, if this regulation does come to pass, I think I’m going to keep it that way. I want to be that buffer so there isn’t panic at the school grounds or panic with the parents.” He mirrored statements from Gajaria and Hollinrake: Growers keep the interests of their communities in mind. “Growers don’t use pesticides because they want to,” he said. “A lot of times, it’s because they have to.”

November/December 2016

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Page 17

WALNUTS

New Bot Management Techniques in Walnut are Finding Success

Janine Hasey University of California Cooperative Extension, Yuba/Sutter/Colusa Counties.

ut crops are major industries in California, with planted acreage in almonds, pistachios and walnuts at almost 2 million acres. Although many fungal diseases have been described causing problems in almond, pistachio and walnut crops had limited reports on fungal diseases. Specifically, on walnut, the major disease which is very difficult to control is walnut blight caused by the bacterium Xanthomonas juglandis. Previously, only two fungal diseases were reported for walnut and these are branch wilt (caused by Neoscytalidium dimitiatum (old synonyms: Hendersonula toruloidea or Nattrassia mangifera) and walnut anthracnose caused by the fungus Marssonina juglandis (ascosporic stage Leptosphaeria juglandis). The branch wilt pathogen is favored by hot and dry conditions and infects often through sunburn wounds; while anthracnose is favored only when there is excessive rainfall in the spring. Since 1985, we have been studying several diseases caused by fungi in the Botryosphaeria family. These include the very devastating disease of pistachio Botryosphaeria panicle and shoot blight, band canker of almond, and in the last five years, Botryosphaeria (Bot) canker and blight disease of walnuts. The first report on a Botryosphaeria disease of walnut was in 1915 on a canker disease recorded in old walnut cultivars, named “melaxuma” that produced black sap and killed major tree scaffolds (Howard, 1915). Another study in 1935 reported on the susceptibility of walnuts to Botryosphaeria ribis. Since then, there was not any concern about BotryosPage 18

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phaeria attacking walnuts for decades until about 2005 when growers started noticing a general reduction in yields and a high incidence of dead spurs with dead fruiting buds that had accumulated over the years in the canopy. Over the last decade, a systematic survey of isolates from dead walnut wood (branches, shoots, and spurs) and black nuts revealed that there are 10 different species of Botryosphaeriaceae that infect walnuts. Both Botryosphaeriaceae fungi and/or Phomopsis species were isolated from Chandler, Tulare, Vina, Howard, Ashly, Serr, Payne, and Livermore walnut cultivars. Samples diagnosed with Bot/Phomopsis diseases were found in Tehama, Glenn, Colusa, Butte, Yuba, Sutter, Yolo, Solano, Placer, San Joaquin, Stanislaus, Merced, Madera, Fresno, Tulare, Kings, San Benito, and Kern counties, indicating the causal fungi are widely spread in our walnut growing regions. There are six types of symptoms characteristic of Botryosphaeria canker and blight disease as following: 1) Blighted branches: These branches look very similar to branch wilt symptoms that typically occur on the southwest ex-

posure but with Bot, can occur on all exposures of the canopy. These may or may not be associated with sunburn, pruning wounds, or other types of wounds. In some instances, both the branch wilt pathogen and Botryosphaeria/Phomopsis can be recovered from the same blighted branch. 2) Shoot, spur, and fruit blight: The hulls of the walnut fruit turn black as they decay by a soft rot and one can easily observe that the infection spreads from one fruit to the other fruit(s). Eventually this decay extends into the peduncle and moves into the spur, developing a canker that kills part of the spur with the buds on it (Photo 1). This blight phase of the disease resembles the panicle and shoot blight of pistachio where infections from fruit clusters move into the sustaining shoot via the cluster’s rachis and develop distinct cankers. Cankered (or blighted) spurs can be seen year-round because they accumulate on the trees from one year to the next. In the fall after leaf drop, infected spurs are readily observed. Cankers in spurs vary in size and some will bear pycnidia Continued on Page 20 Photo Credit: UCCE Cooperative Extension

Themis J. Michailides Plant Pathologist, University of California Davis & Kearney Agricultural Research and Extension Center

Photo 1. Infection of fruit by Botryosphaeria moves through the peduncle (stem of fruit) into the spur causing fruit blight, canker, and bud killing.

November/December 2016

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Continued from Page 18 of Botryosphaeria and/or Phomopsis by September, but the majority will have pycnidia (spore bearing structure) by the spring of the following year. The killing of the vegetative and flower buds on the spurs results in yield reduction. This may explain why walnut growers have been reporting reduced yields in orchards that were supposed to have trends of increased yields. 3) Walnut blight and Botryosphaeria blight: In some instances fruit infected by walnut blight (Xanthomonas juglandis) can also be infected by Botryosphaeria and/or Phomopsis fungi. In this case, the black lesion due to walnut blight that develops at the stylar end of the fruit may have a brown hue, an indication of the presence of fungal infection. In addition to Botryosphaeria and Phomopsis, other fungal pathogens isolated from lesions of walnut blight include, Fusarium, Alternaria, Gloeosporium, Colletotrichum, Acremonium, Aspergillus niger, Nigrospora, and Epicoccum. Among these, Botryosphaeria, Phomopsis, Fusarium, and Alternaria spp. are the most com-

monly isolated from walnut fruit showing walnut blight symptoms. By splitting infected nuts, one can observe mycelia of any of these fungi internally on top of the kernels. 4) Cankers initiated from pruning wounds: Infections of pruning wounds can lead to canker formation that can vary in length as affected by the age of the shoot. Wounds of 3 to 4 year old shoots favor longer cankers than in 1 to 2 year old shoots. The importance of these cankers is that they also supply spore inoculum of the Botryosphaeria and/or Phomopsis fungi. Pruning wounds are susceptible to infection for up to four months. 5) Infected leaf and peduncle scars: These infections occur in the fall after leaf drop or fruit harvest. The pathogens invade the scars and produce a canker around a leaf scar or below the peduncle scar. 6) Scaffold killing: This symptom involves the killing of major branches. Although the killing of these branches was not shown experimentally, it appears there are three major factors that contribute to this killing: i) shade; ii) walnut

scale; and iii) Botryosphaeria/ Phomopsis infections. It is necessary to prune and remove these branches since they are covered with fungal pycnidia. Removing and destroying these branches will result in significant reduction of spore inoculum in an orchard. Causal Fungi Ten species of Botryosphaeria in the Botryosphaeriaceae family were recovered from diseased samples and two Phomopsis species in the Diaporthaceae family. Among the 10 “Botryosphaeria” species the most virulent were Lasiodiplodia citricola, Neofusicoccum parvum, and N. mediterraneum. N. mediterraneum is the most frequently encountered species and widely spread. These three species were found in walnuts from all the counties surveyed. Among the “Botryosphaeria”, six species can infect walnut shoots and cause cankers and the remaining four cannot cause any canker on shoots. However, all ten species can infect the walnut fruit and via the peduncle can invade the spur and cause cankers (photo 1). The two “Phomopsis” species, identified as Diaporthe neotheicola and

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November/December 2016

Photo Credit: UCCE Cooperative Extension

D. rushicola, cannot infect shoots directly but can infect fruit and from the fruit invade the spurs. Infection occurs directly on fruit (via latent infection which will develop symptoms as the fruit mature during summer and fall), invasion of peduncle, and eventually invasion of the spur tip along with the killing of 3 to 4 nearby buds. In the fall, as fruit is harvested and leaves start dropping, one can find infections that start from peduncles, leaflets, and leaf scars. These are black and grow more downwards in the shoot than towards the top of the shoot. After examining many walnut samples , we determined that, in addition to pycnidia formation –which is very common – both the “Botryosphaeria” and “Phomopsis” fungi develop perithecia (sexual spore bearing structure). Perithecia of Botryosphaeria were found in samples of prunings collected from the ground and dead branches in Stanislaus, San Joaquin, Colusa, and Butte counties. Predisposing factors. Factors affecting the infection of walnut by “Botryosphaeria” include environmental stresses and insect infestation. In walnuts, we showed that shoots infested by scales are more susceptible to infection, and resulted in larger cankers caused by three species of “Botryosphaeria” than shoots not infested by scales (Fig. 1). Specifically, 60-75 percent more shoots were infected when scales were present than when scales were not present after inoculating with “Botryosphaeria” species. Disease Spread. “Botryosphaeria” and “Phomopsis” fungi spread in nature mainly by splashing water due to the fact that they produce abundant pycnidia. In walnut orchards, they also can spread by air where perithecia develop. In general,

Figure 1. Incidence of Bot infection of walnut shoots with and without infestation by walnut scale after inoculating them with a spore suspension of three “Botryosphaeria” species. Infection was recorded 2 weeks after inoculation. (Differences between infection of shoots with scales and those without scales for each “Botryosphaeria” species are significant.) “Botryosphaeria” fungi are favored by warm temperatures. B. dothidea has an optimum temperature ranging from 81 to 86°F, and usually most of the disease symptoms from new infections during the growing season show during the summer when the temperatures become high and the crop physiologically mature and susceptible. Pycnidia release spores after a rain event (at least ¼ of an inch) and at least 1.5 hours of wetness is needed for germination and infection of plant tissues. For walnuts, at least ¼ of an inch of rain or irrigation water and temperatures at or over 50°F are needed for infection. Control Managing Botryosphaeria canker and blight disease of walnut needs an integrated approach. Cultural control to reduce inoculum and fungicide sprays to protect tissues from infection. 1.

Dead branches (killed by branch wilt) and /or shade, walnut scales, and “Botryosphaeria” and “Phomopsis” need to be removed because all these tissues can be covered with a dense layer of pycnidia and/or perithecia. Consider deadwood removal in the summer when it is dry to avoid pruning wound infections. (See also details in “Management of Botryosphaeria canker and blight in different age orchards” below.) If sprinkler irrigation is used in an orchard, use a low trajectory angle to avoid wetting the canopy.

Improve water infiltration in orchards to avoid excessive humidity/ moisture due to standing water. Use effective fungicides registered for walnut to combat the Bot disease. Sprays during mid-May, mid-June, and mid-July reduce shoot blight and fruit infection. Last year’s results suggest that bloom and postharvest sprays, a one-time mid-summer spray, and sprays applied based on a leaf wetness model were effective in reducing disease. However, these treatments need to be repeated again in order to reach strong conclusions on the efficacy of these spray timings. 2015 fungicide efficacy can be seen at http://www.ipm. ucanr.edu/PDF/PMG/fungicideefficacytiming.pdf. Managing Bot also depends on the age and the level of infection of an orchard: 1.

November/Decemberr 2016

Orchards with light to medium infection: Prune or hedge these orchards first and then move into heavily infected orchards; remove prunings out of the orchard; apply fungicide spray programs annually to reduce infection and inoculum with time. Orchards with no Botryosphaeria infection (young orchards): if pruning is done, prunings can be shredded and left on the orchard floor. Monitor orchard annually for appearance of blighted spurs and prune them as soon as possible; this approach will delay the invasion of the orchard by the “Botryosphaeria” and “Phomopsis” fungi.

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Page 21

GRAPES

Photo Credit: Kent M. Daane

Vine Mealybug Controls

Using “HPLC” to Follow the Movement of an Insecticide Through the Vine to Optimize Application Methods Kent M. Daane1, Valeria Hochman Adler 1, Geoff Dervishian2, Sonet Van Zyl2, Noemi Fonseca-Espinoza1, Pahoua Yang1, Tyler M. Lutz 1, John Hutchins 1, Jesus Ceja 1 and Monica L. Cooper3 Department of Environmental Science, Policy and Management, University of California Berkeley, CA 94720-3114 2 Department of Viticulture and Enology, California State University, Fresno, CA 93740 3 University of California Cooperative Extension, Napa County, 1710 Soscol Ave, Suite 4, Napa, CA 94559

Abstract he vine mealybug has become one of the more important insect pests of California vineyards. Insecticides are often the best control tool, but in some cases, multiple applications are needed to reduce the vine mealybug population under the bark of the trunk or on the roots. Our overall objective is to improve insecticide application that target this overwintering population. For systemic and translaminar insecticides, understanding the uptake and movement of the insecticide in the vine is needed to optimize management decisions.

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Introduction The vine mealybug, Planococcus ficus, has become one of the most important insect pests of California vineyards, threatening economic production and sustainable practices in this multi-billion-dollar commodity. Insecticides are the primary control tool for vine mealybug, especially when leafroll diseases (GLDs) are a concern. Researchers, PCAs and farmers have developed relatively good controls that target exposed vine mealybugs – those on the leaves or canes. However, controlling the more protected mealybug population found under the bark of the trunk or on the roots has been more difficult. This population can be the most difficult to control even with systemic insecticide applications. Insecticides with systemic action are the best materials to control this protected population – but their proper use can vary among vineyards and regions. Moreover, vineyards with mealybug damage typically have large overwintering populations that are never fully regulated, and annually are the source for new generations throughout the summer that infest leaves and fruit of that vineyard and can disperse to other vineyards. Therefore, it is critical to develop better control programs for this overwintering population. We are conducting field bioassays

November/December 2016

to determine the effect of application timing, soil moisture, vine condition and age and commodity (for example, post-harvest application timing, wine vs. raisin management practices) on systemic insecticide effectiveness. This past year’s work has focused on the movement of Movento® (Bayer CropScience) in the vine using an “HPLC” to determine amounts of different metabolites associated with Movento® in different parts of the vine. For example, two of the questions we plan to address is whether Spirotetramat converts to the metabolite Enol-Spirotetramat (which is the primary toxicant) similarly under different conditions, such as vine nutrient status or cultivar, and where on the vine the metabolites move to and in what concentration are the metabolites found on different vine sections – such as the leaves versus the roots? Materials and Methods During 2015 and 2016, we used field bioassays (visual counts of mealybugs) to look at control effectiveness across vineyards in different regions and with different management practices or vine structures. Commercial vineyards were selected in the central San Joaquin Valley (Fresno County), the Lodi-Woodbridge wine grape region, and North Coast wine grape region. We are also

sampling numerous ‘experimental’ vineyard blocks at the Kearney Agricultural Research and Extension Center that represent wine and table grape blocks undergoing studies for nitrogen, irrigation, and wine grape cultivars. At each site, we have counted mealybug densities on the vine, measured cluster damage and taken vine fresh tissue samples before and after Movento® applications (sections from the leaf, cane and trunk). To study how the pesticide Movento® moves through the vines, the pesticide uptake and movement of key metabolites in the plant was followed by means of high pressure liquid chromatograph methodology (HPLC). A description of how Movento® works to kill mealybugs helps explain why understanding its movement is important. Spirotetramat is sprayed onto the leaves where it has translaminar activity and gets absorbed. It is not the Spirotetramat that primarily kills the mealybug but the first breakdown product or metabolite called “Enol” (Fig. 2). The Enol can change to other metabolites such as Enol-Glycoside and Ketohydroxy, but it is the Enol metabolite that is most important for killing the mealybugs. Whereas some translaminar pesticides remain in the leaves, Spirotetramat and its metabolites can be transported by the phloem (and to some extent the xylem) to other plant parts – and this is key in moving the product to where the mealybugs are. We used the HPLC to obtain the concentration of the active ingredient of Movento® (Spirotetramat) and its three primary metabolites (Spirotetramat -enol) and Enol-Glycoside and Ketohydroxy (the latter two metabolites are not active against mealybugs as far as we know). To analyze the quantity of Spirotetramat, Enol and other metabolites in leaves, the extraction method “QuEChERS” (Quick Easy Cheap Effective Rugged Safe) was followed. This methodology allows the preparation and analyses of several samples at one time, and provides extracts of several structurally different substances with good efficiencies. Adapting this method includes trying different solvents and mobile phases to clean and extract the desired compounds and testing various elution times. Afterwards the obtained results are compared to a standard curve Continued on Page 24

Figure 2. Proposed metabolic pathways of Spirotetramat in targeted crops, from Bayer CropScience Journal 61/2008).

Figure 3. Example of known “standards” of Spirotetramat-Enol (SPTA-enol) and Spirotetramat (SPTA) elution time. These compounds were eluted at 6.14 min at 27 minutes respectively, and are compared with vine tissue samples. November/December 2016

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Continued from Page 23

DAD1 A, Sig=250,4 Ref=off (MOVENTO_SC 2015-08-24 08-50-47\065-0501.D)

Results Leaf tissue analyses show that Spirotetramat is quickly converted into Enol (remember that Enol is the metabolite responsible for killing the mealybugs), and a portion of the Enol is also rapidly converted to Enol-Glucoside (we found this within 5 hours after spraying) (Fig. 5). Note that the Y-axis is using a log scale so there are great differences in the amounts of metabolites. Most important was that some Spirotetramat and Enol was found in the leaf tissue up to 184 days after treatment. It is still unclear (from our studies) if the Spirotetramat found long after the application will eventually convert to Enol, or if this conversion process slows as the material moves from the leaf tissue. These tested vines will continue to be sampled until leaf drop, and other vine tissue (e.g., bark) will be sampled up to a year after the spray application. What surprised us in these leaf tissue analyses was that Enol-Glycoside was the most abundant and consistent (over time) of the four metabolites tested (Fig. 4). It has been reported that under the right circumstances the Enol-Glycoside can revert to Enol, although how common this occurs in vines is not known. At his point, we assume that Enol found after 3-5 months is from either relative stable Enol rePage 24

Progressive Crop Consultant

8.536 6.140

3.620

4.350

4.200

5.410

5.585

4.976

7.077

0 4

min

Figure 4. Example of a leaf sample, processed by HPLC, showing a peak that eluted at 6.14 min, matching the standard for SPTA-enol (see Figure 5) and indicating its presence in the sampled leaf.

Amount of metabolite per leaf sample (in ppb)

created from a known amount of the pure product (Fig. 3), and from this the presence and amount of each tested metabolite can be determined (Fig. 4). In this process, the most appropriate and reproducible cleaning and extraction process was determined for leaves, canes and roots. We are still perfecting a process for smaller bark samples (<10 g) that can be completed without the addition of a “Mass Spectrophotometer” (MS). Our analyzed samples are collected in association with our field bioassays. After counting mealybugs, five portions of the vine were sampled for living tissue: leaves and petiole, trunk above and below the girdle, cane, and arm. If girdle is not applicable, a bottom and middle part of the trunk were taken. This fresh tissue sampling effort in 2016 resulted in approximately 6000 samples, which are being analyzed using the HPLC technology.

mAU

Spirotetramat Enol Enol-Glucoside Ketohydroxy

10000

1000

100

0.1

0.2 (5 hr)

110

184

Days after spray application

Figure 5. Mean concentration (parts per billion) of Spirotetramat and three of its metabolite in leaf samples from 5 hours after spray to 5 months after being treated with a label rate (8 oz per acre) of Movento® in May. maining in the leaves, or Spirotetramat that in the leaves that is much later (in time) converted to Enol. Note also that we found the Ketohydroxy metabolite only on the last sample date and at a very low amount (Fig.5). When looking closer at the amount of Spirotetramat and Enol in leaf tissue

November/December 2016

over the sampling period, it’s clear that the amount Spirotetramat is reduced quickly, from about 100 ppb (parts per billion) 5 hrs after spray to about 40 ppb after 1-3 days, and <5 ppb after 1 month (Fig. 6A). There is not a corresponding Continued on Page 26

November/December 2016

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Page 00

Amount of metabolite per leaf sample (in ppb)

140

(A)

120

Spirotetramat

100

0.2 (5 hr)

110

(B)

120

184

Days after spray application

Enol

0.2 (5 hr)

110

184

Days after spray application

Figure 6. Spirotetramat (A) and Enol (B) content in samples leaves (in parts per billion) at different times after being treated with a label rate (8 oz per acre) of Movento® in May. Continued from Page 24 increase in Enol, which is lower than Spirotetramat initially but shows a more stable presence during the five-month sampling period, around 20 ppb (Fig. 6B). Note that on two sample dates (one and 110 days) we did not detect any Enol and this analysis will be repeated with stored samples to determine if this unusual finding (especially at one day) was a data entry error. What is needed now is a field bioassay that compares the amount of Enol in the plant to mealybug death (e.g., dose response) and information on how long the mealybug must feed to acquire this lethal dose. In another trial, Movento® was applied in May (label rate of 8 oz per acre) in a Crimson Seedless block and we recorded a complete conversion of Spirotetramat to the Enol in the leaves within seven days (data not shown), which then is available to be transported via the phloem to other vine sections. What is interesting in this trial was that based on leaf tissue samples from different vines in the same vineyard, the amount of Enol varied among vines seven days after spray application (data not shown) and this variation was still seen 72 days after application (Fig. 7). There are many explanations for this. For example, it may be the insecticide coverage, or it may be movement of the Enol from leaves in different stages of development. Here, we assume that the Movento® metabolites move passively in the phloem and are therefore carried to new growing tissue. We do not know Page 26

Progressive Crop Consultant

yet what dose is needed on different vine sections to kill the mealybug and this, we hope will be determined next season. It is also good to note that 72 days after application we were still finding relatively high levels of Enol in the leaves, nearly as high as seven days after treatment. This suggests that any mealybugs moving from the trunk onto the leaves two months after application would still find Enol in the leaf tissue. The complete conversion of Spirotetramat to Enol did not always occur. For example, we applied an over-the-label rate (24 oz per acre) to experimental vines at the Kearney Agricultural Research and Extension Center as a late post-harvest treatment (October 13). Our interest here was to see if treatments applied late in the season, when leaves were still green but beginning to senesce, would result in more of the material being moved to the trunk section. HPLC tissue analysis of leaves found very little conversion of Spirotetramat to Enol in the leaves (Fig. 8). We do not know if this material that remained in the leaves was lost to the vine after leaf drop, or if the Spirotetramat that was not converted to Enol initially was moved to the canes, trunk and roots and later converted to Enol. Still, the results suggest that the leaves must be active for efficient conversion of Spirotetramat to Enol and for these late season applications to have a near-term impact. We will follow up on this work in 2017 as we found many vineyards where, months after application, Spirotetramat was found in leaf and trunk tissue that had

November/December 2016

not yet been converted to Enol. We have processed fewer trunk and roots samples than leaf samples as we are refining our techniques for these vine parts. Still, we can report Enol and other ‘downstream’ metabolites such as the Enol-Glucoside and Ketohydroxy were found in the vine trunk and cordon tissue. In 2017, we will set up trials to determine how easily Spirotetramat in the trunk and root tissues is converted to the Enol; perhaps some of this material can move via the xylem back to the leaves in the current or following year. Note however, that most (about 90 percent) of the Spirotetramat and Enol is moved by the phloem in other plant studies and we assume the same will be found in vines. Overall, the tissue analyses show Movento metabolites are moving from the leaves to the trunk as expected. Some of the key findings that we will further study are the different rates of conversion from Spirotetramat to Enol in the leaves – in some vineyards nearly 100 percent conversion and in other vineyards closer to 50 percent conversion. Perhaps this results from vine leaf condition and age of the leaf, vineyard management practices, or even environmental conditions during application. This is important because it is the Enol that kills the mealybugs; however, the impact of this result is harder to interpret. We assume that complete conversion to Enol is most desirable, but perhaps the movement of Spirotetramat through the phloem from leaves to trunk and roots will help kill mealybug

PCC

Spirotetramat and Spirotetramat enol mg / liter

8 oz Movento applied 22 May Leaf petiole samples 72 days after treatment 12 yr old Crimson, flood irrigation

Spirotetramat Spirotetramat enol

zero Average

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Average and Individual samples

Figure 7. Spirotetramat and its Enol concentration (mg/l) at and 72 days after treatment application in leaf petiole samples, with the wider bars (left side of each figure) showing the average of 20 vine samples and the narrower bars showing the results of each vine sampled.

Spirotetramat and Spirotetramat enol mg / liter

later in the season if it is then converted to Enol. We also found a wide range of Enol ‘dose’ (parts per billion) in the leaves and other tissues. By itself, this does not provide any information on mealybug kill rate until we also determine the lethal dose in the vine (which also must include the feeding period). Finally, we have attempted different application timing of Movento® and found that the April-May period was associated with the most efficient conversion of Spirotetramat to Enol (as well as mealybug kill, data not shown here). We must still determine the fate of the unconverted Spirotetramat that is carried from the leaves to other tissue to understand if this material is eventually converted to Enol or if it metabolizes quickly from Enol to non-toxic downstream metabolites in the trunk and root tissue. Finally, remember that Spirotetramat is a tetronic acid derivative and acts as a lipid biosynthesis inhibitor. Lipids include fats, oils, waxes, certain vitamins, hormones and most of the non-protein membrane of cells. As such, lipids are vital to an animal’s existence. For most insects, Movento ® will be most effective against juvenile stages by preventing molting, but can also reduce fecundity and fertility of adult females. The juvenile mealybugs feeding on Enol should then be unable to molt – like a growth hormone – but also will have their energy transport system disrupted and should cease movement and feeding as well. For these reasons, there may be a delay from the time of field application to control of the population if there are large numbers of females already producing ovisacs, which Movento® will not effect. There may also be a time delay as Enol moves through the plant, although we found Spirotetramat or its metabolites in different tissue samples within days after spray application. As for questions of resistance, we sampled leaf tissue in a vineyard that had been treated with Movento but had damaging mealybug densities; however, HPLC analysis did not show clear peaks of Spirotetramat or Enol in any of the tissue samples, suggesting that a more plausible explanation would be that an active product was not delivered to the vine.

24 oz Movento applied 13 October Leaf petiole samples 7 days after treatment 20 yr old Thompson seedless flood irrigation

Spirotetramat Spirotetramat enol

Average

Average and Individual samples

Figure 8. Spirotetramat and Enol concentration (mg/l) found in leaf tissue samples seven days after an over-the-label (24 oz per acre) late season (October 13) application show very little conversion of the Spirotetramat to Enol – perhaps because the application was too late in the season and the leaves had shut down (note that this is a ‘crop destruct’ trial because of the rate tested). November/December 2016

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Page 27

CHERRIES

New Bio-Fungicides for Sweet Cherry J. E. Adaskaveg Professor and Plant Pathologist H. Forster Project Scientist Department of Plant Pathology and Microbiology, University of California, Riverside

he successful marketing of fresh sweet cherries can be a challenge in domestic distribution and worldwide trade. The fresh fruit industry is very competitive and requires high standards in disease management to prevent crop losses during the season, as well as after harvest during handling and marketing of the commodity. The use of pre- and postharvest fungicides is the most effective way to minimize fungal decays. New fungicides with high safety standards and minimal impact on environmental ecosystems are needed. These products will be intensely utilized in the future to ensure that markets remain open for trade with minimal losses from fungal decays while providing wholesome, high qualPage 28

Progressive Crop Consultant

ity crops to consumers. Many new fungicides have been introduced in recent years, and the trend continues with additional products for the sweet cherry industry that were recently or will be introduced in the 2017 season and beyond. We have been involved in evaluating many of these new products over the last several years with several goals in mind including: new active ingredients with unique modes of action than previously registered products, broad spectrum of activity, a low risk for resistance development, and with a high priority on safety for the consumer and the environment. Identifying the safest products will help to harmonize maximum residue limits (MRLs) and food additive tolerances (FATs) between trade partners. In the United States, the term “pesticide” includes many kinds of products including fungicides, insecticides, and herbicides. Fungicides are needed to prevent losses in yield and reduction in crop quality due to fungal pathogens. Before a pesticide is allowed to be marketed and used in the United States,

November/December 2016

the Environmental Protection Agency (EPA) evaluates the proposed pesticide thoroughly to ensure that it will not harm human health or the environment. When a pesticide is registered, there must be a practical method for detecting and measuring levels of pesticide residues so regulatory officials can ensure that chemical residues are within the tolerance or MRL determined to be safe. Some pesticides, however, are exempted from the requirement to have a tolerance when EPA considers them to be extremely safe. Still, EPA must review toxicity and exposure data, the same as for setting a tolerance for conventional pesticides. Biopesticides are certain types of “reduced-risk” pesticides derived from natural materials such as animals, plants, bacteria, and some minerals. Biopesticides fall into three major classes: 1) Microbial pesticides (e.g., a bacterium, fungus, virus, or protozoan) as the active ingredient; 2) Plant-Incorporated-Protectants (e.g., pesticidal substances produced by genetically modified plants); and 3) Biochemical

Table 1. Efficacy of single mode-of-action fungicides and pre-mixtures against major diseases of sweet cherry Jacket rot/ FRAC Resistance Blossom/ Green Powdery Blossom Fruit rot Group risk Fruit rot fruit rot mildew Brown rot

Botrytis

Fungicide product

Active ingredients

Topsin-M/T-Methyl/ Incognito*

thiophanate methyl

high

++++

+++

++++

+++

iprodione-oil

low

++++

NL^

++++

iprodione

low

+++

---+++

Rovral + oil Rovral, Iprodione, Nevado Bumper/Tilt

propiconazole

high

++++

----

Tebucon/Toledo

tebuconazole

high

++++

Indar

fenbuconazole

high

++++

+++

----

+++

Quash

metconazole

high

++++

+++

Procure

triflumizole

high

+++

----

++++

myclobutanil

high

+++

----

++++

Rally Rubigan/Vintage

fenarimol

high

+++

----

++++

penthiopyrad

high

++++

+++

++++

Abound

azoxystrobin

high

+++

----

Cabrio

pyraclostrobin

high

+++

----

Gem

trifloxystrobin

high

+++

----

Quintec*

quinoxyfen

high

ND^

++++

Elevate

fenhexamid

high

+++

++++

Ph-D, Oso

polyoxin-D

high

+++

Fontelis

Vivando Luna Experience**

metrafenone

high

ND^

++++

tebuconazole/fluopyram

3/7

medium

++++

+++

++++

Quadris Top

difenoconazole/azoxystrobin

3/11

medium

++++

+++

Quilt Xcel

propiconazole/azoxystrobin

3/11

medium

++++

+++

fluopyram/trifloxystrobin

7/11

medium

++++

+++

++++

Luna Sensation Pristine

boscalid/pyraclostrobin

7/11

medium

++++

+++

Merivon

fluxapyroxad/pyraclostrobin

7/11

medium

++++

+++

++++

^ -Rating: ++++ = excellent and consistent, +++ = good and reliable, ++ = moderate and variable, + = limited and/or erratic, +/- = minimal and often ineffective, ---- = ineffective, ND = no data, NL = not on label, * - Resistant sub-populations have been detected in some pathogens. **- Pending registration in CA.

pesticides (e.g., naturally occurring substances that control pests). Often, biopesticides are exempt-from-tolerance because they are used at low rates, are inherently less toxic than conventional pesticides, or they have a narrow spectrum of activity with low non-target effects. Biopesticide compounds also benefit from accelerated registration due to their favorable safety characteristics, but still undergo a rigorous review to ensure that they will not have adverse effects on human health or the environment. Ideally, all pesticides are used in integrated pest management (IPM) programs to ensure their overall minimal use and preserve their activity for many years. In the last 15 years, EPA has classified and registered three biofungicides: potassium phosphite, polyoxin-D, and

most recently natamycin (i.e., pimaricin). These products are all exempt from residue tolerance in the United States. All three fit into the EPA Biopesticide category No. 3 and all three are now registered on sweet cherry. Potassium phosphite is registered for control of Phytophthora diseases of sweet cherry. Polyoxin-D and natamycin have activity against several foliar and fruit diseases of sweet cherry. Polyoxin-D (Ph-D, Oso) is a fermentation product of Streptomyces cacaoi var. asoensis and is registered for field use on stone fruit including sweet cherry to manage diseases caused by Monilinia spp., Botrytis cinerea, Alternaria alternata, and Podosphaera spp. Natamycin will be marketed as BioSpectra and is a fermentation product of S. natalensis. It was registered as a postharvest

biopesticide in August 2016 to manage decays caused by Monilinia spp., Botrytis cinerea, and Rhizopus stolonifer. Our research project with the California Cherry Board is focusing on developing information on efficacy, resistance potential, and usage strategies of polyoxin-D, natamycin, and conventional fungicides against several major pre- and postharvest diseases of sweet cherry. Preharvest fungicides for disease management. A number of products are effective for the management of brown rot blossom blight and fruit rot (Monilinia spp.), Botrytis blossom blight, green (jacket rot) and ripe fruit rots (Botrytis cinerea), and powdery

November/December 2016

Continued on Page 30 www.progressivecrop.com

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Continued from Page 29 mildew (Podosphaera spp.) of sweet cherry (Table 1, pg. 29). Polyoxin-D represents a new mode of action for stone fruits and is a Fungicide Resistance Action Committee or FRAC Group (FG) 19. The product is sold as Ph-D or Oso on sweet cherry. We rated the fungicide as a moderately effective material (‘++/+++’), but when tank-mixed with other FGs such as FG 3 or FG 17, the treatment is rated as ‘+++/++++’ for diseases caused by Monilinia spp., B. cinerea, and Podosphaera tridactyla. When visible symptoms of powdery mildew on fruit are already present, fungicides sometimes have to be used as post-infection treatments. For this situation, we showed that Ph-D can be used in mixtures with a multi-site fungicide like Kaligreen or with DMI fungicides like Procure for effective suppression of the disease. Having different modes of action with high powdery mildew activity like FGs 3, 7, 11, and 19, as well as pre-mixtures FG 3/7, 7/11, and 3/11 is critical especially when other FGs such as FG 13 start to show reduced performance in recent years. Postharvest fungicides for decay management. For postharvest decay management, fungicides registered on sweet cherry include: tebuconazole (Tebucon), fludioxonil (Scholar), pyrimethanil (Penbotec), propiconazole (Mentor), and a brand new mode of action called natamycin (BioSpectra). BioSpectra is a 10 percent soluble concentrate (SC). These products can be used alone or in mixtures. Our recent studies focused on the evaluation of natamycin that is a natural fermentation product. BioSpectra has exempt registration status (as mentioned above) and we have been evaluating it under the code name EXP-13 for several years on several sweet cherry cultivars (e.g., Bing, Rainier, Lapins). On fruit that were first inoculated and then treated, BioSpectra was highly effective against the three major decays brown rot, gray mold, and Rhizopus rot when used at rates between 500 and 1000 ppm (Fig. 1). Commercial packingline trials were done with aqueous T-Jet applications of fruit that were inoculated and incuPage 30

Progressive Crop Consultant

Figure 1. Postharvest treatment with BioSpectra and Scholar for decay control of inoculated Bing cherry fruit.

Figure 2. Postharvest spray treatments with BioSpectra and Scholar for decay control of inoculated Bing cherry fruit in a comercial packing study. bated for 14 h at 20°C (68°F) before treatment. In these studies, the fungicide showed excellent performance (Fig. 2). The fungicide performed best in high-volume aqueous or in dilute fruit coating applications (3-5 percent fruit coatings) and worked well on different cherry cultivars of a range of maturities. Natamycin has been used in the food industry for many years as a preservative of dairy and meat products. No filamentous fungus has ever developed resistance to this fungicide under commercial conditions. This is especially important in combating fungicide resistance. Thus, the fungicide was also tested in mixtures with Scholar (Fig. 1). BioSpectra usage should be based on its exempt from tolerance status, its low resistance potential, and in mixtures to reduce rates of both active ingredients and subsequently lower the overall level of pesticides on the food crop. Scholar, but not Penbotec (pyrimethanil), is very stable in the presence of chlorine in re-circulating drench or flooder treatments and in combination

November/December 2016

with other postharvest fungicides, and can be used at reduced rates, making it cost-effective. BioSpectra tolerates peroxyacetic acid and low levels of chlorine and thus, it can also be used in re-circulating postharvest application systems where sanitizing agents are used to meet food safety standards. The availability of several fungicides belonging to different chemical classes is essential for managing the major diseases of sweet cherry after harvest. The development of new products that are considered so safe that they are registered as “exempt from tolerance” is critical for maintaining markets and increasing consumer confidence, while providing high levels of efficacy against postharvest fruit decays is important for the successful marketing of sweet cherries in domestic and global markets. The exempt from tolerance status in the US and Canada will hopefully encourage other countries to follow this designation in the future and help to harmonize global trade of fruit commodities.

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