Navel Orangeworm Plague Might be Growing Out of Control

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When it comes to navel orangeworm control in your pistachio, almond, and walnut orchards in the fall and winter, sanitation is the key. While that sounds simple — destroy any mummy nuts — the truth is there are a lot of factors that can make a simple solution complicated.

These complications have financial implications, as labor to help clean up the orchard can be costly and time-consuming. These complications can also come in the form of weather issues that make postharvest cleanup more of a challenge.

“Although this is a proven practice, we still see some growers are not doing this practice, for whatever reason. Sometimes, it is difficult to do mummy sanitation due to the rainfall in the winter, or due to the heavy ground in some orchards. But it is important to plan in advance considering these factors. Sanitation can be done at any time between October and Feb. 1,” Jhalendra Rijal, University of California Cooperative Extension Area Integrated Pest Management Advisor for the Northern San Joaquin Valley, says.

Prioritize This Winter

As harvest wraps up, it’s a good time to evaluate your overwintering pest pressure, says Emily Symmes, University of California Cooperative Extension Area Integrated Pest Management Advisor for the Sacramento Valley Region. Assess your NOW presence in the mummies in your orchard. This way you can prioritize which orchards need more of your attention in the off-season. Symmes suggests a triage approach. The blocks with the most pressure should be the first to get your attention.

“If economics or orchard access may be an issue this off-season, focus initial and most thorough sanitation efforts where you will get the most bang-for-your buck. Consider harvest damage, overwintering pressure (the combination of mummy density and mummy infestation), history of damage in the orchard or block, and external pressure factors,” she says.

These external pressure factors include increased vulnerability due to nearby infested orchards.

“As an individual grower, you can make a lot of effort to heavily sanitize your orchard. But if your neighbors fail to do the same, you may be at risk of navel orangeworm colonizing from these nearby infested orchards,” says Houston Wilson, University of California Assistant Cooperative Extension Specialist in Integrated Pest Management. “This is a fairly mobile pest, and so sanitation likely works best as an area-wide approach.”

More than Just Sanitation

Yes, sanitation is the most important part of management. But a key component of sanitation isn’t just removing mummy nuts, it’s also crucial to destroy the mummy nuts by shredding or mowing. While this is easier in almonds and walnuts, pistachio orchard sanitation is more complicated.

“Pistachios are small, and that makes them more difficult to destroy.” Wilson says. “Many growers destroy mummy almonds and walnuts by disking, or use of a flail mower, but this is less effective with pistachios.”

Symmes says given the nut size of pistachios, they’re just easier to miss during the removal and destruction process.

“They are more likely to hang up in the trees, tree crotches, cracks on the ground, etc.,” she says. “For any nut crop, make sure to blow nuts off berms, into tree rows, out of crotches, etc., prior to destroying on the ground. Always consider areas around the orchard where mummy nuts might stockpile – make sure not to miss those.”

Think About Harvest … and Beyond

While this season’s harvest is wrapping up, a strategy to consider is doing a second shake in your walnut orchard to clean up low-value nuts and prevent mummies.

“Anything that leaves more mummies behind translates to more potential navel orangeworm carryover, and therefore will require greater investments in sanitation efforts to achieve low damage next year,” Symmes says.

And, it’s a good idea to start thinking about orchard management for 2020 – whether that’s monitoring, mating disruption, or even planning an early harvest before third flight.

“The idea is to harvest the nuts before the beginning of the third or fourth navel orangeworm (NOW) flight to prevent egg-laying by these fresh females,” Rijal says. “Every orchard, in terms of crop vulnerability and NOW pressure, can be different, and a close look of nut development and NOW population is critical to understand what’s going on at a particular time.”

Wilson says the risk of aflatoxin contamination, which is associated with navel orangeworm infestation, adds further pressure on growers. “For many the goal is less than 1% or 2% infestation,” he says, “and we’ve got to meet the growers where they’re at with this.”

Wilson says given the current difficulties destroying mummy pistachios, it may be time for some new technology to meet the growers’ needs. For instance, by developing better tools to help crush and destroy pistachio mummies.

“It’s a technological problem in some regard,” he says. “There’s an insect issue, but developing a better piece of machinery to destroy pistachio mummies is going to require an engineer, not an entomologist.”

Understanding the Pest

Brad Higbee, Research and Development Manager at Trécé Inc., agrees with Symmes that neighboring properties can be an issue – and they don’t have to be nut orchards. “A common cause of navel orangeworm infiltration is adjacent crops that may harbor relatively high populations,” he says.

Higbee says it’s quite common for high populations of NOW to move into different host crops, as they can feed on many different hosts. Since California has nearly 400 crop offerings, there are many places the pest can go. But, naturally, tree nuts are the preferred crop. Plus, in the last 10 to 20 years, there’s been a significant growth in tree nut acreage, so that can compound any pest pressure issues.

“This insect is very good at dispersing — it’s a strong flier,” Wilson says. “They can move quite a bit.”

With an understanding of how navel orangeworm can cover ground, it’s critical to take a broader approach to management.

“Effective navel orangeworm management to get to low damage requires an area-wide approach, no matter the crop,” Symmes says.

Holistic Approach

Rijal agrees, noting growers need to take a holistic approach to pest management.

“Effective NOW control can be achieved by adopting cultural methods, such as mummy sanitation and early harvest, utilizing orchard damage history and seasonal pest and crop monitoring information in combination with mating disruption and insecticide as needed,” he says.

The best way to stop navel orangeworm infestations in the off-season, Symmes says, is to “break the life cycle by removing the population and their overwintering sites. Mummies are also the development sites for early NOW generations next year.”

In sum, when it comes to navel orangeworm, growers have to be paranoid, Higbee says.

“Never think you are safe from NOW,” he says. “Constant vigilance via monitoring is the best approach.”

Why Harvest is a Good Time to Review Grape Disease Management

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This past spring was unusually rainy in many California grape-growing regions, and the warm and moist environment provided excellent conditions for powdery mildew and Botrytis shoot blight. Damage from either or both pathogens has accumulated over the course of the season and is now plainly evident in many vineyards, with symptoms including lesions on shoots, leaves, and scarred, necrotic, or rotted clusters of fruit. As this challenging season comes to a close, vineyard managers should assess damage, review their disease management program, and determine what changes are warranted for next year.

As harvest nears, growers tend to pay extra attention to their vineyards, and judging by the calls I received this year, many were finding that their mildew programs were not as effective as they assumed they would be. Severe mildew infections on immature clusters of fruit can stunt berry growth, induce berry splitting, and even cause the entire cluster to die. Less severe infections can indirectly lead to yield loss by causing scarring that predisposes the berries to cracking during maturation.

Cracking in maturing fruit provides an entryway to other microorganisms that will colonize the wound and develop into sour rot. Poorly controlled mildew will leave characteristic, dark-colored scars on grape shoots, and mildew may infect the preformed shoots in compound buds. Bud infections result in “flag shoots” that are already covered in mildew when they emerge the following spring. Flag shoots extend severe mildew problems from the year before into a new season.

Botrytis shoot blight was also particularly severe in spring 2019. Optimal temperatures and wet weather created the conditions necessary for the disease, which requires that green tissues remain exposed to free moisture for extended periods at appropriate temperatures. Leaf axils, forks in tendrils and rachises, flower parts, and serrated leaf margins tend to collect and hold rain drops, keeping such tissues wet, and Botrytis infections were observed in all these organs.

As the season progressed, temperatures increased, the rain stopped, humidity decreased, and the infections became dormant. However, the high amount of inoculum and dormant infections in the canopy and clusters of some vineyards has increased the risk of Botrytis bunch rot and sour rot occurring after veraison, especially if the fruit are exposed to cool and wet weather.

Plan for Next Year

If powdery mildew or Botrytis were a problem for you this year, review your cultural practices and fungicide program and consider changes for next year. Sanitation can help control Botrytis, which overwinters in infected tissues, including mummified clusters of grapes. Removing infected tissues from the trellis and beneath the vines and disking them into the row middles will reduce inoculum.

In the following spring, employ canopy management practices, such as leaf removal in the fruit zone, that can reduce humidity, improve air movement, and increase exposure of the fruit to morning light. Proper selection and timing of fungicides is critical. Fungicides with activity against Botrytis and powdery mildew are available. Consult the University of California Integrated Pest Management Program (UC IPM) website for an updated list of products that may be used. This website contains a table of data comparing various fungicides, including their potential efficacy against various fungi and the FRAC group which to which their active ingredients belong.

It is important to select appropriate fungicides from different FRAC groups to help prevent the fungi from developing resistance to various fungicides. Selecting appropriate fungicides is important, but efficacy will also depend on spray timing and coverage. Coverage is optimized through proper spray rig calibration and maintenance.

Citrus Greening Scourge on the Spread in California and Texas

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Containing the deadly citrus greening disease has been an impossible task for growers worldwide. No grove is immune to this point. To that end, the USDA-Animal and Plant Health Inspection Service (APHIS) is expanding areas quarantined for citrus greening in California, Texas, and even some parts of Louisiana.

According to a recent pest report from the North America Plant Protection Organization’s Phytosanitary Alert System, APHIS is adding portions of Los Angeles, Orange, Riverside, and San Bernardino counties in California; all of Kleberg, Kenedy, and Webb counties in Texas; and all of Plaquemines and Saint Bernard Parishes in Louisiana to the quarantined area due to detections in plant tissue samples collected in multiple locations in these states.

APHIS is working in cooperation with the respective Departments of Agriculture as well as stakeholders from each state’s citrus industry in this effort.

The specific changes to the regulated areas in California, Texas, and Louisiana can be found at:
https://www.aphis.usda.gov/plant-health/citrus-greening
.

Timorex Gold Biofungicide Now a Tool for California Growers

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Summit Agro USA has announced registration in California for Timorex Gold, its botanical broad-spectrum fungicide. The biofungicide product, which is used in nearly 40 countries worldwide, provides control of many common fungal and bacterial diseases including powdery mildews, early blight, and Botrytis in a wide range of crops.

According to Summit Agro, the development of Timorex Gold was based on a complex blend of natural chemicals from a plant extract from the tea tree (Melaleuca alternifolia). The product features a wide range of features and benefits that include:

  • Multiple modes of action
  • Control of a wide range of plant pathogens, particularly bacterial and ascomycete diseases
  • Resistance management
  • No residues; no MRL
  • No measurable effect on beneficial insects and bees
  • Easily adapted into sustainable and IPM practices
  • Non-persistent in the environment

“Timorex Gold has been specifically formulated to keep early season disease pressures low,” said Fred Yates, Summit Agro Marketing Manager, in a prepared news release. “It also can be used late in the season due to its short PHI and REI requirements.”

Timorex Gold is sold exclusively through Helena Agri-Enterprises and Tenkoz members companies.

Best Practices Issued for Dealing with Deadly Citrus Disease in California

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To provide California citrus growers with a strong toolbox of science-supported strategies and tactics to protect their orchards from Huanglongbing (HLB, aka citrus greening), the Citrus Pest & Disease Prevention Committee endorsed a set of best practices for growers to voluntarily employ.

The recommendations – which were developed based on a grower’s proximity to an HLB detection – represent the most effective tools known to the citrus industry at this time and are meant to supplement the California Department of Food and Agriculture’s required regulatory response. The best practices were developed by a task force consisting of growers from various regions across the state and scientists, all of whom were nominated by the Citrus Pest & Disease Prevention Committee.

Voluntary best practices were developed for growers in the four following scenarios:

Scenario 1: Orchards outside of an HLB quarantine area

Scenario 2: Orchards located between one and five miles of an HLB detection (within an HLB quarantine area)

Scenario 3: Orchards within one mile of an HLB detection but not known to be infected

Scenario 4: Orchards with HLB

The best practices vary in each scenario, but all address: awareness, scouting for the Asian citrus psyllid, controlling Asian citrus psyllids with treatments, protecting young trees and replants, employing barriers or repellents, visually surveying for HLB, testing psyllid and plant material for HLB using a direct testing method like polymerase chain reaction (PCR), and tending to trees’ root health. The voluntary best practices in all four scenarios can be found at CitrusInsider.org.

While HLB has not yet been detected in a commercial grove in California, the disease continues to spread throughout residential communities of Los Angeles, Orange, and Riverside counties. HLB has infected more than 1,400 citrus trees and 1,003 square miles are currently in an HLB quarantine area.

“Our state’s citrus industry has held the line against HLB since the first detection seven years ago. We should commend our efforts but must not forget the devastating impact HLB could have on our orchards and our livelihood,” said Jim Gorden, Chair of the Citrus Pest & Disease Prevention Program and a citrus grower in Tulare County, in a prepared news release.

“We know the cost to manage the Asian citrus psyllid is far less than any potential costs or loss to the industry should HLB take hold throughout our state. These voluntary best practices are meant to serve as a box of tools so growers can use as many as are feasible for their operation in order to limit the spread of the psyllid and disease,” said Keith Watkins, Chair of the task force that developed the best practices and VP of Farming at Bee Sweet Citrus.

The best practices will be explained in depth during Citrus Research Board’s 2019 Citrus Growers Educational Seminars from June 25–27 in Palm Desert, Santa Paula, and Exeter. Individuals interested in attending one of the seminars can register for free at CitrusResearch.org. Growers also may contact their county’s Grower Liaison for more information.

EPA Proposes Ban on Aerial Applications of Antibiotics to Fight Fire Blight

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In her latest update, Dr. Kari Peter, Assistant Professor in Tree Fruit Pathology at Penn State University, says the EPA has proposed prohibiting aerial applications of streptomycin and oxytetracycline, which is included in an interim decision for the two antibiotics.

Peter says aerial applications may be a necessary tool for growers fighting fire blight, especially if conditions are too wet for ground equipment or an area needs to be covered quickly.

She’s encouraging growers to submit comments to the EPA on the importance of aerial applications on the label for streptomycin and oxytetracycline.

Comments will be accepted until May 17 at 11:59 p.m. EST.

• Streptomycin Registration Review to comment on streptomycin aerial applications.
• Oxytetracycline Registration Review to comment on oxytetracycline aerial applications.

California Growers to Lose Controversial Pesticide

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While California growers have been expecting this moment for a while, the California Environmental Protection Agency has officially (CalEPA) announced the Department of Pesticide Regulation (DPR) the sunset of chlorpyrifos in the state.

This announcement follows restricted use by California Department of Pesticide Regulation last fall.

Chlorpyrifos is used on more than 800,000 acres and 60 crops including tree nuts, vegetables, grapes, citrus, cotton, and alfalfa in California alone. Collectively, these crops amount to $23 billion in value for the state. Chlorpyrifos has been a key tool in Asian citrus psyllid control in Florida.

Gov. Gavin Newson also will propose $5.7 million in new funding in the May Revision budget proposal to support the transition to safer, more sustainable alternatives, and plans to convene a working group to identify, evaluate, and recommend alternative pest management solutions.

California formally listed chlorpyrifos as a “toxic air contaminant” in April, which California law defines as “an air pollutant which may cause or contribute to an increase in mortality or an increase in serious illness, or which may pose a present or potential hazard to human health.” The listing requires DPR to develop control measures to protect the health of farm workers and others living and working near where the pesticide is used.

DPR says, in consultation with California Department of Food and Agriculture, the Office of Environmental Health Hazard Assessment (OEHHA), and the California Air Resources Board (CARB), that sufficient additional control measures are not feasible.

DPA will begin the process of canceling the registrations for products containing chlorpyrifos while initiating a cross-sector working group to identify safer alternatives.

DPR also will consult with county agricultural commissioners and local air pollution control districts before filing for cancellation. The cancellation process could take up to two years.

During the cancellation process, DPR’s recommendations to county agricultural commissioners for tighter permit restrictions on the use of chlorpyrifos will remain in place. These include a ban on aerial spraying, quarter-mile buffer zones, and limiting use to crop-pest combinations that lack alternatives.

In a statement, Tom Nassif, President and CEO of Western Growers spoke out against the decision:

“California farmers also face the most stringent regulatory environment in the world, one that often limits their access to many of the tools still available to farmers elsewhere in the U.S. and in foreign countries, including certain types of pesticides. Indeed, over the last 20 years, California regulatory actions have removed several of the most important crop protection tools farmers rely on to fight pests and diseases.

“With yesterday’s announcement that DPR will initiate the cancellation of chlorpyrifos, one of the most widely studied and globally approved insecticides, California farmers now stand to lose yet another arrow in their quiver – without effective and ready replacement tools – making their quest to grow the safest, healthiest and most abundant food supply in the world even more difficult.”

California Growers Get New Bactericide, Fungicide

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California farmers have another bactericide and fungicide option with the approval of Instill fungicide. Instill, distributed by Sym-Agro, is a systemic copper product that is approved for use on nut trees, fruit trees, citrus, leafy vegetables, and berries.

Sym-Agro says that what makes Instill unique is its formulation makes the copper more active, so much lower doses of copper are required to provide the same level of disease control. Instill provides up to 21 days of residual control.

Sym-Agro says key benefits of Instill include:

  • Reduced phytotoxicity due to systemic/translocating technology
  • Tank mix options –due to lower pH
  • Complete plant protection from systemic movement
  • No visible residue on treated surfaces
  • Easy to handle – mixes easily and stays in solution
  • Rain-fastness
  • Reduced potential for russeting from copper residue on the plant surface

Instill’s systemic activity protects against, downy mildew, bacterial blight, fire blight, powdery mildew, botrytis, and rust. It helps reduce postharvest rots and can be used up to the day of harvest.

New Tool a Boost for Crop Protection in Challenging Vineyards

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On the steep slopes of California’s Napa Valley, labor shortages, as well as unique weather and soil conditions, combine to create significant challenges to viticulturalists charged with the health of the vineyards entrusted to them. Remote-controlled aircraft — drones — represent one technology showing considerable promise in allowing viticulturalists to overcome some of those challenges.

According to Brittany Pederson, Director of Viticulture at Renteria Vineyard Management LLC, “strong results” coming from trials she has conducted on various vineyard sites and at the University of California, Davis’ Oakville Experimental Vineyards earlier this decade led to her own use of drone technology in the vineyards she oversees. Pederson’s interest in the potential drones might have as a tool for viticulturalists has put her on the cutting edge of her industry in demonstrating the machines can play a significant part in advancing the state of the art she and her peers practice.

Vineyard Application
Pederson says her interest in remotely piloted aircraft was piqued when, about five years ago, she became aware of the research UC Davis presented in association with the Yamaha Motor Corporation. Yamaha was looking into the feasibility of applying chemical crop protection to grapevines using its RMAX remotely piloted agricultural spray vehicle. Seeing the drone displayed at a UC Davis “Grape Day” presentation for vineyard professionals, Pederson was intrigued.

“This small little helicopter was interesting to me, but it also seemed a little bit crazy. It goes against everything we’ve done in the past but, I thought, ‘I will prove it either way,’” she says. “As a viticulturist, I try to be a creative thinker, to find better ways to be efficient at what we’re doing, so I’m always interested in new things as I look at challenging issues and trying to figure out how to resolve them. How do we change? How do we work with new technologies to better achieve our goals? I thought the drones might hold real promise for my industry, so I decided to learn more.”

Pederson’s interest led to her eventually working closely with Yamaha as it fine-tuned its own approach to the use of drones in a vineyard setting.

“I designed some scientific trials with proper controls to allow a realistic assessment of the technology,” she says. “I went into it with no preconceptions about whether it would work or wouldn’t work.”

Promising Results
The results Pederson put forward have been good enough to encourage her to continue utilizing aerial drones, especially for the application of fungicides, and especially in areas where special challenges to traditional application protocols have posed challenges.

“Hillsides is where we struggle the most to get good coverage with the approaches we have traditionally used,” she says. “Those areas are where I’ve found it to be a great fit; there’s all sorts of variables, but where it’s difficult to spray or costly to spray, those are the areas we use the RMAX.”

Brad Anderson, Division Manager of Yamaha’s helicopter spraying operations, points out drones, while in the early years of use for spraying agrochemicals in the U.S., have an established history in much of the rest of the world.

“Japan has been using remotely piloted helicopters for aerial applications on crops (mostly rice), since 1991. The RMAX was originally introduced in Japan in 1997; in 2003 there was an update (which is called the RMAX Type IIG),” he says. “This is the original platform we received an exemption for to utilize in the U.S. In Japan, 40% of the rice grown is sprayed by a Yamaha remotely piloted helicopter.”

Pederson says the relationship with Yamaha has continued, as she has worked out how to best use the capabilities of drones to benefit her vineyards and as Yamaha has utilized her feedback to improve its own capabilities.

Site-Specific Use
For the present, at least, Pederson agrees with Anderson that the best fit for drones in the Napa Valley comes from their use in areas where terrain, or other factors, make it difficult to apply agrochemicals using traditional methods.

“The decision to use drones is site-specific,” she says. “There are three important questions I always ask when deciding whether to utilize a piece of equipment: ‘One, does it make sense for my team? Two, does it make sense economically? And three, does it work?’”

While pointing to reductions in soil compaction, increased worker safety, and quick response as benefits that drones bring to the table, she says they especially shine in replacing hand labor on steep slopes and other spots that are hard to get to.

“The ability to use them on difficult sites where otherwise I would have to have a backpack spray team is big to me,” she says. “Retaining a trained labor force is one of the most important parts of my job. Backpack spraying is one of the most daunting and difficult tasks to be had in a vineyard with steep slopes; the packs are heavy and the job is difficult even on level ground, much less when you have to hike up a steep hill. My workers don’t like it, and I don’t like having to make them do it. Avoiding that type of work is a number one factor for me and if it’s economical, that’s just another plus.”

New Fungicide Approved for Select California Crops

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Good news for growers in the Golden State, the California Department of Pesticide Regulations has approved another new crop protection tool to consider — Helmstar Plus SC — for use on selected crops.

According to product manufacturer HELM Agro US Inc., the new fungicide product features preventive and curative activity from two powerful modes of action, which quickly knocks down diseases and provides a residual barrier to inhibit newly forming diseases.

In California, the product is labeled for use on almonds, grapes, corn, barley, wheat, grasses grown for seed, and other crops.

As a premix, Helmstar Plus SC hosts Group 3 and Group 11 fungicides and is tank-mix compatible with a variety of crop protection products.