California Ag Network

Category: Pest/Disease Management

  • Varroa Mites and Deformed Wing Virus Make Honeybees More Susceptible to Insecticides

    The first of two apiaries, established in 2014 in Stoneville, Mississippi, provided honey bees for studying the impact of pesticides on honey bees. (Photo by Yu-Cheng Zhu, D5121-1)

    Controlling for Varroa mites, the parasitic mites that feed on honey bees and serve as vectors for viral diseases like deformed wing virus (DWV), can help with improving honeybee populations and make bees less susceptible to harmful insecticides, according to a recent study published in Environmental Pollution.

    Foraging honey bees may be directly exposed to toxic insecticide sprays in the field or exposure may come from honeybees collecting and bringing pesticide-contaminated pollen and nectar back to their hives to feed larvae and young bees. The presence of insecticides, along with other environmental stressors in agricultural areas, can be a factor leading to issues like colony loss — something beekeepers from around the world are trying to overcome.

    “Previous research has shown how chemicals like pesticides make bees more susceptible to mites,” said Yu-Cheng Zhu, a research entomologist at ARS’s Pollinator Health in Southern Crop Ecosystems Research Unit in Stoneville, Mississippi. “In our study, we wanted to see if mites and viral infestations make bees more susceptible to insecticides.”

    In a study, researchers with the U.S. Department of Agriculture (USDA)’s Agricultural Research Service (ARS) applied the miticide amitraz (Apivar), a product commonly used for treating Varroa mites, off-label to four bee hives and left the other four hives untreated. They monitored the mite population density monthly and DWV density in early, middle, and late season.

    Researchers collected bees from miticide-treated and untreated hives, and quantified gene expressions of four immune genes and two physiology-related genes. They also tested bees’ sensitivity to five representative insecticides. In addition, bees’ natural mortalities were recorded during three seasons.

    “Miticide treatment led to minor or undetectable mite and DWV infestations during the whole bee season, while untreated colonies had substantially higher mite and DWV infestations,” said Zhu.

    The data analyses showed that Varroa mite population irregularly fluctuated over the bee season and mite population density was not dynamically or closely correlated with the seasonal shift of honey bee natural mortality. Unlike mites, DWV density in untreated colonies progressively increased over the bee season. The density was highly correlated with the seasonal increase in honey bee natural mortality.

    “In the untreated hives, the increased DWV infestations resulted in decreased physiological and immunity-related functions in late-season honey bees, making the bees more susceptible to insecticides and increasing natural morality rates during the season,” said Zhu.

    According to Zhu, Varroa mites, also known as Varroa destructor, can reduce fat body and body fluids that contain important detoxification enzymes and immune proteins in honey bees. As a result, bees have impaired immune, detoxification/defense systems, and other essential processes. Coupling those impairments with exposure to insecticides can be detrimental to bee populations.

    “Having impaired immunity, especially later in the season with fewer food sources, can be challenging for honey bees,” said Zhu.

    Zhu, whose work focuses on the toxicological impact of pesticides on beneficial insects in the Mississippi Delta Area, said that the study’s results indicated the importance of studying the “bottom-up” effects of mite infestations on the overall health of honey bees in real-world contexts.

    “Chemical control is still a major method in preventing crop loss and controlling insect pest populations,” said Zhu. “It is important to study the effects of chemical control in honey bee populations so we can find best practices for protecting the health of bees.”

    The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in U.S. agricultural research results in $20 of economic impact.

  • Early Season INSV Infections in Lettuce Reduced From 2022 Levels

    Grower-Shipper Association of Central California – Possibly due to colder winter and spring weather conditions as well as mitigation strategies taken by farmers, pest and disease pressure associated with the Thrips-Vectored Impatiens Necrotic Spot Virus (INSV) have lessened in leafy greens fields as compared to 2022. As observed and reported by the Grower Shipper Association’s (GSA) INSV Task Force, this reduced pressure in the early growing season has resulted in dramatically fewer infections and, so far, lower pest populations as we move into the spring leafy greens harvest.

    What is INSV? Lettuce fields are infected by INSV via thrips migrating from infected host plants. Plants infected by INSV can have dark spotting and yellowing, which resembles the effects of sunburn on the leaves. Another plant disease, Pythium wilt (PW), often accompanies INSV infections and causes the plant to wilt or collapse making this truly a complicated pest/disease issue for farmers.

    In 2022, INSV infections in the Salinas Valley resulted in yield reductions in many fields resulting in consumers experiencing limited product availability in some areas.

    To identify and respond to INSV pressure as well as accelerate research mitigation strategies to control INSV, GSA launched its INSV Task Force in 2021. The Task Force is a collaborative effort between industry and the academic/research communities. In addition to funding provided directly by GSA, the organization helped to secure a one-million-dollar grant from the California Department of Food and Agriculture (CDFA) for INSV and soil-borne disease research priorities. And in April 2023, GSA helped obtain a supplemental $200,000 grant through CDFA to further critical efforts.

    “One of our major initiatives was tracking thrips and corresponding disease pressure to identify infection trends that have helped guide research strategies,” explains Christopher Valadez, GSA President. “We found that an important mitigation strategy to lower pest pressure is weed abatement since weeds are good hosts for thrips. By encouraging increased weed control on farms as well as working with the state and county agricultural commissioners’ offices on abatement efforts along roadways, businesses, and open spaces, we’re reducing the opportunity for thrips to find spots to over-winter and lay eggs in spring.”

    Valadez adds that in 2022, disease pressure was exacerbated by unseasonably warm weather stretches which caused prolonged stress on the plant making the lettuce more susceptible to disease impacts. “The unseasonably cold weather we’re experiencing this year is positively impacting early-season INSV infections,” he says.

    In addition, GSA’s Task Force continues to assess varietal resistance, examine treatment efficacy trials and conduct grower education and outreach programs specific to these diseases.

    “Our thanks to Mary Zischke who heads up GSA’s task force as well as the farm advisors, scientists, and industry members for their diligent work on this very complex issue,” Valadez says. “Their efforts are crucial to prevent significant impacts from INSV infections, which can affect many in our communities including farmers, farm workers, processors, and facility employees.

  • New Report Finds 97% of Fruits and Vegetables Sampled in CA Meet Pesticide Safety Standards

    The California Department of Pesticide Regulation (DPR) today released a report finding that 97% of fruits and vegetables sampled within the state in 2021 met federal pesticide safety standards.

    The 2021 California Pesticide Residue Monitoring Program Report shows that 97% of domestically grown and imported produce samples collected in 2021 had either no detectable pesticide residues or had residues within the allowable federally-established tolerances. In addition, more than 98% of produce samples labeled as “grown in California” had no residues or tolerances that exceeded allowable levels. These results, compiled annually, are consistent with the department’s last several years of produce residue monitoring, and reflect the strength of California’s pesticide regulatory program and compliance with it.

    The 2021 report’s findings are based on 3,444 produce samples collected by the department at approximately 500 locations.

    The pesticide residue monitoring program supports DPR’s mission to protect people and the environment. Federally established tolerances identify the maximum allowable residue level of a specific pesticide on food that provides a ‘reasonable certainty of no harm.’

    “DPR’s produce monitoring program is the largest and longest-running state program for testing fruits and vegetables for illegal pesticide residues,” DPR Director Julie Henderson said. “With a focus on food eaten by children, as well as the state’s diverse ethnic communities, this program helps protect all Californians from pesticide residues on both domestic and imported produce.”

    DPR scientists throughout the year visit food distribution centers, stores and outdoor markets to collect samples of foreign and domestically grown produce. The samples are tested by California Department of Food and Agriculture labs for more than 500 pesticide residues and breakdown products.

    U.S.-grown produce continues to have significantly fewer illegal pesticide residues than imported produce. Imported produce accounted for nearly 77% of illegal pesticide residue samples. Of the imported commodities sampled, cactus pads and fruit originating from Mexico continue to show high percentages of illegal pesticide residues.

    When illegal residues are detected, DPR investigators trace the suspect crop through its lines of trade – from store shelves, to shippers, importers or growers. Tainted products and crops are quarantined and subject to reconditioning, such as washing to remove residues, or potential destruction In addition to potentially losing their inventory, growers and distributors whose produce exceeds tolerances can face fines and other penalties.

    During 2021, DPR issued 120 quarantine notices for more than 70,000 pounds of produce carrying illegal pesticide residues. In addition, DPR referred 22 cases of illegal California-grown samples to local County Agricultural Commissioners (CACs) for investigation of potential illegal pesticide uses. CACs issued statutory fines against growers in instances where produce sources were able to be identified.

    As part of enforcement activities, DPR staff provide guidance to growers and importers for ways to prevent sales of illegal produce.

    For previous reports and more information about the department’s residue testing program, please visit the Pesticide Residue Monitoring Program’s webpage.

    ABOUT THE DEPARTMENT OF PESTICIDE REGULATION

    The California Department of Pesticide Regulation’s mission is to protect human health and the environment by fostering safer and sustainable pest management practices and operating a robust regulatory system to monitor and manage the sale and use of pesticides across the state. DPR’s work includes registering all pesticides sold or used in California, conducting scientific evaluation of pesticides to assess and mitigate potential harm to human health or the environment, monitoring for pesticides in the air and water, and enforcing pesticide regulations in coordination with 55 County Agricultural Commissioners and their 500 field inspectors. DPR also conducts outreach to ensure pesticide workers, farmworkers and local communities have access to safety information. DPR invests in innovative research to encourage the development and adoption of integrated pest management tools and practices. More information about DPR can be found at www.cdpr.ca.gov.

  • DPR Awards $3.15M in Research Grants Investing in Safer, Sustainable Grape, Nut & Tree Fruit IPM

    The California Department of Pesticide Regulation today announced it has awarded $3.15 million in research grants to seven projects to support a statewide, systemwide transition to safer and more sustainable pest management.

    DPR’s Research Grants Program funds projects that advance integrated pest management (IPM) knowledge, tools and practices in agricultural, urban and wildland settings. IPM is a pest management approach that uses the least-toxic, effective method to solve pest problems.

    Over the past decade, DPR has awarded more than $13.45 million in research grants.

    “These grants are a cornerstone of DPR’s mission to advance sustainable pest management and continuously improve the state’s protection of people and the environment,” said DPR Director Julie Henderson. “These projects play a central role in developing alternative approaches to pest management that support agriculture, enable the production of an abundant, healthy food supply, and support the well-being of all California communities.”

    In January 2023, DPR released the Sustainable Pest Management Roadmap, which outlines critical goals and actions to accelerate the transition to sustainable pest management.

    Among the projects funded this year, two seek to reduce fumigant use while three others could help decrease farmers’ reliance on neonicotinoids and other pesticides. Fumigants – gaseous pesticides used in agriculture to kill soilborne pests – are a concern because they are often highly toxic and can impact surrounding air. Neonicotinoids are also a concern since they have been linked to pollinator deaths.

    Other grant-funded projects seek to reduce human health effects of spray applications, and to provide effective alternatives to traditional pesticides.

    Award recipients:

    Research projects supporting alternatives to fumigant use:

    • Dr. Cassandra Swett will advance understanding of the emerging fungal pathogen Fusarium falciforme, which affects a range of California crops and drives high-risk fumigant usage. Dr. Swett’s project will seek to evaluate a variety of potential reduced-risk control strategies for this pathogen in lieu of fumigation.
    • Dr. Andreas Westphal will research soils that suppress root lesion nematode in almonds. These efforts will ideally offer alternatives to the current usage of soil fumigants to control these microscopic worms and other soilborne pests and pathogens.
    Research projects supporting reductions in neonicotinoid and other insecticide use:
    • Dr. Paul Rugman-Jones will lead a project developing non-genetically engineered sterile-insect techniques for combating Asian citrus psyllid (ACP). ACP is an insect that spreads a bacterial plant disease called huanglongbing (HLB). HLB is a major threat to California citrus production and one that drives the use of neonicotinoids in citrus.
    • Dr. Hailing Jin will lead research into antimicrobial peptides to combat Pierce’s Disease in grape and HLB in citrus, two highly damaging diseases of perennial crops in California. The project will also focus on their vectors – ACP in citrus and glassy-winged sharpshooter in grape. Alternatives to current vector control practices for these diseases offer the potential to reduce the usage of neonicotinoids and other broad-spectrum insecticides.
    • Dr. Stephanie Bolton will expand the use of canines to rapidly scout grapevine leafroll-associated virus 3 (GLRaV-3) and vine mealybug in grape nurseries and commercial vineyards, which greatly impact California grape production. Early detection is a key IPM practice that will help reduce the use of neonicotinoids and other insecticides to control vine mealybug.

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    Research project supporting reductions in fungicide use:
    • Dr. Mary Wildermuth will research a suite of RNA interference approaches to combat powdery mildew in grapevine, potentially resulting in a tailored, highly specific alternative to repeated usage of fungicides.

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    Research project supporting reductions in spray drift and worker exposure:
    • Dr. Peter Larbi will develop and refine a remote nozzle selector device to allow for rapid, safe changeouts of spray nozzles when operating airblast sprayers. This technology will help minimize spray drift and potential exposure to workers and bystanders. Furthermore, these technological advances will be adaptable to traditional chemistries as well as emerging safer alternatives.

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    For more information on past recipients of DPR’s Grants Program funding, or to learn more about DPR’s Grants Program and grant-related IPM research, innovation, implementation and knowledge-sharing, please visit DPR’s Grants Program webpage.

    ABOUT THE DEPARTMENT OF PESTICIDE REGULATION

    The California Department of Pesticide Regulation’s mission is to protect human health and the environment by fostering safer and sustainable pest management practices and operating a robust regulatory system to monitor and manage the sale and use of pesticides across the state. DPR’s work includes registering all pesticides sold or used in California, conducting scientific evaluation of pesticides to assess and mitigate potential harm to human health or the environment, monitoring for pesticides in the air and water, and enforcing pesticide regulations in coordination with 55 County Agriculture Commissioners and their 500 field inspectors. DPR also conducts outreach to ensure pesticide workers, farmworkers and local communities have access to safety information. DPR invests in innovative research to encourage the development and adoption of integrated pest management tools and practices. More information about DPR can be found at www.cdpr.ca.gov.

  • Draft Mill Assessment Recommendations Released by CA DPR with Call for Public Feedback

    The California Department of Pesticide Regulation (DPR) has released the draft mill assessment recommendations, which are part of an independently conducted study to identify the structure and funding necessary for the department to continue to effectively carry out its pesticide regulatory program and support the state’s accelerated transition to sustainable pest management. The study’s author, Crowe LLC, will collect public feedback on the draft study through May 30 to inform its final recommendations.

    DPR’s mill assessment is paid by a pesticide retailer or manufacturer when a pesticide is first sold into California and provides approximately 80% of the department’s current funding. The mill assessment was last increased in 2004.

    The mill assessment study was commissioned by DPR in 2021 with funding from the Legislature to identify long-term resource needs and mechanisms to address the department’s funding imbalance and meet its increasing programmatic responsibilities. Over the last decade, the department has expanded its programs and outreach to address the evolving risks and impacts of pesticide use on people and the environment.

    To sustainably fund DPR and the pesticide-related work of County Agricultural Commissioners (CACs) and the California Department of Food and Agriculture (CDFA), the draft study recommendations consider incremental increases of the mill assessment from the current $0.021 up to $0.0339 per dollar of pesticide sales. The draft implementation recommendations include phasing-in the increase and continuing the mill assessment’s flat rate structure to start, while considering a tiered mill assessment in the future.

    “Stakeholder consultation is critical to informing the structure and implementation of necessary long-term funding for the department,” said DPR Director Julie Henderson. “We look forward to continued dialogue with stakeholders as we continue to improve the state’s equitable protection of people and the environment from pesticide risks and advance a systemwide transition to sustainable pest management.”

    Crowe LLP is seeking feedback on the draft to inform its final recommendations for department funding, which are expected to be released this summer. The feedback period is open today through May 30 at 5 p.m. Comments may be sent via email to ProjectMillStudy@cdpr.ca.gov, or by mail to 1001 I Street, P.O. Box 4015, Sacramento, CA 95812.

    Crowe LLP is conducting a Q&A session on Tuesday, May 16 (1:30 – 3p.m. PST) for stakeholders. To sign up for a Q&A session, interested participants should email Jamey.Hammond@crowe.com

    More information on the mill assessment study and the current mill assessment are available on DPR’s website. Updates on the progress and findings of the mill assessment study are available by subscribing to the department’s email distribution list.

    ABOUT THE DEPARTMENT OF PESTICIDE REGULATION

    The California Department of Pesticide Regulation’s mission is to protect human health and the environment. The department achieves this mission by fostering safer and sustainable pest management and operating a robust pesticide regulatory system. DPR’s work includes registering all pesticides sold or used in California, conducting pre- and post-registration scientific evaluations of pesticides to assess and mitigate potential harm to human health or the environment for pesticides in the air and water, and enforcing pesticide use laws and regulations in coordination with 55 County Agriculture Commissioners and their 500 field inspectors.

    DPR also conducts outreach to ensure pesticide workers, farmworkers and local communities have access to pesticide safety information. More information about DPR can be found on our website.

  • Citrus Mealybug Field Day, May 5

    To teach PCAs about citrus mealybug (an emerging concern for citrus growers) this field day will focus on lectures on pest identification and biology, scouting/monitoring, and management, lecture on ant control.  With this knowledge, PCAs can monitor the fields for mealybug infestation and develop informed management strategies.  Attendees will receive instruction from Sandipa Gautam and David Haviland from the UC Cooperative Extension.  The field day will take place in a citrus block in Ivanhoe, CA.  Growers can register to attend by April 21 HERE, or by emailing sangautam@ucanr.edu.  Attendees should bring a 10x hand lens. An email will be sent out with a location ping to registrants 1-week prior to the event.  3 hours of Other Continuing Education Units are pending approval with CDPR.

    AGENDA

    8:00 a.m. Registration: Ivanhoe citrus block

    8:30-9:30 am

    1. Introduction: The citrus mealybug problem and best management practices (chemical, biological).
    2. Seasonal phenology and monitoring males using pheromone lure (Georgina Reyes)

    9:30 am: Sugar-feeding ants and their management in orchard systems

    10:15 am: Microscope time: Identification of mealybug stages, and parasitism.

    11:00 am: Field demonstration of pesticide trial.

  • Invasive Plant Pest & Disease Awareness Month

    CDFA is joining the USDA in declaring April 2023 Invasive Plant Pest and Disease Awareness Month .

    This national outreach month is dedicated to highlighting the impact of invasive plant pests and diseases on plants nationwide. The focus is on raising public awareness about the threat and how residents can help.

    Each year, invasive insects and plant diseases cause an estimated $40 billion in damages to plants in the US.

    Nonnative plant pests can hitchhike in untreated firewood, attach themselves to cars, boats, and other outdoor surfaces—or take a ride in the mail. They can travel to new areas on agricultural material such as soil, seeds, homegrown produce, and plants.

    Invasive pests have few or no natural predators in their new environments, so their populations quickly outpace native species and spread. These non-native plant pests and diseases disrupt our ecosystems and reduce biological diversity.

    Climate change can magnify the impact of invasive species by increasing the level of plant pest infestations and disease infection, allowing pests to produce more generations each year, and increasing their suitable habitat.

    To protect domestic plant health:

    • Learn about possible quarantines in your area, as well as the signs of invasive pest infestation on plants.
    • it’s important to clean your car and outdoor gear before traveling with them to new places, because invasive species can travel with you.
    • If you find signs of new invasive plant pests and diseases in your area, report them to your local Extension office,  CDFA’s Pest Hotline, or your USDA State Plant Health Director’s office.
    • Don’t move untreated firewood—even if it looks pest-free on the outside. To avoid unintentionally spreading tree-killing beetles that hide in firewood, buy or source wood locally, or use certified, heat-treated firewood.
    • Source your plants and seeds responsibly. When ordering online, ensure the plant is coming from a domestic source or follow import regulations. If you don’t know where an agricultural product is coming from, don’t buy it online. U.S. regulations apply to the importer of record—meaning the person purchasing and importing the product from overseas—not the online merchant. Learn how to safely and legally order plants and seeds online.
    • Don’t mail homegrown plants, fruits and vegetables to avoid inadvertently mailing a plant pest with them.
    • To comply with U.S. laws and avoid introducing new invasive species into the U.S., declare all agricultural items, including seeds, soil, and handicrafts to U.S. Customs and Border Protection for inspection when returning from overseas travel.

    Link to CDFA’s Report a Pest Page
    Link to the USDA’s Hungry Pests Page

  • Combatting the Arch Nemesis Pest of the CA Grape Industry

    The arch nemesis pest of the California grape industry continues to spread to more grape growing areas. Vine mealybug damage not only leads to black sooty mold on grapevine leaves and clusters, but it can also transmit and spread grapevine leafroll associated viruses that have been devastating vineyards.  Watch this brief interview with UCCE Kern County Entomology Advisor David Haviland as he encourages an integrated or combination approach to combatting this pest.

    Please thank this video’s sponsor Ranch Systems for their industry support.

  • Mitigating the Effects of Grapevine Red Blotch Disease

    With grapevine red blotch disease widespread across the west, what’s a grower to do with a young or old vineyard that contracts this disease?  How does it impact grape yield and quality and are there ways to mitigate the detrimental effects of this disease?  Watch this brief interview with the new UCCE San Joaquin County Viticulture Advisor Justin Tanner to find out.

    Please thank this video’s sponsor Ranch Systems for their industry support.

  • Artificial Light at Night Aids Caterpillar Predators

    To save caterpillars, turn off your porch light.

    Moderate levels of artificial light at night – like the fixture illuminating your backyard – bring more caterpillar predators and reduce the chance that these lepidoptera larvae grow up to become moths and serve as food for larger prey.

    This new Cornell research was published March 8 in the Proceedings of the Royal Society B: Biological Sciences.

    The Cornell scientists placed more than 550 soft clay caterpillar models – lifelike replicas – in a forest setting to ascertain how the mockups were attacked and hunted by predators, compared to a control group.

    “We measured predation rates on the clay caterpillars – which look like the real thing,” said John Deitsch ’22, who conducted the research as his undergraduate honors thesis in the nearly pitch-dark Hubbard Brook Experimental Forest, in the White Mountains of New Hampshire. “Predators left marks on the clay. Predation rates on clay caterpillars and the abundance of arthropod predators were significantly higher on the artificial light at night treatment plots. This suggests an increase of mortality pressure on caterpillars.”

    Deitsch and Sara Kaiser, research ecologist and director of the Hubbard Brook Field Ornithology Program at the Cornell Lab of Ornithology, co-authored the research, “Artificial Light at Night Increases Top-Down Pressure on Caterpillars: Experimental Evidence From a Light-Naive Forest.”

    Scientists can place clay models that look like caterpillars in the woods. Due to the soft clay, the researchers can examine the marks and get a sense of how often larvae are attacked by predators (photo by John Deitsch, Cornell University)

    The caterpillar models, made from green, extruded clay to mimic the color and size of Noctuidae (owlet moths) and Notodontidae (prominent moths) caterpillars, are commonly found at the Hubbard Brook Experimental Forest. The soft clay easily allows for imprints so that the scientists can determine if predators – like arthropods, insects or birds – landed on the model or tried to take a bite.

    While effects of artificial light at night have often been studied on adult insects (such as moths), the larvae (caterpillars) have seen little research.

    Of the 552 clay caterpillars deployed and glued to leaves to look authentic, 521 models were recovered and 249 (47.8%) showed predatory marks from arthropods, during the summer-long nighttime study.

    Further, the research found that caterpillar predation rates were 27% higher on experimental plots – compared to the control areas in the same forest – that had 10 to 15 lux (about the brightness of a streetlight), which is an illumination measurement for LED lighting.

    Given the global ubiquity of artificial light at night, increased threat to caterpillars is yet another ecological problem for lepidoptera, in addition to habitat loss, agricultural-chemical pollutants, invasive species and climate change, according to the paper.

    Caterpillars are the most vulnerable at that larval stage. “They are eating leaves and growing in order to mature to the next stage,” Kaiser said, explaining that real-life caterpillars can move around leaves to avoid detection, but the scientists sought to understand predators when larvae were illuminated.

    “When you turn on a porch light, you suddenly see a bunch of insects outside the door,” Kaiser said. “But when you draw in those arthropod predators by adding light, then what is the impact on developing larvae? Top-down pressure – the possibility of being eaten by something.”

    Funding was provided by the Rochester Academy of Science, the Society for Integrative and Comparative Biology and the College of Agriculture and Life Sciences. For Deitsch, the research was made possible by an Experiential Learning Grant from the Cornell Lab of Ornithology Ivy Scholars Fund. — By Blaine Friedlander, Cornell University