California Ag Network

Category: Pest/Disease Management

  • Honey Bees Can Detect Viruses in Food

    Honey bees encounter viruses in their environments, especially when they forage on flowers and other food sources. Being able to detect viruses is important for reducing infection and the spread of disease. Many insects, including honey bees, can detect viruses indirectly with sick nestmates, but it has been unclear if honey bees can directly detect viruses in food sources.

    To help beekeepers protect their colonies by reducing viral spread, ARS researchers from the Honey Bee Breeding, Genetics, and Physiology Research Unit in Baton Rouge, LA, studied if honey bees could sense viruses such as deformed wing virus, black queen cell virus, and chronic bee paralysis virus in contaminated food sources.

    In an experimental study, the researchers found that when honey bees were presented with the choice between a spiked sugar solution with viruses and a plain sugar solution, the honey bees preferred the virus-spiked solution.

    “These findings demonstrate that honey bees can directly detect the presence of viruses in contaminated food sources, which has important implications for pathogen transmission within pollinator communities and disease management strategies aimed at improving honey bee health,” said Michael Simone-Finstrom, ARS Research Molecular Biologist.

    According to Simone-Finstrom and ARS Research Entomologist Elizabeth Walsh, both co-lead authors of the study, the results highlight the need to control viral infections and spread in bee colonies.

    One major concern is viral spread from Varroa mites, parasitic pests that feed on honey bees. Currently, controlling Varroa mite populations is one of the most effective ways to protect honey bee colonies. Beekeepers can consider changing how they feed honey bees to limit outside insects from getting access to their food, according to Simone-Finstrom and Walsh.

    “Open feeding scenarios where bees from different colonies and other insects, who may carry viruses, get food from the same source may not be in the honey bees’ best interest,” said Walsh. “Beekeepers can consider an alternative like an individual colony feeder where only honey bees from one colony have access to the food.”

    It is unknown what mechanisms cause bees to gravitate towards the contaminated food sources. More research is underway to better understand honey bees’ foraging behaviors and how the viral presence affects their behaviors.

    “The study’s findings will help us with providing data-driven decisions in honey bee management and ecological decisions,” said Walsh. – By Jessica Ryan, ARS Office of Communications

  • DPR Releases New Report on Pesticide Reevaluation Process

    In compliance with Assembly Bill 2113, the California DPR has released a new report on how it is making its pesticide reevaluation process more efficient.

    “Reevaluation is one tool in DPR’s Continuous Evaluation and Mitigation program,” A release from the California DPR stated. “It gives the department authority to require pesticide companies to develop and submit scientific studies when important data is missing, and then to use those results to evaluate risks and put any necessary protective measures in place. AB 2113 requires DPR to initiate one reevaluation per year, increasing to two per year beginning in 2029.”

    DPR has also updated its public Continuous Evaluation and Mitigation tracker, noting that as of June 2026 the department has 7 reevaluations, 2 risk assessments, and 10 mitigation efforts underway. The report can be found here. — Story contributed by the California Department of Pesticide Regulation

  • Hearing Set for Proposed Regulation on Pesticide-Treated Seeds

    The California Department of Pesticide Regulation (DPR) announced that it will hold a virtual public hearing on the recently proposed rules to regulate pesticide-treated seeds. The department released the proposed regulation on May 15 to formally define pesticide-treated seeds in the state — specify conditions under which those seeds are exempt from pesticide registration requirements — and require reporting on the use of pesticide-treated seeds in California.

    DPR will hold a public hearing to receive verbal or written comments on July 6. The hearing will be conducted virtually to ensure statewide accessibility.

    The hearing will be conducted in English with Spanish interpretation provided. Information on accommodations, including requesting interpretation in additional languages, can be viewed within the regulatory notice, available on DPR’s website.

    Meeting Details

    Date: Monday, July 6

    Time: 9:30 to 11:30 a.m.

    Location: Zoom (Virtual)

    The virtual hearing will also be accessible via public webcast for persons who would like to watch this hearing without participating. — Story contributed by the California Department of Pesticide Regulation

  • Roof Rat Bait Stations Available for Pistachio Growers

    American Pistachio Growers (APG) is offering free roof rat bait stations to all grower members.

    There is no limit on the number of bait stations growers may receive. Bait stations can be picked up at the APG office, or by contacting Joe Coelho to inquire about delivery options that may be available in the grower’s area.

    Roof rats can cause significant damage in orchards, and proper bait station placement is an important part of an effective management program. To help get the most from this resource, APG included links to a roof rat bait station guide, instructional video tutorials, and informational article below.

    If you have questions or would like to arrange pickup or discuss delivery options, please contact Joe Coelho at JCoelho@americanpistachios.org.

  • Sweet Orange Scab Quarantine Boundary Expands

    Effective June 18, the CDFA is expanding the sweet orange scab (SOS) quarantine in the Burbank, Los Angeles and Long Beach areas of Los Angeles County and the Anaheim and Garden Grove areas of Orange County (grids 438, 439, 455, 456, 457, 470, and 471). A map of the new boundary can be found at https://www.cdfa.ca.gov/citrus/pests_diseases/sos/regulation.html.

    Regulated articles and conditions for intrastate movement under the quarantine can be found at Title 3 of the California Code of Regulations (CCR) section 3443. Pursuant to 3 CCR § 3443, any interested party or local entity may appeal a quarantine area designation.

    Process to Appeal the Expanded Boundary

    The appeal must be submitted to the Department in writing and supported by clear and convincing evidence. The appeal must be filed no later than ten (10) working days from the date of this notification. During the pending of the appeal, the designated quarantine boundary under appeal shall remain in effect.

    Mail Appeals to: CDFA – Citrus Division 1220 N Street Sacramento, Calif. 95814

    Electronic Notification of Boundary Changes

    California Code of Regulation allows interested parties to be notified of quarantine area boundary changes, as well as the opportunity to submit quarantine boundary appeals. If interested in receiving notifications, please sign up for regulatory updates through the email notification at: https://public.govdelivery.com/accounts/CADFA/subscriber/new

    For questions regarding the regulations or map, email Raymond Niem (Raymond.Niem@CDFA.ca.gov) or call (916) 274-6300. — Story contributed by the California Department of Food and Agriculture

  • Mexican Fruit Fly Quarantine in Portion of SD County

    A portion of San Diego County has been placed under quarantine for the Mexican fruit fly following the detection of one mated female fly in and around the unincorporated community of Spring Valley. This new quarantine will overlap a portion of the existing La Mesa Mexican Fruit Fly quarantine by 19 square miles. The USDA, the San Diego County Agricultural Commissioner and the CDFA are working collaboratively on this project.

    The new quarantine area in San Diego County measures 76 square miles, bordered on the north by El Cajon; on the south by Proctor Valley; on the west by Lemon Grove; and on the east by McGinty Mountain. A link to the quarantine map may be found here: www.cdfa.ca.gov/plant/mexfly/regulation.html.

    Sterile male Mexican fruit flies will be released in the area as part of the eradication effort. The release rate will be up to approximately 250,000 males per square mile per week in an area up to 50 square miles around the infestation.

    The quarantine will affect growers, wholesalers and retailers of susceptible fruit in the area as well as nurseries that grow and sell Mexican fruit fly host plants. The quarantine will also affect local residents; home gardeners are urged to consume homegrown produce on site and not move it from their property.  These actions protect against the spread of the infestation to nearby regions where it could affect California’s food supply and backyard gardens and landscapes.

    The Mexican fruit fly can lay its eggs in and infest more than 50 types of fruits and vegetables, severely impacting California agricultural exports and backyard gardens alike. For more information on the pest, please see the pest profile at: www.cdfa.ca.gov/plant/go/MexFly. Residents who believe their fruits and vegetables may be infested with fruit fly larvae are encouraged to call the state’s toll-free Pest Hotline at 1-800-491-1899.

    The eradication approach used in the Spring Valley area of San Diego County is the standard program used by CDFA and it is the safest and most effective and efficient response program available.

    While fruit flies and other invasive species that threaten California’s crops and natural environment are sometimes detected in agricultural areas, the vast majority are found in urban and suburban communities. The most common pathway for these invasive species to enter our state is by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions of the world. To help protect California’s agriculture and natural resources, CDFA urges travelers to follow the Don’t Pack a Pest program guidelines (www.dontpackapest.com). — Story Contributed by the California Department of Food and Agriculture

  • Blue Diamond Releases Early June Crop Report

    California’s Central Valley experienced variable weather conditions during May, with wide temperature swings serving as the norm for the period, punctuated by a few days of rain.

    Daily maximum temperatures ranged from the lower 60’s to nearly 100 degrees during the month, while minimum temperatures exhibited more stability, ranging from the lower 40’s on the chilliest mornings to mid-50’s under “balmier” conditions. Brisk winds also blew through the orchards on several days during the month, with sustained speeds at double digit levels and gusts reaching over 20 mph. While skies were clear and dry on the majority of days, late season storms in the opening and closing days of the period brought measurable rain to much of the Central Valley. Rainfall totals were generally limited to a few hundredths of an inch. However, the final storm of the month proved more vigorous. While most areas reported receiving from .25 to .60 inch of rain, a particularly strong cell passing over Yolo County dropped over an inch of rain near the community of Davis.

    May 2026 continued the pattern of late-spring storm systems that began in April. Grower activities were largely focused on vegetation management, fertilization, and irrigation, which was offset by adequate rainfall in some cases. While the wet conditions have increased concerns for fungal infections on the foliage and developing nuts, most growers feel that they have adequate protection provided by previous treatments. The rain events have limited the expansion of web-spinning mites and observers are reporting that the orchards are in generally good condition in all areas of the valley. Areas with the strongest winds experienced some blown-over trees, broken branches, and nut loss. However, losses have been minimal.

    Kernels in all varieties became fully solidified during the month, providing the first confirmation of the crop maturity since the completion of the bloom. There is now strong solidarity that the crop is running approximately 10 days ahead of “normal” in all areas. While June temperatures can influence exact timing, many believe the hull split will follow the current advanced timing, with the split in advanced examples of early maturing varieties expected during the week of June 21.

    As May concludes, many growers were winding down applications of fertilizer materials, and mowing vegetation in the orchard middles to manage the orchard floor in advance of the upcoming harvest. Growers whose orchards have high populations of almond feeding ants have begun the earliest treatments using bait formulations to target them. Some of these materials require several weeks to effectively reduce the ant populations and need to be applied as much as eight weeks prior to harvest.

    Growers and their pest control advisers, (PCAs), have been monitoring orchards for signs of leaffooted plant bugs and stink bugs. Brown spot, the damage resulting from the feeding of these insects on the developing nuts has been increasing for several years. Pheromones have been developed and are being tested in orchards to combat leaffooted plant bugs as PCAs work with university researchers to develop protocols for implementation. Growers have treated increasing populations of these insects where warranted.

    Growers have also begun preparations for hull split treatments to control navel orangeworm (NOW). In anticipation of the advanced timing this year, growers are shifting their attention to spotting the discoloration and splitting of blank nuts at the top of the orchard canopy and along the tree rows at the edge of the orchards. These blanks (nuts that formed a hull and shell but were not fertilized during the bloom and have no kernel) split approximately ten days ahead of the sound nuts that contain almond kernels. These serve as a signal of the approaching hull split. By monitoring the split of blank nuts, growers and their pest control advisers can fine tune treatment timing during the split to optimize control.

    Low and minimal care orchards, as well as abandoned plantings, are present in all areas. Pest management programs have grown complicated for many growers managing plantings near abandoned/low care orchards due to adult NOW moths moving into their orchards to lay eggs on the splitting hulls. Orchard sanitation (the reduction of NOW residing within the orchards) is the foundation of NOW management. NOW adults migrating from nearby sources have created significant financial hardship and mounting frustration for growers in recent years. — Story contributed by Blue Diamond Growers

  • New Study to Support Water Quality Protection in the Smith River Plain

    The California Department of Pesticide Regulation (DPR) is announcing a new, multi‑year scientific study to better understand how copper concentrations in tributaries of the Smith River Plain may be affecting local fish species and the broader aquatic ecosystem. The study will provide new data to support the North Coast Regional Water Quality Control Board’s (North Coast Water Board’s) ongoing oversight and water quality protection efforts in the Smith River watershed.

    Beginning this year, DPR will fund a two-year toxicity study led by researchers at Cal Poly Humboldt, using field collected water and laboratory testing to assess potential effects on fish health and behavior, and on sensitive invertebrate species.

    This study responds to questions raised by community members, Tribal representatives and other interested groups about pesticide runoff in the Smith River Plain, where copper fungicides are widely used in lily bulb production. The work will generate additional data needed to better understand copper bioavailability, or how much copper organisms can absorb and how quickly it may have an effect.

    The results of this study will support the North Coast Water Board’s ongoing water quality protection efforts in the Smith River Plain, including development and implementation of waste discharge requirements for lily bulb farming operations (a.k.a. Lily Bulb Order

    (external link)

    ). The study represents a collaboration between the Water Boards and DPR on continued work across both departments to protect the environment and engage with local communities and Tribes.

    The study will initiate in 2026 and is anticipated to conclude in 2028.

    More information on the Smith River Watershed is available on the North Coast Water Board’s website

    (external link)

    . — Story contributed by the California Department of Pesticide Regulation

  • CDFA Expands Sweet Orange Scab Quarantine in Southern California

    Effective June, the CDFA is expanding the sweet orange scab (SOS) quarantine boundary in the Artesia area of Los Angeles County and Buena Park area of Orange County (grids 470 and 471). A map of the new boundary can be found at https://www.cdfa.ca.gov/citrus/pests_diseases/sos/regulation.html.

    Regulated articles and conditions for intrastate movement under the quarantine can be found at Title 3 of the California Code of Regulations (CCR) section 3443. Pursuant to 3 CCR § 3443, any interested party or local entity may appeal a quarantine area designation.

    Process to Appeal the Expanded Boundary

    The appeal must be submitted to the Department in writing and supported by clear and convincing evidence. The appeal must be filed no later than 10 working days from the date of this notification. During the pending of the appeal, the designated quarantine boundary under appeal shall remain in effect.

    Mail Appeals to: CDFA – Citrus Division 1220 N Street Sacramento, CA 95814

    Electronic Notification of Boundary Changes

    California Code of Regulation allows interested parties to be notified of quarantine area boundary changes, as well as the opportunity to submit quarantine boundary appeals. If interested in receiving notifications, please sign up for regulatory updates through the email notification at: https://public.govdelivery.com/accounts/CADFA/subscriber/new

    For questions regarding the regulations or map, email Raymond Niem (Raymond.Niem@cdfa.ca.gov) or call 916.274.6300. — Story contributed by the California Department of Food and Ag

  • NMPF Releases Statement on New World Screwworm

    The National Milk Producers Federation (NMPF) released a statement following the detection of New World screwworm in Texas last week. NMPF President and CEO Gregg Doud weighed in on the news stating:

    “The return of Wew World screwworm to the United States decades after its initial eradication is a disappointing milestone, but it’s also one for which dairy producers have been preparing for more than a year, in collaboration with USDA and across agriculture. It’s important to remember that this development has no effect on food safety, and that measures to combat both the screwworm and its spread are in place and time-tested. We appreciate the U.S. Department of Agriculture’s proactive efforts to prepare for this moment, and we stand ready to work with the department to address any ongoing challenges.

    Now that USDA has confirmed that screwworm is here, dairy farmers and all livestock producers pledge close collaboration with USDA, state and local officials, and producer organizations to mitigate any harmful effects and educate farmers on how to protect their herds. We have been creating resources to guide farmers in their responses, and we will keep our members well informed of any important screwworm developments.

    We also urge officials to follow scientific guidance in any decisions affecting animal movements and regulatory responses to avoid causing economic harm that could be greater than the screwworm itself. We also ask that adequate resources be provided to combat this problem, which causes suffering in animals and creates risk for producers.”

    Currently, no instances of New World screwworm have been reported in California.