California Ag Network

Category: Pest/Disease Management

  • Asian Citrus Psyllid Infestation in California: A Guide for California Citrus Growers

    SPONSORED CONTENT

    California’s vibrant citrus industry, renowned for its oranges, lemons, and limes, is under threat from the Asian citrus psyllid (Diaphorina citri , ACP). This small invasive pest not only jeopardizes the health of citrus trees but also acts as a carrier of Huanglongbing (HLB), a bacterial disease that causes citrus greening. Here’s what growers need to know about ACP, its impact, and how Kemin Crop Technologies can help with effective botanical solutions to manage and prevent infestations.

    Understanding the Asian Citrus Psyllid

    The Asian citrus psyllid is a sap-sucking insect native to Asia, Africa, and the Saudi Arabian Peninsula. It was first detected in the United States in 2005 in Florida and in California in 2008 and has continued to spread across the major citrus growing regions. This insect’s feeding behavior damages citrus trees by causing leaves to curl and blacken. However, the real threat lies in ACP’s role as a vector for Huanglongbing (HLB). HLB is one of the most devastating diseases affecting citrus crops worldwide. HLB is caused by the bacteria Candidatus Liberibacter asiaticus, which infects the phloem of citrus trees, disrupting nutrient flow. Once a tree is infected, there is no cure, and the disease eventually leads to the tree’s death. Infected trees can be stunted, have reduced fruit yield, blotchy mottled leaves, and produce misshapen, bitter fruit, rendering them unmarketable. The economic and ecological impact of ACP and HLB is profound, putting California’s multibillion-dollar citrus industry at significant risk.

    Identifying an ACP Infestation

    Early detection of ACP infestations is crucial for effective management. Growers should regularly inspect their orchards for the following:

    • Adult Psyllids: Small (3-4 mm long), brown, winged insects perched at a 45-degree angle on leaves.
    • Nymphs: Tiny (0.25-2 mm long), yellowish-orange immature psyllids found on new growth.
    • Honeydew: Sticky substance excreted by psyllids, often leading to sooty mold development.
    • Leaf Curling: Deformed leaves caused by psyllid feeding.

    Regular monitoring and application during ACP’s active growth stages can significantly reduce infestations and aid in limiting the spread of HLB through psyllid vectors.

    Unlock Superior Protection with TetraCURB™ MAX: Kemin’s botanical-oil based Solution

    For growers seeking a sustainable and effective solution, Kemin’s botanical oil-based biopesticide, TetraCURB MAX, offers a promising option. TetraCURB MAX is a rosemary, peppermint, clove and castor oil-based contact miticide-insecticide and repellent specifically designed to target soft-bodied insects like ACP. Its unique composition is formulated from a proprietary blend of essential oils and synergizers to have multiple modes of action that paralyze, suffocate, desiccate, repel, and disrupt the pest’s feeding and reproductive cycles.

    Here are the key benefits of TetraCURB MAX, and excellent tool for citrus growers to leverage:

    • Smart Blend for Maximum Impact: TetraCURB MAX is formulated with a proprietary blend of active ingredients, including castor oil, rosemary oil, clove oil, and peppermint oil. It also contains an adjuvant, soap and emulsifiers ensuring optimal spray contact, spread, and improves active ingredients efficacy without phytotoxicity. This unique combination ensures multiple modes of action, such as neurotoxic effects, contact suffocation, desiccation, and repellency aiding in fast pest knockdown. The multiple modes of action also help to reduce the likelihood of pests developing resistance.
    • Broad-Spectrum: TetraCURB MAX is effective against a range of pests, being specially formulated to target small, soft-bodied insects. ACP fits perfectly into this category, and we see excellent ACP knockdown in 3rd party assays.
    • TetraCURB MAX Kills on contact with a quick knockdown thanks to the smart blend technology.
    • Safety for Labor, Workers, and Consumers: TetraCURB MAX is made from safe-to-use ingredients, providing peace of mind for laborers and workers. Use of TetraCURB MAX requires minimal personal protective equipment (PPE) and allows a zero-hour restricted-entry interval (REI)
    • Minimal Disruption to Harvest Activities: With a zero-day pre-harvest interval (PHI) TetraCURB MAX can be applied at any time during the season, including on the day of harvest.
    • Versatility: TetraCURB MAX is labeled for use on all crops and has no restrictions on the number of applications per growing cycle.
    • Environmental Safety: TetraCURB MAX does not cause phytotoxicity in plants when used according to the label direction.
    • Easy Application: Applying TetraCURB MAX is simple. It can be used as a stand-alone or in a tank mix. Shake well before use, dilute in water, and apply as a foliar spray with standard equipment ensuring full plant coverage until runoff. ​ With a recommended spray volume of 100 gallons per acre and a treatment interval of 5-10 days, TetraCURB MAX fits seamlessly into your crop protection routine.
    • Exemption from Food Tolerance Requirements: These biopesticides are exempt from Maximum Residue Limits (MRLs) in the United States, as the pesticide residue expected to remain on crops after application is minimal.

    Proven Efficacy in Lab and Field Trials

    Recent studies conducted at the University of Florida and in Oviedo, Florida have demonstrated the efficacy of TetraCURB MAX against ACP. First, in lab bioassays, TetraCURB MAX at a 1% rate achieved a 59% mortality rate of ACP nymphs within just three days of the application, outperforming the positive control Spinosad-based product. ​A field trial on sweet orange trees showed that two applications of TetraCURB MAX at 0.5% 21 days apart, significantly reduced the nymphal population by 86%, matching the performance of conventional insecticides like Cyazypyr at 16 fl.oz/100 gal. ​ Download the crop sheet to see the full data set HERE:

    Protecting California’s Citrus Legacy

    The battle against ACP and HLB is ongoing, but with vigilance and innovative solutions like TetraCURB MAX, California’s citrus growers can protect their orchards and ensure the industry’s longevity. By adopting sustainable practices, we can safeguard the future of citrus farming for generations to come.

    Don’t let ACP infestations compromise your citrus yield. ​Add TetraCURB™ MAX to your rotation in an IPM program and experience the benefits of superior pest control. ​

    For more information, visit kemin.com/tetracurbmax or contact your Kemin Sales representative today.

  • Why this Grape Grower Urges a Yes Vote on the Pierce’s Disease Glassy-Winged Sharpshooter Referendum

    California wine grape growers have the opportunity to vote on whether to continue assessments to support the Pierce’s Disease Glassy-Winged Sharpshooter (PD/GWSS) Board. Ballots are being sent in the mail this month. Administered by CDFA and led by the wine grape industry for the last 25 years, this program funds research and activities to lessen the impact of threatening vineyard pests & diseases. Watch this brief interview with Lodi wine grape grower Aaron Lange as he shares with Matthew Malcolm on California Ag Network why he is voting “yes” on the referendum and explains what the Board has been working on that he finds so critical to the future of the industry.

    Please thank this video’s sponsor SIPCAM AGRO USA for their industry support.

  • Bird Flu Causes Massive Impact on California & National Milk Production

    To date, H5N1 avian influenza virus type A (bird flu) has been confirmed in dairy cattle across 17 states, and has infiltrated the epicenter of the nation’s milk production — the Central Valley of California. As of April 7, it has been detected on 758 California herds. While new cases and the spread of the virus has slowed with the onset of springtime (and conditions have improved since the time of the interview), the virus’ impact on lower milk production in the Central Valley was felt by the nation. California Dairy Editor Matthew Malcolm met with Senior Dairy Analyst at Rabobank Lucas Fuess at the World Ag Expo to discuss the impact the virus has had on cows, national production and prices. Watch this brief interview and read more about the economic impact of H5N1 in the latest issue of California Dairy Magazine.

  • Foundation Plant Services Detects No Viruses in 2025 Distributed Grapevines

    Recent testing of material distributed from the Foundation Plant Services Classic Foundation Vineyard at the University of California, Davis, detected zero cases of grapevine red blotch and grapevine leafroll associated virus-3 infections, after one positive result during annual testing last fall.

    “At this time there is no concern but we cannot get complacent,” Director Maher Al Rwahnih said of the results. “We will continue testing all individual vines every year and reconfirm that orders of Foundation Plant Services source vines are negative.”

    Foundation Plant Services, or FPS, annually tests grapevines at its Classic Foundation Vineyard for grapevine red blotch virus, grapevine leafroll associated virus-3 and other economically important viruses. In October 2024, one vine out of 4,881 tested positive for grapevine leafroll associated virus-3, an infection last seen in the vineyard in 1994.

    That vine was removed and surrounding vines were re-tested to ensure they were negative as well. The infected vine was also inspected for mealybug, which can transmit the virus, and none were found.

    FPS recently conducted additional tests on all plant material distributed this year — and those vines that had been near the infected vine last year — and did not detect any virus. Monitoring of the surrounding vines will continue through the summer.

    A source for industry

    FPS provides high-quality, virus-tested grapevine material to the grapevine industry in the United States and serves as the primary source for plant materials sent to nurseries under the California Department of Agriculture’s Grapevine Registration and Certification Program.

    The Classic Vineyard is home to more than 2,450 wine, table, raisin and rootstock grape selections. In 2024, Foundation Plant Services opened a new greenhouse to protect and propagate those plants in an environment safe from insects.

    The grapevine leafroll associated virus-3 detection underscores the need to safeguard the vineyard’s clean grapevine collection, Al Rwahnih said. Foundation Plant Services is fundraising for a new screenhouse to further protect and make room for up to 2,000 more grape selections. The estimated cost is $3.6 million.

    “Leafroll virus-3 is a severe virus,” Al Rwahnih said. “There is zero tolerance for it, red blotch or other economically important viruses. We cannot have them present.”  — By Emily C. Dooley, UC Davis

  • Pierce’s Disease Investment Saves Wine Grape Growers $56M Annually

    According to a new economic impact study, the California Department of Food and Agriculture’s Pierce’s disease (PD) and glassy-winged sharpshooter (GWSS) prevention, control and research efforts save California winegrape growers $56 million annually by reducing losses from the fatal grapevine disease. Without the program’s efforts, growers’ losses would more than double from $48 million to $104 million. The study found that if GWSS spread unchecked, outbreaks of PD could cost winegrape growers an additional $56 million a year in lost production and vine replacement.

    The Costs of Pierce’s Disease in the California Grape and Wine Industry

    “This study highlights the serious threat Pierce’s disease and the glassy-winged sharpshooter pose to our industry and reinforces the importance of grower-funded research,” said Randy Heinzen, a Paso Robles winegrape grower on the Pierce’s Disease and Glassy-Winged Sharpshooter Board. “The public-private partnership led by the Pierce’s Disease Control Program is vital, allowing grower assessment funds to drive research that improves pest and disease management and to develop practical, sustainable solutions for the long-term viability of our industry.”

    The unique funding partnership the winegrape industry forged between growers, the state and federal government and industry fuels the essential research and control operations that have significantly blunted the most severe impacts of PD and GWSS. Even with these efforts, PD still costs an estimated $110 million annually in California, including $45 million for control, prevention and research, $48 million in lost winegrape production and vine replacement and $17 million in lost table and raisin grape production and vine replacement. Without these critical programs, the industry’s losses in production and vine replacement would be even higher, putting greater financial strain on growers and threatening the long-term stability of California’s vineyards.

    With industry and government support keeping PD and GWSS in check, grower-funded research continues to drive advancements in pest and disease management while supporting field trials for promising solutions. According to the study’s authors, the economic burden of PD and GWSS could decrease as this research yields practical, vineyard-ready innovations.

  • Almond Day Updates Growers on New Pest, Disease in California

    Late in 2023, California almond growers – responsible for a crop valued at $3.88 billion in 2023 – started to hear about a potentially devastating new pest, the carpophilus beetle (Carpophilus truncatus).

    With virtually no information about this species in California, Jhalendra Rijal and his colleagues spent 2024 investigating its extent in the almond-growing regions of the state and learning from peers in Australia, where the insect has been a persistent scourge for a decade.

    A hullsplit almond showing a large number of carpophilus beetles (Carpophilus truncatus). Photo by Jhalendra Rijal.

    “This year, we at least have the one year of experience with this pest, and we have generated information that is relevant and practical for the growers,” said Rijal, a University of California Cooperative Extension integrated pest management advisor. For example: After an insecticide trial was largely ineffective (likely because the beetle spends most of its life cycle protected within the nut), Rijal has been emphasizing cultural practices like orchard sanitation.

    Sharing those crucial updates is one reason why the annual UCCE North San Joaquin Valley Almond Day is essential for growers, industry professionals and pest control advisers. This year’s event was held on Jan. 21 at the Modesto Centre Plaza.

    During Almond Day 2025, Jhalendra Rijal, UCCE IPM advisor, discusses the differences between Carpophilus truncatus and related beetle species. Photo by Mike Hsu

    “It’s the meeting on everyone’s calendar,” said Rijal, who co-organized the event alongside his UC Agriculture and Natural Resources peers, Brent Holtz and Cameron Zuber.

    With support from Farm Credit, the 2025 Almond Day attracted about 140 people, who heard about a range of best practices on almond production and pest management from six UC experts.

    “This is a great educational tool,” said meeting attendee Ali Arshad, a Blue Diamond grower who operates several ranches in San Joaquin and Stanislaus counties. “I like to come attend their seminars as much as possible; they’re very educational and informative – and very helpful too.”

    Scientists offer advice on managing carpophilus beetle, red leaf blotch in almonds

    Fellow grower Donny Hicks, who has attended 14 Almond Day meetings, concurred about the usefulness of the event. “Everything that was covered today is applicable to what I do,” he said.

    Troubled by the presence of Carpophilus truncatus on his orchard in Hughson, Stanislaus County, Hicks said he recently partnered with Rijal to set some traps on his property, hoping to grow scientists’ understanding of the pest.

    “It takes growers to help advance that knowledge and be the ‘guinea pigs’ somewhat,” Hicks explained. “At the same time, if it helps us growers as a whole, that’s a good thing.”

    During his opening talk, Rijal reiterated the need for growers to clean up the remnant “mummy” nuts on the ground that serve as overwintering habitat and a food source for the next generation of beetles in the spring.

    “Do the sanitation so you can destroy the population from the beginning and you will have less of a problem,” said Rijal, who also shared a visual ID guide that can help growers identify the specific pest in their orchard and thus better target their control methods.

    Growers also heard practical advice on an emerging almond disease, red leaf blotch, caused by the fungus Polystigma amygdalinum. Named for the orange-red patches of discoloration on leaves, red leaf blotch in almond has led to significant crop loss across Mediterranean countries. Unknown in California prior to last year, there was an explosion of reports throughout the San Joaquin Valley during 2024.

    “It was pretty surprising, both the quickness and vastness of the spread,” said Alejandro Hernandez-Rosas, a UC Davis Ph.D. candidate in the lab of Florent Trouillas, UC Cooperative Extension specialist in the Department of Plant Pathology at UC Davis.

    During his presentation, Hernandez-Rosas said a preventative application of fungicide at petal fall – and then again at two and five weeks after petal fall – appear to work best to manage this disease. Fungicide applications made after the blotchy leaf symptoms appear will not be effective, Hernandez-Rosas said, and further research needs to be done to determine the most effective products and optimal timing for growers to make the most of their applications.

    And because leaf litter is the “primary source” of the disease inoculum, Hernandez-Rosas added that cultural practices focused on speeding cleanup or decomposition of leaf litter are critical to reduce disease severity. However, it is only effective if done over a wide area in conjunction with neighbors.

    Advanced symptoms of red leaf blotch (RLB) include large, yellow-orange blotches (roughly 1/2″) that turn reddish-brown in their center. Photo credit: Alejandro Hernandez and Florent Trouillas

    Rodents, irrigation, replanting and whole orchard recycling

    Both Arshad and Hicks mentioned that they intend to tackle the gopher problem in their orchards.

    “I plant a cover crop every year and the gophers tend to really like it – so I get overrun with those gophers,” Hicks explained. “I’m trying to find that balance of not letting them overtake my orchard but still being able to cover crop – because that’s beneficial too.”

    With many growers voicing a desire to learn about burrowing rodents, Almond Day organizers were pleased to schedule a presentation by Roger Baldwin, professor of Cooperative Extension in the Department of Wildlife, Fish and Conservation Biology at UC Davis.

    Baldwin presented the available control options for not only pocket gophers but also ground squirrels and meadow voles. He stressed the need to understand the biology and ecology of the rodents to maximize efficacy; for example, whereas ground squirrels prefer green foliage as their main food source in the spring, they switch to seeds in the summer/fall – which would thus be a better time to use pelletized baits.

    In choosing from baiting, trapping, habitat modification, burrow fumigation, biocontrols and other options, Baldwin recommended combining different strategies and approaches in an integrated way.

    “Mixing and matching tools will give you the best possible results,” he said.

    The utility of combining methods was also a key takeaway from the presentation by Moneim Mohamed, UCCE irrigation and soils advisor. Highlighting the latest tools and innovations, Mohamed outlined the soil-based, weather-based and plant-based methods to collect data that can help growers make the most of their water.

    Mohamed said using even just one approach is beneficial in optimizing irrigation scheduling – but more is even better. “A combination of the three methods is the best,” he said.

    Cameron Zuber, UCCE orchard crops farm advisor for Merced County, discussed considerations related to replanting an orchard, including field and soil conditions and the management of plant-parasitic nematodes and aggressive pathogens and pests. He also encouraged attendees to visit growingthevalleypodcast.com for more information on tree nuts and a host of other topics.

    Finally, Brent Holtz, UCCE orchard systems farm advisor for San Joaquin County and a trailblazer for whole orchard recycling, presented an overview of WOR. He then shared recent findings on its effects on fungal pathogens, and ways to mitigate drawbacks of WOR – such as the initial carbon-to-nitrogen imbalance when the recycled almond wood chips are first spread on a field.

    Hicks, who has already tried WOR in his orchard, is also the grower relations manager for RPAC, a Los Banos-based company that grows, processes and markets almonds. Hicks said he also brings what he learns during Almond Day to his fellow growers – illustrating the multiplier effect of such educational events.

    “I have growers who possibly will be doing whole orchard recycling, and I can share that information,” Hicks said.

    UC Agriculture and Natural Resources brings UC information and practices to all 58 California counties. Through research and Cooperative Extension in agriculture, natural resources, nutrition, economic and youth development, our mission is to improve the lives of all Californians. Learn more at ucanr.edu.

  • Monitoring Spider Mites in Almond Orchards

    Almond growers are all too familiar with the challenges posed by pests in their orchards. Despite not being on the top of a grower’s concern list, spider mites can inflict serious damage to an almond orchard, and rather quickly if populations get out of control. However, effective monitoring and the use of beneficial insects can play a crucial role in managing these pests and ensuring a healthy almond harvest.

    Understanding Spider Mites
    Spider mites are tiny arachnids that thrive in warm, dry conditions, making almond orchards an ideal habitat. These pests feed on the leaves of almond trees, causing stippling, yellowing, and eventually leaf drop. Severe infestations can lead to reduced photosynthesis, weakened trees, and lower yields. Therefore, it is essential to keep a close eye on spider mite populations and take timely action to prevent economic losses.

    The Role of Beneficial Insects
    One of the most effective natural treatments for spider mites is the use of beneficial insects, such as six-spotted thrips. These tiny predators feed on spider mites and can significantly reduce their populations. David Haviland, a University of California Cooperative Extension (UCCE) entomology farm advisor, emphasizes the importance of relying on six-spotted thrips for mite management. These thrips are highly adaptable, reproduce quickly, and provide numerous operational benefits. They occur naturally, are free, and do not leave residues, pre-harvest intervals, or worker safety issues to worry about.

    In addition to six-spotted thrips, other natural enemies of spider mites include predatory mites and lady beetles. These beneficial insects can help maintain a balance in the orchard ecosystem, reducing the need for chemical interventions. However, it is crucial to monitor the populations of both spider mites and their natural enemies to make informed decisions about pest management.

    Effective Monitoring Techniques
    Monitoring for spider mites involves regular inspections of the orchard, particularly in dusty or water-stressed areas where mites are most likely to thrive. Checking on the underside of leaves for the presence of spider mites is the most effective way to identify them in the orchard. According to the University of California Agriculture and Natural Resources (UC ANR) Integrated Pest Management (IPM) Program, growers should check for spider mites at least weekly during the warmer months. Presence-absence leaf sampling is a useful tool for determining whether treatment is necessary. If there are 1.4 mites per leaf or 38% of leaves are infested, it is time to consider intervention to prevent the population from reaching damaging levels.

    To-Do List for Growers

    1. Seasonal Monitoring: From March to early May, monitor orchards for both predators and spider mites at least once every two weeks. Increase monitoring frequency to at least once a week from June to September when mite populations can rapidly increase.
    2. Weekly Inspections: Regularly inspect your orchard, especially in dusty or water-stressed areas, to check for spider mites. Use a hand lens to detect mite eggs, hatched spider mites, and predators.
    3. Presence-Absence Leaf Sampling: Use this method to determine if treatment is necessary. If there are 1.4 mites per leaf or 38% of leaves are infested, take action.
    4. Monitor Beneficial Insects: Assess the populations of natural enemies like six-spotted thrips, predatory mites, and lady beetles to ensure they are sufficient to control spider mites.
    5. Consider Selective Miticides: If natural predators are not enough, consider using selective miticides that are less harmful to beneficial insects.
    6. Follow ABC Guidelines: Utilize resources and guidelines provided by the Almond Board of California (ABC) for effective mite management.

    For more detailed information on monitoring spider mites, growers can refer to the guidelines provided by the UC ANR IPM Program here.

    Spider mites could pose a significant threat to almond orchards, but effective monitoring and the use of beneficial insects can help manage these pests without increasing inputs. By relying on natural predators like six-spotted thrips and other beneficial insects, growers can reduce the need for chemical interventions, lower costs and promote a healthier orchard ecosystem. — By the Almond Board of California

  • Got Carpophilus Beetle? Make it Official with Ag Commissioner

    The carpophilus beetle, a serious pest threatening California’s almond industry, is officially documented in only four counties — Stanislaus, Merced, Madera, and Kings. However, according to entomologists and industry experts, its presence is far more widespread, raising concerns about the limitations of official reporting and its impact on securing resources for control and mitigation.

    Houston Wilson, a Cooperative Extension specialist in the Department of Entomology at UC Riverside, has been surveying reports and conducting research on the beetle in collaboration with other UC and USDA researchers. “We’ve identified infested orchards — both almonds and pistachios — from every county within the San Joaquin Valley,” Wilson said. “We’re also hearing reports of crop damage from the Sacramento Valley (Sacramento through Butte County), but we have yet to directly confirm it there due to limited survey efforts.”

    The Importance of Official Documentation

    Despite mounting evidence of the carpophilus beetle’s spread, official state records remain limited. Wilson explains that for a find to be considered “official,” the county Agricultural Commissioner must collect a sample and submit it to the California Department of Food and Agriculture (CDFA) for verification. The current process means that many beetle infestations, though identified by researchers, remain unofficial.

    “While we have unofficial records from our survey efforts, my understanding is that the official records only reflect what has gone through the CDFA process,” Wilson said.

    For growers, the discrepancy between unofficial and official findings is more than just a technicality — it could also affect the allocation of resources. According to the Almond Alliance, securing state and federal assistance depends on having documented proof of the beetle’s widespread presence.

    “The widespread documentation of the carpophilus beetle serves as a vital indicator of the extent and severity of the issue,” said Almond Alliance CEO Alexi Rodriguez. “When more counties report official beetle findings, it underscores the pervasive nature of the problem, highlighting its impact beyond isolated areas.”

    Challenges in Reporting

    Wilson acknowledges that the reporting process can be complicated, but he and his team actively assist growers. “If a grower contacts me about suspected beetle damage, I usually visit the farm to assess the situation,” he said. “If we confirm the presence of the carpophilus beetle in a county that hasn’t had an official report, we advise them to contact their Agricultural Commissioner and guide them through the reporting process.”

    Rodriguez recognizes the difficulties growers face in reporting. “I want to acknowledge that the reporting process is not easy; however, expanding the network of official findings will allow us to advocate for more effective solutions by highlighting the problem’s regional and national significance,” she said.

    Identifying the Carpophilus Beetle

    For growers looking to detect the beetle, Wilson advises examining nuts in windrows, where nuts can be easily sampled. “The most apparent sign is a fine, powdery white frass on the nut, which results from beetle larvae tunneling into the kernel,” he said. “If you blow that frass away, you might see a circular hole in the shell where the adult beetle chewed through to lay its eggs. Inside, the larvae create distinctive oval-shaped tunnels in the kernel itself.”

    Wilson is part of a team that last year developed a pest identification guide to help growers differentiate carpophilus beetle damage from other pests, such as navel orangeworm or ants.

    Securing Support for Growers

    To address the growing concern, the Almond Alliance continues to work with officials at both the state and federal levels. “This engagement is expected to lead to more coordinated and robust interventions, mobilizing the necessary support and funding to mitigate the impact of beetle infestations on ecosystems, agriculture, and local economies,” Rodriguez said.

    Meanwhile, research efforts continue. “We’ve secured funding from the Almond Board of California and the California Pistachio Research Board for a second year, and we’ve now leveraged that into a larger pool of funding from the USDA,” Wilson said.

    Growers can also take advantage of upcoming pest identification workshops organized by the Almond Board of California in March, where they can learn more about identifying carpophilus beetle damage.

    A Call to Action

    With the evidence pointing to a much wider distribution of the carpophilus beetle than official records reflect, the push for more growers to report infestations is crucial. “If we don’t have official documentation, we can’t make the case for more resources,” Rodriguez emphasized. “We urge growers to work with their local Agricultural Commissioners to ensure the beetle’s spread is formally recognized.”

     

    By increasing official reports, the almond industry can strengthen its efforts to combat the carpophilus beetle, securing the necessary funding and support to protect California’s valuable almond crops. — By the Almond Board of California

  • Tolerance of Lettuce Varieties to Fusarium Wilt – 2024

    Fusarium wilt of lettuce, caused by Fusarium oxysporum f. sp. lactucae (FOL), is an economically significant disease on the Central Coast of California.  We conducted field trials to evaluate 30 iceberg and 21 romaine varieties for tolerance to Fusarium wilt.  The trials were located in commercial fields in Greenfield, CA (wet date of May 27, 2024) and Salinas, CA (wet date of June 8, 2024).  Foliar disease severity was visually evaluated on July 31-August 2, 2024 at Greenfield and on August 5-7, 2024 at Salinas and converted to a marketability (yes or no) rating.  Disease pressure was high at both locations.  Iceberg varieties that exceeded 50% marketability at both locations were Powerball and two coded entries from Vilmorin-Mikado.  Nine varieties exceeded 50% marketability at Greenfield but not Salinas, and two varieties exceeded the same threshold at Salinas but not Greenfield.  For romaine, 19 out of 22 varieties exceeded 90% marketability at Greenfield, but only two of those varieties (Holbrook and Momentus) also exceeded the same threshold at Salinas.  In a greenhouse experiment, isolates from Greenfield showed a susceptible reaction on variety Costa Rica #4, which is consistent with the Costa Rica FOL race variant.  Although FOL race 1 is suspected to be present at the Salinas location, greenhouse testing is not complete.  These trials provide public data on the tolerance of iceberg and romaine varieties to Fusarium wilt.

    Methods

    Field trials were conducted in Greenfield, CA and Salinas, CA to evaluate both in-slot and out-of-slot varieties (30 iceberg and 21 romaine) for tolerance to Fusarium wilt in commercial fields with disease history.  At Greenfield, bed center spacing was 80 inches, and plots were 1 plant line wide by 100 ft. long.  Due to space constraints, 4 iceberg and 10 romaine varieties were not included in the Salinas trial.  At Salinas, bed center spacing was 40 inches, and plots were 1 plant lines wide by 40 ft. long.  Iceberg and romaine varieties were evaluated separately, and plots of each type were arranged in a randomized complete block with four replications.  Treatments were direct seeded using the grower-cooperators’ planters at Greenfield and using single-line push planters at Salinas.  The wet dates were May 27, 2024 for Greenfield and June 8, 2024 for Salinas.  The Greenfield trial was maintained to commercial standards for lettuce production, whereas the Salinas trial was not.  After thinning by commercial crews, 50 plants at Greenfield and 30 plants at Salinas in the center of each plot were counted, and the section was marked with stakes.  Data were collected from this center section.  Evaluations were performed on July 31-August 2 at Greenfield and August 5-7 at Salinas, which was before maturity at the Salinas trial.  Foliar disease severity was assessed on a 0 to 4 scale where: 0 = healthy; 1 = wilting or chlorosis of one to three outer leaves; 2 = up to moderate stunting and wilting or chlorosis of <25% of leaf area; 3 = head is severely stunted or absent and between 25% and 75% of leaf area is wilting or chlorotic; and 4 = head is absent and >75% of leaf area is chlorotic and nearly dead, or plant is entirely dead.  For analysis, foliar disease severity was converted to marketability, where: disease severity of 0 or 1 = marketable; and disease severity of 2, 3, or 4 = not marketable.  Marketability data was analyzed by an analysis of variance (P < 0.05), and variety means were separated using Tukey’s honestly significant difference test.

    Results – Race of the FOL pathogen present

    Two races of FOL are present on the Central Coast: race 1, and a novel race variant (Nayak et al., 2024).  We are using the temporary name “Costa Rica FOL variant” for the novel race variant until it is officially named following completion of the upcoming ring test, which is a collaborative experiment between researchers and seed companies.  To determine the FOL race present, isolates from each location were evaluated in a race typing experiment in the greenhouse.  Variety Costa Rica #4 showed a susceptible reaction to both Greenfield isolates, which supports the observation that the Costa Rica FOL race variant is present at the Greenfield location.  We suspect FOL race 1 is present at the Salinas location.  However, greenhouse testing of the Salinas location isolates is ongoing.

    Results – Marketability

    Disease pressure was high at both locations.  Iceberg varieties that exceeded 50% marketability at both locations were Powerball and two coded entries from Vilmorin-Mikado (Table 1).  Nine varieties exceeded 50% marketability at Greenfield only: Balboa, Fontinas, Meridian, Paraiso, San Andreas, San Miguel, two coded entries from Salinas Valley Seeds, and one coded entry from Sakata.  In contrast, two varieties exceeded the same threshold at Salinas only: Fredonia and a coded entry from Takii.  This pattern of some varieties showing large differences in performance between locations whereas others showed similar performance suggests that a different race is present at each location, but this has not yet been confirmed by greenhouse testing.

    Of the 21 romaine varieties evaluated, two varieties exceeded 90% marketability at both locations: Holbrook and Momentus (Table 2).  A total of 17 out of 21 varieties exceeded the same threshold at Greenfield but not Salinas.  At the Salinas location, Holbrook and Momentus were not statistically different from four varieties (Boronda, Copious, Patton, and Solid Heart) with average percent marketability ranging from 77% to 88%.

    If you have additional questions about these trials, please contact Alex Putman at 951-522-9556 or aiputman@ucr.edu.

    Please Send Us Samples

    We are continuing to collect samples of lettuce Fusarium wilt to determine the distribution of races and to monitor the pathogen. To support this research, please contact the person in your region. Your help would be greatly appreciated.

    • Monterey, San Benito, or Santa Cruz Counties – Yu-Chen Wang (831-201-9689 or yckwang@ucanr.edu)
    • San Luis Obispo, Santa Barbara, or Ventura Counties – Chris Greer (805-888-1355 or cagreer@ucanr.edu)
    • Any other California county – Alex Putman (951-522-9556 or aiputman@ucr.edu)

    Acknowledgements

    We are grateful to D’Arrigo Brothers Co. of California and an anonymous grower for the space and maintenance of the variety field trials.  We thank seed producers for providing seed for the trial. Funding for this project was made possible by a grant from the U.S. Department of Agriculture (USDA) Agricultural Marketing Service. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA.  Funding was also provided by the California Leafy Greens Research Program.

    References

    Nayak, S., K.L. Richardson, A.I. Putman, N.R. LeBlanc, F.N. Martin, N. Li, and J.D. McCreight. 2024. Detection of novel pathogenic variants of Fusarium oxysporum f. sp. lactucae in California. Plant Pathology Early View. doi:10.1111/ppa.14019

  • Little Birds, Little Poops, Little Food Safety Risk

    It doesn’t require a degree in ornithology, a lab test or even an app for most growers to determine whether bird poop near their crops presents a food safety risk. They just need to ask themselves a simple question: How big is it?

    That’s according to a study from the University of California, Davis, published today in the Journal of Applied Ecology. The study said an informed, nuanced view of food-safety risks and wild birds could help growers avoid crop losses and manage farms for food safety, biodiversity conservation and crop production.

    Since 2006, when an E. coli outbreak devastated the U.S. leafy greens industry, growers have been pressured to remove natural habitat to keep wildlife — and the foodborne pathogens they sometimes carry — from visiting crops. Growers are often advised not to harvest crops within a roughly three-foot radius of any wildlife feces, lest they risk failing a food safety audit or losing a buyer contract. Growers often cite such concerns as a barrier to implementing conservation actions they would otherwise consider taking on their farms.

    “We wanted to find out the true risk of wild birds to food safety,” said lead author Austin Spence, a postdoctoral researcher in the UC Davis Department of Wildlife, Fish and Conservation Biology. “Which birds have pathogens, which birds are spending time on farms, and if a bird has a pathogen, does that pathogen survive long in bird poop? Our findings indicate that we can co-manage our areas for both agriculture and conservation.”

    Northern harrier on sprinkler in leafy-green field, coastal CA (image by Rose Albert, UC Davis)

    Where pathogens persist

    Through field and greenhouse experiments, bird surveys, point counts and fecal transects, the authors assessed food-safety risks from nearly 10,000 birds across 29 lettuce farms on California’s Central Coast. They spent hours following turkeys, bluebirds and other wild birds at the UC Davis Student Farm and nearby Putah Creek, collecting hundreds of fecal samples. They compared E. coli survival in bird droppings on lettuce, soil and plastic mulch to measure pathogen persistence.

    After all of these efforts, they landed on a simple finding: Smaller poops from smaller birds carry very low risk of foodborne pathogens, which were rare in birds overall. If a bird were to become infected, pathogen survival depends heavily on the bird’s size.

    “Birds that are large produce really big feces, and that’s where pathogens are more likely to survive,” said Spence. “Birds that are small have tiny feces, and the pathogens die off quickly. So farmers don’t have to know the species of bird it came from. They just need to know the size. If it’s the size of a quarter, don’t harvest near that. If it’s a tiny white speck, it’s very low risk and probably fine.”

    Loggerhead shrike in a cabbage field with farmworker in background (Image by Rose Albert, UC Davis)

    Balancing conservation, crop yields, and food safety

    Beyond fecal size, what the birds pooped on — be it the crop, soil or plastic — made a difference for pathogen survival. In the study, E. coli survived longer on lettuce itself than on soil or plastic mulch.

    Fortunately, about 90% of birds observed on the farms were small and tended to poop mostly on soil, where pathogens perish quickly. By avoiding no-harvest buffers when food-safety risks are low, growers of leafy greens could harvest about 10% more of their fields.

    “Birds generally present really low food-safety risks,” said senior author Daniel Karp, a UC Davis professor in the Department of Wildlife, Fish, and Conservation Biology. “The industry has been concerned about birds for a while. But pathogenic E. coli and Salmonella are vanishingly rare in wild, farmland birds. And we now know E. coli tends to die off quickly in most bird poop.”

    The study opens up new strategies for growers to better balance conservation and food-safety risks. For example, growers could erect nest boxes to attract small, beneficial insect-eating birds, like bluebirds and swallows, that help control pests without risking food safety.

    The work also contributes to a growing body of research that suggests growers do not need to remove habitat to improve food safety.

    “There have been no studies to date that suggest habitat removal improves food safety,” Karp said. “Habitat around farms is actually likely to favor the small, insect-eating birds that are unlikely to carry pathogens. Studies like ours are giving farmers science-based permission to conserve habitat — and many species of wild birds — on their farms again.”

    The study’s additional co-authors are Jeffery McGarvey and SangIn Lee at the USDA Agricultural Research Service, Olivia Smith at Michigan State University, Elissa Olimpi at Conservation Science Partners, and undergraduates Wentao Yang and Meirun Zhang at UC Davis.

    The study was funded through the Center for Produce Safety, the California Department of Food and Agriculture and the U.S. Department of Agriculture. — By Kat Kerlin, UC Davis