California Ag Network

Category: Pest/Disease Management

  • ARS Citrus Rootstocks: A Success Story

    Remember that old commercial that declared, “A day without orange juice is like a day without sunshine”? Thanks to the Agricultural Research Service (ARS), consumers can enjoy “citrus sunshine” whenever they like. Begun by USDA more than a century ago, the citrus research program has helped to ensure a bounty of not only oranges, but also grapefruits, mandarins, lemons, and more.

    But that bounty was severely threatened in 2005 with the appearance of a new and destructive disease. Citrus greening, or huanglongbing (HLB), has caused Florida citrus production to plummet around 70 percent in the 15 years since the disease hit U.S. citrus groves. HLB, which causes low yields, yellowed leaves, and bitter-tasting fruit, is caused by a bacterium, Candidatus Liberibacter asiaticus. So far, there is no cure.

    Like other crops, citrus crops are susceptible to a variety of diseases and pests. One reliable way to fend off those threats is to graft the fruit-producing part of a tree (the scion) to the lower trunk and root system (the rootstock) of a different tree that has been bred to resist the disease or pest. Rootstocks are also used to obtain specific tree sizes, yields, and fruit quality, among other goals.

    A 6-year-old Owari Satsuma Mandarin tree on US-942 rootstock developed by ARS. In this trial, US-942 was the highest yielding rootstock, averaging more than 300 pounds of fruit per tree (Photo by Jake Price, University of Georgia).

    With ARS’s long history of helping growers keep their groves healthy and productive, the agency had the expertise required when HLB appeared. To quickly address the problem, the ARS citrus breeding project was refocused in 2005 partly to develop new, HLB-tolerant, highly productive citrus rootstocks.

    Led by Kim Bowman, a plant geneticist in the ARS Subtropical Insects and Horticulture Research Unit in Fort Pierce, FL, the team released 12 new HLB-tolerant citrus rootstocks between 2007 and 2018. Before and after the releases, Bowman conducted dozens of field trials to evaluate and validate the rootstocks’ performance, providing the scientific data needed to demonstrate their potential and gain industry acceptance. These rootstocks, all with the prefix “US,” have since become a key component in the survival of the Florida citrus industry.

    ARS plant geneticist Kim Bowman in front of 5-year-old Valencia orange trees on HLB-tolerant rootstocks he and his colleagues developed (Photo by Diane Helseth).

    Not surprisingly, demand for the rootstocks was extremely high, and growers also needed assurances that they’d be getting the real deal. Bowman arranged for the plant material to be certified disease-free by the Florida Department of Agriculture, paving the way for the rootstocks to be commercially propagated on a large scale.

    Bowman and his colleagues have also done a great deal of research on rootstock propagation. Even though most common citrus rootstocks can be grown uniformly from seeds, it takes several years for a young tree to produce a lot of seeds, and the seeds of many new rootstocks don’t grow into true-to-type plants. The scientists have shown that using plant cuttings or tissue culture is an acceptable alternative to starting new rootstock trees from seed, and it’s a much faster way to create hundreds of thousands of plants.

    The use of these alternative methods has dramatically increased propagation for some of the new rootstocks, so that nurseries are not limited by seed supply.

    From 2018 to 2020, the HLB-tolerant “US” rootstocks were used to produce nearly 3 million new citrus trees, or about 37 percent of all trees propagated in Florida. These rootstocks have also proven effective in areas affected by other diseases besides HLB. The rootstock “US-942” demonstrated the most consistent outstanding performance in field plantings and was the most popular rootstock in Florida from 2018 to 2020, with about 1.8 million trees propagated during that 2-year period, or about 22 percent of all propagations.

    For more information, visit Citrus Rootstocks.—By Sue Kendall, USDA-ARS Office of Communications.

  • New Monitoring Tool for Navel Orangeworm in Mating Disrupted Orchards

    Traditional navel orangeworm monitoring tools have proven less effective in the presence of mating disruption technology in the orchard. Watch this brief video with UC IPM Advisor Jhalendra Rijal as he addresses the issue and shares about some new technology that can help growers more effectively monitor this tree nut pest.  Read more about it in Pacific Nut Producer Magazine.
    Please thank this video’s sponsor Trece for their industry support.

  • Managing Walnut Husk Fly in the Orchard

    Walnut growers should start monitoring for walnut husk fly in May.  Watch this video with emeritus UCCE IPM Specialist Bob Van Steenwyk as he provides timely step by step directions on how to monitor and manage this pest.  Read more about orchard pest management in Pacific Nut Producer Magazine.
    Please thank this video’s sponsor Trece for their industry support.

  • The Many Faces of Foxtails

    Hare barley in the spring, with fluffy spike seedheads.

    From roadsides in the city of Fresno to the oak woodlands in nearby Sequoia National Park, annual barleys and bromes are going to seed. In addition to a variety of other grasses, I often hear landowners, weed managers, pet owners, and veterinary advice blogs call these species “foxtails”. This common name is applied to so many species that if someone tells me they have a foxtail issue, I have to ask to see it so that I know what species we need to manage.

    Red brome after senescence in the spring, showing spiky seeds. These seeds, when found in animal fur, are often identified as “foxtails”.

    The term “foxtail” also means different things in different contexts*. In the veterinary context, the term “foxtail” typically describes a grass seed that has barbed awns that catch on animal hair and can cause serious injury, often affecting dogs. In the landscape context, the term “foxtail” typically refers to one of many grass species that produce a characteristic spike of awned seeds, and/or produces the kinds of seeds which hitch rides and cause injury in animals.

    Here I compiled a brief table of grasses commonly called “foxtails” (or their seeds are; in Fresno and Madera Counties):

    NOTE: This list is not comprehensive. There are many grass species in California that have seeds which can hitch a ride on livestock, clothing, and equipment. In addition, there are grass species (Setaria spp.) whose common name is actually “foxtail”, but they are uncommon in my counties and they are not typically associated with animal injuries.
    Mediterranean barley in the spring, showing a similar spike seedhead but is slightly bluer than hare barley.

    As you can see, many different species are commonly labeled “foxtails”. Most of them have the same impact to landscapes and animals: the grasses outcompete desired species, and they typically stick their awns in anything they touch. Livestock can carry the seeds in their hair, hide, or hooves, and avoid eating these grasses once the seedhead has developed, due to the barbed awns. People can find the seeds stuck in shoes, socks, and any other clothing, equipment, or pets that have somewhere for an awn to attach.

    While it’s fine to consider all of these species “foxtails” – the impact to you, your animals, or the landscape is similar, though not identical, across these grasses – it’s important to know what species you are dealing with before attempting any control methods.

    Medusahead in the summer, showing long, twisted awns on a seedhead that is otherwise similar to the annual barleys.

    Each species poses its own challenges and has different vulnerabilities. For instance, foxtail barley is the only perennial in my list; it will respond differently to management than the annual species. The bromes and annual barleys are winter annuals, sprouting in the fall and going to seed in spring. Medusahead can also sprout in the fall, but goes to seed later than the other annuals.

    For assistance identifying which kind of “foxtail” might be troubling you, I recommend checking out the Weed Research and Information Center (Weed RIC) resources on weeds by crop/topic or contacting your local farm advisor who can help with plant ID and management options. — By Rebecca Ozeran, Livestock & Natural Resources Advisor, UCCE

    *In a physical activity context, a foxtail is a toy where a ball has a fabric tail attached to it for throwing. Fortunately, this kind of foxtail doesn’t seem to be an invasive species unless you have a neighbor with poor aim.

  • Healthy Roots, Healthy Trees: HLB & Soil Microbes

    The rhizosphere, defined as the soil environment that surrounds the plant roots, is a rich and diverse habitat for microbes. Some members of the rhizosphere microbiome (or collection of microbes), are good, others bad while many are just there and don’t provide any benefits or harm to the host. One function of the good microbes in the rhizosphere is to help facilitate the availability and assimilation of nutrients and water from the rhizosphere. Just like the human gut, the plant rhizosphere conveys key nutritional functions and the analogy was made that “plants wear their gut on the outside”. One example is the symbiotic relationship between legumes (peas, beans) and rhizobia. Those bacteria help the plant fix atmospheric nitrogen in exchange for carbon supply. Another example is the symbiotic relationship between the plant and mycorrhizal fungi, whereby the mycorrhizae receive carbon from the plant in exchange for increased nutrient uptake (principally phosphorus and nitrogen). There is undeniable evidence that plants have developed a mechanism for recruiting good microbes to cope with environmental stress such as protection against opportunistic pathogens or drought. The rise of ‘omics’ technologies have helped profile entire microbial communities associated with plants and shed light in their biological functions. This research has fueled the development of novel commercial bioproducts to address the increasing consumer’s demand of environmentally-friendly products. As a result, there has been several commercial ‘probiotics’ and ‘prebiotics’ that have been marketed for agricultural use including many biocontrol agents such as fungal- (e.g., Trichoderma) and bacterial- based (e.g., Bacillus, Streptomyces, or Pseudomonas) bioproducts.

    One goal of my research program is to identify beneficial microbes for tree and vines crops, promote practices that support the presence and abundance of beneficial microbes and figure out how good microbes help combat pathogens and support plant health. As part of a collaborative project (UC Riverside, University of Florida, USDA-ARS) funded by the California Citrus Research Board and the USDA-NIFA, we profiled the microbiome of citrus trees in the context of Huanglongbing disease (or HLB). HLB is a highly destructive and lethal disease to all commercial citrus cultivars making it a threat to citrus production globally. Finding strategies that do not only rely exclusively on management of the insect vector of the bacterium (the Asian Citrus Psyllid), is a priority to the citrus industry. In our research, we found that there were significant tissue-specific microbial shifts occurring within the citrus microbiome as trees get sicker, especially in the root compartment. As HLB progressed, there were depletions of beneficial species in roots, such as mycorrhizal fungi, and enrichments of parasitic microorganisms, such as Fusarium and Phytophthora (see Figure). HLB-affected trees decline because of the clogging the phloem sieve tubes, which limit movement of sap and translocation of sugar to the roots, hence leading to feeder root collapse. Once tree is weakened, it becomes more susceptible to pathogens such as Phytophthora which further weakens the trees and exacerbate above ground HLB symptoms. In addition, several studies from Florida suggested that cultural practices that supported root health and rhizosphere microbiome richness and diversity limited root collapse.

    Figure: Citrus decline caused by HLB (https://apsjournals.apsnet.org/doi/10.1094/PBIOMES-04-20-0027- R – Ginnan et al. 2020. Phytobiomes); canopy thinning, wood dieback, feeder roots decline, collapse of beneficial microbes and enrichment of pathogens in roots.

    Our group was recently awarded another research funding by the USDA-NIFA Emergency Citrus Disease Research and Extension program (project director, M.C. Roper, Microbiology and Plant Pathology, UC Riverside). This research effort in collaboration with UC Agricultural and Natural Resources, UC Davis, University of Florida, and the USDA-ARS aims at investigating the root collapse associated with HLB- impacted trees and finding ways to mitigate it by promoting root health. In the proposed work, we will test how different sectors of the root microbiome contribute to or lessen fibrous root loss and if soil amendments (e.g., humic acid treatment, mulching) and planting of HLB tolerant rootstocks (Poncirus trifoliata and P. trifoliata hybrids) can be used to mitigate root loss associated with HLB in Florida, and how tree respond to those practices under a HLB free environment in California. While these approaches will not cure trees from HLB, it will provide a science-based information for strategies that support root and tree health and sustain orchard longevity until remedies are discovered. — By Philippe Rolsausen, Professor in Cooperative Extension, UC Riverside

  • Tarped Against Asian Citrus Psyllid

    Researchers at the California Data Analysis and Tactical Operations Center (DATOC) have analyzed Asian citrus psyllid (ACP) trapping data along major transportation routes before and after tarping regulations for bulk citrus shipments were enacted. The purpose was to determine the effectiveness of the policy.

    DATOC is an independent group of scientists sponsored by the Citrus Research Board and the California Citrus Pest and Disease Prevention Program. The group was formed in 2016 to create and amend tactical response plans for huanglongbing (HLB) suppression and management for California citrus.

    DATOC found a significant reduction in the rate of ACP finds throughout the San Joaquin Valley (SJV) after tarping regulations went into effect. The SJV contains more than 70% of California’s packinghouses. Coastal and Southern California counties ship more than 63 million pounds of bulk citrus into the SJV annually for processing.

    Source: Citrus Pest & Disease Prevention Program

    In years past, ACP populations have soared as they presumably “hitchhiked” on trucks that weren’t properly covered, coming from Southern California into the SJV and threatening the livelihood of commercial groves throughout California along the way. However, after the California Department of Food and Agriculture (CDFA) required tarping in 2017, DATOC data shows that tarping has effectively reduced ACP movement.

    While these results are encouraging, scientists say that growers must continue to remain vigilant. In a recent letter, Citrus Pest & Disease Prevention Committee (CPDPC) chairman Jim Gorden stated that ACP populations are expected to “flare up” occasionally, such as the late 2020 ACP detections in Kern, Madera, San Luis Obispo, Santa Barbara, Santa Clara, Tulare, Contra Costa and other counties.

    The CPDPC emphasizes that growers, packers, transporters and other stakeholders must continue to stay on top of this elusive ACP pest and the dangerous HLB disease it spreads. The upfront cost to manage ACP is much less than the potential hit to the citrus industry if HLB spreads throughout the state.

    In order to move bulk citrus from an ACP regional quarantine zone or a HLB quarantine area under the terms of the permit(s), growers, grove managers, haulers and harvesters must comply with the CDFA’s transporting requirement as detailed in their order. Get specific details here. — By Ben Faber, UCCE Advisor, Ventura & Santa Barbara Counties

  • Biopesticides: Categories and Use Strategies for IPM and IRM

    Biopesticides contain active ingredients of natural or biological origin that include plant extracts, microorganisms, microbial metabolites, organic molecules, minerals, or other such natural materials that have pesticidal properties.  Pests such as herbivorous arthropods, pathogens, parasitic nematodes, mollusks, rodents, and weeds cause significant crop damage when they are not managed.  Pest suppression is a critical part of crop production to maintain plant health, prevent yield losses, and optimize returns.  As agriculture advanced from subsistence farming to a global enterprise, crop protection also evolved over millennia.  When farming was less organized, nature maintained a balance and provided solutions initially.  Then natural solutions were actively implemented until industrialization led to the use of synthetic inputs in the 20th century.  While synthetic fertilizers and pesticides contributed to a tremendous improvement in the yield potential, the indiscriminate use of some of them and the resulting damage to the environment and human health steered food production in the recent past towards organic farming with the use of nature-based solutions.

    Although biopesticides have been around for a few decades, the growth of organic farming gave an impetus to the biopesticide industry during the past few years resulting in the development of new active ingredients and improved formulations.  Now, biopesticides are considered an important part of integrated pest management (IPM) strategies in both organic and conventional systems.  With a considerable industry investment in research and development, the quality and efficacy of biopesticides have also significantly improved.  This has also contributed to optimizing the cost of some formulations.  However, there is still a need to fill the knowledge gaps in biopesticides and their use.  Depending on the active ingredient, the mode of action for biopesticides, their target pests, their storage and handling, and the use strategies are quite diverse, and a thorough understanding of these aspects is critical for their successful use.  As emphasized in the new IPM model (Dara, 2019), while biopesticide use is an integral part of crop protection, understanding the pest biology, using biopesticides appropriate for the target life stage of the pest, applying them at the right time and rate using the right technology, avoiding incompatibility issues, building and sharing effective use strategies, and continuously investing in research and outreach are essential elements of biopesticide use.  Biopesticides also play an important role in insecticide resistance management (IRM) to address resistance issues associated with synthetic pesticides.  This article provides an overview of various biopesticide categories and general strategies for their successful use for IPM and IRM.

    Biopesticides can be used for managing arthropod pests, bacterial or fungal pathogens, plant-parasitic nematodes, weeds, and snails and slugs.  Some formulations or active ingredients have multiple roles and can be effective against more than one category of pests.  While some active ingredients are very specific to a particular pest or related species, others have a broad-spectrum activity.  Based on the source, biopesticides can be placed in four broad categories: i) botanicals, ii) microbials, iii) toxins, and iv) minerals and other natural materials.

    Botanical extracts: Plants are a rich source of numerous phytochemicals or secondary metabolites that have a wide range of properties including pesticidal activity.  Acids, alkaloids, flavonoids, glycosides, saponins, and terpenoids in plant extracts or oils obtained from seeds and other plant parts are some of the compounds present in various biopesticides (Pino et al., 2013).  Azadirachtin, BLAD (polypeptide from sweet lupine seeds), citric acid, essential oils, pyrethrins, soybean oil, and extract of the giant knotweed are used for their acaricidal, insecticidal, fungicidal, nematicidal, or herbicidal properties.

    Microbials: Some of the microbial pesticides have live microorganisms (such as entomopathogens, Bacillus spp., Streptomyces spp., and Trichoderma spp.) while others (such as Burkholderia rinojensis and Chromobacterium subtsugae)have heat-killed microorganisms and fermentation solids as the active ingredients.  Entomopathogenic microorganisms [Bacillus thuringiensis (bacterium), Beauveria bassiana and Cordyceps fumosorosea (fungi), Heterorhabditis spp. and Steinernema spp. (nematodes), and granuloviruses and nucleopolyhedroviruses] primarily kill their hosts through infection; microbe-based fungicides antagonize plant pathogens through competitive displacement and production of toxic metabolites; nematophagous fungi parasitize plant-parasitic nematodes; and plant pathogenic bacteria, fungi, and viruses infect and suppress weeds.  Bacteriophages, which are viruses that parasitize bacteria, are used against the plant pathogenic species of Clavibacter, Erwinia, Pseudomonas, Xanthomonas, Xylella, and other genera.

    Toxins and other organic molecules: There are multiple examples of toxic organic molecules derived from various organisms.  Avermectins from the bacterium Streptomyces avermitilis and spinosad from the bacterium Saccharopolyspora spinosa, strobulurin from the mushroom Strobuluris tenacellus, and cerevisane from the yeast Saccharomyces cerevisae are some of the microbial toxins that are effective against insects, plant-parasitic nematodes, or snails and slugs.  A venom peptide from the Blue Mountains funnel-web spider, Hadronyche versuta, from Australia is a recently developed insecticide active ingredient with its unique mode of action class.  Chitosan, a polysaccharide from the exoskeleton of shellfish, is a fungicide.

    Minerals and other natural materials: Diatomaceous earth, mineral oil, and minerals such as sulfur are used for controlling multiple categories of pests.  Potassium salts of fatty acids of plant or animal origin, known as insecticidal soap, have insecticidal and fungicidal properties.  Organic acids such as acetic acid and citric acid are derived from plants and have fungicidal and herbicidal properties.  Since these are different from other botanical extracts, they are placed in this category.

    Except for the microbial pesticides that have live microorganisms, most biopesticides have chemical molecules of microbial, fungal, botanical, or mineral origin and work through various modes of action similar to synthetic pesticides.  Several synthetic pesticides are developed from natural molecules.  Abamectin, pyrethroids, neonicotinoids, spinetoram, and storbulurins are synthetic analogs based on avermectins, pyrethrins, nicotine, spinosad, and strobulurin, respectively, and were developed for improved stability, safety, or ease of commercial-scale production.

    Integrated pest management and resistance management: Biopesticides are very diverse in their origin and mode of action and have been successfully used in several cropping systems for managing a variety of pests.  They have complex interactions with plants, soil microbiota, pests, and environmental conditions.  It is critical to have a good understanding of the source of biopesticides and how they act on their target pests.  Certain biopesticides may have special storage and handling requirements or tank-mixing restrictions.  It is essential to refer to the manufacturer’s guidelines or label instructions to avoid incompatible tank-mix combinations, understand proper application sequences, and to store, transport, and apply under unfavorable conditions.  While it is very important to use biopesticides as a part of the IPM program and tools for IRM, caution is warranted to avoid repeated use of the same or a similar type of biopesticide.  Pests can develop resistance to biopesticides just as they do to synthetic pesticides (Dara, 2020).

    Strategies for using biopesticides: From the seed or transplant treatment to soil or foliar application, biopesticides can be used throughout crop production.  Certain combinations can have an additive or a synergistic effect on pest suppression.  At the same time, certain inputs or practices can negatively impact biopesticide efficacy.  For example, alkaline tank-mix components breakdown the protein coat of entomopathogenic viruses and Bacillus thuringiensis.  Botanical oils can be incompatible with cold water.  Some fungicides such as captan and thiram are incompatible with entomopathogenic fungi like Beauveria bassiana while several others are compatible (Dara et al., 2014).

    Investing in biopesticides: Environmental safety and resistance development are two major concerns for excessive use of synthetic pesticides and incorporating biopesticides into IPM will help address both issues.  Substituting biopesticides for synthetic pesticides will reduce the total amount of the latter during a production season and their potential negative impact on the environment and human health.  Several biopesticides are not harmful to pollinators and in some production systems, pollinators are used to deliver biopesticides to the crops they pollinate.  Adding biopesticides to the standard crop protection program will also increase pest control efficacy.  Additionally, by not continuously using synthetic pesticides, the risk of resistance will be reduced and thus their efficacy will continue to be maintained.  Although some biopesticides can be more expensive than synthetic pesticides, investing in them will be a good strategy for both the short-term benefit of effective pest suppression and the long-term benefit of a healthy and resilient ecosystem.  Since pests do not have boundaries, area-wide implementation of good agricultural practices with a balanced use of synthetic and natural inputs is necessary for maintaining the productivity of the cropping systems.

    Productive collaborations among the pesticide industry, researchers, extension educators, and the grower community are critical for successfully using biopesticides for sustainable food production.  While research helps to develop effective formulations and their use strategies, outreach helps with the implementation of those strategies. — By Surendra K. Dara, UC Cooperative Extension Advisor, Entomology & Biologicals

  • New, Cross-Sector Work Group will Speed CA’s Shift to Safer Pest Management

    Yesterday, the California Department of Pesticide Regulation and California Department of Food and Agriculture launched a broad new work group to accelerate the systemwide adoption of safer, sustainable pest control practices.

    The 25-member Sustainable Pest Management Work Group includes farmers, community members, university researchers and representatives from commodity groups and the pesticide industry. They are charged with identifying pathways to minimize the use of toxic pesticides and expand the use of integrated pest management practices; better protect public and environmental health; and engage, educate and promote collaboration to achieve these goals.

     “Transitioning away from toxic pesticides requires us to speed up the development of effective alternatives,” said CalEPA Secretary Jared Blumenfeld. “By giving our farmers a suite of integrated pest management tools, we can better protect farmworkers and some of California’s most vulnerable communities. This dynamic task force will give us the roadmap to achieve this bold vision.”

    “California agriculture is recognized not only for its quality and quantity, but also for the sustainable, innovative, forward-thinking way it is grown,” said CDFA Secretary Karen Ross. “Our farmers have been leaders in adopting integrated pest management and partnering with universities and technical assistance providers to meet our high standards for food, environmental and worker safety. This work group represents a broad array of perspectives to inform the next decade of research and development investment and new partnerships to continue the production of nutritious, delicious food and high quality agricultural products with the least impact to our surrounding communities.” 

    Funded in last year’s budget, the group’s work will build upon the recommendations of the Alternatives to Chlorpyrifos Work Group whose 2020 report identified alternatives to the hazardous insecticide and outlined actions to further support agriculture and the health of local communities, farmworkers and the environment. A new status update details additional actions DPR has taken based on the 2020 report, and how DPR and CDFA are working together to provide additional funding to the University of California and California State University to expand integrated pest management research and education. California prohibited virtually all uses of chlorpyrifos as of Dec. 31, 2020.

    The Sustainable Pest Management Work Group is part of the State’s larger commitment to accelerating the transition away from hazardous pesticides. To support the move, Governor Newsom is proposing to fund additional support for the transition by replacing the current flat-fee mill assessment on pesticide sales with a new risk-based tiered mill assessment, where higher toxicity pesticides are assessed a higher fee.

    The members of the Sustainable Pest Management Work Group include:

     

    1. Jenny Broome, Driscoll’s
    2. Don Cameron, Terranova Ranch
    3. Casey Creamer, California Citrus Mutual
    4. Jim Farrar, UC Integrated Pest Management (IPM)
    5. Chris Geiger, City of San Francisco
    6. Kim Harley, UC Berkeley
    7. Lisa Herbert, Sutter County Agricultural Commissioner
    8. Nina Ichikawa, Berkeley Food Institute
    9. Dan Kaiser, Environmental Defense Fund
    10. Susan Kegley, Pesticide Research Institute
    11. Margaret Lloyd, UC Extension – small farm advisor
    12. Suguet Lopez, Líderes Campesinas
    13. Gabriele Ludwig, Almond Board of California
    14. Pam Marrone, Chestnut Bio Advisors, Formerly Marrone Bio Innovations
    15. Nayamin Martinez, Central California Environmental Justice Network
    16. John McKeon, Taylor Farms
    17. Cliff Ohmart, Pest Control Advisor (PCA)
    18. Scott Park, Park Farms
    19. Margaret Reeves, Pesticide Action Network
    20. Taylor Roschen, California Farm Bureau
    21. Sarah Ryan, Environmental Director Big Valley Band of Pomo Indians
    22. Daniel Sonke, Campbell Soup Company
    23. Paul Walgenbach, Bayer
    24. Ron Whitehurst, Pest Control Advisor (PCA)
    25. Houston Wilson, UC Organic Agriculture Institute

  • Leaffooted Bug Species May be Changing

    Almond Board of California — Insect pest management in almond and pistachio orchards largely focuses on reducing damage from navel orangeworm (NOW). Yet, after navel orangeworm, large bugs such as leaffooted bugs (LFBs) and stinkbugs are considered to be among the most damaging insects.

    Leaffooted bug species of particular concern in the past have included Leptoglossus clypealis, Leptoglossus occidentalis, and Leptoglossus zonatus. Leptoglossus clypealis is occasionally noted to be numerous: In 2013, L. clypealis was a particularly abundant LFB in orchards; however, since that time, L. clypealis seems to be less common than another LFB, L. zonatus.

    Recognizing and understanding the differences between these two LFB is key to effective management.
    L. clypealis is shown on the left and L. zonatus on the right. Photo courtesy of Dr. Joyce.

    L. zonatus is a larger LFB than L. clypealis and has longer mouthparts that allow it to feed on developing fruits longer into the growing season. Prior to 2013, L. zonatusdid not appear regularly in almonds in California, and it was not noted in University of California Integrated Pest Management manuals as being a pest of almonds – while this species was present in California, perhaps it was not particularly numerous. Since 2013, L. zonatus has frequently been observed in almonds during the growing season and at harvest, and now seems to occur more regularly in orchards than L. clypealis. It may be that the larger LFB L. zonatus is displacing L. clypealis.

    From 2014-2016, researchers identified LFB collections in almond and pistachio orchards from Chico to Bakersfield as consisting of two species: L. clypealis and L. zonatus. A 2017 study by Dr. Andrea Joyce, an entomologist at the University of California, Merced, investigated population genetics of these two species and found that L. clypealiscollections have high genetic diversity and many genetic types (haplotypes). This suggests that these L. clypealiscollections from the Central Valley are within this insect’s native range. However, the insect collections of the other species, L. zonatus, consisted of two genetically divergent types, or strains. One L. zonatus strain was widespread, and occurred through the Central Valley from Chico to Bakersfield, and the second genetic type occurred in the central and southern San Joaquin Valley. Work to geographically map out where the two genetic types of L. zonatus occur is ongoing.

    The presence of two strains of L. zonatus is important for insect pest management. It is highly likely that each insect strain is susceptible to different parasitoids, predators and pathogens. Two insect strains can also vary in their response to insecticides, as well as their attraction to pheromone lures.

    Currently, pheromone attractants are being developed for this LFB. It is vital to determine if the same pheromone blend will equally attract the two strains of L. zonatus. Dr. Joyce and colleagues will continue research on the two strains of L. zonatus this year, comparing their biological parameters, examining whether the two strains are cross attracted in lab bioassays, and if they cross mate in the field. The hope is that any pheromones and attractants developed for L. zonatus can be used to manage both strains of this species. A monitoring tool such as a pheromone trap for these insects would be particularly useful in a grower’s IPM toolbox.

    Growers can support researchers in determining the distribution of the two strains by collecting any LFBs they identify or notifying Dr. Joyce when large numbers of LFBs are observed. Growers may email Dr. Andrea Joyce if they sight LFBs or have questions about this pest at      ajoyce2@ucmerced.edu.

    Note: Additional Almond Board-funded research is being conducted by Dr. Jocelyn Millar to identify pheromones and related attractants for the two major LFB pests in California nut crops. These tools could potentially be utilized for monitoring or control of these species.

  • How to Prevent Crown Gall in the Orchard



    Keep getting crown gall in the orchard? Watch this brief interview with Kern County Area Orchard Systems Advisor Mohammad Yaghmour as shares a few simple steps on how to effectively prevent this detrimental infection.  Read more in Pacific Nut Producer and California Fresh Fruit Magazines.
    Please thank this video’s sponsor Trece for their industry support.