California Fruit and Vegetable

Category: Pest/Disease Management

  • MSU Researchers Seeking Solutions for Invasive Cherry Pest

    Spotted wing drosophila (SWD), a small fly native to Asia that first appeared in Michigan in 2010, isn’t like most pests. Populations of crop-damaging insects tend to have distinct generations. Not SWD. Several generations overlap and build through the year, attacking vulnerable agricultural crops and wild plants. The situation has created a major challenge for the Michigan berry and cherry industries.

    Spotted wing drosophila in the lab.

    Rufus Isaacs, a professor in the Michigan State University Department of Entomology, was one of the first to discover the pest in the state 13 years ago. While researchers didn’t know much about SWD then, they’ve had to get up to speed quickly.

    Rufus Isaacs, professor of entomology at MSU.

    “SWD is so destructive because it can insert eggs into ripening fruit,” said Isaacs, whose work is supported in part by MSU AgBioResearch. “Larvae can be present in harvested fruit, which can be a big problem for producers. It is also able to reproduce so quickly to build up the population, and it can infest wild fruit outside of farms, creating a reservoir population that continually invades crop fields after they’re treated.”

    After hearing about SWD arriving in California in 2008 and then being detected in Florida in 2009, concerns began to mount.

    “Shortly after SWD was found in Florida, I went to a conference in Oregon where we discussed measures we may need to take to get ready for the pest,” Isaacs said. “We expected it would be in Michigan before too long.”

    Sure enough, Isaacs was right. He received a grant from Project GREEEN — a partnership among MSU AgBioResearch, MSU Extension and the plant agriculture industries of Michigan — in 2010 to monitor for SWD. Isaacs worked with members of the MSU Fruit Team to set small plastic traps with holes that were filled with a cider vinegar lure.

    In late 2010, SWD was collected from a site in West Michigan. At that point, the difficult work began and persists today. Research in Isaacs’ lab has been performed in partnership with mostly blueberry and raspberry growers.

    The team has tested already-registered pesticides to determine their efficacy, as well as non-chemical controls such as pruning, mulching and physical exclusion methods, where growers place netting around and on top of crops as they begin to ripen.

    As a result of this research, online resources have been created to assist growers with SWD identification, pesticide timing and other management strategies.

    “We want to ensure we’re responsive to grower needs, first and foremost,” Isaacs said. “That’s why the pairing of research and grower education programs through MSU Extension is so valuable to our team.”

    Dennis Vander Kooi, a blueberry grower and owner of Woodland Enterprises Berry Farms in Zeeland, Michigan, and his family have been working with MSU researchers for many years. He is also a board member of the Michigan Blueberry Commission (MBC), helping to set research priorities for the industry.

    “Rufus is one of the nation’s leading researchers on this issue, and we’ve worked with others at MSU as well,” Vander Kooi said. “He’s run several experiments on our farm, and we’ve learned a lot from them. The MBC has supported this work and will continue to in the future as we look for effective ways to manage this pest.”

    Vander Kooi said the blueberry industry is undergoing a rejuvenation in Michigan, adopting newer genetics and planting varieties that meet the demands of today’s consumers. This, in conjunction with SWD, makes it a critical time for growers as they look to protect an industry that contributes nearly $132 million to the state’s economy, according to the Michigan Ag Council.

    “With the creation of the MBC in 2017, we got the opportunity to start advocating for more dollars for research, and MSU has been instrumental in that,” he said. “To date, we’ve supported more than $390,000 worth of research, much of that going to MSU, and leveraged an additional $600,000 in other funding.”

    In addition to the MBC, Project GREEEN has been a significant supporter of Isaacs’ SWD efforts, along with state funding through the Specialty Crop Block Grant program and national projects funded by the U.S. Department of Agriculture (USDA).

    Assessing biological control options

    One of the primary challenges for scientists is focusing on immediate grower needs while also investigating long-term management tactics. It’s a monumental task to balance both simultaneously.

    Marianna Szucs, assistant professor of entomology at MSU.

    Alongside Isaacs, Marianna Szucs, an assistant professor in the Department of Entomology, has been exploring biological control to reduce populations in the long run. As she noted, when SWD came to the U.S., its natural predators did not.

    “Anytime there is introduction of an invasive pest, one of the main issues is that the new landscape doesn’t have natural enemies for it,” she said. “They don’t come with the pest, and the native insects in the new place aren’t equipped to deal with it right away. What we wanted to know is if we exposed parasitoid wasps native to Michigan to SWD, would they begin to see them as a food source?”

    A parasitoid insect lays its eggs in or on a host insect, and the developing larvae consume the host until it eventually dies.

    Szucs and her team chose two parasitoid wasp species commonly found throughout North America. Researchers initially saw that attack rates in the wild were quite low, and the ability of native species to rapidly adapt to a new food source was unknown. In the lab, the parasitoids were exposed to SWD and forced to prey on them.

    Within three generations of selection from a small number of parasitoids — 30 wasps or fewer — successful parasitism improved by 259% for one species and 88% for the other.

    “Obviously this is an artificial scenario because we only gave them one option, and in the wild they only attack something if they know to do it,” Szucs said. “But this was a novel way to show that there is some potential to raise native parasitoids and influence their fitness to attack SWD.”

    Besides improving native species, the other biological control option is to introduce natural predators. That’s what an MSU team including Isaacs has done with the samba wasp, which is native to Asia. After years of testing and applying for permits, the USDA Animal Plant Health Inspection Service and Michigan Department of Agriculture and Rural Development (MDARD) approved the release of the samba wasp in SWD-threatened locations.

    The samba wasp detects already-infested fruit and targets the smallest stages of SWD larvae. Laying its eggs inside its host, the growing samba wasp feeds and ultimately kills the larvae, emerging as a wasp in roughly a month.

    Isaacs and Julianna Wilson, an assistant professor in the Department of Entomology, have led the charge to rear large enough populations to eventually release. Last summer, releases took place at the Southwest Michigan Research and Extension Center in Benton Harbor and across the fruit belt of West Michigan, as well as select cherry orchards near the Northwest Michigan Horticulture Research Center (NWMHRC) in Traverse City.

    Spotted wing drosophila on a blueberry.

    The team will continue to evaluate the wasps’ success in the coming growing season, as well as assessing the ability to survive Michigan winters.

    “Hopefully they’re able to survive the winter and the populations are robust enough to be successful next year,” Isaacs said. “We don’t expect results right away, but this is a long-term project for us to determine if this can help reduce the need for insecticides and other management strategies moving forward.”

    ‘Perfect conditions for SWD’

    The northwest portion of Michigan’s Lower Peninsula is world renowned for its cherry production. Growers in the Great Lakes State are responsible for 70% of the U.S. supply of tart cherries, about 80% of which are grown in the northwest Lower Peninsula. But the industry is under siege from a variety of sources, from invasive pests and climate change to competition abroad.

    SWD, however, has hit the industry particularly hard. Nikki Rothwell, the coordinator of the NWMHRC and fruit specialist with MSU Extension, said this challenge affects every Michigan cherry grower.

    Nikki Rothwell, coordinator of the Northwest Michigan Horticulture Research Center.

    “If an orchard starts with 100 flies in mid-June, and each female can lay 300 eggs each week, even the best growers with the best programs have a hard time controlling millions of flies,” she said. “Plus, cherries are so attractive that it’s hard to monitor the populations once the fruit get ripe, which makes it hard to make good management decisions based on traditional trapping and integrated pest management strategies we’ve successfully used with other pests.”

    One of Rothwell’s initial studies showed that tart cherries create the optimal conditions for SWD. While the flies leave most cropping systems during the day to avoid the hot sun, tart cherry canopies provide a cool layer of protection for them to mate and infest fruit. She found that simply pruning the trees and keeping grass clipped helps immensely.

    “We did a pruning study in which we removed different numbers of branches and found that if you remove six to 10 branches in a tart cherry canopy, you can reduce SWD infestation by 40% even without insecticides,” Rothwell said. “We also showed that mowing grass short between tree rows reduced infestation.”

    Recent research includes modeling SWD in cherries. Rothwell hypothesized that flies seem to be in the orchard at all times during the summer and begin to lay eggs suddenly. She believed flies were present and waiting for the right time to infest ripening fruit.

    To better understand this timing, Rothwell and her team have monitored tart cherries as they ripen over the course of the growing season and brought fruit back to the lab. There, they look at when flies begin infestation. Using this information, the team is producing a model for growers that will more precisely indicate ideal timing for pesticides and other management techniques.

    “We’re refining the model now, but we’re hoping to have something soon that growers can use,” Rothwell said. “The industry really depends on MSU to help work through this problem.”

    Rothwell’s work has been supported by the Michigan Cherry Committee, MDARD, Project GREEEN and the Foundation for Food and Agriculture Research. — By Cameron Rudolph, Michigan State University

  • Citrus Mealybug Field Day, May 5

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

    AGENDA

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

    8:30-9:30 am

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

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

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

    11:00 am: Field demonstration of pesticide trial.

  • Weed Management Critical Needs for CA Processing Tomatoes

    Amber Vinchesi-Vahl, UCCE — The Pest Management Strategic Plan for Processing Tomatoes in California (see attachment) was published in May 2021 and encompasses a wealth of information on pest issues and farming practices for processing tomatoes in California.

    Myself, Cooperative Extension Specialist Cassandra Swett, and UC IPM collaborated on creating this document directly from stakeholder input and funding from the Western IPM Center. Below I have highlighted the documented critical needs for managing weeds in processing tomato production in California (more detail on each can be found in the PMSP, cited below). These needs were prioritized by growers, PCAs, academics and industry for the state, the northern growing region and the southern growing region and include research, regulatory and education priorities.

    “Statewide Critical Needs for Weeds

    Research

    1. Develop and identify management methods (including, but not limited to, herbicides) that work for difficult-to-control and perennial weeds, particularly nutsedge and field bindweed.
      1. Better understand weed biology and how to influence weed biology for the purposes of weed management, especially methods to break the dormancy of belowground structures (especially field bindweed and nutsedge).
    2. Develop effective, affordable methods to eradicate branched broomrape from processing tomato fields, prevent its spread, and manage infestations if it becomes well established in California (see Northern Region Critical Needs for Weeds for more information).
      1. Identify effective and practical sanitation methods, especially for eliminating broomrape seed on harvesting equipment (See Statewide General Critical Needs #3).
      2. Develop methods to detect branched broomrape and Egyptian broomrape in tomato fields more easily.” (p. 12).

    “Northern Region Critical Needs for Weeds

    Research

    1. Develop integrated weed management methods (including herbicides) for difficult weeds such as fleabane, horseweed, groundcherries, velvetleaf, nightshades, and glyphosate-resistant ryegrass and sunflowers.
    2. Conduct necessary efficacy research to register herbicides as described in the Northern Region Critical Needs for Weeds, Regulatory Needs.
    3. Identify environmental conditions and production practices that produce different weed problems, including soil quality and water management, and the efficacy of cultural practices to manage such weeds.
    4. Determine effective management practices for broomrape infestations.Research management practices (including herbicides) that control nightshades and reduce reliance on the costly practice of hand weeding.Research management practices (including herbicides) that control nightshades and reduce reliance on the costly practice of hand weeding.
      1. Determine the efficacy of methyl bromide alternatives (e.g., metam sodium/metam potassium, solarization, conventional herbicides).
      2. Identify biological control agents that may attack broomrape and test potential options.
      3. Determine or confirm how broomrape spreads from field to field, and ways to prevent its spread.
    6. Test efficacy of more postemergence herbicides (particularly those that can be sprayed over the top of the crop) and herbicides available for fallow bed weed control.

    Regulatory

    1. Add or expand herbicide registrations.
      1. Register more fallow bed and preplant herbicides and increase application options (especially aerial and helicopter applications) to give growers weed control options to use in wet preplant conditions.
      2. Explicitly register herbicides for fallow bed management, not just preplant use.
      3. Identify and register herbicides that can be used near almond orchards.
      4. Register herbicides for difficult weeds such as fleabane, groundcherries, horseweed, nightshades, velvetleaf, and glyphosate-resistant ryegrass and sunflowers.
      5. Pursue 24(c) labels or Section 18 exemptions where necessary and possible.
      6. Register postemergence herbicides that are safe to apply over the top of the tomato crop to kill late-season weeds.

    Education

    1. Educate growers and pest control advisers on how to reduce herbicide drift. Many of the herbicides registered in processing tomato (e.g., carfentrazone) have drift issues.
    2. Conduct outreach to growers and pest control advisers about impacts of soil quality, water management, and other conditions that produce specific weed problems and how to avoid them via cultural practices.
    3. Educate growers and pest control advisers on how to reduce and manage glyphosate-resistant weeds (especially ryegrass, fleabane, and sunflower).” (p. 17).

    “Southern Region Critical Needs for Weeds

    Research

    1. Develop effective alternatives to glyphosate, especially those that are systemically translocated.
    2. Enhance cultivation methods for removing weeds, such as via finger and torsion weeders or robotic technology.
    3. Increase efforts to find effective biological control agents for weeds (e.g., research the effectiveness of the herbivorous mite that attacks Russian thistle).

    Regulatory

    1. Register any effective and viable alternatives to glyphosate, especially systemically translocated herbicides.

    Education

    1. Educate growers on whether or how natural enemies can be used to manage Russian thistle and other relevant weeds.” (p. 17).

    Weeds come up frequently in other areas of the PMSP, especially in relation to insect pest management.

    You can also find descriptions of common weed problems on page 45 and weed management practices are included in the Farming and IPM Practices section starting on page 58. There is a weed occurrence table on page 75 in Appendix I, and efficacy tables for herbicides and nonchemical management starting on page 93 in Appendix II.

    Martin, T., C. Swett, A. Vinchesi-Vahl, and S. Parreira. 2021. Pest Management Strategic Plan for California Processing Tomato Production. https://ipmdata.ipmcenters.org/documents/pmsps/2021_07_22_Processing_Tomato_PMSP_final.pdf

  • Establishing Residue Decline Curves for Pesticides in Blueberries

    The U.S. Highbush Blueberry Council (USHBC) has collaborated with Oregon State University, Michigan State University, Ag Metrics Group and Synergistic Pesticide Laboratory, LLC to establish residue decline curves for pesticides that have no established Maximum Residue Limits (MRL) and MRLs that are lower than U.S. tolerances.

    The objective was to investigate the residual level of multiple pesticides at different consequential timings after application on blueberry, thus understanding their degradation ratio and speed for better application/harvesting strategies. These findings would in turn allow for the development of low residue programs that meet the low MRL standards.

    Specifically, research entities have applied 18 insecticides and 15 fungicides on highbush blueberries for three years in five growing sites (to account for variation in climate, varietals, and pest and disease vulnerability). Research entities sent samples to Synergistic Pesticide Laboratory LLC for chemical residue extraction and analysis over the span of three years.

    As a result of this research study, several insecticides and fungicides can be applied to blueberries for export markets that could not have been used previously. Read the full report and in-depth findings on each pesticide here. — By the U.S. Highbush Blueberry Council

  • UC Davis Seeks Mighty Bacteria-Resistant Lettuce

    Maeli Melotto and her team at the UC Davis Department of Plant Sciences are looking for strains of lettuce that are genetically stronger at resisting bacteria that can make people sick. Their work has led to the identification of a gene that could play a role in the plant’s susceptibility to E. coli, a bacterium that causes potentially lethal intestinal illness.

    If the team could develop lettuce that can fight off the bacterium, that would avoid thousands of cases of sickness each year, cut production costs for farmers and save millions of dollars in public health expenses.

    Lettuce “sweats” substances onto the surface of leaves that E. coli and other bacteria can eat. In addition, bacteria can live just below the surface of lettuce leaves. Melotto, a professor specializing in the interactions between plants and microbes, is studying the genetic factors that determine how long bacteria can endure in the leaves. She and her team looked at more than 300 samples of lettuce and how they react to the pathogens, identifying the gene responsible for letting them in.

    Their next step is to test whether removing that gene could make lettuce more resistant to bacteria.

    Maeli Melotto, a professor in the UC Davis Department of Plant Sciences, and her team have found a gene she thinks governs whether lettuce can resist bacteria such as E. coli. (Trina Kleist/UC Davis)

    Some lettuce more likely to “feed” bacteria

    In a related study, Melotto’s team is looking at the surface of lettuce leaves and the layer just below the surface, which has tiny spaces where bacteria can live. The researchers want to learn what natural chemicals are in these two areas, and what compounds lettuce releases onto the surface of leaves that bacteria can use as food. Melotto expects to find that some types of lettuce are genetically disposed toward “feeding” bacteria.

    Melotto presented her findings at meetings earlier this year of the California Specialty Crops Council and the California Leafy Greens Research Board. Her work is funded in part by a five-year grant from the National Institute of Food and Agriculture.

  • Preventing Alternate Bearing Patterns And Freeze/Frost Protection (Avocado Field Day)

    The California Avocado Commission will host a grower field day at Pine Tree Ranch in Santa Paula on January 25, 2023 from 9:30 a.m. – 11:30 a.m.

    During the event, California avocado growers will have an opportunity to meet CAC’s new president, Jeff Oberman. In addition, Tim Spann of Spann Ag Research & Consulting and Ben Faber, UC Farm Advisor, will lead a discussion on cultural management practices specific to the winter 2023 season. The topics will include:

    • Preventing severe alternate bearing patterns. Many groves have a very light crop for the 2023 season, which can lead to trees becoming set in a severe alternate bearing pattern. Discussion will center on cultural management practices to alleviate this problem.
    • Post-freeze/frost grove care. Winter brings with it the risks of frosts and freezes. Presenters will focus on best practices for managing groves after frosts and freezes have occurred.

    Attendees are encouraged to ask questions about concerns they are facing within their own groves and are welcome to walk through the various grove plantings at Pine Tree Ranch.

  • Tightening CA Soil Fumigation Regulations Require Grower Attention

    Are you considering fumigating your soil soon? California regulations are changing and there are some things growers should know about, and consider getting involved in the conversation. Watch this brief interview with Gabriele Ludwig from the Almond Board of California for more information.

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

  • NIFA Invests $21.7M in Emergency Citrus Disease Research and Extension

    USDA-NIFA’s Emergency Citrus Disease Research & Extension (ECDRE) program brings the nation’s top scientists together with citrus industry representatives to find scientifically sound solutions that combat and prevent citrus greening (HLB)​ at the farm-level. For the first time in the program’s history, NIFA is supporting an HLB-focused Coordination Network (CN) Project led by an interdisciplinary team of scientists representing all three major citrus producing states. This CN project will benefit the US citrus by providing a much-needed synthesis of existing HLB research in an easily accessible online database as well as developing region specific decision support tools for citrus industry stakeholders, the HLB-research community, and research organization administrators.

    Among the funded research includes virus-induced gene silencing at UC Davis using insect specific viruses to manipulate psyllid as a strategy to control HLB in citrus. Read about all the funded research projects HERE.

  • New Commercial HLB Detection Response Guide

    To ensure California citrus growers are well prepared in the event of a potential commercial grove detection of Huanglongbing (HLB), the deadly citrus plant disease that can be spread by the Asian citrus psyllid (ACP), the Citrus Pest and Disease Prevention Program (CPDPP) has developed a response guide for growers to utilize and educate themselves on the California Department of Food and Agriculture’s (CDFA) action plan.

    The Response Guide for a Confirmed HLB Positive Detection in a Commercial Grove details the steps taken by CDFA and actions required of the property or grove owner, as outlined in CDFA’s Action Plan.

    The actions in the response guide represent the most effective tools known to the citrus industry at this time and are meant to protect California’s citrus groves and support CDFA’s current required regulatory response. While, as of today, there have been no positive detections of HLB in a commercial citrus grove, the CPDPP recognizes the importance of proper preparation.

    In addition to the requirements outlined in the guide, growers are encouraged to use as many methods as feasible for their operation in order to limit the spread of the ACP and HLB.

    To read or download the response guide, please click HERE. If you have any questions or would like to order physical copies of this response guide, please visit our Resources page. — By the California Citrus Pest & Disease Prevention Program

  • Recent IPM Challenges for Western Desert Vegetable Growers

    University of Arizona Extension Specialist John Palumbo was honored recently by the California Association of Pest Control Advisors with their Outstanding Contribution to Agriculture award. Visiting from Arizona, watch this brief video as he shares some of the challenges desert vegetable growers were up against this season.