California Fruit and Vegetable

Category: Pest/Disease Management

  • Invasive Stink Bug Habitat Could Expand with Climate Change

    A foul-smelling, voracious, wide-spread pest of fresh fruits and tree nuts could become even more ubiquitous with climate change.

    A recent modelling study found that changing weather could increase suitable habitat for the brown marmorated stink bug in the United States by 70%. The study, published in Pest Management Science, draws on data from a three-year stink bug monitoring effort in 17 states as well as several potential climate scenarios. However, whether the insects will thrive in new places depends on the conditions of each area and potential mitigation measures.

    “Every system will change with climate change, so the fact that you can grow garbanzo beans, lentils or wheat without these pests now, doesn’t mean that you will not have them in a few years,” said study lead author Javier Gutierrez Illan, a Washington State University entomologist. “There are mitigating things that we can do, but it is wise to prepare for change.”

    The study found that overall, there is likely to be a northward shift in stink bug-friendly conditions. Regions that may be particularly affected include the Mid-Atlantic, areas surrounding the Great Lakes, and the valleys of the West Coast, such as the Sacramento Valley in California and the Treasure Valley in Idaho.

    The brown marmorated stink bug is a generalist herbivore — it is known to feast on nearly 170 different plants including crops and ornamental plants. Originating in Asia, this type of stink bug first appeared in the U.S. about 20 years ago and has since spread coast to coast. It’s been detected in 46 states and considered a pest in 15 of them.

    Brown marmorated stink bug on a blackberry plant. Photo by Gheorhge on iStock

    Homeowners may recognize brown marmorated stink bugs because they like to overwinter indoors. In fact, the study found that proximity to populated areas appeared to help the insects get established in new places, but once there, they did not need to be near people to proliferate. Other factors like availability of water mattered more for their abundance.

    People are likely inadvertently transporting stink bugs in vehicles or farm equipment to areas that would otherwise be hard for them to reach by flying alone, said Gutierrez Illan.

    Stink bugs dislike cold winters, but the rising temperatures brought by climate change are not necessarily a good thing if the land becomes too dry. They need water, so the researchers said that changing patterns of precipitation will likely influence where the stink bugs will thrive.

    In some states including Washington, officials and researchers are employing a parasitoid insect, called the samurai wasp, to control stink bugs. The wasps lay their own eggs inside stink bug eggs. This not only destroys the affected eggs, but when the wasp larvae hatch, they eat other developing stink bugs. Measures like these might help prevent or minimize stink bug spread into new areas, Gutierrez Illan said.

    For Washington growers, the researcher recommended using WSU’s DAS, or Decision Aid System, a web-based tool which provides information to help prepare for changes to their agricultural systems, including the possible appearance of these pests.

    Gutierrez Illan also advised growers to familiarize themselves with the brown marmorated stink bug through sites like stopbsmb.org, even if they have never had the pest in their fields.

    “Most growers learn from their parents or from the previous generation, but the information that they had is probably no longer as useful because the climate is changing, so they need these types of tools,” Gutierrez Illan said.  — By Sara Zaske, Washington State University

  • Darkling Beetle Overwintering Locations and Movement into California Tomato Fields

    Darkling beetles girdle seedlings at or below soil line by chewing which can cause significant damage and plant death when beetles are in high numbers. Darkling beetles are not usually a problem once plants are big enough to withstand the chewing damage. They move in from field edges, including weedy areas or adjacent crops like grains or alfalfa. Conventional control includes insecticide baits, but organic growers have more limited options.

    The UC Cooperative Extension conducted a study funded by the California Tomato Research Institute to better understand darkling beetle movement into tomato fields and develop a monitoring strategy to assist with control before beetles migrate into crop fields. Probable habitats for darkling beetles were scouted March-May 2022. These sites included weedy vegetation, hedgerows, field borders, and other locations in close proximity to crop fields (examples of trap sites pictured below). To determine darkling beetle presence, pitfall traps and visual observations were used. Pitfall traps consist of plastic cups buried in the soil, so that the opening is even with the soil line and filled with a preserving liquid. Insects walking across the ground fall into the cup as they travel and are unable to escape.

    Four organic field sites were monitored, with a total of 30 pitfall traps. The data is still being analyzed and beetles are currently being identified but the figure below shows a generalized overview of what was captured in the pitfall traps in Spring 2022. Because pitfall traps are better at measuring insect activity rather than density, they were not very effective at capturing darkling beetles. Darkling beetles do not move around as frequently as other insects like predatory ground beetles, which were caught in high numbers. However, darkling beetle damage was also not readily observed in these tomato fields. One field did however have significant damage from vegetable weevils which feed on foliage and stems, defoliating the plant, rather than girdle young plants at the base.

    Ground beetles were the most abundant insects captured, followed by miscellaneous beetles (not including darkling beetles) which included carrion beetles, click beetles, lady beetles, rove beetles and others in smaller numbers. Earwigs were also commonly captured along with isopods, spiders and ants (data not included). — By the UC Cooperative Extension with Funding from the California Tomato Research Institute

  • New Nanoparticle-Based Sensors to Measure Residual Herbicides in Food

    Two newly developed, low-cost tests that use nanoparticles to detect chemicals can accurately measure tiny amounts of two potentially harmful herbicides in fruits, vegetables and their products.

    Reporting in the journal Food Chemistry, a Washington State University research team used two testing methods to measure the levels of two herbicides, namely atrazine and acetochlor, in samples of apples, strawberries, cabbage, corn and fruit juices. The work shows the real-world viability of their easy-to-use and inexpensive methods of testing.

    “We applied this technology for real sample detection – which is an important step in moving towards commercialization,” said Annie Du, research professor in WSU’s School of Mechanical and Materials Engineering and the principle investigator of the project.

    Annie Du

    The Food and Drug Administration (FDA) regularly tests a broad range of commodities for approximately 800 pesticide residues, and producers are required to keep the chemical residues on food below a certain level that is considered safe. The two herbicides the researchers measured are widely used in crop production in the U.S. At high exposures, they are potentially toxic for people and have been linked to a range of maladies from allergies to hormone disruption to cancer.

    Doing the testing, however, currently requires sophisticated and expensive instruments as well as a trained technician.

    “We want to come up with a low-cost method that can be used in the field or in the laboratory,” said Bernie Van Wie, corresponding author on the paper and a professor in WSU’s Gene and Linda Voiland School of Chemical Engineering and Bioengineering.

    Bernie Van Wie

    In the past few years, the researchers have developed and patented their idea that uses nanoparticles of palladium and platinum to amplify the signal of molecules. The nanoparticles attach to an antibody, which recognizes the chemical, and then stimulate the production of a signal.  The amplification allows the researchers to know that tiny amounts of the chemicals are present and at what level.

    In this latest work, the researchers used the nanoparticles in two types of tests to measure two chemicals simultaneously. The chemicals were spiked into fruit and vegetable samples that were pureed in a blender.

    One of the tests uses the palladium-platinum nanoparticles to catalyze a reaction that causes a color change in a sample when the herbicide is present. The test can be done using a small unit that can be carried into the field.  The other test the researchers developed uses the nanoparticle in a low-cost paper strip that looks like a COVID-19 or pregnancy test and can be read with a smartphone reader.

    The tests were sensitive enough to measure the chemicals down to the maximum acceptable levels and were validated using traditional testing methods.

    “We’re actually able to detect below the maximum concentration limits. If there’s any pesticide or herbicide in the sample,” said Van Wie. “That’s good because while this can be done by other methods, this method is low-cost and portable in the field.”

    Du has recently started a company that is negotiating with WSU’s Office of Commercialization to license the technology for additional applications. The work was supported by the USDA/National Institute of Food and Agriculture (NIFA) Agriculture and Food Research Initiative (AFRI) program (grant number 2018-67021-27970). — By Tina Hilding, Voiland College of Engineering and Architecture, Washington State University

  • Fumigation Considerations Before Replanting an Orchard

    It’s that time of the year when orchards are being pulled and growers begin preparing their soil for future plans.  For growers looking to replant their orchards, watch this brief interview with UC Riverside Nematologist Andreas Westphal as he shares some considerations to take for fumigation when it comes to nematode pressure.

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

  • Thirteen UC Davis Scientists Contribute to Special Journal Edition on Spotted-Wing Drosophila

    Thirteen UC Davis scientists or former affiliates are among authors from eight countries who contributed to research articles for the Journal of Economic Entomology’s Special Collection: Research Advances in Spotted-Wing Drosophila suzukii Management.

    The recently published Special Collection showcases 14 articles.

    Native to Asia, the agricultural pest is a worldwide threat to the berry production industry, which includes raspberries, blackberries, blueberries, strawberries, and cherries. The tiny insect, about 1/12 to 1/8 inch long, invaded the continental United States in 2008.

    “All of the papers were by invitation of the co-editors of the special collection—Jana Lee, Cesar Rodrigue-Saona, and me,” said journal editor-in-chief Frank Zalom, a UC Davis distinguished professor emeritus and recall professor in the Department of Entomology and Nematology. Zalom’s research includes the spotted-wing drosophila.

    Lee, formerly with the UC Davis laboratory of the late chemical ecologist Steve Seybold, is a research entomologist with the Horticultural Crops Research Unit,  U. S. Department of Agriculture, Agricultural Research Service, Corvallis. Rodriguez-Saona, who received his doctorate from UC Riverside, is an Extension entomologist with the Department of Entomology, Rutgers University, the State University of New Jersey.

    In addition to Zalom and Lee, the UC Davis-linked authors include Joanna Chiu and Antoine Abrieux (Joanna Chiu lab); Zain Syed and Kevin Cloonan (Walter Leal lab); Gregory Loeb (Rick Karban lab); and Kelly Hamby, Hannah Burrack, Fatemeh Ganjisaffar, Brian Gress, Nicole Nicola and Mark Demkovich (Zalom lab).

    Overall, the Special Collection includes authors from Austria, Brazil, Canada, Italy, Spain, Sweden, United Kingdom, and the United States that represent perspectives from universities, federal and state laboratories, growers, and pest product companies, according to the editors.

    One paper, Spatio-temporal Variation of Spinosad Susceptibility in Drosophila suzukii (Diptera: Drosophilidae), a Three-year Study in California’s Monterey Bay Region, is from the Zalom lab and includes co-author, molecular geneticist and physiologist Joanna Chiu, professor and vice chair of the Department of Entomology and Nematology.

    The work of molecular geneticist and physiologist Joanna Chiu, professor and vice chair of the UC Davis Department of Entomology and Nematology, is included in the Journal of Economic Entomology’s special collection targeting research on the spotted-wing drosophila. (Photo by Kathy Keatley Garvey)

    UC Davis Department of Entomology and Nematology communication specialist Kathy Keatley Garvey provided the cover photo of the spotted-wing drosophila feeding on a raspberry.

    Since 2008, “D. suzukii has become a key economical pest of raspberries, blackberries, blueberries, strawberries, and cherries in the United States and worldwide,” the editors wrote in their introductory remarks. “Not surprisingly, the number of publications has proliferated from 29 publications as of 2010 to 978 additional publications between 2011 and 2021 from a Web of Science search for ‘Drosophila suzukii.’ While many publications are available, this special collection will highlight advances in D. suzukii pest management since its U.S. invasion. We solicited papers by open call and received 66 abstracts, and selected 14 papers covering: 1) review, 2) monitoring and risk, 3) behavioral control, 4) biological control, 5) cultural control, and 6) chemical control.”

    The collection is meant to serve “as a key reference point for entomologists across many institutions (e.g., academia, government, and industry) on important advances in D. suzukii pest management,” according to the Entomological Society of America. “The articles in this collection will also provide scientists information on potential research gaps that will help guide future research directions on this important pest. The goal is to preserve and catalog articles on various aspects of D. suzukii pest management, i.e., monitoring, cultural control, chemical control, behavioral control, and biological control, that will be shared among entomologists.”

  • Results from New Citrus Rootstock, Scion Combination Experimental Grove on HLB Tolerance

    As citrus growers in the west dreadfully anticipate the arrival of the citrus killing disease Huanglongbing, researchers in the already severely impacted state of Florida are making significant strides in learning how to combat this disease.

    Early results from a groundbreaking, large-scale citrus trial looking for solutions to the devastating citrus greening disease have given early hope for growers in the Indian River District. The new UF/IFAS research shows tree size does not seem to affect citrus susceptibility to greening.

    In the trial, researchers are testing which citrus rootstock and scion combinations will tolerate citrus greening, a deadly global citrus disease that nearly decimated the Florida citrus industry.

    Martin Zapien on one of the Millennium Block citrus cultivar trial planting days in 2019.

    Martin Zapien, a graduate student at the University of Florida Institute of Food and Agricultural Sciences Indian River Research and Education Center (UF/IFAS-IRREC), presented data from the Millennium Block citrus cultivar trial in Fort Pierce, Florida. At his thesis defense, the information Zapien represented was research from a 20-acre grove with grapefruit, navel orange and mandarin cultivars on a wide range of newly released and commercial rootstocks. Planted in 2019, the trees grow in a region where citrus greening is now endemic.

    Lorenzo Rossi, UF/IFAS plant root biologist and Tom James, a local citrus industry veteran, supervised Zapien’s research. Advisors on the project were UF/IFAS plant improvement team faculty Fred Gmitter, Jude Grosser and William Castle.

    Nearly 80% of Florida’s grapefruit crop is produced by Indian River District growers, who export their crop to Europe and Asia. That’s why scientists study the fruit so closely, said Rossi.

    “One of our objectives is to evaluate and compare the early performance of several new grapefruit hybrids grown on three commercial rootstocks under citrus greening conditions,” said Zapien.

    In the first two years of growth, the researchers compared UF rootstocks and scions by measuring tree growth and the trees’ ability to tolerate citrus greening. They expect to collect yield and fruit data after the third year, Zapien said.

    Rossi said data sets were specific to tree size, bacteria amount, the severity of citrus greening symptoms such as irregular yellow patches in the leaves, and leaf and soil nutrient concentrations.

    “We have seen many rootstocks that promote large and small tree size, but we have not seen any correlation between tree size and susceptibility to citrus greening,” Zapien said.

    But so far, the research does not support a theory that tree size affects citrus greening susceptibility, but there is a trend in small trees showing less citrus greening symptoms, Zapien said.

    Zapien said published research findings prove that high-density plantings produce higher fruit yields by increasing yield efficiency — fruit number per green foliage. The researchers will evaluate if the trees correlate with the published work or if the larger trees in the test grove produce more fruit.

    ‘Ray Ruby’ grapefruit on UFR-15 rootstock promotes vigorous trees — the trees show the largest canopies and are already flowering. But for UF/IFAS researchers to recommend a particular rootstock and scion combination, more data are required. The experimental grove must be examined for up to four more years before UF/IFAS scientists can make reliable recommendations.

    “All trees in the Millennium Block are infected with citrus greening. However, some trees are thriving,” Zapien said. “Trees on sour orange have shown significantly fewer disease symptoms than trees on x-639 and US-942 rootstocks, but we have to consider that sour orange’s drawback is the susceptibility to citrus tristeza virus.”

    As to citrus greening severity, ‘Star Ruby’ grapefruit showed only 4% symptoms in the green foliage. In contrast, ‘US Seedless Surprise’ symptoms were 24%. The other varieties fall between the two.

    “The data we compiled is nascent as the trees were only two years old at the analysis,” said Zapien. “University researchers will continue to monitor the top performer combinations to determine if the early findings are consistent.”

    With research in the UF/IFAS-IRREC experimental grove, Zapien completed a master’s degree in horticultural sciences. Zapien recommends that researchers improve sampling methods to assess the bacteria as the trees mature to advance the research. Zapien and his colleagues will evaluate flowering patterns to determine when the fruit is ready to harvest and reveals market windows. A long-term goal is to measure the yield or the amount of marketable fruit each tree produces. — By Robin Koestoyo, University of Florida, Institute of Food & Agricultural Sciences

  • A New Way to Battle Powdery Mildew in Strawberry

    Strawberry farmers worldwide may get help from new University of Florida research that shows a way to battle one of the fruit’s fiercest foes.

    The key: combine genomic data with phenomics. The genome amounts to all the DNA in an organism. Phenomics is the study of plant growth, performance and composition. Through phenomics, scientists use DNA to measure plant traits. In a newly published study, UF/IFAS scientists found a new way to help strawberry growers battle powdery mildew.

    Ronald Tapia, a doctoral student at the Gulf Coast Research and Education Center (GCREC), led the research. Tapia worked under the supervision of Seonghee Lee, an assistant professor and Vance Whitaker, an associate professor, both in horticultural sciences.

    Ronald Tapia, a doctoral student in horticultural sciences, points a sensor at a strawberry plant at the UF/IFAS Gulf Coast Research and Education Center. Credit: Courtesy, Ronald Tapia, UF/IFAS.

    Prior research already showed this method detects diseases in other crops, Whitaker said.

    “We already have a lot of technology that helps us understand the genes in strawberries, but those genes still need to be connected to their actual effect on the plant – in this case how the plant resists powdery mildew disease,” said Whitaker. “That’s why we combined genomics and phenomics. Any technology that reduces the cost or increases the speed of evaluating any trait — like disease resistance — in our breeding trials can help us out.”

    Whitaker cautions this method is not guaranteed to work in all situations, but he’s hopeful.

    To reach their findings, Whitaker and his colleagues conducted a field trial of strawberry plants at GCREC. They took DNA from each strawberry and looked at its genes.

    Vance Whitaker, associate professor of horticultural sciences at the UF/IFAS Gulf Coast Research and Education Center. Credit: Tyler Jones, UF/IFAS photography.

    Then they rated the disease using two methods:

    • Their own eyes, which gives them a visual scale. The plants were evaluated the traditional way by eye, recording the severity of the disease, rated on a scale of 0 to 6 for each plant.
    • A handheld sensor. Whitaker and his colleagues used the device to detect wavelengths of light that you can’t see with your eyes. The wavelengths gave researchers data about the health and disease status of strawberry plants.

    “We showed that by combining the DNA information (genomics) and the spectroscopy information (phenomics), we can predict the visual rating of disease resistance surprisingly well,” Whitaker said. “In the future, we can eliminate the work of the visual rating.”

    The finding should help scientists assist strawberry growers globally as they look for powdery mildew in their crop. While Florida produces most of the nation’s domestic winter crop on about 11,000 acres, California produces strawberries nearly year-round. Nationwide, strawberries are valued at about $2.2 billion. — By Brad Buck, University of Florida, Institute of Food & Agricultural Sciences

  • AI Helps Detect Watermelon Disease Quickly, Accurately

    If you savor a juicy watermelon in the scorching summer heat, farmers toil to meet your tastes. But, like all farmers, those who produce watermelons seek ways to control diseases, so they don’t lose all or part of their crops. The needs of growers drive Yiannis Ampatzidis to use artificial intelligence to detect pathogens early and accurately.

    One such disease, downy mildew, spreads like wildfire, said Ampatzidis, an Associate Professor of Ag & Biological Engineering at the University of Florida.

    For a new study, Ampatzidis used AI to help find downy mildew.

    In newly published research, Ampatzidis used spectral reflectance —  the energy a surface reflects at specific wavelengths — of plant canopies and machine learning to quickly and efficiently detect downy mildew in several stages of the disease.

    Hopefully, farmers can take advantage of this technology.

    “If left unchecked, downy mildew can destroy a farmer’s entire crop within days. That’s why it gets the nickname ‘wildfire.’ It spreads rapidly and scorches leaves,” said Ampatzidis, a faculty member at the Southwest Florida Research and Education Center.

    Ampatzidis and his research team successfully detected downy mildew in several stages of severity.

    “Our most important result was finding downy mildew in its earliest stage, which is critical to growers’ ability to manage this disease,” he said.

    Ampatzidis and his research team developed two methods, utilizing hyperspectral imaging and AI — one in the laboratory and the other using UAVs (drones) for field detection.

    Downy mildew does not affect stems or fruit directly. But it can defoliate the plants, leaving fruit exposed to sun damage, making it unmarketable.

    As long as consumers continue to buy watermelon — and those who grow the fruit want to reap a good harvest — Ampatzidis will continue to find ways to find pathogens that could damage the fruit.

    As next steps in his research, Ampatzidis wants to develop a simple and inexpensive drone-based sensor to improve detection of downy mildew in watermelon plants. — By Brad Buck, University of Florida, Institute of Food & Agricultural Sciences

  • Promising Advancements in Biocontrol Treatment that Slows Citrus Greening

    Citrus growers may have a new tool to help them slow the presence of citrus greening in already diseased trees. While there is no cure for Huanglongbing (HLB), researchers at the University of Florida Institute of Food and Agricultural Sciences found that injecting a benign Xylella fastidiosa EB92-1 bacteria biocontrol into infected citrus trees over a period of six years reduced the incidence of trees with severe HLB symptoms. The potential result is providing growers with a strategy to keep trees alive and productive longer even when infected with the citrus greening bacterium.

    Donald Hopkins, an emeritus professor of plant pathology at the UF/IFAS Mid-Florida Research and Education Center, conducted three trials in central and eastern Florida with commercial groves of Valencia orange and Rios grapefruit trees at different maturity stages. All of the trees tested positive for citrus greening disease at the beginning of the trial but had varying ranges of symptoms from asymptomatic, mild to severe. Trees in the trials included young 2-year-old and mature (greater than 20-year-old) trees.

    “Using EB92-1 provided a level of control of HLB in two mature citrus tree trials and in a trial initiated in young 2-year-old trees,” said Hopkins. “This biocontrol strain has the potential to prevent or delay severe symptoms of HLB and prevent the loss of production both in mature and young citrus trees.”

    All trees in the trials remained positive for HLB throughout the six-year trial. The injections of EB92-1 did not prevent or reverse infection of HLB. But key findings indicated that trees that were treated had less increase in symptoms than untreated trees. Injected trees also had increased yield than untreated trees. In mature trees, results from the trials indicated that the most effective control of HLB may require once-a-year treatment for at least the first 2-3 years. Retreatment may be required yearly for best biocontrol.

    Using EB92-1 especially combined with nutrition, fertilizer and pesticide best management practices could prolong the life and productivity of citrus trees.

    Hopkins believes that the biological control of HLB by EB92-1 is not from direct competition with the HLB pathogen since the EB92-1 bacterium operates in a tree’s xylem and the HLB bacterium colonizes the tree’s phloem. Rather the impact in more likely an instance of induced resistance. Induced resistance occurs when a plant’s resistance mechanism is activated by infecting a plant with a pathogen, such as the benign strain EB92-1. In this case, injecting EB92-1 provided some control of HLB in a tree’s tissues not infected with EB92-1 resulting in a slowing of HLB symptoms.

    This research was published online in Plant Disease, the journal of the American Phytopathological Society (APS). The project was partially funded by the United States Department of Agriculture HLB Multi-Agency Coordination (MAC) group and UF/IFAS. This treatment is patented and licensed to an external company but is not currently available to growers. The trials continue in central and eastern Florida. — By Ruth Borger, University of Florida, Institute of Food & Agricultural Sciences

  • California Citrus Growers Invited to Apply for CA-CRaFT ACP Mitigation

    Through support from the USDA Huanglongbing Multi-Agency Coordination Group (HLB-MAC) the Citrus Research Board (CRB) is initiating a California focused Citrus Research and Field Trials (CA-CRaFT) project. The overarching goal of CA-CRaFT is to demonstrate the effects of additional mitigations on Asian citrus psyllid control within commercial citrus groves across the various citrus growing regions in California. This project will measure psyllid levels within treated groves as a year-by-year measurement and relative to the regional psyllid levels. The additional mitigations are expected to help reduce psyllid populations and inform growers of best practices. The project results will be shared on a regional, statewide, and national basis.

    To be considered for the program, growers should be actively following current UC IPM guidelines and interested in working with the CRB to test the effect of additional psyllid control methods

    Producers may choose one or more of the following mitigations:

    Preventative Mitigations

    • Barrier mesh fencing
    • Living windbreaks
    • Trap crops

    Threshold-based Mitigations

    • Biological control agent releases
    • Pesticide treatments (border sprays, psyllid repellents, ant control)

    Priority will be given to CA citrus groves with ongoing psyllid pressures and/or in proximity to major psyllid risk factors (i.e., transportation corridors, residential areas).

    Compensation will be provided based on mitigations adopted.

    Informational webinars will be held on September 8 and September 14, 2022. To learn more and register, please click on the respective links below.

    Submit the application BELOW no later than October 1, 2022.