California Fruit and Vegetable

Category: Pest/Disease Management

  • Glassy-Winged Sharpshooter Infestation Detected in Solano County

    A local infestation of the glassy-winged sharpshooter (GWSS) has been detected in a residential area of Vacaville in Solano County. The pest is primarily a threat to grapevines because it can spread a fatal bacterium that causes Pierce’s disease (PD); however, the pest and disease can also impact susceptible types of citrus crops. Five adult GWSS were found Oct. 1 in traps set as part of a broad array designed specifically to detect this pest throughout areas of the state that are not infested. Additional traps have since been deployed at a higher density near those two initial detection sites, detecting approximately 35 additional GWSS. Visual surveys of plant material in the area have also detected egg masses in the same neighborhood. No GWSS or egg masses have been detected outside this immediate area.

    Working with the Solano County Agricultural Commissioner’s office and others in the region, the California Department of Food and Agriculture (CDFA) is continuing to survey the area, inform local growers and the broader community, and develop appropriate next steps to eradicate this infestation.

    If agricultural officials determine that pesticide treatments are necessary to eradicate this infestation, treatments would be made by ground equipment only and would consist of applications to the root zone and leaves/branches of the host plants to target adult GWSS and provide long-term, systemic protection against re-infestation. In previous eradication projects for this pest, properties with host plants within a 150-meter radius around each detection site were treated.

    Residents of affected properties will be invited to a public meeting with officials from CDFA, the county agricultural commissioner’s office, the Department of Pesticide Regulation and the Office of Environmental Health Hazard Assessment to address residents’ questions and concerns. Residents would be notified in writing at least 48 hours in advance of any treatment.

    GWSS is an invasive and aggressive vector of PD, which is considered one of the most devastating diseases of grapevines in the world. It currently infests 12 California counties, with established populations across Southern California. While grapevines are the pest’s most famous target, other crops and ornamental plants such as almonds, citrus, stone fruit and various shade trees are also at risk from the PD’s strain of the bacterium.

    For additional information and details on the infestation, please visit CDFA’s website here. — Citrus Pest & Disease Prevention Program

  • University of Florida Researchers Publish Award-Winning Findings on Grove Design to Produce Oranges Under HLB

    University of Florida Institute of Food & Agricultural Sciences —The American Society for Horticultural Science recently honored University of Florida scientists for new guidelines citrus growers may apply to their operations. The researchers study ‘Valencia’ orange production while trees are under the most serious citrus disease worldwide.

    “The 7-year study broke new ground on data we provide to local citrus growers who remain in business despite huanglongbing, or HLB,” said Ronald D. Cave, Director of the University of Florida Institute of Food and Agricultural Science’s Indian River Research and Education Center in Fort Pierce (UF/IFAS-IRREC).

    A few of the findings citrus growers may employ immediately from the study are:

    • High-density plantings produce more fruit—from 86% up to 300% more than trees not planted in high-density configurations under HLB.

    • The study showed that advanced management practices that included high tree density, fertigation, and drip irrigation led to higher fruit yield.

    • Additional research is needed to determine optimal fertilization rates for high-density sweet orange orchards under HLB-endemic conditions

    The award-winning publication, “Sweet Orange Orchard Architecture Design, Fertilizer, and Irrigation Management Strategies under Huanglongbing-endemic Conditions in the Indian River Citrus District,” appears in the December 2020 issue science of the scientific journal HortScience. The paper describes the scientists’ hypothesis, the entire research procedure, outcomes, and recommendations for further research.

    Members of the American Society for Horticultural Science (ASHS) Fruit Publication Selection Committee wrote about the paper’s significance. “Huanglongbing, also known as citrus greening, affects all citrus cultivars and causes serious tree decline. It is currently a major threat to the citrus industry. The results can influence the whole citrus industry to deal with HLB including orchard architecture design, fertilizer, and irrigation management strategies.”

    Rhuanito “Johnny” Ferrarezi and his colleagues conducted experiments to determine the variables that promote healthy fresh fruit harvests with the presence of HLB. Ferrarezi, along with fellow professors Mark Ritenour and Alan Wright, accepted the “Outstanding Fruit Publication Award” for papers published in 2020 at the ASHS annual meeting awards ceremony in Denver, Colorado, Aug. 6. Ferrarezi is an Assistant Professor of Citrus Horticulture; Ritenour, Professor of Postharvest Technology; Wright, Professor of Soil and Water Science.

    Others who contributed to the research and the award-winning publication are Arun D. Jani, a post-doctoral research assistant; Thomas James III, who manages citrus research groves; and Cristina Gil, an agricultural research assistant.

    “We strive to keep citrus growers in business even though HLB is reducing the profitability of infected trees over time,” said Ferrarezi. “The point is to sustain younger trees for a number of harvests to produce the healthy, delicious fruit that made the Indian River District famous.”

  • Yeast and Bacteria Together Biosynthesize Plant Hormones for Weed Control

    Plants regulate their growth and development using hormones, including a group called strigolactones that prevent excessive budding and branching. For the first time, scientists led by UC Riverside have synthesized strigolactones from microbes. The work is published in the open-access journal, Science Advances.

    Strigolactones also help plant roots form symbiotic relationships with microorganisms that allow the plant to absorb nutrients from the soil. These two factors have led to agricultural interest in using strigolactones to control the growth of weeds and root parasites, as well as improving nutrient uptake.

    These root-extruding compounds don’t come without risks. They also stimulate germination of witchweeds and broomrapes, which can cause entire crops of grain to fail, making thorough research essential prior to commercial development. Scientists are still learning about the physiological roles played by this diverse group of hormones in plants. Until recently, manufacturing pure strigolactones for scientific study has been difficult and too costly for agricultural use.

    Yanran Li

    “Our work provides a unique platform to investigate strigolactone biosynthesis and evolution, and it lays the foundation for developing strigolactone microbial bioproduction processes as alternative sourcing,” said corresponding author Yanran Li, a UC Riverside assistant professor of chemical and environmental engineering.

    Together with co-corresponding author Kang Zhou at National University Singapore, Li directed a group that inserted plant genes associated with strigolactone production into ordinary baker’s yeast and nonpathogenic Escherichia colibacteria that together produced a range of strigolactones.

    Producing strigolactones from yeast turned out to be very challenging. Although engineered yeast is known to modify the strigolactone precursor, called carlactone, it could not synthesize carlactone with any of the specific genes used by the researchers.

    “This project started in early 2018, yet for over 20 months there was basically no progress. The gatekeeping enzyme DWRF27 is not functional no matter how we try in yeast,” Li said. “Kang developed a microbial consortium technique to produce a Taxol precursor in 2015 and that inspired this wonderful collaboration.”

    The team turned toward E. coli, which had already been shown capable of producing carlactone. The carlactone it produced, however, was unstable and could not be further modified by engineered E. coli into any strigolactones. Li’s group managed to optimize and stabilize the carlactone precursor.

    To their delight, when the yeast and bacteria were cultured together in the same medium, the E. coli and yeast worked as a team: E. coli made carlactone, and the yeast transformed it into various final strigolactone products. The method also produced enough strigolactones to extract and study. Using this platform, the group identified the function of multiple strigolactone biosynthetic enzymes, showing that sweet orange and grape have the potential to synthesize orobanchol-type strigolactones.

    The team also engineered microbe metabolism to boost strigolactone production threefold to 47 micrograms per liter, enough for scientific study. Though commercial production of strigolactones is still a long way off, the new method for biosynthesizing them from a yeast-bacterium consortium will help scientists learn more about this important group of plant hormones, especially the enzymes involved.

    Enzymes are protein catalysts and are responsible for modification of carlactone by yeast. Because carlactone is unstable, it cannot be purchased from commercial sources. As a result, many plant scientists have difficulty studying new enzymes that may work to transform carlactone into strigolactones.

    “The new yeast-bacterium co-culture provides a convenient way for scientists to complete such works because the bacterium makes carlactone in situ,” Zhou said. “With discovery of more enzymes and optimization of the microbial consortium, we can manufacture strigolactones in quantity in the future.”

    Li and Zhou were joined in the research by Sheng Wu, Anqi Zhou, and Alex Valenzuela of UC Riverside; and Xiaoqiang Ma at the Singapore-MIT Alliance for Research and Technology. The paper, “Establishment of strigolactone-producing bacterium-yeast consortium,” is available here. — By Holly Ober, UC Riverside

  • Researchers & Grower-Shipper Association Collaborate to Battle INSV

    Grower-Shipper Association of Central California (GSA) — Implementing effective disease and pest management strategies is a continual challenge for farmers. While these challenges are not new in agriculture, they impact more than just farmers. Lower yields due to disease and pest pressure affects farm employees and harvesting crews too and can also inhibit our ability to provide a steady supply of affordable and healthy produce to consumers.

    Unfortunately, farmers of leafy greens are now dealing with the re-emergence of a damaging disease called thrips-vectored Impatiens Necrotic Spot Virus or INSV. According to local farm advisors this increase in INSV is often accompanied by Pythium wilt infections, which is a relatively new problem in the region.

    Lettuce fields are infected by INSV via thrips migrating in from infected host plants in the early spring. Fields infected by INSV cause stunting, yellowing, wilting of the outer leaves and eventual death for leafy greens. Currently, there are no effective treatments for INSV and Pythium wilt on organic and conventional lettuce farms.

    To support farmers as they battle INSV, GSA created a new task force to identify major research questions, examine treatment strategies, develop treatment efficacy trials and build a grower education program specific to these diseases.

    Mary Zischke, former Executive Director of the California Leafy Greens Research Board, was hired by GSA to lead and coordinate Task Force activities. In addition, to assist local farm advisors and help advance University of California cooperative research efforts, GSA added Jasmine Rodriguez to its team. Rodriguez is currently working toward her biology degree at California State University, Monterey Bay and also serves as a laboratory assistant for entomology research projects at the UC Cooperative Extension in Monterey County.

    “Mary and Jasmine will provide our industry with the additional personnel resources and experience as we combat this complex disease and pest control problem,” says Christopher Valadez, GSA president.

    To further expand resources and personnel, GSA has applied for a California Department of Food and Agriculture Specialty Block Grant. The grant would allow scientists to conduct multi-year field research trials assessing the effects of common crop rotation sequences, monitor Pythium wilt and INSV occurrence in commercial fields, conduct greenhouse studies to characterize the interactions between Pythium wilt and INSV in lettuce to understand their impacts on overall plant health and disease management.

    If awarded the grant, the GSA team will work with researchers from California State University, Monterey Bay and U.S. Department of Ag, Agricultural Research Service in Salinas. Grant outcomes would include knowledge of the impact of crop rotation on Pythium wilt and thrips populations as well as the interplay between Pythium wilt and INSV and how to jointly manage them.

    While GSA is hopeful the grant provides future resources, we will continue moving needed work forward to uncover potential answers and treatment strategies so farmers in our region can minimize losses. Farming equates to surmounting challenges and GSA is committed to supporting farmers as they face those challenges.

  • Study Shows Pest Attack-Order Changes Plant Defenses

    The dining time of different insects impacts a plant’s defenses and nutritional quality—a complexity uncovered in new research with implications for pest management strategies.

    A piercing-sucking, virus-carrying aphid has long worried pea plant farmers, but a more innocuous-seeming weevil that only takes tiny bites from leaves was found to also play a significant role in plant health. Depending if the weevils eat before, or after, the aphids, they can increase or decrease the plant’s ability to fend off the virus.

    While many studies have focused on the impacts of a single pest, this study, published Aug. 4 online in Molecular Ecology, is one of the few to look at the interaction of several antagonists, in this case, two pests and a virus.

    “Plants in the field have a chance of being exposed to many different types of biotic stress elements, what we call antagonists,” said Saumik Basu, a WSU post-doctoral fellow and the study’s lead author. “Based on how these antagonists are coming to the plants, that can change the plant responses and ultimately leads to changes in their overall productivity.”

    Through a set of greenhouse experiments, Basu and colleagues from the Crowder Laboratory at WSU and Cornell University attempted to understand what happens to the pea plant fields of Eastern Washington’s Palouse area. In the field, plants face alternating infestations of pea leaf weevils, Sitona lineatus, and pea aphids, Acrythosiphon pisum, and a pathogen the pea aphids are also known to carry, Pea enation mosaic virus, or PEMV.

    The researchers created experiments where first the weevils feasted on the plants then the aphids, and others that reversed the order. They also included scenarios where the plants were infected with the virus and some where they did not as well as a control group.

    After removing the pests, the researchers let the plants grow for a week. Then, they ran plant samples through different sets of analyses to assess the plants’ defense hormone levels and associated defense genes as well as nutritional qualities.

    Saumik Basu (Photo by Bob Hubner, WSU)

    They found that when the weevil feasts first on the pea plants, it enhances some of the plants’ anti-pathogen defense responses, helping them become more resilient to a virus infection.

    If the weevil dines second, after the aphids, it usually reduces the anti-pathogen defense responses, so the virus spreads more easily.

    In turn, virus-infected plants had stronger anti-herbivore responses, putting out compounds that interfere with the plant-eating pests.

    Further complicating the issue, the study found that when the weevils helped induce the anti-pathogen responses it lowered the nutrition of the plant by reducing the plants’ available amino acids.

    These complex interactions hold important implications for pest management, Basu said.

    “If we know beforehand when these interactions are happening, that information gives farmers a best possible remedy to prevent their fields from the attack,” he said. “This kind of information is really important for designing sustainable pest and pathogen management strategies.”

    Pea aphids (Photo by Bob Hubner, WSU)

    This study is part of a series of investigations into the interactions among many organisms that plants encounter. An earlier study in Functional Ecology looked at the antagonism between a plant virus and nitrogen-fixing bacteria called rhizobia that live in the soil. An upcoming study looks at the interaction between the weevils and rhizobia.

    These complex relationships are critical to understanding plant responses, said Basu.

    “In a natural environment, a plant is exposed to different types of organisms, not just one or two, but many,” he said. “The order and the complexity—how many there are, what different types there are and their interactions—affect how the plant responds to all these attackers.” — By Sara Zaske, Washington State University

  • Growers Urged to Participate in Kern County Coordinated Treatment

    Citrus Pest & Disease Prevention Program — A significant number of Asian citrus psyllid (ACP) detections in Kern County – more than 115 since this time last year – is a stark reminder to remain vigilant against the pest and the deadly disease it can spread, Huanglongbing (HLB). Last week, an adult ACP was confirmed from a commercial citrus trap in the east Edison area. This detection, along with two recent detections in Arvin residential properties, provides more urgency for growers with citrus east and south of Bakersfield to participate in the upcoming coordinated treatment.

    The preferred timing of the treatment is mid-August through mid-September to prevent ACP populations from building on the fall foliar flush. Coordinated treatments like this were done during the same time period in 2018 and 2019 with great success in significantly suppressing ACP populations in commercial citrus orchards.

    The San Joaquin Valley ACP/HLB Task Force recommends growers treat all commercial citrus orchards located south or east of Bakersfield – including young, non-bearing trees. For more information on ACP treatments and effective materials, see the University of California’s UCIPM Pest Management Guidelines for Asian Citrus Psyllid.

    Past coordinated treatments in the county have been successful in suppressing ACP populations. By participating in this late summer/early fall treatment, Kern County can greatly reduce the number of psyllids, and thus reduce the risk of HLB being transmitted to our commercial citrus.

    If you suspect ACP in your orchard, please notify the California Department of Food and Agriculture Pest Hotline at 1-800-491-1899. For questions, contact Kern County Grower Liaison Judy Zaninovich at jsleslie@msn.com or 559-730-8691 or the Kern County Agricultural Commissioner’s Office at 661-868-6300.

  • 2020 Vegetable Crops Chemical Use Report

    The 2020 Agricultural Chemical Use Survey of vegetable producers collected data about pesticide use as well as pest management practices on acres planted to 22 different vegetable crops. NASS conducted the survey among producers in 18 states, focusing on the states that were major producers for the surveyed crops. (Fig. 1)

    Data are for the 2020 crop year, the one-year period beginning after the 2019 harvest and ending with the 2020 harvest. Data are available online for all 22 vegetables (see sidebar for how to access). This report highlights the three vegetables sampled in the most states: onions, pumpkins, and snap beans.

    Who Uses Agricultural Chemical Use Data?

    Producers, consumers, suppliers, policymakers, USDA and other federal and state agencies rely on chemical use and other pest management data to make decisions about health, environment, safety, and trade issues. Some examples of how the data are used:

    • To evaluate the quality and safety of U.S. food products, providing assurances to both domestic and international customers.

    • To identify industry trends and determine the impact of on-farm chemical use and pest management.

    • To assess the quality of streams, rivers, and groundwater; the impact of human activities; the benefits of conservation practices; and the effectiveness of integrated pest management.

    • To identify which chemicals farmers count on, making it more likely regulators will re-register the product.

    Pesticide Use

    The pesticide active ingredients used on vegetables are classified as herbicides (targeting weeds), insecticides (targeting insects), fungicides (targeting fungal disease), and other chemicals (targeting all other pests and other materials, including extraneous crop foliage).

    Onion growers applied herbicides to slightly more acres (91% of planted acres) than fungicides or insecticides (90% and 73% of planted acres, respectively). Pumpkin growers applied herbicides and fungicides to 79% and 75% of planted acres, respectively. Snap bean growers applied herbicides to 94% of planted acres but insecticides and fungicides to fewer acres. (Fig. 2). Further detail on the top pesticides can be found in Table 1.

    Pest Management Practices

    The survey asked growers to report on the practices they used to manage pests, including weeds, insects, and diseases. Vegetable growers reported practices in four categories of pest management strategy, widely referred to as PAMS – prevention, avoidance, monitoring, and suppression. Table 2 shows the top practice in each category.

    • Prevention practices involve actions to keep a pest population from infesting a crop or field.

    • Avoidance practices use cultural measures to mitigate or eliminate the detrimental effects of pests.

    • Monitoring practices involve observing or detecting pests through systematic sampling, counting, or other forms of scouting.

    • Suppression practices involve controlling or reducing existing pest populations to mitigate crop damage. 

  • COVID & Logistical Issues Reduce US Stone Fruit Exports into Taiwan

    Taiwan’s peach production for MY2021/22 is forecast to increase to 17,000MT. Peach and nectarine imports are forecast down to 13,500 MT due to reduced demand at peak fruit season caused by Taiwan’s COVID-19 outbreak in May and June. Cherry consumption for MY2021/22 is forecast flat at 12,400 MT. In 2020, total import volume from the United States decreased by almost 25 percent and market share fell to 50 percent, mainly due to decreased supply. Because of COVID restrictions on shopping at wet markets and local fruit shops as well as logistical problems, domestic fruit demand is expected to decrease in MY 2021/22. 

    MY 2021/22 peach production is forecast up to 17,000 metric tons (MT) due to less than expected damage from rain. Taiwan faced severe drought conditions during spring to early summer 2021, the critical period for peach growth. Peach fruit size this year is expected to be smaller but sweeter. Although the previous forecast had MY 2020/21 production recovering and surpassing that of MY 2019/20, 2020 production was essentially flat at 16,000 MT.

    Taiwan’s peach harvest season runs from March to August depending on the variety and planting elevation. In Taiwan, half of peach production is located near Taichung City, with the remainder followed by Taoyuan City, Hsinchu County, and Nantou County. There are several peach varieties sold through auction market. By order of harvest, there are: early peach (早桃) from March, followed by sweet peach (甜桃), Fu-Shou peach (福壽桃), Ying-Go peach (鶯歌桃), and honey peach (水蜜桃) in July and August. The sweet peach variety is the largest by volume in the local auction market. Read the full report from the USDA Foreign Agricultural Service HERE. 

  • Detection of Citrus Disease (HLB) in San Diego County Establishes New Quarantine Area

    The California Department of Food and Agriculture (CDFA) has declared a quarantine in north San Diego County following the detection of the citrus disease Huanglongbing (HLB), or citrus greening, in two citrus trees on one residential property in the city of Oceanside. This is the first time the plant disease, which does not harm people but is deadly to citrus, has been detected in San Diego County. CDFA is working with the United States Department of Agriculture (USDA) and the San Diego County Agricultural Commissioner on this cooperative project.

    The detection will require a mandatory 68-square-mile quarantine area around the find site to restrict the movement of citrus fruit, trees and related plant material. The quarantine area is bordered on the north by Stagecoach at Camp Pendleton; on the south by Tamarack Ave in Carlsbad; on the west by the Pacific Ocean; and on the east by North Santa Fe in Vista. HLB quarantine maps for San Diego County are available online at: https://www.cdfa.ca.gov/plant/hlb/regulation.html. Please check this link for future quarantine expansions, should they occur. An HLB quarantine area currently exists in parts of Orange, Los Angeles, Riverside and San Bernardino counties, where more than 2,400 trees have tested positive for the disease and have been removed.

    The quarantine prohibits the movement of all citrus nursery stock or plant parts out of the quarantine area. Provisions exist to allow the movement of commercially cleaned and packed citrus fruit. Fruit that is not commercially cleaned and packed must not be moved from the property on which it is grown, although it may be processed and/or consumed on the premises. This includes residential citrus, such as oranges, lemons, grapefruit and kumquats.

    Residents are urged to take several steps to help protect citrus trees:

    – Do not move citrus plants, leaves or foliage into or out of the quarantine area or across state or international borders. Keep it local.
    – Cooperate with agricultural officials placing traps, inspecting trees and treating for the pest.
    – If you no longer wish to care for your citrus tree, consider removing it so it does not become a host to the pest and disease.

    HLB is a bacterial disease that affects the vascular system of citrus trees and plants. It does not pose a threat to humans or animals. The Asian citrus psyllid can spread the bacteria as the pest feeds on citrus trees and plants. Once a tree is infected, there is no cure; the tree will produce bitter and misshaped fruit and die within a few years.

    CDFA staff are scheduling removal of the infected trees and are in the midst of surveying citrus trees in a 250-meter radius around the detection site to determine if any other trees are infected with HLB. A treatment program for citrus trees to reduce Asian citrus psyllid infestations will also be conducted within 250-meter radius of the find site. By taking this action, a critical reservoir of the disease and its vectors will be removed, which is essential to protect surrounding citrus from this deadly disease.

    CDFA, in partnership with the USDA, local County Agricultural Commissioners, and the citrus industry, continues to pursue a strategy of controlling the spread of the Asian citrus psyllid while researchers work to find a cure for the disease.

  • Third Edition of NMSU’s Extension Troublesome Weeds Publication Now Available

    The third edition of a booklet to help identify noxious and invasive weeds in New Mexico is now available.

    “Noxious and Troublesome Weeds of New Mexico” provides information on about 67 plant species that are ranked in five categories – noxious weeds categories A, B and C, watch list, and troublesome weeds not included on the noxious weeds list.

    New Mexico State University’s College of Agricultural, Consumer and Environmental Sciences Cooperative Extension Service has published the third edition of this booklet in cooperation with the New Mexico Department of Agriculture, Bureau of Land Management, U.S. Forest Service, New Mexico Vegetation Management Association, U.S. Department of Agriculture and New Mexico State Highway and Transportation Department.

    “It has been more than a decade since the booklet was updated,” said Leslie Beck, NMSU Extension weed specialist. “We tried to include a wide spectrum of plants within different families so when people use the booklet, they will have a starting point for identification.”

    The booklet includes species common and scientific name with description of the plant, including its stems, leaves and flower appearances; various names it is known as; how it reproduces; and the do’s and don’ts for managing the plants.

    “The state map has been updated to indicate which counties each species is found,” Beck said. “Also we have included photos of each of the plants to help with the identification.”

    First published in 2006, and revised in 2010, “Troublesome Weeds of New Mexico” has been a popular tool for identifying the plants.

    “Since the last revision a lot of the species have shifted into new noxious weed categories, or the plant may have been taken off or added to the list,” Beck said.

    The 41 noxious species are divided into three categories in regards to how prevalent they are across the state from currently limited distribution, to severe infestation, to widespread.

    Six species that have the potential of becoming problematic are on the watch list.

    “This is the part of the publication that has changed the most,” Beck said. “More data is needed to determine if these species should be considered a problem. We ask people to document the location of these plants and contact appropriate authorities, such as their local county NMSU Extension offices or NMDA.”

    In addition to the noxious weed and watch list species, the 2021 edition includes 20 species that are considered troublesome weeds.

    “These are plants that have been commonly observed as invaders of multiple cropping systems, such as landscapes, gardens, agriculture, rangelands and pastures,” Beck said. “They may be native to the Southwest but commonly invade certain cropping systems as a weed.”

    This list does not include every plant species with the potential to negatively affect the state’s environment or economy.

    “These species were selected because they have frequently been sent to me for identification,” Beck said. “Some of them are a little bit more common than others.”

    The PDF version of the publication is available at https://aces.nmsu.edu/pubs/_circulars/CR698.pdf. A printed copy of the booklet, sized to fit in a back pocket, will be available soon. — By Jane Moorman, New Mexico State University