California Fruit and Vegetable

Tag: HLB

  • 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.

  • Successful HLB Management Strategy in CA Focuses on Everyone Doing Their Part

    What Nobel Prize-winning Economics Research Tells Us About ACP and HLB Management in California

    As you have likely heard many times, coordinating management measures for the Asian citrus psyllid (ACP) and Huanglongbing (HLB) over a larger scale than individual properties is key to achieving effective control and limiting the spread of the disease. Coordination is important in terms of surveying for HLB-positive trees and removing them from the ground as soon as possible, applying insecticide treatments at the same time for multiple citrus groves within a Psyllid Management Area (PMA) or a Pest Control District (PCD), complying with quarantine measures for the movement of bulk citrus, using certified budwood and sharing information with neighbors.

    But this coordination comes at a cost, and some individuals may be tempted to skip the costs of treating within the recommended window for ACP, correctly tarping their trucks, or even investing some time to convince their neighbors about the importance of these measures. Yet, if everyone skipped these costs and relied on the efforts of others, the ability of the citrus industry to combat HLB would be greatly reduced, leading to a higher risk of HLB spread in California.

    This temptation to free-ride on the efforts of others exists in the management of many natural resources, such as groundwater, fisheries or forests. In 2009, social scientist Elinor Ostrom received the Nobel Prize for Economics for studying how societies organized themselves to manage these types of resources and avoid the problem of free-riding. Throughout her career, she studied many different cases of this problem in different parts of the world, and she identified eight principles that were associated with sustained collective action. Interestingly, most of these principles are present in the strategy for HLB management in California, as shown in the table below.

    Due to a lack of participation in coordinated mitigation tactics – the free-rider problem – a similar HLB-management program in Florida was not as effective in keeping HLB at bay. But California has so far been more successful in achieving collective action than other infected areas like Florida, and as is seeing more success in preventing the spread of ACP and HLB, including keeping HLB out of commercial groves.

    To continue to stay a step ahead of HLB, it is crucial that California’s citrus industry and residents remain vigilant and engage in coordinated management efforts and follow best practices and regulatory requirements.

    Although Ostrom’s principles do not offer a universal solution to all free-riding problems, they can be useful to guide our efforts as we continue to work together to face the threat of HLB.

    More information on her research, which was recently published in Food Security Journal, can be found on https://doi.org/10.1007/s12571-020-01133-9 — By Sara Garcia Figuera, Citrus Pest & Disease Prevention Program

    Design Principle (Ostrom, 1990) HLB Management in California
    1. Clearly defined boundaries: the boundaries define who is responsible for the collective effort and over what area, reducing the cost of monitoring behavior.
    • PMAs
    • PCDs
    2A. Congruence between rules and local conditions: the rules that are established for the management and maintenance of a resource are aligned with the predominant social norms, culture and agro-ecological conditions in a community.
    • Rules defined by the citrus industry through Citrus Pest and Disease Prevention Committee (CPDPC) in collaboration with County Agricultural Commissioners (CACs) and California Department of Food and Agriculture (CDFA)
    • Some pre-existing PCDs
    • Quarantine zones and rules defined by local conditions (citrus production, ACP populations and/or climatic suitability)
    2B. Congruence between appropriation and provision rules: correspondence between the rules governing contributions to the maintenance of the resource system, and the rules governing withdrawal of resources from the system.
    • Insecticide treatments for ACP funded by individual growers.
    • Other assessments based on production volume (CPDPP) or acreage (PCD)
    3. Collective-choice arrangements: if local users who directly interact with one another can define the rules that regulate the day-to-day decisions about the use of a shared resource, they will be in a better position to incorporate local knowledge.
    • AWM organized locally through PCDs or PMAs
    • CPDPC establishes rules in collaboration with CDFA
    4A. Monitoring users: a community needs to be able to identify users that do not comply with rules; otherwise there can be no credible commitment. Monitoring should be undertaken by the resource users, better than by external authorities.
    • Seasonal reports of areas treated for ACP
    • Packinghouse inspections of grate cleaning or spray & harvest
    4B. Monitoring the resource: assesses the extent to which the collective effort is being achieved.
    • ACP monitoring by CDFA, CACs, Citrus Research Board (CRB) and pest control advisors (PCAs) hired by growers
    5. Graduated sanctions: Although sanctioning prevents an excessive violation of community rules, sanctions should be graduated based on the severity and/or repetition of violations to ensure proportionality. And they should be imposed by the resource users or officials accountable to them, to maintain community cohesion.
    • If less than 90% of the acreage is treated in a PMA or PCD, it will not qualify for the residential buffer treatment
    • When there is a violation of the tarping requirement, a notice of violation is sent before further sanctions
    6. Conflict-resolution mechanisms: Low-cost conflict resolution prevents the cost of conflict from outweighing the benefits of successful collective action.
    • Task Force meetings and other public meetings have been used for addressing conflicts
    7. Minimal recognition of rights to organize:Local institutions are more effective when higher levels of government allow users to self-organize in ways that reflect local social and ecological contexts.
    • CPDPC
    • PCDs
    • Grower leader in PMAs
    8. Nested enterprises: refers to the importance of connecting smaller social systems that manage different parts of a larger resource system to facilitate cross-scale coordination.
    • Statewide program coordinated at the regional, county and local level
    • Grower liaisons

  • 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.

  • 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

  • Adding ACP-Effective Materials to Suppress Kern County HLB Vectoring Pest in Citrus

    ACP/HLB San Joaquin Valley Task Force – To Citrus Growers in the Kern County area: last fall and early this year, there has been a significant number of Asian citrus psyllid (ACP) trap detections (over 100) in Kern County. The detections occurred in residential properties, as well as commercial citrus areas in Kern County – especially the City of Bakersfield and areas south and east of it. Unfortunately, in addition to the trap detections, live breeding populations of ACP were discovered by CDFA survey crews in both residential and commercial citrus. Although these detection areas were treated, there is significant concern low level ACP populations may still exist undetected and left to build on the new spring flush. It is imperative for us to continue our efforts to protect Kern County citrus from the devastating effects of Huanglongbing (HLB) – especially in light of the significant level of HLB-positive citrus trees found just south in Los Angeles, Orange, San Bernardino and Riverside counties. An established population of ACP increases the threat of HLB but will also cause the need for additional insecticide treatments to try to suppress the population. Additionally, if HLB is detected and confirmed by CDFA, critical regulatory changes may affect everyone. Given the posed risks, it is important the San Joaquin Valley keep ACP populations as close to eradicated as possible.

    The San Joaquin Valley ACP/HLB Area-Wide Task Force has been tracking and analyzing all ACP detections to date in Kern County. After recent review of the data, the Task Force strongly recommends growers add an ACP-effective material to their pre-bloom or spring foliar treatments – the sooner, the better since ACP build populations on the young leaf flush.  Fortunately, this timing coincides with pre-bloom treatments and treatments for katydid, worms, thrips and other pests.  See below for material examples from the University of California.

    IMPORTANT: If there is any open bloom in the orchard, state bloom regulations and pesticide label pollinator protections must be followed.  Contact the Kern County Agricultural Commissioner’s Office for details at (661) 868-6300.

    WHAT WE NEED YOU TO DO:

    1. Consider treating ALL your citrus blocks in Kern County, especially if they are located east and south of Bakersfield – including non-bearing trees and blocks not normally treated at this time.
    1. Use an ACP-effective insecticide next time you are treating the block. The sooner, the better – click on the link below for a list of ACP-effective insecticides from the University of California: Asian Citrus Psyllid / Citrus / Agriculture: Pest Management Guidelines / UC Statewide IPM Program (UC IPM) (ucanr.edu)

    Examples of ACP-effective materials which also suppress Katydids (from the UCIPM Guidelines):

    • Danitol
    • Baythroid
    • Mustang
    • Micromite
    • Entrust

    Examples of ACP-effective materials that can be used during the bloom period – some with restrictions (ALWAYS check the pesticide label and state bloom regulations prior to use):

    • Sivanto
    • Sefina
    • Micromite
    • Beleaf
    • Fujimite
    • ** = Restricted use to only 1 hour after sunset until 5 hours before sunrise.
    • **Delegate
    • **Entrust
    • **Exirel
    1. Suggested Dilution – 100 to 300 g.p.a. for airblast sprayers. FYI – many nutritional products are compatible with ACP insecticides however you should always check with your PCA before tank mixing.
    1. Please treat the borders of the block first, if possible, since ACP tend to populate block borders first. This way ACP will be driven toward the center of the block where they will get treated instead of away from the block and miss treatment.

    By adding an ACP-effective material to your spring foliar treatment, we will greatly lower both the ACP population and the risk of HLB being transmitted into our trees. Please let me know if you have any questions or concerns regarding this important effort by the SJV ACP/HLB Area-Wide Task Force.

    Sincerely,
    The ACP/HLB San Joaquin Valley Task Force

    For additional information on Kern County operations, please contact:
    Judy Zaninovich
    ACP/HLB Grower Liaison for Kern County
    (559) 730-8691
    jsleslie@msn.com

  • Novel Treatment Causes Killer Citrus Disease to Leak & Die

    New research affirms a unique peptide found in an Australian plant can destroy the No. 1 killer of citrus trees worldwide and help prevent infection. Huanglongbing, HLB, or citrus greening has multiple names, but one ultimate result: bitter and worthless citrus fruits. It has wiped out citrus orchards across the globe, causing billions in annual production losses.

    Untreated citrus plants on the left, as compared to treated ones on the right. (Hailing Jin/UCR)

    All commercially important citrus varieties are susceptible to it, and there is no effective tool to treat HLB-positive trees, or to prevent new infections. However, new UC Riverside research shows that a naturally occurring peptide found in HLB-tolerant citrus relatives, such as Australian finger lime, can not only kill the bacteria that causes the disease, it can also activate the plant’s own immune system to inhibit new HLB infection. Few treatments can do both.

    Research demonstrating the effectiveness of the peptide in greenhouse experiments has just been published in the Proceedings of the National Academy of Sciences.

    The disease is caused by a bacterium called CLas that is transmitted to trees by a flying insect. One of the most effective ways to treat it may be through the use of this antimicrobial peptide found in Australian finger lime, a fruit that is a close relative of citrus plants.

    “The peptide’s corkscrew-like helix structure can quickly puncture the bacterium, causing it to leak fluid and die within half an hour, much faster than antibiotics,” explained Hailing Jin, the UCR geneticist who led the research.

    When the research team injected the peptide into plants already sick with HLB, the plants survived and grew healthy new shoots. Infected plants that went untreated became sicker and some eventually died.

    Arrows point to areas of fluid leakage from the bacterial cell after treatment with the antimicrobial peptide. (Hailing Jin/UCR)

    “The treated trees had very low bacteria counts, and one had no detectable bacteria anymore,” Jin said. “This shows the peptide can rescue infected plants, which is important as so many trees are already positive.”

    The team also tested applying the peptide by spraying it. For this experiment, researchers took healthy sweet orange trees and infected them with HLB-positive citrus psyllids — the insect that transmits CLas.

    After spraying at regular intervals, only three of 10 treated trees tested positive for the disease, and none of them died. By comparison, nine of 10 untreated trees became positive, and four of them died.

    In addition to its efficacy against the bacterium, the stable anti-microbial peptide, or SAMP, offers a number of benefits over current control methods. For one, as the name implies, it remains stable and active even when used in 130-degree heat, unlike most antibiotic sprays that are heat sensitive — an important attribute for citrus orchards in hot climates like Florida and parts of California.

    In addition, the peptide is much safer for the environment than other synthetic treatments. “Because it’s in the finger lime fruit, people have eaten this peptide for hundreds of years,” Jin said.

    Hailing Jin, research leading UC Riverside geneticist

    Researchers also identified that one half of the peptide’s helix structure is responsible for most of its antimicrobial activity. Since it is only necessary to synthesize half the peptide, this is likely to reduce the cost of large-scale manufacturing.

    The SAMP technology has already been licensed by Invaio Sciences, whose proprietary injection technology will further enhance the treatment.

    Following the successful greenhouse experiments, the researchers have started field tests of the peptides in Florida. They are also studying whether the peptide can inhibit diseases caused by the same family of bacteria that affect other crops, such as potato and tomato.

    “The potential for this discovery to solve such devastating problems with our food supply is extremely exciting,” Jin said. — By Jules Bernstein, UC Riverside

  • First CLas-Positive Asian Citrus Psyllid Found in San Diego

    An Asian citrus psyllid (ACP) sample – confirmed positive for Candidatus Liberibacter asiaticus (CLas), the bacteria that causes Huanglongbing (HLB) – was collected from a residential property in the Fallbrook area of San Diego County. Confirmed by Citrus Research Board’s Jerry Dimitman Laboratory, this adult psyllid sample is the first CLas-positive ACP found in San Diego County.

    While the first confirmation of a CLas-positive ACP in San Diego County is concerning, as of today, HLB has not been detected in any San Diego County trees but surveying and sampling of area trees is ongoing. This find signals a critical time for homeowners and growers alike to continue to control ACP populations to stop the potential spread of this deadly disease, as oftentimes a CLas-positive ACP precedes the detection of an HLB-positive tree.

    The HLB quarantine zone will not be expanded as a result of this CLas-positive ACP detection and CDFA staff is swiftly conducting surveys and collecting samples from HLB host plants that are located within a 250-meter radius around the find, per the ACP/HLB Action Plan.

    While treatment is not mandatory for area commercial growers as a result of the detection, San Diego County commercial growers who have additional questions can contact Sandra Zwaal, San Diego County Grower Liaison, at szwaal2@gmail.com.

    CLICK HERE for additional information from Citrus Pest and Disease Prevention Program (CPDPP) Citrus Insider.

    Source: Citrus Pest and Disease Prevention Program (CPDPP) Citrus Insider

  • Stay Vigilant with Asian Citrus Psyllid Finds on the Rise

    In the past few months, we have seen sporadic Asian citrus psyllid (ACP) detections popping up across California. While the citrus industry’s efforts have thus far kept Huanglongbing (HLB) out of commercial groves, these recent ACP detections are a reminder that we cannot let our guard down. The most effective way to prevent the spread of HLB is to keep psyllids out of our orchards.

    After ACP detections in multiple counties (Kern, Madera, San Luis Obispo, Santa Barbara, Santa Clara, Tulare, Contra Costa and others) were confirmed earlier this fall — including areas with historically low ACP activity — the Citrus Pest & Disease Prevention Committee is encouraging all growers to stay informed, scout for ACP and treat when advised.

    The recommendations outlined in the Voluntary Grower Response Plan, developed collaboratively by growers and scientists, represent the most effective tools known to the citrus industry at this time and are meant to supplement the California Department of Food and Agriculture’s required regulatory response. You can help prevent the spread of ACP by following these best practices, participating in recommended winter treatments and ensuring haulers and transporters are tarping loads.

    While we should expect to see this type of “flare up” occasionally, we need to remain vigilant – even when things are quiet – to ensure we continue to stay on top of this elusive pest and the dangerous disease it spreads. The upfront cost to manage ACP is much less than the potential hit to our industry if HLB spreads throughout the state. To date, HLB has only been identified in backyard citrus trees in Los Angeles, Orange, Riverside and San Bernardino counties, and hasn’t made its way into a commercial citrus grove yet. To keep HLB out of commercial citrus, psyllid control is especially critical this season with warmer weather encouraging more pests.

    Here is what you can do:

    • Follow the best practices outlined in the Voluntary Grower Response Plan for Huanglongbing
    • Participate in treatment strategies recommended by the University of California (UC)
    • Adhere to tarping regulations that help keep pests from hitching a ride to new areas of the state

    Visit citrusinsider.org for more information and resources on the voluntary grower best practices, tarping regulations and UC treatment recommendations.

    Questions?
    Contact your regional grower liaison for the latest information on detections near you and coordinated or area-wide treatment schedules. Find your grower liaison here.

    Let’s work together to protect California citrus for your businesses, neighbors and generations to come.

    Sincerely,
    Jim Gorden
    Chair, Citrus Pest & Disease Prevention Committee

  • Root Bacteria Could Help Defeat Fatal Citrus Disease

    A UC Riverside-led team is looking at tiny underground microorganisms for a way to prevent a huge problem — Huanglongbing, a disease with no cure that has decimated citrus orchards worldwide.

    The disease, also known as HLB or citrus greening, has multiple names but the same ultimate result: bitter and worthless citrus fruits. By some estimates, the end of citrus orchards in California and Florida could amount to $14 billion in lost commercial revenue.

    Fruit affected by Huanglongbing. (UCR)

    “Often times, it is thought of as an above-ground disease of the fruits, leaves, and stems,” said Caroline Roper, plant pathology professor and director of the new research effort. “However, we have seen the roots of trees decline with infection, and we want to understand why.”

    The National Institute of Food and Agriculture has awarded the UCR-led team $10 million over the next five years to investigate the role of soil and root microbes in the disease.

    Roper said data from previous studies shows the microbiome of the infected tree — which includes bacteria and fungi as well as protozoa and viruses — plays a role in the disease.

    “We have seen a shift in the root microbiome as trees get sicker,” she said.

    The microbiomes shift to contain more potentially parasitic organisms that may act as secondary invaders to a tree that is suffering from HLB, according to Roper. The invasion of these root pathogens may be causing trees to die faster when they have HLB.

    Part of this new research effort will test whether soil amendments like manure and compost might suppress parasitic microorganisms in the roots as well as the soil, and give the trees more strength to combat diseases including HLB.

    In addition, the research team will try to determine the molecular basis of HLB resistance shown by citrus root stocks developed in Florida. They’ll then see how those rootstocks perform in California, which has different soil and climate conditions.

    The research team will examine both younger trees, because a lot of citrus growers have had to re-plant their orchards after infection, as well as older trees to see if mature groves can recover.

    It will also be important to note how well root stocks from Florida, where there has been a heavy infestation of HLB, perform in California, where much less of the disease has been detected.

    “One of the great things about this grant is that we’re able to leverage existing field trials being done by our collaborators in Florida and at the UC’s Lindcove Research and Extension Center in central California,” Roper said. “This may lead to faster results than we’d otherwise have had.”

    Collaborators on the project include UC Davis; California State University, Sacramento; the University of Florida; and the U.S. Department of Agriculture’s Agricultural Research Service in Ft. Pierce, Florida. — By Jules Bernstein, UC Riverside