Posts Tagged: Asian citrus psyllid
Invasive Spotlight: Asian Citrus Psyllid and Huanglongbing Disease
The Asian Citrus Psyllid (ACP) is a small, aphid-sized insect that poses a serious threat to...
ACP Updates
Asian Citrus Psyllid Update
Winter and spring rains have given us a robust growing season this year. Tender new citrus flush is ideal habitat for ACP to feed, lay eggs and build new populations. An increase in ACP numbers and feeding can increase the risk of HLB spreading and building up. University of California recommends growers monitor trees regularly for ACP, paying careful attention to new flush, and treat when populations reach the detection threshold. The UC IPM website lists a range of materials effective against ACP, including organic options. Growers are also encouraged to work with a pest management professional to better detect and manage ACP.
Advanced notification of nearby beekeepers is required before pesticide treatments. Use the BeeWhere BeeCheck system, or contact the County Agricultural Commissioner's office, 805-681-5600, for more information. Always follow label instructions for bee safety.
If your citrus is no longer being cared for or is not worth the resources required to protect it from ACP and HLB, consider removing it.
HLB Quarantine Update
As of May 5, a total of 5.007 trees and 709 ACP have been confirmed positive for the bacterium that causes HLB. Trees confirmed positive are treated for ACP and removed, and the HLB quarantine may be expanded. Additional ACP treatments and HLB detection surveys are conducted on a recurring basis to remaining citrus within 250 meters of each detection.
Counties where HLB has been detected via PCR testing are Los Angeles, Orange, San Diego, Riverside, San Bernardino and San Diego, with the majority of detections in Orange County. To see a map of the current HLB quarantine areas, and other details of locations and numbers of HLB detections, please visit maps.cdfa.ca.gov/WeeklyACPMaps/HLBWeb/HLB_Treatments.pdf.
HLB Detection Response Guide for Growers
To ensure California citrus growers are well prepared in the event of a potential commercial grove detection of Huanglongbing (HLB), the Citrus Pest and Disease Prevention Program (CPDPP) has developed the Response Guide for a Confirmed HLB Positive Detection in a Commercial Grove, which details the steps taken by CDFA and actions required of the property or grove owner, as outlined in CDFA's Action Plan and Information for Citrus Growers/Grove Managers.
Citrus Pest and Disease Prevention Committee Meetings -- Webinar and In Person
All meeting agendas and eventually the minutes are posted at www.cdfa.ca.gov/citrus committee/. The 2022-23 schedule for the Full Committee is here, and the schedule for Subcommittees is here.
Upcoming Meetings
- Operations Subcommittee, Wednesday May 10 at 9 am (agenda and webinar link)
- Outreach Subcommittee, Wednesday May 10 at 1:30 pm (agenda and webinar link)
- CPDPP Full Committee, Wednesday August 9 (agenda pending)
All meetings are free and open to the public to listen to or make public comment. Meetings are currently in person and accessible via phone and/or webinar. Links to register for and join meetings are included in agendas when posted.
For a list of current committee members, click here.
Additional ACP/HLB Resources
- CDFA Citrus Division website: https://www.cdfa.ca.gov/Citrus/
- General ACP/HLB
oInformation on the state ACP/HLB program including maps, quarantine information, and a signup option for email alerts: citrusinsider.org/
oBiology of ACP and HLB, detection maps and recommendations for monitoring, eradication and management: ucanr.edu/sites/acp/
oUC IPM recommendations for ACP insecticides
oWeb-based map to find out how close you are to HLB: ucanr.edu/hlbgrowerapp
oVideo on Best Practices in the Field, available in English and Spanish
oSpanish-only ACP/HLB presentation video presentation and audio-only recording.
- Research
oLatest Science Advisory Panel Report
oUC Ag Experts Talk presentations on management of various citrus pests and diseases are available for viewing here and here on YouTube.
oSummaries of the latest research to combat HLB: ucanr.edu/sites/scienceforcitrushealth/
oScience-based analyses to guide policy decisions, logistics, and operations: www.datoc.us
- Regulatory/Quarantine
oSign up for program updates from the Citrus Pest and Disease Prevention Division at www.cdfa/signup-email-updates.
oRegulatory requirements for moving bulk citrus: Information for Citrus Growers
oSummary of regulatory requirements in the event of an HLB detection in commercial citrus: citrusinsider.org/Regulatory-Flyer
oSanta Barbara County Ag Commissioner's Office
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Cressida Silvers
CA Citrus Pest and Disease Prevention Program
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
805 284-3310 (phone or text)
acp (2)
ACP and Biological Control
Two DPR CE unit (other) and two CCA CE unit (IPM) are pending.
Just as a reminder, here are the requirements for receiving the CEUs:
-register separately with your own name and email address and log in from your own device
-participate in the entire session
-complete and pass a final test with 70% or higher; if not passed, the test can be retaken
If you are not familiar with Zoom, log in a few minutes early to familiarize yourself with the Zoom interface.
. Registration information is at:
https://ucanr.zoom.us/webinar/register/WN_w0BKQR7YQ_-_IzAn29KW-g
ACP and nypmphs
Asian citrus psyllid study: Vigilance urged but ‘no cause for panic’
Preliminary results indicate 3.5% of ACP collected showed signs of bacterium that can cause huanglongbing
An ongoing study in the commercial citrus groves of coastal Southern California is looking at whether Asian citrus psyllids – the insect vector of huanglongbing “citrus greening” disease – are carrying the bacterium that can cause HLB.
Thus far, the project has tested more than 3,000 adult ACP collected from 15 commercial citrus sites across the region, of which 138 – just over 3.5% – had some level of the bacterium present, according to researchers from UC Agriculture and Natural Resources, UC Davis, UC Riverside and the University of Arizona, Tucson.
“While the results are a cause for concern, the situation in California is much better than in Florida and Texas, where ACP carrying the bacterium make up the majority of the population and HLB is widespread in commercial citrus,” said Neil McRoberts, a UC Davis plant pathologist and UC Integrated Pest Management program affiliate advisor. “The results indicate that there is no room for complacency, but also no cause for panic.”
Since the first HLB-infected tree in California was found in 2012, nearly 4,000 infected trees have been detected and removed from residential properties in Southern California, mainly in Orange and Los Angeles counties. According to McRoberts, “to date, no HLB has been found in commercial citrus” in California.
He stressed, however, that the aforementioned ACP study – funded by the HLB Multi Agency Coordination Group and managed by USDA-APHIS – does not involve any testing of trees for HLB and focuses only on looking at the insect which spreads the bacterium.
McRoberts also emphasized that the project's detections of the bacterium cannot be considered “official” because the researchers' lab procedures differ from the official testing protocols of the California Department of Food and Agriculture.
“Follow-up sampling by CDFA staff would allow official samples to be collected for further investigation, but is entirely voluntary for the growers involved,” he said, adding that his research team is currently wrapping up the sampling phase of the project, with data analysis continuing into 2023.
While commending the “huge coordinated effort” by the California citrus industry, California Department of Food and Agriculture, UC ANR and other partners to suppress the ACP vector and slow the spread of HLB, McRoberts also urged continued vigilance.
“Our study results indicate that it is not time to declare the emergency status for ACP/HLB in California over – the situation is still evolving,” he said.
For further information about the research, contact Neil McRoberts at nmcroberts@ucdavis.edu or (530) 752-3248.
ACP and Natural Enemies
Natural enemies have significantly suppressed Asian citrus psyllid populations in southern California
Ivan Milosavljevi, Department of Entomology, University of California, Riverside, CA
Christina D. Hoddle, Department of Entomology, University of California, Riverside, CA
David J.W. Morgan, California Department of Food and Agriculture, Mt. Rubidoux Station, Riverside CA
Nicola A. Irvin, Department of Entomology, University of California, Riverside, CA
Mark S. Hoddle, Department of Entomology, University of California, Riverside, CA
Is California facing a citrus apocalypse?
Asian citrus psyllid (ACP) (Diaphorina citri) is an invasive pest of citrus first discovered in urban citrus in San Diego County California (CA) in 2008 . ACP presents a significant economic threat to CA's citrus industry because it vectors a bacterium, CLas, which causes a citrus-killing disease, huanglongbing (HLB). There is currently no cure for HLB which kills susceptible commercial citrus varieties in as little as 5 to 8 years. Since HLB was first discovered in Florida (FL) in 2005 (ACP was discovered in FL in 1998), citrus production in that state has fallen by 80% . In CA, the first case of HLB was detected in 2012 in Los Angeles County and infestations of ACP-CLas are largely restricted to urban-grown citrus in southern CA. Should HLB spread north into the San Joaquin Valley, where 75% of CA's citrus fruit is grown, it would jeopardize ~262,000 fruit-bearing acres, which generates over $3 billion annually and provides over 26,000 jobs. Because ACP-HLB poses such a significant threat to CA's citrus industry, ACP population suppression is key to slowing the spread of CLas into CA's commercial citrus groves.
Biocontrol suppresses ACP populations
In CA, ACP has been the target of a classical or introduction biological control program with two tiny parasitic wasps or parasitoids, Tamarixia radiata and Diaphorencyrtus aligarhensis, sourced from Pakistan, a part of the ACP's presumptive native range. CA's biocontrol program against ACP began with the release of T. radiata in December 2011, and in December 2014, D. aligarhensis was added to the release program with the intent of establishing a complementary set of parasitoids that specifically attack ACP nymphs. To date, >24 million parasitoids (T. radiata and D. aligarhensis combined) have been mass-produced and released at >19,500 sites in southern CA by the Applied Biocontrol Lab at UC Riverside and the California Department of Food and Agriculture. Of these two parasitoids, T. radiata established readily and rapidly spread into sites in CA where it was not released. Conversely, D. aligarhensis failed to establish following release in CA and mass production and release of this parasitoid was subsequently discontinued in 2019.
The ongoing biocontrol effort: So far, so good, but there is room for improvement
Since the inception of the ACP biocontrol program in CA in 2010 and the first release of T. radiata in 2011, densities of ACP infesting urban citrus have declined by ~70%. Two different multi-year and multi-site studies in urban citrus in southern California has clearly demonstrated that the proximate causes of these widespread population declines are due to natural enemies, specifically parasitism of ACP nymphs by T. radiata and predation by generalist predators, of which syrphid fly larvae are key predators of ACP nymphs . Consequently, reduced ACP densities may have slowed the spread of CLas in CA and subsequent development of HLB in infected citrus trees. However, the efficacy of natural enemies attacking ACP eggs and nymphs has been reduced by the presence of another invasive pest, the Argentine ant (AA) (Linepithema humile). Field work on ACP biocontrol in CA identified AA as a significant impediment to natural enemies. When present on trees, AA reduced the abundance of natural enemies interacting with ACP and suppressed the efficacy of T. radiata and syrphids by over 50 percent. When AA is excluded from ACP colonies, natural enemy abundance and attack rates increase significantly, particularly impacts by T. radiata and syrphid fly larvae.
Why are Argentine ants problematic, and what can we do about them?
AA aggressively protect >55% of ACP from natural enemies. In return for this protection, AA is rewarded with food, honeydew, which is a sugary waste product excreted by ACP nymphs. Consequently, AA protection exacerbates infestations of ACP and other honeydew producing pests in citrus (e.g., brown soft scale and mealybugs). This results in a positive feedback loop – more pests survive due to AA protection and their populations increase which in turn produces more food for AA which results in increasing ant populations. An undesirable outcome of these population increases is greater applications of insecticides to control sap sucking pests and AA. Ironically, sprays of contact insecticides targeting AA (and ACP) kill natural enemies needed for “free” pest control and this disrupts IPM programs which aim to reduce insecticide use.
To ameliorate this problem of increased insecticide use, biocontrol ACP (and other sap sucking pests) can be enhanced through three management practices: (1) monitoring AA activity with infra-red sensors to determine when ants have reached densities that need controlling, (2) controlling AA with highly targeted applications of ultra-low concentrations (i.e., 0.0001%) of insecticide delivered to foraging inside of biodegradable hydrogel beads that are infused with 25% sucrose water and insecticide, and (3) floral resources that provide food and shelter to natural enemies, especially hover flies, that attack ACP nymphs. This three-pronged management approach for controlling AA and the pests ants protect (e.g., ACP) is undergoing field evaluation in commercial citrus orchards in southern California. The outcomes of these large, replicated field trials will be discussed in an upcoming article in Topics in Subtropics: “Maximizing IPM of Argentine ant and sap sucking pests with biodegradable hydrogels, infra-red sensors, and cover crops in commercial citrus orchards.”
aRGENTINE ANT