Posts Tagged: psyllid

Watch Out Argentine Ant. Watch Out Citrus Psyllid

Asian citrus psyllids transmit a disease that can ruin your oranges. Even worse, Argentine ants protect them in exchange for the psyllids' delicate ribbons of sugary poop, called honeydew. So, researchers are helping orange growers fight back with invisible lasers, ghastly wasps and more trickery.

A tiny insect called the Asian citrus psyllid is threatening your oranges, lemons and limes. Smaller than a grain of rice, the agricultural pest sucks the sap from citrus trees and in doing so spreads a disease that ruins the fruit and eventually kills the citrus trees. “It's pretty straightforward to tell if you have an Asian citrus psyllid infestation in your citrus,” says Mark Hoddle, who leads a laboratory at UC Riverside that studies the pest and how to beat it. “Just check the tender young green leaves at the tips of the branches. If you see the white curly cues, the insect poop dripping off of those leaves, that's almost certainly a characteristic symptom of an Asian citrus psyllid infestation.” Hoddle's team is studying novel ways to keep psyllids out of citrus orchards, but that task is complicated by the psyllid's relationship with another insect, the Argentine ant. “Their relationship is rather sinister,” says Hoddle. “The Argentine ants harvest the honey dew that the Asian citrus psyllid nymphs excrete because it's nice and sugary and the ants love eating sugar. In return for providing that sweet delicacy, the ants protect the Asian citrus psyllids from their natural enemies like the predators and the parasitic wasps that we have introduced from Pakistan.” “The psyllids need protection from the ants because they lack defense systems,” says Hoddle. “They have recruited mercenaries to protect them.” So to protect the valuable citrus industry, Hoddle and his team are going after the psyllids' ant bodyguards.

https://www.youtube.com/watch?v=MtPXows1FWs

ACP nymphs sam droege

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

ACP and nypmphs

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

Biología y Manejo del Psílido Asiático de los Cítricos (PAC)

psyllids on citrus leaf

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