Asian Citrus Psyllid Quarantine Areas Expanded; Predator Wasp to Be Released

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The disease-carrying pest Asian citrus psyllid (ACP) has moved north from southern California and now threatens the central and northern regions of the state. To combat the pest, the California Department of Food and Agriculture (CDFA) has increased areas under quarantine, mounted a comprehensive search-and-destroy effort, and is preparing to release swarms of psyllid-killing wasps to route the pest.

ACP Impact and Challenges

ACP carries a bacterium that causes a deadly disease in citrus trees and related tree species called huanglongbing or citrus greening disease. Infected trees first exhibit symptoms such as leaf discoloration and misshapen fruit, and as the disease progresses, the tree is unable to take up nutrients and, ultimately, dies. The disease has devastated the Florida citrus industry, with an estimated 80% of trees infected. University of Florida estimates it has caused $7.8 billion in revenue losses since the disease was first detected in 2005.

The conventional treatment for ACP is applying a pyrethroid insecticide to foliage and neonicotinoid insecticides to soil. Fortunately, researchers at Cal Poly Pomona are raising Tamarixia radiata, a tiny wasp that preys on ACP and parasitizes ACP nymphs. CDFA reports that the wasps will be released in Kern County in an effort to prevent movement of the pest into the San Joaquin Valley, and will be released in southern California neighborhoods as well.

Expanded Quarantine to Stop ACP

As of July 7, 2016, 55,000 square miles in the state were under quarantine. The quarantine covers all of Imperial, Los Angeles, Orange, Riverside, San Bernardino, San Diego, Santa Barbara, Tulare, and Ventura counties, as well as regions in Fresno, Kern, Kings, Madera, Merced, San Benito, San Joaquin, San Luis Obispo, San Mateo, San Francisco, Santa Clara, Alameda, Stanislaus, and Monterey counties.

According to CDFA, “The quarantine prohibits the movement of citrus and curry leaf tree nursery stock, including all plant parts except fruit, out of the quarantine area and requires that all citrus fruit be cleaned of leaves and stems prior to moving out of the quarantine area. An exception may be made for nursery stock and budwood grown in USDA-approved structures which are designed to keep ACP and other insects out. Residents with backyard citrus trees in the quarantine area are asked not to transport or send citrus fruit or leaves, potted citrus trees, or curry leaves from the quarantine area.”

Authorities in California are trying to avoid losses to the California citrus industry and are conducting intensive surveys of backyard citrus trees in southern California to nip growth of ACP populations in the bud.

Other ACP Resources

For the most up-to-date information on ACP and huanglongbing, visit the CDFA ACP website. The CDFA offers a free iPhone app to report and identify diseases affecting citrus, as well as quarantine maps and numerous other resources.