Expanded ACP Quarantine
Two portions of San Joaquin County have been placed under Asian citrus psyllid (ACP) quarantine following detections of one ACP within the City of Manteca and one within the City of Lodi. The quarantine zone in Manteca measures 105 square miles and in Lodi it measures 95 square miles.
The quarantine prohibits the movement of citrus and curry tree nursery stock 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 that are designed to keep ACP and other insects out. Residents with backyard citrus trees in the quarantine area are asked not to transport citrus fruit or leaves, potted citrus trees, or curry leaves from the quarantine area.
Asian citrus psyllid (Source: UC ANR)
The ACP, a tiny (0.125 in. length) mottled brown insect that is about the size of an aphid, is an invasive species of grave concern because it can carry the disease huanglongbing (HLB), also known as citrus greening. All citrus and closely related species such as curry trees are susceptible, and there is no cure. Once infected, a diseased tree will decline in health with yellowing shoots, asymmetrical leaf mottling and abnormally shaped bitter fruit until it dies—typically within three years. HLB was detected once in California, in 2012, on a residential property in Hacienda Heights, Los Angeles County. This plant disease does not affect human health.
Residents in the area who think they may have seen ACP or symptoms of HLB on their citrus trees are urged to call CDFA’s Pest Hotline at 1-800-491-1899. For more information on the ACP and HLB, please visit: www.cdfa.ca.gov/go/acp
ACP Effective Treatments
The University of California Agriculture and Natural Resources’ Integrated Pest Management (IPM) Program has developed treatment guidelines for citrus growers within the quarantine zones. A general principle when applying insecticides to control ACPs in commercial citrus is that no one insecticide fully controls ACP across all life stages because:
- All stages are difficult to contact with insecticides; eggs and nymphs are tucked inside new foliage and adults can fly.
- Some insecticides show better efficacy against one stage over another.
- Because systemic neonicotinoid insecticides require root activity for uptake, they are best applied during June through September.
The UC IPM Guidelines for Citrus provides a ranked list of insecticides that are effective against the Asian citrus psyllid with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honeybees, and the environment are at the top of the table.
According to Mark Hoddle, UC Riverside (UCR) Director, Center for Invasive Species Research, “The science of biological control, the use of a pest’s natural enemies to suppress its populations to less damaging densities,” shows promise against the ACP with releases over the last three years of Tamarixia radiata–a parasitic wasp from Pakistan–in urban areas of southern California. Thus far, this natural ACP enemy helps to control ACP growth in residential areas, but is inadequate for commercial application.
Biological Control Scholarship Fund
Harry Scott Smith (Source: Citrus Research Board, “Citrograph”)
Harry Scott Smith was the first to use the phrase “biological control” in 1919 at the meeting of Pacific Slope Branch of the American Association of Economic Entomologists at the Mission Inn in Riverside. Smith worked on the biological control of gypsy moth with USDA, then moved to the University of California Riverside where he eventually created and chaired the Department of Biological Control, which offered the only graduate degree in biological control in the world.
The Harry Scott Smith Biological Control Scholarship Fund at UCR aims to attract the brightest students to study biological control by providing assistance to its students to attend conferences to present their research or to participate in training workshops. More information on the Scholarship, past awardees, and a list of donors can be reviewed on the website.
Sources: CDFA; UC IPM; UC Riverside (UCR); UCR Center for Invasive Species Research; USDA Animal and Plant Health Inspection Service (APHIS)