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Local growers urged to keep inspecting citrus trees for invasive insect

While quarantine efforts seem to be working locally to prevent the spread of the Asian Citrus Psyllid, a bug known to host an incurable citrus disease, University of California's Agriculture and Natural Resources Department is urging growers to remain vigilant in examining their citrus trees for the tiny invasive insect.

“We encourage home citrus growers and farmers to go out with a magnifying glass or hand lens and look closely at the new growth,” said Beth Grafton-Cardwell, UC ANR citrus entomologist. “Look for the various stages of the psyllid – small yellow eggs, sesame-seed sized yellow ACP young with curly white tubules, or aphid-like adults that perch with their hind quarters angled up.”
Asian citrus psyllids are feared because they can spread huanglongbing (HLB) disease, an incurable condition that first causes yellow mottling on the leaves and later sour, misshapen fruit before killing the tree.

ACP, native of Pakistan, Afghanistan and other tropical and subtropics regions of Asian, was first detected in California in 2008. Everywhere Asian Citrus Psyllids have appeared – including Florida and Texas – the pests have spread the disease. A few HLB-infected trees have been located in urban Los Angeles County. They were quickly removed by California Department of Food and Agriculture officials.

“In California, we are working hard to keep the population of ACP as low as possible until researchers can find a cure for the disease,” said Grafton-Cardwell. “We need the help of citrus farmers and home gardeners.”

Grafton-Cardwell has spearheaded the development of the UC ANR ACP website for citrus growers and citrus homeowners that provides help in finding the pest and what to do next. The site has an interactive map tool to locate residences and farms that are in areas where the psyllid has already become established, and areas where they are posing a risk to the citrus industry and must be aggressively treated by county officials.

The website outlines biological control efforts that are underway, and directions for insecticidal control, if it is needed. An online calculator on the website allows farmers and homeowners to determine their potential costs for using insecticides.

A total of three Asian Citrus Psyllids have been detected in Stanislaus County since October of last year, and while these insects are known to carry HLB, Stanislaus County Agricultural Commissioner Milton O’Haire wanted to make it clear to citrus growers that none of the insects found in Stanislaus County were carrying the citrus greening disease.

“The psyllid is a vector of the disease and we don’t have it here yet. Hopefully we never do,” said O’Haire. “Even though we don’t have a lot of commercial citrus here—less than 300 acres—we have tens of thousands of acres of residential citrus that would be in jeopardy.”

O’Haire was happy to report that after applying additional traps in both quarantine areas, with over 300 traps in the Turlock quarantine alone, and checking them regularly, they have not picked up any new psyllids.

“If we don’t find anything for two straight years, then the quarantine could be lifted, although what we heard from the USDA is that the additional traps will stay out and we’ll still be looking just in case,” said O’Haire.

Under quarantine, growers are prohibited from moving citrus and curry leaf tree nursery stock, including all plant parts except fruit, out of the quarantine area. They are also required to clean all citrus fruit of leaves and stems prior to moving out of the quarantine area. 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 now from the quarantine area.

Pictures of the Asian Citrus Psyllids and its life stages are on the UC ANR website at If anyone finds signs of the insect, they should call the California Food and Agriculture (CDFA) Exotic Pest Hotline at (800) 491-1899.