Update on Asian Citrus Psyllid for Organic Producers

The Asian Citrus Psyllid (ACP) is spreading throughout California. Organic and non-organic citrus growers are concerned about the spread of ACP because it can spread HuanLongBing (HLB), also known as Citrus Greening disease. This report is an update on activities around detection, quarantine, and control of ACP and HLB.

In the last three months, a number of new ACP finds in new counties are causing quarantined areas to expand rapidly. New quarantines exist in Madera, Fresno, and Santa Clara counties where recent finds have indicated breeding populations of ACP. View the statewide map and county by county quarantine maps.

The entire counties of Imperial, Los Angeles, Orange, Riverside, San Bernadino, San Diego, Santa Barbara, Tulare, and Ventura are already under quarantine and are moving towards area-wide control strategies. In this treatment strategy, neighboring growers coordinate treatments during the same short time period to achieve maximum protection against the ACP. There are few organic options among the recommended treatment materials, that organic growers can use to maintain their organic system rather than be forced into mandatory chemical spraying. Each region has a grower liaison who coordinates the spray periods. Many counties are holding meetings this month to inform and organize growers for this approach. More information on this has been provided by the Citrus Pest & Disease Prevention Program.

New quarantine areas that are not yet in an area-wide program, but commercial citrus are also having informational meetings to set the stage for future efforts. The new quarantine in Santa Clara County encompasses most of the eastern portion of the city of San Jose and includes the airport. This very urban area will need to have a different approach to control since homeowners with backyard citrus are hard to find, communicate with, and encourage to take action. The state is focusing on releases of beneficial insects for situations like these in southern California.

Beneficial insect releases with the parasitic wasp, Tamarixia radiate, have been underway in southern California for most of the last growing season. These releases focus on urban areas but some counties make them available for organic growers. The state is ramping up its ability to raise more of these insects for future availability. A second beneficial wasp species, Diaphorencyrtus aligarhensis, has been released on an experimental citrus grove at UC Riverside. These wasps are from Pakistan, but underwent three years of quarantine before release. This species attacks psyllid nymphs in their second and third developmental stages while Tamarixia attacks the fourth and fifth stages. This could lead to more options for citrus growers when both these species are commercialized.

Fortunately the disease HLB has not been found in California since the one infected tree in a Hacienda Heights backyard in 2012. Vigorous sampling and testing continues for HLB. During 2014, two samples tested positive for HLB coming into the state at border crossings: one was on a potted tree from Arizona and the other on a box of shipped fruit from Georgia. Vigilance and educational efforts are still very important to keep additional sources of the disease out of the state.

Although organic producers are still subject to quarantines and area-wide programs, there is far better cooperation now with regulators, growers, and scientists to meet the challenge this issue poses to citrus in California.