A New Pest in California, Diaphorina citri (Asian Citrus Psyllid): Provisional Treatment Guidelines for Citrus in Quarantine Areas

(Updated 1/11)

The Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae), is a tiny (1/8 inch, 3 mm in length) mottled brown insect that is about the size of an aphid. It attacks citrus and very closely related ornamental plants in the family Rutaceae (mock orange, Indian curry leaf, orange jasmine and other Murraya species). This pest attacks new citrus leaf growth and, because of the salivary toxin that it injects, causes the new leaf tips to twist or burn back. However, the more serious damage that it causes is vectoring the bacteria (Candidatus Liberibacter asiaticus and related species) that cause Huanglongbing (HLB or citrus greening) disease. Huanglongbing causes shoots to yellow, assymetrical leaf mottling, and abnormally shaped fruit with bitter juice. The disease can kill a citrus tree within 3 to 5 years, and there is no known cure for the disease. Asian citrus psyllid arrived in southern California from Mexico in 2008. At this point, Huanglongbing has not been detected in California. However, in Florida the psyllid rapidly spread throughout the state on Murraya, and a few years later began to spread Huanglongbing. It is thought that Huanglongbing was present in Florida backyard citrus trees, and it took the arrival of Asian citrus psyllid to move the disease into commercial citrus orchards. Florida citrus growers are now treating up to 8 times per year with broad-spectrum pesticides to reduce Asian citrus psyllid and slow the spread of the disease. Pesticides can reduce the number of psyllids, but an adult psyllid carries the bacteria its entire life and can transmit the disease faster than some pesticides will kill it.

Because Asian citrus psyllid has only recently entered California, we are relying heavily on research done on this pest in Florida and Texas. Currently, treatments that are applied to California citrus orchards in the quarantine zone are designed to disinfest trees and thus minimize the risk of moving Asian citrus psyllid in bins of harvested fruit and to limit the natural spread of Asian citrus psyllid throughout California. Adult psyllids can be detected through visual surveys and yellow sticky cards. Immature stages (eggs and nymphs) are limited to new growth so direct monitoring efforts towards “feather flush” to detect these stages.

For more information, read UC ANR Publication 8205, Asian Citrus Psyllid, and 8218, Citrus Bacterial Canker Disease and Huanglongbing (Citrus Greening).

If you see the Asian citrus psyllid, please contact the CDFA Exotic Pest Hotline at 1-800-491-1899. Personnel from CDFA will inspect plants for the presence of this psyllid and send any specimens to diagnostic laboratories for identification and determination of the presence of Huanglongbing.

The following treatment guidelines have been developed for citrus growers within the quarantine zones. Treat with both a foliar insecticide for immediate control and a systemic insecticide for long-term control. Systemic insecticides take time for uptake and should not be depended on for immediate control. The most important treatment periods are when Asian citrus psyllid adults are found during visual surveys or on yellow sticky traps and during periods of new growth flush when immature stages are developing. Because the systemic insecticides take some time for uptake, apply them before the initiation of flush. For resistance management purposes, rotate between insecticides from different classes.