The Asian citrus psyllid, Diaphorina citri, is a tiny, mottled brown insect about the size of an aphid (Figure 1). This psyllid feeds on all varieties of citrus and some related ornamental plants like orange jessamine. It damages citrus leaves by feeding on new leaf growth, causing the leaves to twist or notch as they mature. More seriously than this plant damage, ACP can infect citrus trees with the bacterium Candidatus Liberibacter asiaticus, which causes huanglongbing disease. Huanglongbing (or HLB) can kill a citrus tree in as little as 5 years. There is no known cure, and all commonly grown citrus varieties are susceptible to the disease.
Controlling ACP infestations is the only way to save citrus trees from this disease. To keep ACP and the disease it can carry from spreading, quarantines have been established in California. Citrus trees sold within an ACP quarantine area will have a blue or yellow tag indicating they must stay within the quarantine area.
Best Practices for ACP Within the Retail Nursery
Citrus trees in wholesale nurseries are treated with insecticides before sale but this protection only lasts for three months. In retail nurseries and garden centers, trees are protected from ACP infestations by placing them inside a screened-in structure or in shaded areas of the store. This is especially important in ACP quarantine areas but is prudent in other nearby areas. It's important to know where the quarantine boundaries are, so refer to the California Department of Food and Agriculture (CDFA) for information.
As you are shopping for citrus trees, carefully check for psyllids. Be sure to inspect new leaves that are forming on the trees. If you see ACP in a retail setting, notify the nursery and have them contact your county agricultural commissioner as soon as possible.
Best Practices for ACP in the Home Garden
Once you purchase your citrus trees, you can help minimize spread of the ACP and HLB disease from your garden. Be sure to plant the trees locally, near where you purchase them.
Home gardeners should treat for ACP and control ants on your citrus trees. Anyone growing citrus trees must watch for HLB symptoms and if you suspect that a tree is infected, you must report it to your county agricultural commissioner's office or call the CDFA Exotic Pest Hotline at 1-800-491-1899. Home gardeners need to support ACP treatments and removal of HLB-infected trees if you are in an area with HLB.
See the recently revised Pest Notes: Asian Citrus Psyllid and Huanglongbing Disease for more information on identification and management.