ACP - bugwood
Image: Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services,

Asian Citrus Psyllid is a small insect, about the size of an aphid that may vector the fatal Huanglongbing (HLB) bacterium, sometimes referred to as Citrus Greening disease.  ACP is the only known insect that can carry the disease which starts as overall decline in health of the tree, with bitter and misshapen fruit, and always results in death of the tree.  There is no known cure once infected with HLB.  As noted in its common name, citrus and closely related species may host the insect and disease.

In San Mateo County there were two confirmed finds in the fall of 2015 of the insect Diaphorina citri, also know as Asian Citrus Psyllid (ACP).  Asian Citrus Psyllid was first discovered in California in 2008 and has spread throughout the southern part of the state. Insect traps have been deployed throughout the county to detect further populations and establish the distribution of the pest. 

As of January 2018, the entire County of San Mateo is under a new set of regional ACP quarantines. The County is now under regional Nursery Stock Quarantine Zone 2, and Bulk Citrus Quarantine Zone 7. Nursery stock can move from our zone to anywhere else in our zone (regardless of County lines) or to the higher-level quarantine zones in California. Production nurseries located in ACP Nursery Regional Quarantine Zones 2 or 3 with ACP host plants offered for intrastate sale or distribution are required to operate under a compliance agreement with the California Department of Food and Agriculture. Any ACP host material (citrus nursery stock) offered for sale in the county must be marked with either a yellow or blue CDFA citrus tag in order to be legally sold. Backyard citrus should not be taken out of San Mateo County.

Production nurseries are required to treat all ACP host plants available for sale or distribution on a 90-day cycle. ACP host plants not grown and maintained in an APHIS approved exclusionary facility, are only eligible to be moved within the nursery regional quarantine zone within 90 days of the approved treatment. The approved treatment consists of both a systemic and foliar application with Program approved products.

With California's $2 billion citrus industry at risk, it is important that we work together as a community to stop the insect from spreading.  Watch this video to see how you can help.  If you suspect the insect or disease is on your citrus trees, please call our office at (650) 363-4700 or CDFA's pest hotline at (800) 491-1899.    

More identification, management and educational information may be found at: California Citrus Threat's Website, UC Davis IPM for Asian Citrus Psyllid and UC Division of Agriculture and Natural Resources.

Quarantine information including maps are available at the California Department of Food and Agriculture.