ACP Quarantine in Northern San Mateo County Includes Portion of San Francisco County

Dan Citrus, General, Industry News Release

A 64-square-mile quarantine is in place in northern San Mateo County for the Asian citrus psyllid (ACP). The quarantine was established following the detection of two psyllids within the cities of Pacifica and Daly City. The quarantine also takes in the southern portion of San Francisco County along its border with San Mateo County. The quarantine zone is bordered on the north by Lawton Street in San Francisco; on the south by Linda Mar Boulevard in Pacifica; on the west by the Pacific Ocean; and on the east by the San Francisco Bay. The quarantine maps for both San Mateo and San Francisco are available online at:

The quarantine prohibits the movement out of the quarantine area of any citrus trees and nursery stock, including all parts of citrus trees. Fruit is not regulated, however, before moving any citrus fruit out of the quarantine area it must be cleaned of leaves and stems. Nursery stock and budwood grown in USDA-approved structures, which are designed to keep ACP and other insects out, may be moved out of the quarantine zone under regulatory supervision. Residents with


Adult Asian citrus psyllid, Diaphorina citri Kuwayama. Photograph by Douglas L. Caldwell, University of Florida.

backyard citrus trees in the quarantine area are asked not to transport or send citrus fruit or leaves, potted citrus trees, or curry leaves from the quarantine area.

Since first being found in California in 2008, the Asian citrus psyllid has slowly been spreading throughout California and there are now county-wide quarantines in place in Imperial, Los Angeles, Orange, Riverside, San Bernardino, San Diego, Santa Barbara, Tulare and Ventura Counties, with portions of Alameda, Fresno, Kern, Madera, Merced, San Benito, San Joaquin, San Luis Obispo, Santa Clara, and Stanislaus counties also under quarantine.

The introduction of ACP is of concern because it can carry the disease huanglongbing (HLB), also known as citrus greening. All citrus and closely related species, such as curry leaf trees, are susceptible hosts for both the insect and disease. There is no cure once the tree becomes infected, the diseased tree will decline in health and produce bitter, misshaped fruit until it dies. In California, HLB has been detected in 2012 and 2015 on residential properties in Los Angeles County. This plant disease does not affect human health. Since the detection of Asian citrus psyllids in Daly City and Pacifica in late October, no additional psyllids have been found. Treatment of citrus trees within 400 meters of the detections sites has been completed. Traps for ACP have been placed throughout San Mateo County and monitoring will continue through December and then resume in the spring.

Residents in the area who think they may have seen Asian citrus psyllid or symptoms of Haunglongbing on citrus trees are urged to call CDFA’s Pest Hotline at 1-800-491-1899 or the local agricultural commissioner’s office. The number for San Mateo County is 650-363-4700 and for San Francisco County, (415) 252-3830. For more information on the ACP and HLB, please visit: