Asian citrus psyllid – the vector of Huanglongbing (HLB) disease – has been officially detected in Santa Clara County and the San Gabriel area of Los Angeles County in California; following the confirmation, an existing quarantine has been expanded to include an additional portion of Santa Clara County as well as a portion of southern Alameda County along its border with Santa Clara County. (Maps of the quarantine area are available online at http://www.cdfa.ca.gov/plant/go/acp-maps.)

The quarantine prohibits the movement of citrus and curry leaf tree nursery stock, including all plant parts except fruit. It also requires that all citrus fruit be cleaned of leaves and stems prior to moving out of the quarantine area. According to the state’s Department of Food and Agriculture’s Plant Health & Pest Prevention Services, “an exception may be made for nursery stock and budwood grown in USDA-approved structures which are designed to keep ACP and other insects out.”

Thanks to the Asian citrus psyllid, citrus greening disease was detected in plant material taken from a kumquat tree in San Gabriel. A California Department of Food and Agriculture (CDFA) crew has removed and disposed of the infected tree and began treatment of trees within 800 meters of the site.

Found throughout Asia, India, Saudi Arabia and Brazil, citrus greening disease was first detected in the United States in 2005.

Host plants and life cycle

The Asian citrus psyllid host range includes 25 genera in the Rutacceae with the most common hosts being Citropsis, Citrus and Murraya. All varieties of citrus and closely related plants should be monitored. Being just 3 to 4 mm in length, the pest’s short life progresses from egg through five nymphal instars to the adult stage. Adults feed on the underside of leaves and live for one to two months.

How to spot Asian citrus psyllid

To monitor the pesky Asian citrus psyllid, the University of California Davis suggests including a search for all insect stages, including gray to brown adults and brightly colored yellow-orange eggs and nymphs. Eggs can be found inside leaf folds and crevices and can also be detected by the presence of sooty mold, white wax and twisted shoot tips.

There is no cure once the tree becomes infected. The tree will decline in health and produce bitter, misshaped fruit until it dies, but the good news for humans is that it doesn’t affect our health.

More than 15 states are under full or partial quarantine due to Asian citrus psyllid. It is also present in Mexico, Puerto Rico and the U.S. Virgin Islands. With the disease present in all 30 citrus-producing Florida counties, the University of Florida estimates that the disease cost growers $2.994 billion in lost revenue since it was first detected in the state in 2006.

There’s excellent information available from the University of California’s Statewide Integrated Pest Management Program; you can download a rather comprehensive pdf at http://www.ipm.ucdavis.edu/PDF/PESTNOTES/pnasiancitruspsyllid.pdf.

Cover photo iStock | kekko73