Asian citrus psyllid and huanglongbing disease threaten California citrus

Abstract

Research news Asian citrus psyllid and huanglongbing disease threaten California citrus Santa Clara San Benito Merced Madera Fresno Inyo Tulare Monterey Kings San Luis Obispo Kern M.E. Rogers A sian citrus psyllid is slowly spreading in California, and huanglongbing disease (also known as citrus greening) will likely become established in the state, requiring citrus farmers and residents with citrus in their landscapes to become ac- customed to a new reality. “Asian citrus psyllid and huanglongbing dis- ease have played out this way around the world, including in Florida, Texas and other states,” said UC Cooperative Extension specialist Beth Grafton- Cardwell. “There is no reason to believe California will be immune to the natural progression of this dis- ease complex.” The aphid-sized Asian citrus psyllid was first iden- tified in California in 2008 and is currently found in Imperial, San Diego, Los Angeles, Orange, Riverside, and San Bernardino counties. Asian citrus psyllid injects a toxin when it feeds on citrus leaves or stems, causing shoot deformation and plant stunting. Of greater concern is the fact that it vectors the bacterium associated with huanglongbing disease. Every tree infected with the pathogen will suffer a premature death, sometimes in as little as 3 years. But that doesn’t mean UC researchers and UC Cooperative Extension specialists and advisors are Asian citrus psyllid carries the vector of huanglongbing disease, also known as citrus greening. One symptom of the disease is mottling and chlorosis of leaves. giving this serious citrus disease free rein in the Golden State. UC is working with officials from the citrus industry, U.S. Department of Agriculture and California Department of Food and Agriculture (CDFA) to wage an all-out battle. They aim to contain psyllid populations, catch the infection early in order to rapidly remove infected trees, and monitor commercial citrus using geospa- tial technology. Meanwhile, scientists in university laboratories are exploring the trees, the pest and the pathogen at the molecular and genetic levels to find a long-term cure, while advisors are engaging and educating the public to help in the fight against the disease’s spread. Spread of the psyllid San Bernardino In March 2012, huanglongbing disease was de- tected in California for the first time. The multigrafted citrus tree in a Los Angeles County backyard was destroyed, but it is likely there are more infected trees nearby or in other areas. The disease is also spreading Riverside Orange northward in Mexico toward California. The psyllid and disease together present a grave ACP Observations Imperial threat to California’s $2.1 billion citrus industry, the Commercial Citrus San Diego livelihood of citrus farmers and thousands of farm- Counties workers, and the fragile economies in California’s rural citrus belt, extending from San Diego through Asian citrus psyllid total trap count, 2008–2012. The Geographic Information Systems Facility interior and coastal Southern California and up at the UC Kearney Agricultural Research and Extension Center in Parlier has entered a into the San Joaquin Valley. Their presence prevents partnership with the Citrus Research Board and CDFA to develop a statewide citrus mapping database, enabling the citrus industry to make strategic responses to ACP and HLB outbreaks. exports to countries that do not have this pest and To date, the database has mapped 29,865 Asian citrus psyllid detections. disease. The loss of citrus trees in urban areas of Santa Barbara Ventura Los Angeles http://californiaagriculture.ucanr.edu • October–December 2012 127