Background

In 2008, the tiny, aphid-sized Asian citrus psyllid (ACP) was first identified in California. ACP injects a toxin when it feeds on citrus leaves or stems, causing shoot deformation and plant stunting. But this damage isn’t the growers’ greatest concern. ACP is a vector of the bacterium associated with huanglongbing disease (HLB), the most serious citrus disease in the world. HLB causes leaves to yellow and fruit to become small, misshapen, and develop a bitter taste.

There is no cure for the disease, and trees infected with the HLB pathogen eventually die, sometimes in as little as three years. In March 2012, HLB was detected in a residential citrus tree in Los Angeles County. That tree was destroyed, but it is likely there are more infected trees in California. The disease is also spreading northward from Mexico toward California.

ACP and HLB together present a grave threat to California’s $2.1 billion citrus industry, the livelihood of citrus farmers and thousands of farmworkers, and the fragile economies in California’s rural citrus belt. The presence of ACP and HLB prevents exports to countries that do not have this pest and disease. Loss of citrus trees in urban areas of California will change the face of the landscape and reduce local fruit availability. UC is working with the citrus industry to wage an all-out battle against both the pest and disease. Much of the research is conducted with funding from the citrus industry through the Citrus Research Board. Other funding sources are UC Agriculture and Natural Resources, CDFA (Specialty Crops Block Grants), and the USDA-NIFA (National Institute of Food and Agriculture).