Asian citrus psyllid study: vigilance called for, but ‘no cause for panic’

By Mike Hsu, UCANR

Preliminary results indicate that 3.5% of collected ACP showed signs of bacteria that can cause huanglongbing

An ongoing study in commercial citrus groves in coastal Southern California examines whether the Asian citrus psyllid—the insect vector huanglongbing disease “citrus greening”. – are carriers of the bacteria that can cause HLB.

So far, the project has tested more than 3,000 adult ACPs collected from 15 commercial citrus sites in the region, of which 138 — just over 3.5 percent — had some level of the bacteria present, according to researchers from UC Agriculture and Natural Resources, UC. Davis, UC Riverside and University of Arizona, Tucson.

“While the results are a cause for concern, the situation in California is much better than in Florida and Texas, where ACP carrying the bacterium is the majority of the population and HLB is widespread in commercial citrus,” he said. Neil McRoberts, a UC Davis plant pathologist and affiliate advisor to the UC Integrated Pest Management program. “The results indicate that there is no room for complacency, but no cause for panic.”

Since the first HLB-infected tree in California was found in 2012, nearly 4,000 infected trees have been detected and removed from residential properties in Southern California, primarily in Orange and Los Angeles counties. According to McRoberts, “to date, no HLB has been found in commercial citrus fruits” in California.

He pointed out, however, that the aforementioned ACP study — funded by the HLB Multi-Agency Coordinating Group and managed by USDA-APHIS — does not involve any testing of trees for HLB and focuses only on the insect that spreads the bacteria.

McRoberts also stressed that the project’s detection of the bacterium cannot be considered “official” because the researchers’ laboratory procedures differ from the California Department of Food and Agriculture’s official testing protocols.

“Further sampling by CDFA staff would allow for official sampling for further investigation, but is entirely voluntary for the growers involved,” he said, adding that his research team is currently completing the sampling phase of the project with data. analysis continues in 2023.

While praising the “huge coordinated effort” by the California citrus industry, the California Department of Food and Agriculture, UC ANR and other partners to suppress the ACP vector and slow the spread of HLB, McRoberts also called for continued vigilance.

“The results of our study indicate that it is not time to declare a state of emergency for ACP/HLB in California, the situation is still evolving,” he said.