While only one case of HLB has been confirmed with the PCR test, Morse warned there could be 10 more HLB positive trees. He says the additional citrus trees in question are within a 700 meter radius of the HLB positive find.

“I am pretty convinced that HLB has spread from the area of the original infected tree,” Morse said.

Results from samples of the nearby 10 trees tested with three of the experimental test methods conclude the trees are HLB positive by at least one method, and in some cases by two or three methods. Meanwhile, state regulators are awaiting official PCR results.

Seven of the 10 trees have been removed. Morse says the other three should be cut down.

Citrus was just one of the topics discussed at the 24th Annual Fall Desert Crop Workshop, attended by growers, pest control advisors, consultants, and other industry members representing low-desert agriculture in California’s Imperial and Riverside counties and southwestern Arizona.

One-third of the California citrus crop is grown in Southern California. The balance is grown in the San Joaquin Valley. 

Morse explained that the largest populations of psyllids in California are in residential areas, mostly in the greater L.A. area. Some psyllids have been found in commercial groves over the last few years and are increasing, including finds this year in California’s top citrus-producing county, Tulare.

The adult psyllid not only flies but is wind blown into new areas.

While a variety of different insects can feed on citrus trees, the adult Asian citrus psyllid is easily distinguishable. Its body forms a 45-degree angle against the stem when feeding.

The first psyllid found in California was in the greater San Diego area in 2008. The pest was then found to the east in neighboring Imperial County.

Morse expressed concern for the desert citrus industry; not so much about the potential spread of HLB from L.A. south into the desert. He believes the disease will eventually move north from Mexico where it is spreading into the desert areas.