How Arizona Has Avoided HLB

Although the Asian citrus psyllid (ACP) is found in Arizona at very low levels, the devastating huanglongbing (HLB) disease, also known as citrus greening, is not.

John Caravetta, associate director of the Arizona Department of Agriculture (AZDA), discussed successful efforts to control the psyllid and prevent HLB from infecting orchards.

Caravetta reported that “AZDA is conducting trapping for ACP in commercial citrus orchards and nurseries, and both AZDA and PPQ are conducting visual surveys statewide in all citrus-production areas including residential landscapes.” PPQ is the Plant Protection and Quarantine program of the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service.

“The prevalence of ACP is very low in Arizona with nine ACP detected in AZDA traps in 2019,” Caravetta said. “These are blunder traps and less effective in very low population scenarios, therefore we also incorporate visual surveys to detect any infested trees.”

An aggressive coordinated spray program has helped keep psyllid levels low. “The Yuma Citrus Pest Control District, covering most of the geographic area of Arizona’s commercial citrus production acreage, established a CHMA (citrus health management area) to coordinate control activities,” Caravetta reported. “The well-over 90 percent participation rate has kept the region’s ACP populations to near undetectable levels as a result of these coordinated spray activities.”

In 2019, AZDA tested more than 6,400 citrus trees for HLB, and all samples were negative “and continue to be,” Caravetta said. “PPQ has also contributed to these numbers, which include tissue as well as ACP samples. Trees statewide are identified for sampling, whether in commercial or residential situations, based on symptomology, presence or absence of psyllids on the tree or in the area, and also to fill in any data gaps on trees not yet sampled. The USDA guidance for sampling trees and creating composite samples for analysis is followed, as other citrus-producing states are doing. Additionally, we are refining root sampling procedures to add a further analytical step should any trees have less than definitive negative results from the leaf tissue PCR analysis.”

If any tree is found infected with HLB, it and the orchard it is in will be destroyed, according to Caravetta. “AZDA will work with the public and industry partners to affect eradication of the disease if detected,” he said. “This three-way partnership has worked very well in achieving the results Arizona has experienced so far.”

Caravetta said the HLB-spreading ACP don’t seem to do as well in Arizona as they do in Florida. “And we get some significant help from Mother Nature over the summer period, when the populations do not thrive,” he added. “Additionally, our psyllid numbers are very low as we began with a very aggressive psyllid control effort aimed at eradication initially when the insect was first found in October of 2009, keeping populations from gaining a significant foothold from the inception of the incursion forward.”