HLB was found in Mexico in 2009 in the Yucután Peninsula and has spread to several other areas.

“We need to keep an eye on Mexico,” said Jim Cranney of the Citrus Quality Council.

Preventive efforts include a two-year partnership with Mexico to tackle the pest and disease threat on an area wide basis. The Mexicans have large trapping programs underway. The U.S. is sharing technology to compliment local control efforts.

“We want to coordinate the suppression program in Sonora and Baja California including intensive ACP testing, nursery screening, and a tight movement of plants,” Cranney explained. “We want to build on the suppression efforts on the border and keep the pest bottled up in Mexico to prevent the spread.”

Insecticide control

The best way to keep HLB out of California is to eliminate or minimize the vector, says Beth Grafton-Cardwell, University of California, Riverside entomologist and director of the Lindcove Research and Extension Center located near Visalia.

“Many different insecticides have good efficacy against the Asian citrus psyllid including the pyrethroid group, the neonicotinoids, older groups of organophosphates and carbonates, plus new chemicals,” Grafton-Cardwell said. “All of these have the ability to kill one or more life stages of the psyllid.”

The best strategy for ACP control is to utilize two different insecticides, Grafton-Cardwell says. Nearly 100 percent of current insecticide treatments are in urban backyards as the insect is not currently found in commercial citrus.

A psyllid found in the backyard triggers an insecticide treatment with two products: cyfluthrin (Tempo), a foliar pyrethroid; and imidacloprid (Merit), a systemic neonicotinoid.

CDFA has used this one-two punch since the first psyllid was first found in California in San Diego County in Summer 2008. The insect was later found in Orange, Los Angeles, and Imperial counties which triggered quarantines.

Commercial citrus

“We expect the psyllid to move into commercial citrus,” Grafton-Cardwell predicts. Commercial growers have many available insecticides.

Of the foliar products, Grafton-Cardwell says pyrethroids are the best chemical class to kill the ACP. The neonicotinoid insecticide group is very effective in a systemic application. A problem lurking with some products in both groups is its broad spectrum component where the ACP and beneficial insects are both killed.

For now, the organic route for ACP control is limited.

“Organic insecticides have too short of a residual to be useful for eradication at this point,” Grafton-Cardwell said. “They do not knock down the population as low as the synthetics and lack a long residual so the animal pops back up quickly.”

The entomologist has an organic insecticide study underway where an oil is sprayed in the orchard. She is evaluating how frequent oil sprays could impact fruit quality and the tree’s growth characteristics. 

Grafton-Cardwell believes the ACP will move into commercial citrus in three phases. Phase One, which already occurred in Imperial County, involves finding several psyllids in a trap in a commercial orchard followed by insecticide treatments to suppress the infestation.

Phase Two would involve multiple site finds (backyards and commercial simultaneously) where area wide treatments would begin. Phase Three would involve psyllid finds less than nine months after previous finds. Continuous area wide treatments with up to three treatments per year could be required for insect suppression.

“In Phase 3, my initial recommendation for psyllids found in commercial citrus is to hit them hard immediately with the most effective chemicals using at least two different kinds,” Grafton-Cardwell said.