“That means you’ve got a full life cycle and that they’re breeding,” he says.
Meanwhile, a similar eradication effort is underway in northern Baja California and Sonora, where the U.S. Department of Agriculture is assisting Mexican authorities as they place traps and spray suspect trees. A total of 280 psyllids have been found just south of the international border since last June. The United States has supplied $1.2 million to the Mexican extermination project, and on April 29 and 30 officials from Mexico’s citrus industry will meet in San Diego with United States industry stakeholders to discuss further cooperative strategies that might stop the spread of the Asian citrus psyllid. Officials have pointed out that only a collaborative effort can prevent a disaster.
According to Lyle, commercial citrus operations are expected to address their own infestation problems, but the two most effective pesticides — Merit and Tempo — pose a dilemma for farmers like Al Stehly. Stehly manages 200 acres of certified organic oranges, lemons, and grapefruit near Valley Center, and a single application of either pesticide to his trees will result in withdrawal of certified organic status by the United States Department of Agriculture.
“Maybe what this means is that we’ll no longer have organic citrus in California,” says Stehly, who plans to wait until absolutely necessary to treat his orchards.
Currently, Stehly practices “integrated pest management,” a system designed to eliminate most harmful insects, but not all.
“The idea is to knock them down and allow the beneficial insects to prey on the remainder, but citrus greening is a new one for agriculture,” he explains. “It only requires a single insect to transmit the disease, so you can’t leave 5 percent of the psyllids for other insects to eat. Just one psyllid can kill your entire orchard if it’s got the bacteria.”
Developing disease-resistant citrus varieties would be ideal, says Stehly, but not if it took genetic modification to get there.
“Again, that would mean organic farmers couldn’t use it.”
The Citrus Research Board’s Batkin says that isolating a variety of citrus naturally tolerant of the huanglongbing bacterium is a very likely possibility — but not an answer.
“The goal is not to find a tolerant variety, but to find a solution that we can apply to all the trees to save all the varieties.”
Finding a disease-resistant lime, for example, would not save the orange industry, Batkin points out.
Batkin, too, is an organic farmer, and he concedes that the Citrus Research Board and other investigators have made little to no progress in developing organic sprays effective against the Asian citrus psyllid.
Stehly says that in the worst-case scenario, he and other farmers — organic or not — might have to invest in new crops.
“I’d be lying if I said I wasn’t already looking at alternatives to citrus. Wine grapes are a possibility out here. And houses. That would be a good crop.”
In spite of the quarantine levied against San Diego and Imperial counties last summer, 17 Asian citrus psyllids were discovered in early March near Niland, in northern Imperial County. The quarantine zone was subsequently edged northward to include part of Riverside County, but this abrupt jump reveals just how easily a moderate breeze could dash all efforts to control the psyllid. Exactly how the insect first arrived in Tijuana and San Diego no one knows, but the likelihood is very real that the disease is already here. That would give the industry several years before the first branches turn yellow and the first fruits go blotchy green.