Some Florida citrus growers are experimenting with supplemental chemical controls to suppress Asian citrus psyllid populations.
They're adding perimeter, or wrapping, sprays aimed at psyllids in between regularly scheduled major pesticide applications over their entire groves. Focusing on borders and other hot spots can provide a quick and less expensive check to pest populations, says Michael Rogers, associate professor of Extension Center in Lake Alfred.
"Psyllids tended to accumulate on the outside of the grove," Rogers says. "Probably 80 percent of psyllids are found there."
Spraying only the outer edges allows applicators to cover more area in the same amount of time, making a broader swath to keep out fly-ins, says Frank Youngman, owner and president of Florida Grove Foggers in Lake Placid.
"If we can wrap four to five groves at a time, it creates a bigger buffer," Youngman says. "It's harder for [outside] psyllids to fly over."
Scout your groves to guide your decisions, says Brandon Page, Citrus Health Management Area program assistant at the university's Lake Alfred center. "If you're finding most [of the psyllids] on the edges and none in the center, you probably want to do perimeter sprays," he says.
But all three men emphasize that perimeter spraying should only supplement a full control program and not replace major overall sprays.
"It's a preventive practice to keep psyllids from moving in, but eventually they're going to get there," Page says.
By helping to hold down overall psyllid numbers, the entire control program has a better shot at slowing the spread of greening, the key disease that the pest vectors, Rogers says.
"It's not as expensive and can take the edge off the population between the big planned sprays," he says.
Part of a larger puzzle
A test of the practice in one grower's groves showed perimeter spraying reduced psyllid numbers by 70 percent to 80 percent between full-grove applications. Follow-up sprays are more effective because they're targeting lower populations, Rogers says.
Scouting reports across the state show a large drop in psyllid populations, Youngman says. But he attributes that to the combination of all the measures growers are deploying against the pest, with perimeter sprays only one piece of the puzzle.
A high percentage of the psyllids found in Florida are infected with the bacteria that causes greening, he says.
Holding down the populations and keeping the pest from traveling from one grove to another will reduce the rate of new tree infections.