A biological control agent of a common peach tree pest may be an effective alternative to chemical applications, if U.S. Department of Agriculture entomologists can make it economically worthwhile for large-scale commercial growers.

USDA-Agricultural Research Service entomologists at the Southeastern Fruit and Tree Nut Research Laboratory in Byron, Ga., are studying the implementation of entomopathogenic nematodes on the peachtree borer and lesser peachtree borer to determine the optimum level of application and formulation for effective control.

“In small field plots, we demonstrated that the nematode Steinernema carpocapsae can control peachtree borer damage at levels similar to that of recommended chemical insecticide treatments, and that application costs are likely to be highly economical,” said USDA-ARS research entomologist David Shapiro-Ilan.

“The primary challenge that remains is to determine how best to apply the nematodes at a commercial scale so growers can adopt the practice.”

Shapiro-Ilan received a $226,100 Southern Sustainable Agriculture Research and Education Grant (SARE) to study the best and most economical application methods in large-scale orchards.

Other research participants include USDA research entomologists Ted Cottrell and Robert Behle; University of Georgia assistant professor Greg Colson; University of Georgia professor Dan Horton; USDA research chemist Christopher Dunlap; University of Florida-North Florida Research and Education Center professor Russ Mizell; and Georgia peach grower Sean Lennon.

Previous USDA-ARS research has found that entomopathogenic nematodes are effective in controlling, on a small scale, the peachtree borer and lesser peachtree borer — two pests whose feeding can injure trees, invite pathogens, and cause a decline in fruit productivity. Eventually the pests will kill the tree.

“The nematodes are the coolest organisms on the planet,” said Shapiro-Ilan. “They share a mutualistic relationship with a bacterium that lives inside of them. And when they attack the peach tree pests, they release the bacterium that kills the insect and provides the nematode and the bacterium with a food source.

“In addition, the nematodes are host specific and are not harmful to the environment or other beneficials.”

Shapiro-Ilan said the entomopathogenic nematodes, soil-borne organisms, are most effective in controlling the peachtree borer, whose larvae feed on underground tree roots at the base of the tree during the spring.