“The peachtree borer is a sitting duck,” said Shapiro-Ilan. “However, the lesser peachtree borer is more of a challenge to control, because the larvae attack the tree above ground.”

In the SARE-funded work, the USDA researchers are studying the best ways to apply the entomopathogenic nematodes for both pests.

“We’ve identified the applicable rate of nematodes at 300,000 per tree, but since there is no way of knowing which tree may or may not be infected, we have to apply the nematodes to every tree. When you are dealing with 1,000 acres of trees, that’s a lot to handle, from an efficiency and economic standpoint,” said Shapiro-Ilan.

One solution the researchers are looking at to control the peachtree borer is a microinjection irrigation system that allows growers to make multiple targeted applications at the spot of the infestation.

Another technology showing promise is a sprayer system that senses and applies nematode treatments just at the base of a tree trunk, eliminating overlap and waste.

For the lesser peachtree borer, the researchers are studying the effectiveness of a spray gel that could be applied to the tree.

“It’s important that whatever products we use protect the nematodes from desiccation and UV light, as the nematodes are sensitive to UV light and require moisture to survive,” said Cottrell.

Interest in using microbial biocontrol agents continues to increase due to increasing limitations of chemical applications.

For example, growers are allowed a limited number of applications per year of the broad-spectrum pesticide chlorpyrifos, which is commonly used to control both the peachtree borer and lesser peachtree borer.

For lesser peachtree borer, insect activity in the orchard from March through November far exceeds the residual activity of the applied insecticide.

“When the peachtree borer goes through one or two generations per year, and the lesser peachtree borer goes through three or more generations, that insecticide application won’t last long,” said Cottrell.

“This is the opportune time for us to find an alternative to controlling these pests which is just as effective as chemical applications,” said Shapiro-Ilan.

The biggest challenge the researchers face is the technology transfer — putting in growers’ hands a new method whose inputs would be economical, as well produce a profitable end result.

“We are on our way,” said Shapiro-Ilan. “We’ve found that the cost of applying the nematodes may be as low as $15 an acre, which is similar to current pesticide applications (about $12 an acre). That could be the cheapest nematode application in any commodity.”

For more information on the project, “Enhancing Natural Enemy Systems: Biocontrol implementation for peachtree borers,” visit the national SARE projects database and refer to project number LS11-241.