Ash borer battle under way

from the Evanston Review

July 16, 2009

Evanston and U.S. Forestry officials have turned to a parasitic insect, no larger than a poppy or sesame seed, as their new hope in the fight against the emerald ash borer pest.

Paul D'Agostino, city superintendent of Parks and Recreation, and Mark Younger, the city's arborist, were met by a crew from the U.S. Forest Service Wednesday near a stand of infected ash trees along the side of the Peter N. Jans Community Golf Course, near Isabella Street and Girard Avenue.

Forest Service official Leah Bauer joined them, toting a shopping bag that contained plastic cups, each holding 20 of the parasitic wasps.

Evanston was selected as one of two test sites for the experimental treatment -- Chicago is the other -- by the Forestry Department.

Bauer was pleased with the site selected by local officials; red dye marked the trees for easy identification.

"A nice cluster, so there's plenty of food," she said. "That's what we need, plenty of food."

The specialized wasps search the bark of ash trees for emerald ash borer eggs. The beetle larvae infect the trees and lead to their death.

The wasps are not dangerous to humans or animals, but in relation to the ash borer, "they tend to act more like predators," Bauer said. "They kill them."

Bauer took precise markings of the location of the trees where the wasps were introduced. Forestry officials will return to check out results.

City officials, who laid out the city's case as a site for the experimental treatment, are hopeful. Since the borer was discovered several years ago, the city has seen its ash trees go from 12 percent of the estimated 28,000 parkway trees, to probably closer to 10 percent at this point, said D'Agostino.

While its early in the process, the wasps have produced some good results in parts of Michigan, he said, which has been decimated by the emerald ash borer.

"It's great to have hope in a (form) of control that doesn't require pesticides," Younger said.

The treatment, however, may prove too late for older trees that show signs of advanced ash borer infestation. Still, Younger said, the parasitic wasps offer hope as an important prevention strategy in future years.