Researchers step up efforts to exterminate ash borers

CHAMPAIGN – Don't give up on America's ash trees yet.

Even though an imported beetle poses grave danger to them, scientists are exploring solutions that, in time, may slow or stop the ravaging of the trees.

University of Illinois Extension entomologist Phil Nixon recently collaborated with other Midwestern experts to prescribe pesticides to deter the so-called "emerald ash borer."

Meanwhile, scientists are contemplating other ideas, such as bringing in parasitic wasps and breeding resistance into ash trees, as other possible long-range solutions, Nixon said.

The beetle, first spotted in the Midwest in 2002, is believed to have come into the Detroit area when wood products were shipped there from Asia.

It has since spread from Michigan to other states, including parts of Ohio, Indiana, Illinois, Wisconsin, Kentucky and Missouri. In Illinois, the pest has been detected primarily in the northeastern part of the state.

The sightings closest to Champaign-Urbana have come in McLean County, with "small numbers" seen in Bloomington and a "heavy" presence in Chenoa on the county's far north side, Nixon said.

Chenoa "has one of the highest infestation rates and possibly the oldest," even though the beetles weren't spotted there until 2008, he said.

Even though some of the heaviest damage is there, the beetles seem to have been contained since Chenoa is surrounded by corn and soybean fields, Nixon said.

"Outside Chenoa, ash trees are few and far between," Nixon said, noting that beetles would have to fly a half-mile on their own.

"They would have to pack a lunch to get to the next ash tree," he quipped.

The beetle destroys ash trees by devouring the layer under the bark.

That disrupts the tree's ability to transport water and nutrients, according to, an Illinois Department of Agriculture Web site devoted to the pest.

Nixon said UI Extension is now recommending that a pesticide known as emamectin benzoate (sold under the trade name "Tree-age") be injected into the trunk of ash trees every other year.

Previously, researchers had recommended applying Imidacloprid (an insecticide sold under the trade name "Merit") annually, either by injecting it into the surrounding soil or applying it as a "soil drench," he said.

The new recommendation calls for applying emamectin benzoate to ash trees within 15 miles of an emerald ash borer sighting. So while it might be wise for McLean County tree owners to have the pesticide applied, it's a little too soon for folks in the rest of East Central Illinois to do so.

However, "it wouldn't hurt to be thinking about it," Nixon said.

Emamectin benzoate, though, needs to be applied by an arborist or landscaper who offers that service to customers, he added.

Property owners who want to apply pesticide themselves would have to use the soil-drench product, which is available at garden centers under the name Bayer Advanced Tree & Shrub Insect Control. Nixon said if it's applied within a 2-foot radius of the trunk, it provides protection for a year.

Nixon said "Merit" gives about 80 percent to 85 percent control of the insect, while "Tree-Age" gives 98 percent to 99 percent control.

Given the rapid spread of the beetle, it will be difficult to preserve ash trees. But Nixon said, "There's always hope when there's life."

"Certainly individuals can protect ash trees. But it's hard to protect trunks that are more than a foot in diameter," he said. "The bigger the tree, the more likely it is someone will want to save it. But you're looking at an annual or every-other-year cost, forever."

The long-term solution to the beetle will probably come from "some other direction," such as bringing in parasitic wasps from China that attack the beetle, Nixon said.

The wasps, which are "half the size of a pinhead," were released last year in Michigan and last week in Evanston and Chicago, he added.

Researchers in Ohio and Michigan and at the Morton Arboretum have been studying Asian species of ash trees and trying to figure out how resistance can be bred into American ash trees, either through traditional crosses or gene implementation, he said.

Meanwhile, scouts are once again on the lookout for the beetle, with the number of traps in the Champaign-Urbana area approximating the number from last summer.

In East Central Illinois, it's up to local municipalities, not the state, to set up the traps. Area communities taking part in the program include Champaign, Urbana, Rantoul, Danville, Hoopeston, Paxton, Gibson City, Charleston, Paris, Watseka and Crescent City, as well as the Champaign County Forest Preserve District and the Vermilion County Conservation District.

Champaign Arborist Bill Vander Weit said about 25 traps have been set up in the Champaign-Urbana-Savoy area, mostly duplicating the locations where traps were set last year.

The three-sided purple traps are treated with manuka oil to lure the beetle, and their surfaces are coated with a sticky material to trap the insect. The beetle's flight season runs from May to August, and the traps will be picked up from communities by Agriculture Department officials after the Illinois State Fair in August.

When traps were checked in previous years, agriculture department officials found all sorts of things inside – including grass clippings, leaves and parts of squirrel tails, said Juliann Heminghous, the department's outreach coordinator for emerald ash borer.

"We even had a salamander one time," she said. "They were able to free him and let him go. He saw a buffet of bugs."

Vander Weit said the beetle has been found in 13 states, with Minnesota, Kentucky and New York added this year. He's glum about prospects for halting the spread to Champaign-Urbana.

"The fact we haven't turned anything up yet isn't really reason for optimism," he said. "From our perspective, it's a matter of when, not if."

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