The emerald ash borer is a serious threat to North America’s ash trees, but an infestation isn’t a death sentence.
Steps can be taken to preserve trees, said Dan Herms, an entomologist at Ohio State University’s Ohio Agricultural Research and Development Center.
Treating ash trees is difficult, but insecticides are available that are sometimes effective, according to Insecticide Options for Protecting Ash Trees From Emerald Ash Borer, a publication Herms wrote with colleagues from Michigan State and Purdue universities and the universities of Wisconsin and Illinois.
Insecticide treatments work best if they’re started when the tree is still relatively healthy, the publication says. Homeowners can treat trees preventively before they show signs of infestation, but the authors don’t recommend doing so until the borer has been found in the county where the tree is located or within 15 miles of the tree.
The website http://ashalert.osu.edu has links to infestation maps, along with other information on dealing with the insect.
Insecticide treatments need to be repeated periodically, although the costs and methods involved are changing as research progresses.
Most insecticides are for professional use and are either injected or poured onto the soil, injected into the trunk or sprayed onto the bark or leaves. One insecticide, imidacloprid, is also available for homeowner use under the name Bayer Advanced Tree & Shrub Insect Control. It’s most effective on smaller trees, Herms said.
What doesn’t work, he said, is cutting down healthy trees in an attempt to slow the insect’s spread. That approach was sometimes suggested when the insect was first discovered here, but it’s ineffective, Herms said. The insects just fly farther to find trees.
— Mary Beth Breckenridge