Another Weapon Found for Emerald Ash Borer Arsenal

  • Pin It

Valuable landscape ash trees may now be protected from emerald ash borer (EAB) with a new insecticide called emamectin benzoate.

MSU research showed that the new product, which will be sold as Tree-ägeT, was “remarkably effective” in controlling EAB, said Deborah McCullough, MAES forest entomologist and EAB researcher. The Michigan Department of Agriculture (MDA) approved a special registration for the product for use in ash trees for controlling EAB. It has also been used on fruit and vegetable crops.Researchers study the emerald ash borer

“The results from 2007, our first year of research with the product, were dramatic,” McCullough said. “We had seen some preliminary tests with the product and thought it might work, so we set up research trials in three sites in May 2007.”

The researchers looked at the mortality rate of adult EAB beetles that were caged with leaves from emamectin benzoate-treated trees, trees treated with other insecticides and non-treated trees. They repeated the trial three times during the summer. In all three trials, leaves from the emamectin benzoate-treated trees killed all the beetles. In contrast, at least 70 to 80 percent of the beetles survived on the untreated leaves, and no more than 80 percent of the beetles died when they fed on leaves from trees treated with other products.

Last fall, some of the emamectin benzoate-treated ash trees were felled and debarked to see how many EAB larvae were feeding on each tree. The emamectin benzoate-treated trees showed more than 99 percent fewer larvae than untreated ash trees.

Though the results are promising, McCullough cautions that more study is needed.

“This is only one year’s worth of data, so the study will continue,” she said. “This year we will treat some of the trees again, but others won’t be treated so we can see if emamectin has to be applied every year or every other year.”

Entomologist Therese Poland, from the U.S. Department of Agriculture (USDA) Forest Service, is assisting with the study, and Phillip Lewis, from the USDA Animal and Plant Health Inspection Service, is measuring the amount of each insecticide product that is present in the ash leaves throughout the summer.

Emamectin benzoate can be purchased and applied only by trained, certified pesticide applicators, who inject the product into the base of the tree. To be effective, the insecticide must be transported by the tree up the trunk and into the branches and leaves. This means that the product will probably be most effective if the tree is still relatively healthy when it is treated. (EAB feeds on the tissues that transport nutrients up into a tree, so if the pest has already killed those tissues, it is too late to save that part of the tree.)

“This product affects insects that eat ash tree tissue,” McCullough said, “but it won’t hurt anything that lands or climbs on the tree, such as butterflies, birds and squirrels.”

“Though this is not a ‘silver bullet’ for eradicating EAB across the country, it could be a quantum leap forward in our ability to slow the spread of this deadly insect,” said Ken Rauscher, director of the MDA Pesticide and Plant Pest Management Division. “This product affords municipalities, homeowners and others the opportunity to save landscape trees, municipal park trees or other trees of value that would have otherwise received a death sentence because of EAB.”

Tree-ägeT will be available beginning May 14. Certified applicators can order it now.An emerald ash borer

“We are excited about this product’s possibilities,” McCullough said. “This could be a tool that we can integrate with our other options to slow the advance of EAB in newly discovered infestations.”

For more information on emerald ash borer, go to

Click to subscribe to our e-publications: