Canadian researchers rearing new parasitic wasp to fight emerald ash borer

emerald ash borer

A new type of parasitic wasp is the latest weapon to be used in the fight against the emerald ash borer.

To combat this invasive species, researchers at the Great Lakes Forestry Centre in Sault Ste. Marie are rearing a new type of wasp—typically found in China—that will be used against the borers.

Ten to twelve thousand of these wasps, which are known as Tetrastichus, will join the American and Chinese wasps that were released in 2016 for the same purpose. According to reports, the first batch of these “made in Canada” bugs is expected to emerge this week.

“What we’re hoping is that, over the long term…it could be decades…that as you have new ash regenerating, hopefully you’ll have these wasps present and keep the emerald ash borer at a lower level,” Dr. Krista Ryall, a forest ecological entomologist with Natural Resources Canada, told CBC.

Ash tree killed by emerald ash borer. Photo by K Steve Cope/

The emerald ash borer is native to China and is believed to have come to North America about 20 years ago through imported wood products. Since then, the insect has killed millions of ash trees in parts of the United States and Canada, which includes forests in Southern Ontario and around the Great Lakes.

 According to Ryall, the female Tetrastichus wasps will search the ash tree’s bark for the larvae of an emerald ash borer. Once the wasp senses the larvae that’s destroying the tree underneath, it will drill a hole through the bark and lay eggs onto it—a practice that’s been known to cause mortality in emerald ash borer populations overseas.

Eventually, the wasps will be spread across six sites in Ontario and Quebec. Ryall assured reporters that the wasps’ presence shouldn’t alarm anyone, as they don’t bite or sting.

“They’re not like wasps that most people would think of,” she says. In fact, the emerald ash borer is the one and only host that this parasite is looking for, which is one reason Ryall says they’re considered safe to release into the environment, despite the fact that they’re also a foreign a species.

“[It] doesn’t attack any other insect species, or have any other human health risks.”