The state of Minnesota is trying to use a foreign species of wasp to delay the spread of the emerald ash borer — a pest that is also a potential threat to thousands of ash trees in Thunder Bay's urban forest.

An invasive species specialist with the Minnesota Department of Agriculture said the "stingless" wasp, brought in from Asia, eats the larvae of the emerald ash borer.

Monika Chandler

Monika Chandler, an invasive species specialist with the Minnesota Department of Agriculture, said the "stingless" wasp eats the larvae of the emerald ash borer. (

But it may be less effective in areas where the weather is more severe.

"What we've learned from laboratory studies is that we think the parasitoids will establish in the southern part of Minnesota, but we are very worried about very cold areas of northern Minnesota,” Monika Chandler said.  

Chandler said more than 130,000 of the tiny wasps have been released in Minnesota at more than 20 sites, in the twin cities of Minneapolis and Saint Paul, and in more southern portions of the state.


The green emerald ash borer was first detected in Detroit, Mich. in 2002 before moving to Toronto, where they are blamed for the deaths of thousands of ash trees. (David Cappaert/Michigan State University)

"We're part of a national program. So our United States Department of Agriculture did the field work in Asia, where the Emerald Ash Border is from … to identify insects that control emerald ash borer in its native range,” Chandler said.

"There was a long testing process before the wasps, in this case, could be permitted for release in the United States."

The watch is on for the emerald ash borer in the Thunder Bay area but, so far in Ontario, the insect has only been found as far north as Sault Ste. Marie.

stingless wasp infographic