Putting emerald ash borer in its place: Sault forestry centre rearing wasps to combat destructive beetle.

• Author: Kelly, Lindsay
• Position: Forestry

As the emerald ash borer (EAB) continues to devastate ash tree populations across the province, researchers at the Great Lakes Forestry Centre (GLFC) in Sault Ste. Marie believe they may have found a way to effectively combat the ravenous beetle--using a species of tiny wasp that originated in China.

Since 2013, more than 80,000 of the Tetrastichus planipennisi wasps--which measure no more than 4 millimetres in length--have been released by the GLFC at selected sites in Ontario and Quebec.

Dr. Krista Ryall, a forest ecological entomologist with the GLFC's Insect Production and Quarantine Laboratories (IPQL), said EAB is the only known food source for the wasps, which don't pose a threat to humans or native insect populations.

"The female wasp lays her eggs in the larva of EAB, and then they develop inside the larva and they eventually kill it and emerge," Ryall said. "We call that a parasitoid."

For the last three years, the GLFC has been working closely with the U.S. Forestry Service and the Animal Plant Health Inspection Service (APHIS), which originally did the research and brought the wasps over from China.

The American researchers have donated tens of thousands of wasps to the GLFC to release at sites in southern Ontario, Quebec, and eastern Ontario. The sole Northern Ontario site selected for the project is on St. Joseph Island, outside Sault Ste. Marie.

But the GLFC's work turned a new corner this past spring when researchers reported success, for the first time, in rearing the wasps, in the lab, on their own.

In the lab, small pieces of ash logs--researchers call them mini bolts--are artificially implanted with EAB eggs, which then hatch into larva that will feed on the ash. The wasps are then introduced and encouraged to feed on the EAB larva for about a week.

From there, the researchers can put the bolts into cold storage for up to five months, until they are ready to introduce the bolts to a site. Once the bolts are hung at a site, the wasps finish their development under the bark of the bolt and chew their way out, emergeing into the field.

Though it might sound like a straightforward process, Ryall said it's exacting work.

"Even with all (the U.S. researchers') detailed instructions, it's very challenging," Ryall said. "This is a very finicky system to work with, and if the wood's too dry or too wet, or too hot or cold, nothing will rear and everything dies."

There are still a lot of unknown factors, such as how many wasps need...