Canadian Forestry Services plans release of Chinese wasps to attack emerald ash borers

Tetrastichus wasp

SAULT STE. MARIE—Scientists in Sault Ste. Marie are growing their very own Chinese parasitic wasps in the battle against the invasive emerald ash borer (EAB) with the hope of releasing between 10,000 and 12,000 of the tiny insects over the summer months.

The wasps, called Tetrastichus, are not new to Ontario or the Canadian Forest Service that oversees their release, but this is the first time the wasps have been bred in Canadian captivity.

The Expositor caught up with Krista Ryall, a research scientist with the Canadian Forest Service who works at the Great Lakes Forestry Centre in Sault Ste. Marie, at a Toronto airport Monday. Ms. Ryall was en route to Delaware where she will be meeting with other entomologists specializing in the Chinese wasps who find emerald ash borers a tasty treat.

For the past few years, the United States Forest Service has been supplying their Canadian counterpart with two different types of Chinese wasps that specialize in seeking out and destroying EAB larvae.

Ms. Ryall confirmed with the Expositor that the Great Lakes Forestry Centre was able to rear some of its own wasps last week. These and more will be released over the summer in yet-to-be-determined locations in Ontario, along with the American-bred wasps.

She explained that the female wasps work by seeking out EAB larvae, boring through ash bark and laying their eggs (up to 60 of them) on EAB grubs. When the eggs hatch, they eat the grubs and emerge as new baby wasps. The wasps are only a couple of millimetres in size and pose no threat to humans, Ms. Ryall assures. “They’re like the size of an ant,” she added. “They’re not big yellowjackets or anything like that.”

Chinese wasps were imported to do the job as EABs are themselves an invasive insect with no North American enemies. There are two Chinese wasps that have been approved for use in Canada and the United States and another Russian wasp that is pending approval by the Canadian government. The Russian wasp, Ms. Ryall explained, survives colder climates.

The Canadian Forest Service had not yet picked out the spots for the release of the Tetrastichus, but guessed Algoma would be a spot as it is rich in ash trees and has an outbreak of EAB. When asked if Manitoulin would be under consideration, Ms. Ryall said she would look into the status and said the island could be put forward for consideration for a wasp release.

“They’re very EAB specific,” Ms. Ryall reiterated. “She knows what she wants,” she added of the female wasp.

Ms. Ryall said people need to realize that this is a long term project. “It’s important to note that it could even be several decades” before results for future ash trees are seen. “It’s not an overnight solution.”

The scourge of the EAB continues to spread across the province, largely through human movement of infested materials, such as firewood.

“Every year they (EAB) continue to find new areas,” Ms. Ryall said. “In 2016, EAB was found in Thunder Bay for the first time and it had likely been there for a couple of years before it was discovered.” It’s now in Quebec too.

According to Natural Resources Canada, within six years of EAB infecting a woodlot, more than 99 percent of the ash trees will be killed.

EAB was confirmed on Manitoulin in the fall of 2013.