The Canadian Forest Service announced Wednesday it is releasing parasitic wasps in Ontario and Quebec this week in an effort to control the population of emerald ash borers.

Krista Ryall, a research scientist for the Canadian Forest Service, told CBC News that 1,600 of the non-stinging wasps native to China are meant to combat the emerald ash borers that have killed ash trees in more than 260,000 hectares of Ontario forests.

Emerald ash borers, also a native to China, were accidentally introduced to North America two decades ago, likely through unsecured shipping crates involved with international trading, says Ryall.

The CFS says emerald ash borers kill up to 99 per cent of ash trees in infested areas, because they have no natural predators here.

"When the species was introduced to a new environment, it found no natural enemies," says Ryall.

Not anymore, it seems.

NH Invasive Bug

Emerald ash borer larva are removed from an ash tree at in Saugerties, N.Y. (Mike Groll/Associated Press)

'It's a fairly long-term project'

Although 1,600 wasps have been released this time around, Ryall says CFS will release wasps nine times over the summer and have already released tens of thousands since 2013, when efforts to curb the population of emerald ash borers first started.

The wasps were supplied by the U.S. Department of Agriculture, after an environmental assessment was conducted to ensure the wasps will adapt to the climate and not impose undue environmental risks.

Oobius agrili non-stinging parasitic wasp fights emerald ash borer eggs

One species of the parasitic wasps released, the Oobius agrili, will lay eggs inside the eggs of the emerald ash borer. (Houping Liu/Michigan State University)

One species of the wasp, the Oobius agrili, will lay their eggs inside the eggs of the emerald ash borer and consume the larva from the inside, eventually emerging from the egg as an adult wasp.

Another, the Tetrastichus planipennisi, inserts its larva into the larva of the beetle, which, when they hatch, consume the ash borer larva. They are released across 12 locations in southern Ontario — including Ottawa, London and Newmarket — and three locations in Quebec, one in Gatineau and two in Montreal.

Ryall says progress has been made, but adds the process to control emerald ash borers will take time.

"It's a fairly long-term project," she says. "Could be decades."