It’s a case of fighting fire with fire.
The emerald ash borer was found in the USA near Michigan in 2002, suspected of having hitch-hiked a ride from northern China in wooden shipping crates. And now, importing tiny wasps, the natural EAB predator from northern China, is being touted as the way to slow down the spread of the beetle.
The Canadian Food Inspection Agency has approved the release of two species of stingless Chinese wasps in Canada as biological control agents in areas infested by the emerald ash borer. The wasps deposit their eggs on the larvae of emerald ash borers, and after hatching, the young wasps feed on the host larvae, killing them.
Canadian approval follows extensive testing by the US Department of Agriculture’s Northern Research Station and the University of Michigan.
At this point, CFIA says it is releasing only one of the approved wasps, the Tetrastichus planipennisi, under controlled conditions.
The first batches of Chinese wasps were released at an experimental site in Huron County in southwestern Ontario in June, with more releases in the same area to continue throughout the summer.
According to CFIA, the wasps “were introduced in blocks of ash wood which contained wasp pre-pupae already inside them. The blocks were suspended from EAB-infested ash trees at experimental sites on June 4, 2013. The wasps will emerge from the larvae and fly off in search of other EAB to target.”
The release of a new foreign species into Central Canada and the American Midwest has raised concerns of environmentalists who fear the wasps will create a new set of problems. However, CFIA says that T. planipennisi is very species-specific, and is not considered a threat to native species.
A third parasitic wasp from China was approved for use in the US, but CFIA has not approved it for use in Canada as it cannot withstand Canadian winters.
American researchers turned to the Chinese parasites when wasps and other predators native to North America proved ineffective at stopping the spread of EAB.
Native parasitic wasps used in test conditions made little inroad on EAB larvae, with a kill-off rate of less than one percent. Enthusiastic woodpeckers did better, but still only managed a 17-percent kill-off.
The emerald ash borer has devastated ash stands in parts of Ontario and Quebec, and the biggest concern in Canada is stopping the continuing spread of the beetle. The most common ways of spreading EAB is through the transporting of infested ash firewood, nursery stock and timber.
CFIA says it is continuing to work closely with the provincial governments in Ontario, Quebec and Manitoba to manage the threat of the emerald ash borer.
Source: The Manitoba Woodlot, Issue 100, Summer 2103, page 5
