Natural Resources Canada’s Canadian Forest Service (CFS) scientists are hoping to fight nature with nature by growing parasitic wasps that target and attack the emerald ash borer.
The emerald ash borer (EAB) is a devastating invasive beetle which has killed millions of ash trees in Canada and the United States since it was discovered here in 2002. In response to this threat, CFS is partnering with its U.S. counterparts in a classical biological control program against this invasive pest in an attempt to limit or slow its continued spread and impact in Canada.
After conducting surveys in the native range of EAB in China and Russia, the U.S. Forest Service (USFS) and the Animal Plant Health Inspection Service (APHIS) selected four species of parasitic wasps for release in North America against the borer. The tiny wasps are known technically as “parasitoids” because they end up killing the host insect on which they feed. Early results in the US are promising, with fairly high establishment rates of at least two parasitoid species and a reduced rate of growth of EAB populations.
Researchers at the Great Lakes Forestry Centre (GLFC) in Sault Ste. Marie, ON, have developed a strong international collaboration with the USFS and APHIS on this urgent issue. In 2013, scientists from GLFC began importing two species of these parasitoids into Canada and have released them at sites infested with EAB across Ontario and Quebec. Over 80,000 wasps have been released since 2013. Preliminary results have found that at least one of the two species of parasitoid has a high rate of establishment and recovery from release sites.
Since December 2016, the GLFC Insect Production and Quarantine Laboratories (IPQL) has initiated a rearing program to grow one of the parasitoid species in the laboratory to augment numbers available for release in the affected area in Canada. This wasp, known only by its scientific name Tetrastichus, inserts its eggs through the bark and onto the EAB grub feeding under the bark. The first batch of these “Made in Canada” wasps began to emerge just this week. Our goal for 2017 is to produce enough wasps to establish at least six new release sites across Ontario and Quebec, requiring at least 12,000 wasps.
Long-term research is ongoing to evaluate the ability of the wasps to reduce EAB populations and protect ash trees. Moreover, these parasitoids are very targeted in their approach, and are specialists in attacking their natural host, EAB. They do not sting or pose a threat to humans.