Keeping the Legacy Alive

Biocontrol Research in Canada

Biocontrol of the Hemlock Woolly Adelgid in Canada

Classical biological control (biocontrol) takes natural enemies from the native range of HWA (Pacific Northwest, Asia) and introduces them to the invaded range of HWA in eastern North America. Predatory insects from HWA’s native range are the best bet for control of HWA in eastern North America, but before release in eastern Canada, rigorous testing must occur to make sure that the risk they will attack non-target species is low.

For biocontrol to stand the best chance of working in Canada, the predators must attack both generations of HWA (sistens, progrediens) and they must be able to tolerate cold winter temperatures. Research in the United States shows that several predator species are able to tolerate cold winter temperatures in the HWA invaded regions of Canada. Biocontrol is a long term, costly solution for protecting what remains of Canada’s eastern hemlock resource. A significant investment in infrastructure is critical for the mass production of predators.

Laricobius nigrinus beetle and the Leucopis silver fly

The beetle Laricobius nigrinus and the Leucopis silver flies complement each other since they feed at different times of the year. The beetles are fall-feeders, reducing the populations of sistens-generation HWA that will survive to lay eggs of the year’s second HWA generation. The silver flies are spring-feeders that eats the eggs of HWA’s second generation to reduce the amount of individuals that will hatch. Reducing both the amount of egg-laying HWA and hatching HWA  helps protect hemlock twigs from the damage of HWA feeding. 



To learn more about biocontrol, visit our resource page.