Douglas-fir Tussock Moth

The Douglas-fir tussock moth is a destructive native defoliator of Douglas-fir. This moth kills trees, and the caterpillars' hairs are a serious human health risk.

Outbreaks occur every 10 to 12 years, causing significant damage and mortality to Douglas-fir stands in B.C.'s interior. These outbreaks tend to last up to four years before natural controls such as predators, parasites, pathogens and starvation lead to population collapse.


Douglas-fir Tussock Moth outbreaks can cause extensive mortality of interior Douglas-fir.  The outbreaks are usually located in low elevation Douglas-fir stands.  Aside from the loss of timber value, outbreaks are often on private land causing great concern to landowners for the health of their trees. As well, outbreaks can harm people allergic to the caterpillars' hairs. 

Biology & History

Outbreaks begin as localized epicentres, spreading and coalescing into larger areas of defoliation. They occur only in low-elevation stands.


Successful management depends on carefully monitoring populations within high-hazard stands during the non-outbreak and building phases. Once the outbreak begins, viable treatment options decrease significantly.

Information for landowners on spray programs, protecting trees and preventing spread.

Management Programs

Treatment programs have been conducted to manage the damage caused by the Douglas-fir Tussock Moth.

Under B.C.'s Integrated Pest Management Act, defoliator spraying in B.C.'s forests must be authorized by the B.C. Government through an approved pest management plan.