Western blackheaded budworm

Distribution

British Columbia

British Columbia

Micro-habitat(s)

Bud, Needle

Damage, symptoms and biology

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The western blackheaded budworm is among the most destructive defoliators in coastal British Columbia.

During outbreaks, severe defoliation occurs in the tree crown. In extreme situations the entire tree may be defoliated. Severe defoliation may result in top-kill or tree mortality in young trees, especially in the exceptional case of an outbreak continuing more than two years in one location.

Eggs are laid singly on the underside of needles in late summer. Larvae hatch the following spring and are greenish in colour and measure up to 18 mm at the end of their development. The head is black in the initial stages and turns brown in the last stage. Larvae feed on expanding buds and web needles together to form protected feeding shelters. Western blackheaded budworm prefer to feed on current-year's foliage but during outbreaks will feed on old foliage after the new foliage is consumed. Larvae pupate on the twigs within a web made of dead needles in late summer. Adults emerge 2 to 3 weeks later and have diverse color patterns on their forewings.

Life cycle (West of the Rockies)

Other information

Extensive, periodic outbreaks have occurred in western hemlock forests in coastal BC and the Pacific Northwest at approximately 10 to 15 year intervals. The most recent outbreaks have been restricted to Haida Gwaii and adjacent coastal forests.

Main host(s)

Amabilis fir, grand fir, mountain hemlock, subalpine fir, western hemlock

Secondary host(s)

Black spruce, Douglas-fir, Engelmann spruce, Rocky Mountain Douglas-fir, Sitka spruce, white spruce