Western Blackheaded Budworm, Acleris gloverana

Fig. 5   Mature western blackheaded budworm larva and webbing.	Fig. 6  Western blackheaded budworm only partially consumes needles.	Fig. 7   Hemlock stand defoliated by western blackheaded budworm.
Fig. 8   Western blackheaded budworm often defoliates the upper crown first	Fig. 9   Western blackheaded budworm initially feeds on current foliage

Distribution:  Throughout B.C. except the ponderosa pine biogeoclimatic zone.  Occurs from 0 to 1400 m elevation.  The most serious defoliation is found on the Queen Charlotte Islands and northern Vancouver Island.

Tree Species Attacked: Western hemlock and true firs are the preferred hosts, but spruce and Douglas-fir can also be fed upon. All ages are susceptible.

Insect Description & Damage Symptoms: When young, larvae are pale yellow-green with a brown to black head. With age, the larvae become bright to yellow-green with a brown to black head. Full grown larvae are about 1.8 cm long. Visible defoliation occurs from late June to late July in the interior and from mid-July to mid-August on the coast. Needles of opening buds are usually only partially eaten and some are clipped off at the base and webbed together on the twigs. From a distance, the damaged stand has a reddish-brown hue. Current foliage is preferred, but older needles will be attacked during heavy infestations. Pupation takes place within webs spun in the twig foliage in late August to early September. Pupae are green to brown and 1.2 cm long. 

Damage: The western blackheaded budworm prefers to feed on the upper crowns of dominant and codominant trees. Trees can be completely defoliated from a heavy attack. This severe defoliation can result in growth reduction and predisposition to attacks from secondary organisms. Successive years of severe defoliation may result in tree mortality. Some second-growth hemlock stands that have been severely defoliated for two successive years have sustained greater than 10% mortality; 75% of the remaining trees have suffered an average of 8 m of top-kill. 

Similar Damage: Other defoliators, such as the western spruce budworm, cause similar damage. The yellow-green body without spots and the dark head capsule distinguish the blackheaded budworm.

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Contact Tim Ebata if you have comments on the presentation of this information.

BC Ministry of Forests
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136

Last updated March 04, 2002