White Pine Weevil
The white pine weevil, Pissodes strobi (Peck), is becoming more of a pest of spruce and pines in the urban landscape. Infested spruce exhibit a characteristic shepherd's crook and death of the terminal leader.
Trees more commonly attacked in Colorado include: Austrian pine (Pinus nigra), Scotch pine (Pinus sylvestris), White spruce (Picea glauca), Colorado blue spruce (Picea pungens glauca), Eastern white pine (Pinus strobes), Norway spruce (Picea abies).
Adult weevils have a long snout-like beak and knobbed antennae. The 1/4" long insects are brownish black with white patches near the end of the wing covers. The larvae are white, legless worm-like creatures with a dark brown head capsule that feed underneath bark.
Adults emerge as adults from terminal branches in late July through August. They feed in the upper limbs and when temperatures drop, hibernate in duff under trees. In March, April or May, adults emerge and climb trees, feeding in the upper branches or terminal leader. Females lay eggs in feeding wounds which hatch in about one week. They larvae feed underneath the bark, girdle and eventually kill the shoot. Larvae mature and pupate in chip cocoons. Chip cocoons are made from shredded bark "glued" together in mounds under the bark.
If the terminal leader of a Colorado blue spruce is brown and crooked like a cane, pull back a piece of the bark. The presence of chip cocoons is diagnostic for white pine weevil.
Prune out dead infested branches and destroy the branches. Train a new leader from a lateral branch. Clean up duff around spruce and pine trees each fall. This eliminates spring adult migration from the duff the terminal leader. Apply a registered pesticide such as permethrin to terminals in the spring when adult feeding begins.
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Updated Friday, April 19, 2013