Pinus: White Pine Weevil

Problem
The main shoot at the top of the tree stops growing and turns yellow in midsummer. The shoot tip usually droops, producing a "shepherd's crook." Several new shoots may develop from below the dying shoot so that the top of the tree is forked. In fall and winter the drooping shoot appears brown and dry. There is a white resin on the bark, and small holes in the dead shoot.

Analysis
(Pissodes strobi)

The white pine weevil attacks the leaders of both pine and spruce. This small (1/5 inch), brown, snouted beetle with white patches spends the winter in dead plant material at the base of the tree. In the spring, just before new growth begins, it moves to the top of the tree to feed on the inner bark tissue. Eggs are then laid in small punctures in the bark. Resin droplets that ooze from the punctures later dry and turn white. The ¼-inch larvae that hatch from these eggs bore into the wood. The feeding cuts off the flow of water and nutrients through the stem, causing the shoot to droop and die. Several new shoots often develop from below the dead shoot, destroying the natural shape of the tree. In late summer, the larvae mature and return to the ground to spend the winter.

Solution
Control the adults with an insecticide containing lindane in spring when the buds begin to swell. Spray the top of the tree thoroughly. It is usually impractical to spray large trees. Prune out and destroy infested twigs in early summer before the beetles emerge. Train 1 side branch to replace the dead leader by pruning all but 1 of the new shoots to half the length of the newly selected leader.