We have recently seen numerous confirmed infestations of the White Pine Weevil. So, if you notice that the upper 1-2′ of your spruce and/or pine trees have died suddenly, the White Pine Weevil may very well be the culprit.
I’ve copied below some pertinent information from the OSU Fact Sheet “White Pine Weevil” (HYG-2556-95) by Dr. DAvid J. Shetlar, Entomologist with the OSU Extension.
White Pine Weevil
The white pine weevil, Pissodes strobi (Peck), is most common in Ohio in the northern and eastern counties.
White pine weevils prefer eastern white pine and various spruces. They will occasionally attack other pines and rarely Douglas-fir.
The larvae do the most damage by killing leaders of infested trees. Leaders with expanding buds droop, forming the typical “Sheppard’s hook.” The larvae may travel past the first whorl of branches resulting in their death. The adults feed on branches and shoot causing considerable sap flowing. However, this generally does not kill the branches.
Description and Life Cycle
The weevils are often hard to find but their damage, die back of the leader, is easy to spot. The larvae can be found under the bark of the dying leader.
This pest overwinters in the adult stage hiding in the duff under trees. In early spring, early to mid-April, the adult females climb to the leaders of trees and feed through small holes chewed in the bark. This feeding causes sap to run down the leader. Eventually, the females will insert eggs into these feeding wounds. The larvae hatch in about a week and feed just below the bark. The larvae continue to feed downward, girdling and killing the shoot as the go. The larvae mature and pupate in mid-July. the pupae rest in cells carved in the sap wood and lined with straw like sawdust. The adults emerge in late July and early August. The adults feed on the upper tree branches, making small puncture wounds. As winter approaches, the adults return to the duff to hibernate.
All controls should be targeted to kill the adults or larvae before the tree leaders are damaged.
(1) Prune Infested Leaders – As soon as infested leaders droop, cut the leader out just below where the bark discoloration stops.
(2) Systemic insecticides are often more effective because they kill any larvae which may already be inside the leader.
I recommend the following course of action:
1. Direct Sapstream Injection to kill any adult weevils that may yet be actively feeding. This is a one-time treatment.
2. Annual Fall Insect Control Soil Application done sometime in September to provide control for the following season.