White Pine Weevil

Destructive insect attacks top of evergreens


Q. I have a pine tree that seems to be dying at the top. It is fairly tall, and I cannot see what is happening up there. I noticed that some of my neighbors' pine trees look the same. Is there some kind of blight or something hitting pine trees? Is it going to kill the tree, or can I do something to save it?

A. Judging from your description and the digital photo attached to your question, an insect called the white pine weevil is responsible for the damage to the top, or terminal leader, of your Norway spruce. White pine weevil damage will not kill your spruce, but it can destroy the natural shape of the tree.

This pest is a small (1/4-inch long) reddish-brown beetle with white spots on the ends of its wing covers and an elongated snout. White pine weevils overwinter as adults in leaf litter and other debris on the ground.

As the weather warms in spring, they migrate to the leaders of white pines, Norway and Colorado spruces (and other susceptible trees), where they mate. Adult females bore out a circular cavity and deposit anywhere from one to five eggs. Hundreds of eggs can be laid in a single leader.

After the egg hatch

Once the eggs hatch, the larvae bore into the leader to feed. Their feeding activity cuts off the flow of water and nutrients through the stem, which causes it to wilt and die. New growth usually sprouts below the dead leader, but the damage destroys the shape of the tree. The larvae pupate and hatch out as adults by late summer. They drop to the ground to overwinter and the cycle starts over again.

White Pine is a very popular landscape tree

White Pine is a very popular landscape tree

To protect undamaged trees, direct your control efforts at the adult females as they lay eggs. Begin scouting for white pine weevil activity as the weather warms in spring, from mid-March through mid-April. When the females begin laying eggs, you will see resin oozing from the punctures she makes to lay her eggs (binoculars can be a big help if you have a large tree). Only the terminal leader needs to be sprayed to protect against white pine weevil damage.

Use insecticides?

Unfortunately, there are no insecticides on the market that are available to home gardeners. A licensed pesticide applicator can spray your tree for you. Since your tree is large, it is probably a good idea to hire someone with the training and equipment to spray it safely and thoroughly.

Another control option is to prune out the infested leader and physically remove the larvae from the tree. This will reduce the number of overwintering adults and perhaps protect your tree from further damage. It is best done as soon as the leader droops, often in early June. Prune the infested leader out just below where the bark is discolored and discard it by sealing it tightly in a trash bag or burning it immediately.

New growth

There should be a flush of new growth at the base of the dead terminal. You can select the most upright shoot of this new growth to become the new terminal. Try to tie it into an upright position with wide, nonbinding masking tape or the plastic tape used to stake tall flowers. Remove all ties after one growing season. Prune out the rest of the new growth near the leader to preserve the shape of the tree.


Evergreen tree photos

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