It seems that many spruce are losing their tops in recent years. The usual suspects are white pine weevil larvae that feed underneath the bark of the spruce leader.

The larvae are the most damaging life stage of the weevil. The adult form over-winters in protected areas and becomes active as temperatures warm in spring. Female weevils seek out spruce leaders and lay eggs underneath the bark. The eggs hatch and the young larvae tunnel deep into the bark. The larvae then pupate and emerge two weeks later as adult weevils. The exit holes are evidence of infestation.

The damage caused by weevils results in girdling the leader. The top will dry up and curl becoming completely dead in a few weeks. A diseased leader should be removed.

Once the top is dead, some side branches will try to become the new leader. A good practice is to allow only one of the branches to become the main leader. This is accomplished by training a new leader through splinting and binding it upward.

Death of the spruce’s leader can be prevented by applying insecticide in spring. Sevin (carbaryl) is the favored insecticide to control white pine weevil. The treatment time in usually late March or early April depending on spring temperatures. The bad news is that spraying in spring may be necessary for several years to protect the top. The good news is once the spruce grows to 15’, it usually is no longer attacked.

For any questions you have on this article, or any topic of concern, email us—or better yet, come by and talk to one of our professional staff members. Remember, Phelan Gardens is open year-round!

For additional information, check the following links:

• The White Pine Weevil Homepage
• White Pine Weevil, HYG-2556-95
• Evergreen Trees