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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:
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