Shoot Boring Insects By Deborah McCullough

Many different kinds of insects feed in the shoots of pine trees. Some insects, such as the white pine weevil, can severely damage the growth, form or appearance of trees. Other insects, such as the pitch nodule maker, rarely cause serious damage. Still other insects, like the pine shoot beetle, may cause infested trees to be regulated by state or federal restrictions on shipping.

This flow chart is intended to help Christmas tree growers, landscapers and foresters determine what insect has caused damage to shoots of pine trees. Regular scouting of trees and plantations during the growing season will help you detect shoot borers before damaging populations can build up. Although it is always best to actually collect the insect causing the damage, occasionally this may not be possible. Growers who learn to recognize the "clues" that shoot-boring insects leave behind will be better able to plan future scouting and pest management activities. Some helpful clues include the location of damage on the tree, the species and age of the damaged tree, and the time of year that specific life stages of the insect are present.

To use the flow chart, begin by determining whether the terminal leader or lateral shoots are damaged. It is also very helpful to know whether the damage was caused by a caterpillar (moth larva) or a beetle. See the illustrations in this bulletin for examples of the life stages of moths and beetles. Once the insect pest has been identified, the amount of damage to the tree, field or stand should be assessed. An integrated management plan can then be developed to prevent economic loss while protecting the environment. Refer to the table in this bulletin for information on the hosts, life cycle and control of common shoot-boring insects.

Scotch pine shoot exuding pitch, a common symptom of trees attacked by pine shoot beetle (Tomicus piniperda).
Photo courtesy of USDA Forest Service
North Central Regional Extension Publication No. 528
From Insect Biology by Howard Evans. Copyright 1984 by Addison-Wesley Publishing Company. Reprinted by permission.

Flow Chart

Moth and Beetle Life Cycle

If you have questions or would like additional information, please contact
Dr. Karen Potter-Witter, Professor, MSU Department of Forestry