Forest Insect and Disease Newsletter

Bark beetles and blow-down in pine trees

Bark beetles construction galleries and laying eggs in fresh phloem of blown down red pint

Bark beetles constructing galleries and laying eggs in fresh phloem of blown down red pine. Photo by M. Albers, DNR

Strom damaged red pines with roots still attached

Storm damaged red pines with roots still attached. Photo by M. Albers, DNR

Wind storms last summer damaged and blew down lots of trees, many of which were pines. Bark beetles like wind storms; hey create lots of fresh phloem for beetles to feed on and start a family or two. Bark beetle populations can begin to build up during the year of the storm damage but we often don't see problems in nearby standing trees until one or two years after the storm.

Bark beetles are attracted to recently killed and damaged trees, which are easy for them to attack and colonize because tree defenses are down. During the year of the storm, the beetles have so much fresh phloem to feed on in the down and damaged trees that they usually don't need to try attacking the nearby healthy, standing trees that still have their defenses intact.

The Ips bark beetles emerged from the storm-damaged trees last fall and dropped to the ground to overwinter in the duff layer near the base of the trees. This summer, the phloem in trees killed by the storm last year will be too dried out to be good bark beetle food, and the beetles are likely to attack ?nearby surviving trees. If there are still storm-damaged trees that were blown over but part of the root system is still intact and the needles are still green, bark beetles are likely to attack these trees before the healthy trees nearby. So this year, you should concentrate on cleaning up and removing leaning trees with green needles first and then hope for a wet or at least normal rainfall summer. If we get normal rainfall, the standing live trees will be much better able to defend themselves and are unlikely to be attacked and killed by bark beetles.