Bark beetles in north Metro

North Metro began to see signs of a bark beetle outbreak in 2000. The dry fall and mild winter continued the problem into 2001. With the mild winter we just experienced this year, we may see a continuation into 2002. So residents with mature pine ought to be on the look out.

map of pine at risk of bark beetle attack in north Metro area

Although there is no cure for pine bark beetles, they can be prevented. Drought prone soils, dry weather conditions and overly dense stands are the three factors that most commonly lead to bark beetle infestations in the Metro area. Alleviating these factors will go along way toward preventing future problems. But first, infested trees have to be removed and the wood disposed of properly or existing infestations will spread into healthy trees nearby.

Inspect your trees and look for the following:

  • Small randomly scattered holes 1/16" in size
  • Sawdust accumulating at the base of the trees or in bark crevices,
  • Off-color needles or dead branches in the crown,
  • Dead areas of the bark with beetle galleries underneath.

Larger holes, 1/8" or so in size, and pitch tubes (yellow to pink masses of dried resin protruding from the tree) are an indication of a secondary infestation by other boring insects taking advantage of the weaken trees. Bark beetles are often found on the same tree as these other beetles.

Remove infested trees, preferably by the end of May to remove the first generation of bark beetles. Debark, burn or bury the logs and chip or burn the slash. Talk to a forester about the need to thin your pine stand to alleviate competition related stress. Periodic thinning is needed to keep pine stands healthy and vigorous. For more information, request a pamphlet "How to identify and manage pine bark beetles" from your local DNR forestry office.