By Michael Hillstrom, Forest Health Specialist, Fitchburg
Michael.Hillstrom@wisconsin.gov

An adult bark beetle found infesting a white pine branch in 2024. / Photo Credit: Michael Hillstrom, Wisconsin DNR

Conifer mortality in southern Wisconsin has increased in 2024. Regardless of the conifer species, the common theme has been heavy infestation by bark beetles.

This increased bark beetle activity is likely linked to the 2023 drought, which lasted from May to September. Wisconsin experienced the fifth-driest May-July period on record and the fifth-driest meteorological summer (June-August) summer on record. The drought peaked during the middle of September before much-needed rain finally arrived.

The intense drought primed forests for increased insect activity, including bark beetles. Hopefully, with the regular rain during 2024, most trees will be able to recover from the drought stress and become healthy enough to fight off the beetles and fungi, such as Armillaria, that also take advantage of drought-stressed trees.

For bark beetle management guidance, see the Wisconsin Department of Natural Resources fact sheet on conifer bark beetles.

Bark beetle exit holes and galleries in a white pine branch. / Photo Credit: Michael Hillstrom, Wisconsin DNR