By Bill McNee, DNR Forest Health Specialist, Oshkosh
Bill.McNee@wisconsin.gov

A Wisconsin map showing drought conditions as of October 6, 2026. Map created by David Mocko, NASA/GSFC/SSAI. / Graphic Credit: Wisconsin DNR

Property owners and land managers in the northern half of Wisconsin are encouraged to monitor forest stands and ornamental trees for signs of decline and mortality due to the intensity of the current drought. In late September, parts of several counties reached the “Exceptional Drought” condition on the U.S. Drought Monitor (see maps). This is the most severe drought category used and it has only been seen in Wisconsin one other time since the U.S. Drought Monitor was created in 1999 (source: National Weather Service).

Weakened trees are often colonized by opportunistic organisms such as Armillaria root disease and the twolined chestnut borer beetle, leading to tree decline and mortality. Trees may not show signs of weakness until next spring, when they leaf out normally but then begin to show signs of decline or pest infestation.

Monthly comparison of the drought’s progression in Wisconsin during the 2026 growing season. / Map Credit: U.S. Drought Monitor, droughtmonitor.unl.edu

It is recommended that landowners and managers planning forest management activities consult a local forester about drought impacts on their property. Stand thinning may add more stress to trees that are already weak from the intense drought, leading to mortality in the residual stand.

In general, yard trees should be watered weekly during droughty conditions until the hardwood trees lose their leaves in the fall. Conifers that retain needles over the winter (such as pine and spruce) need more stored water going into winter than hardwoods, as the conifers are susceptible to winter dehydration through their needles during the cold winter. The Arbor Day Foundation offers information about watering yard trees in the fall.