Article By: Bill McNee, DNR Forest Health Specialist, Oshkosh
bill.mcnee@wisconsin.gov or 920-360-0942
In 2021, gypsy moth populations increased for a second consecutive summer due to favorable weather conditions. Populations typically increase with an average or mild winter, below average spring precipitation and above average May through June temperatures.
Regional variation in weather can result in significant differences in populations. If weather conditions are favorable again in 2022, the most noticeable increase in caterpillar numbers would likely occur in southern counties, where conditions were driest during this past spring and summer.
Populations experience the fastest growth rate and are first noticed on:
- Dry sites with sandy soil and abundant oak
- Mowed lawns with preferred tree species (oak, crabapple, birch, etc.)
- Large oaks (bur, in particular) with rough bark, especially on or adjacent to mowed lawns

Gypsy moth egg masses found in Walworth County in fall 2021.
Photo Credit: Gypsy moth egg masses KMSU
Continue reading “Take Action! Look For Gypsy Moth Egg Masses”

Do you have a tree inventory but have had a hard time keeping it current, or you’re interested in inventorying some trees of your own? The Wisconsin Department of Natural Resources (DNR) is funding several accounts for communities or organizations to edit data within the
The latest version of the USDA Forest Service’s Tree Owner’s Manual is now available online
Leafing Out, Episode 6: Small Insects Can Cause Big Tree Problems with August Hoppe
Leafing Out, Episode 5: Common Tree Diseases With Brian Hudelson
Oak wilt is a serious disease that occurs when insects carrying oak wilt fungal spores land on a healthy oak tree’s fresh wound. To prevent oak wilt infections, it is important to avoid pruning, wounding and harvesting oaks when these insects are abundant, generally April through July.
The Wisconsin Department of Natural Resources (DNR) Urban Forestry and UW-Madison, Division of Extension Fall 2020 Workshop Series is now available for viewing on YouTube. Use the links below to watch the videos: