Spongy Moth
Spongy Moth in Middleton
City staff conducted an egg mass count in the fall of 2023. Egg mass counts are a proven way to estimate an upcoming year’s spongy moth population. From this information, the staff has determined the boundaries where spongy moth populations are high enough to have a significant impact on trees and, therefore, would benefit from aerial spray application for control. This does not mean that other areas outside the blocks do not have spongy moths present; however, the numbers are low, will not significantly impact trees, and do not warrant aerial spraying.
Aerial Spraying in Middleton
Two applications are conducted in early spring, 7-14 days apart. The exact timing depends on the weather as treatment is timed to tree leaf development and spongy moth caterpillar size. The contractor will make the application using a helicopter. The exact product used is Bacillus thuringiensis kurstaki (Btk), a naturally occurring soil bacterium commonly used by organic vegetable farmers. The WI Department of Agriculture, Trade, and Consumer Protection has an excellent summary of this product, along with additional resources on the topic:
https://datcp.wi.gov/Pages/Programs_Services/SMAerialSpray.aspx
What Can You Do Now?
Oak trees in good health and free from other stresses can handle the defoliation caused by a spongy moth infestation. Consider watering trees during drought and maintaining a proper mulch ring at the base of the tree. If you have a spongy moth in your oak tree, you can follow the guidelines from the UW-Extension web page Spongy Moth in Wisconsin:
Don't hesitate to get in touch with an International Society of Arboriculture (ISA) Certified Arborist for additional expertise:
https://www.waa-isa.org/find-certified-arborist/