Spongy Moth

The accepted name for this insect is now Spongy Moth.


Spongy Moth in Middleton

Spongy moth is an exotic invasive species that we have had to deal with in Middleton. This insect prefers to munch on our Oak trees and has the potential to completely defoliate stands of trees when numbers are high. Middleton had taken part in the DNR suppression spray program in 2008, 2009, and 2010. The DNR ended this program the year after this and has no intent to restart it.  The only spraying now is in the "Slow the Spread" program which now focuses along the Mississippi River area of the state. 

In the past spongy moth in Middleton has been generally confined to the center of Middleton (the area that has the highest concentration of oak trees). When the DNR conducted the spongy moth spray program, the spray block for both 2009 and 2010 is shown below and was approximately 520 acres in total area.
Gypsy Moth Map 1.png
Since 2010 spongy moth populations have been very low in large part due to natural enemies (Entomophaga fungus, nucleopolyhedrosis virus - NPV, and the Encyrtid Wasp Ooencyrtus kuvanae).  The past 2-3 years have seen a marked increase in populations unfortunately.  The drought in 2021 and the unseasonably hot weather in 2022 has significantly hindered the fungus as it needs cool, wet conditions to thrive and the virus and wasp have not been able to make a dent on their own. 

Current Status in Middleton

City staff are aware of the situation and the impact it is having on residents.  There was a request in the 2022 capital budget for spongy moth suppression but it was not approved by the Finance Committee and Common Council.  As such we are limited in what we can do.   

What You Can Do Now

From the UW-Extension web page Spongy Month (lymantria dispar) in Wisconsin

August-September: Watch for pinholes in egg masses

Mid-October-Mid-April: Destroy egg masses

Late April: Place barrier bands on tree trunks

May-June: Apply insecticides

Early June: Replace barrier bands with collection bands

July: "Crush & brush" pupae and adult females

Most of these items can be done by a homeowner, however these could also be done by a tree service.  It is recommended to look for a service that has International Society of Arboriculture (ISA) certified arborists on staff. 

What About the Future?

If funding is approved, the City could possibly undertake aerial spraying on our own.  There are however a number of issues that work against us doing so.

From the DNR document: Organizing an Aerial Spray for Forest Pests

On page six of this document it states "If the problem area is only a few trees or a few acres, aerial spraying is unlikely to be appropriate.  Physical controls, an insecticide spray from the ground, or application of a systemic insecticide into the soil or the tree itself, are likely to be more practical treatment options."  As stated above, the previous spray block was over 500 acres and as of 2022 the area of highest impact is not nearly as large as that. 

On page 2 of the document requirements for consent are explained.  Property owner consent is required prior to any aerial spraying could occur - every property owner.  If not, there are possible ways of still conducting the spray, but as these all revolve around limiting drift, it becomes impractical if there are numerous objections.