Suppression Spray Program

The Wisconsin DNR Gypsy Moth Suppression Program is a voluntary partnership that involves the state, counties, municipalities, and landowners in a state-organized aerial insecticide treatment to suppress damaging gypsy moth populations in eligible and participating counties. This program generally serves the eastern part of Wisconsin and gypsy moth quarantined counties [exit DNR].

(In the western part of Wisconsin where small, isolated populations of this pest are emerging in non-quarantined counties [exit DNR], a distinct program called Slow The Spread (STS) [exit DNR] is run by the Department of Agriculture, Trade and Consumer Protection (DATCP). The STS program is not voluntary and DATCP does not take landowner or municipal requests for sprays.)

Participation in the DNR’s aerial suppression spray treatment allows communities and property owners to manage gypsy moth outbreaks with more confidence than is typically possible with privately arranged treatments.

County officials initiate and coordinate the suppression spray program with assistance from the DNR. Participating counties provide a local coordinator who acts as a contact for the public and the DNR and who is responsible for a number of duties that are best performed or can only be performed at the local level. For example, counties typically collect the full cost of spraying from communities and landowners. The DNR will apply for a federal cost-share grant that is available only to states. If cost sharing is available, the state reimburses participating counties up to 50% of the cost of treatment and administrative expenses. The county official then distributes the federal cost-sharing reimbursements to communities and landowners who originally paid.

If you are having a problem with gypsy moth on your property, in a gypsy moth quarantined county of Wisconsin, and would like to apply for the DNR's Suppression Spray Program, you may contact your county and municipal coordinators for the spray program. These people help in the process of suppressing gypsy moth populations in your area. Not all counties participate in this program. In that case, the county will not have a coordinator and properties in that county will not be sprayed. If your county is not currently participating in the program, you may contact your county government officials and the local community government to report the problem and express interest in participating if your neighborhood is heavily infested. The suppression program sprays in May and June and areas proposed for spray treatment are determined in September, October, and November of the previous year. Government officials, county coordinators and local contacts need to be aware of a landowner’s interest in participating in the suppression spray program as early as possible. You can also look into other options for treatment of your property if your county is not currently participating in this program. Ground based sprays can treat a few yard trees and are typically applied by a certified arborist [exit DNR]. If you have more than 20 acres, you can also organize a private aerial spray project.

Insecticides used in the DNR Suppression Spray Program are either Foray, a formulation of the bacterial insecticide Bacillus thuringiensis kurstakii (Btk) or Gypchek, a viral insecticide specific to gypsy moth caterpillars. Gypchek is only used where endangered or threatened moths or butterflies are present. Both Btk and Gypchek are unlikely to cause any adverse health reactions. Small airplanes will spray Btk and Gypchek in late May and early June, beginning very early in the morning. Homeowners in areas to be sprayed are encouraged to stay indoors with windows closed in order to avoid direct exposure to the spray.

The Suppression Program is managed under State Statute 26.30 and Natural Resources Board Rule number 47.