By Bill McNee, DNR Forest Health Specialist, Oshkosh
bill.mcnee@wisconsin.gov or 920-360-0942

Spray aircraft used in spongy moth control. Photo: Bill McNee, Wisconsin DNR

The Wisconsin Department of Natural Resources (DNR) is taking action in the coming weeks in its battle against spongy moth (formerly known as gypsy moth) caterpillars.

An airplane will spray parts of four DNR properties to reduce the population of the hungry pest.

This year, high numbers of spongy moths threaten to strip trees of their leaves and may even kill high-value trees at these properties.

The spraying will take place in late May to early June, with treatment depending on weather conditions and caterpillar development.

Aerial spraying will take place on a total of 625 acres at the following locations:

Big Foot Beach State Park (one site):

• Campground and forest surrounding the day-use area

Devil’s Lake State Park (two sites):

• North Shore day-use area and the Northern Lights/Quartzite campgrounds, plus a portion of the Ice Age campground
• South Shore day-use area

Governor Dodge State Park (two sites):

• Twin Valley campground
• Southern half of Cox Hollow campground

Kettle Moraine State Forest – Southern Unit (three sites):

• Horseriders campground
• Muir/Nordic trailheads
• Oak restoration area at the intersection of State Highway 67 and County Trunk Highway S

You can check out detailed maps of the treatment areas on the DNR Forest Health website. Each site will be sprayed once; the spraying will take 10 to 30 minutes per site, depending on the size of the treatment area.

Spray information

• The plane flies very low and loud over the treatment sites and surrounding areas. Spraying will only occur within the physical treatment boundaries.
• Planes may begin spraying as early as 5 a.m. and may continue into the late morning or afternoon if weather conditions are favorable. Spraying can take place any day of the week. There are no plans to conduct spraying over the extended Memorial Day weekend.
• Law enforcement, local governments nearby schools and medical facilities will be notified of the spraying ahead of time.
• Sites will be sprayed with “Foray,” a bacterial insecticide which contains Bacillus thuringiensis Kurstaki (Btk). Btk is a naturally occurring soil bacterium that kills only caterpillars when it is eaten. Btk is not toxic to people, bees, pets or other animals. However, some people with severe allergies may wish to remain indoors during nearby applications.
• The “Foray” product being applied is listed with the Organic Materials Review Institute as acceptable for use in certified organic food production.
• You can sign up for email notification of when the spraying will happen by visiting the Spongy Moth Information Portal.

“Slow The Spread” Treatments To Begin This Month

The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) will treat approximately 71,250 acres at 37 sites in 10 western counties as part of the national “Slow the Spread” program. This program treats low, leading-edge populations of spongy moth to slow the westward spread of the pest.

Slow the-Spread treatments use either the same “Foray” insecticide as the DNR treatments, or a pheromone mating disruptor that prevents moth reproduction by interfering with the ability of male moths to find female moths. Learn more in this news release.

For more information about spongy moth and aerial spraying, visit the Spongy Moth Information Portal or call the toll-free Spongy Moth Hotline at 1-800-642-MOTH (1-800-642-6684) to talk to staff or hear a recording of up-to-date spray plans.