Spongy moth insect management proposed in Olmsted County

The Minnesota Department of Agriculture (MDA), in collaboration with federal partners, has identified five areas in Olmsted County that need to be managed to slow the spread of spongy moth in Minnesota.

What is spongy moth?

Spongy moth (Lymantria dispar) is an invasive insect that is a significant threat to the economy, environment, and human health. Spongy moth has caused billions of dollars in property damage and defoliated millions of acres of forest. Spongy moth caterpillars can feed on more than 300 tree species, including some of Minnesota’s most common trees. 

How can spongy moth be managed? 

The proposal is to use a mating disruption product, SPLAT GM-O (Specialized Pheromone and Lure Application Technology Gypsy Moth-Organic). This is a pheromone that stops male moths from finding females, preventing mating. It is applied via low-flying aircraft to the tree canopies. Applications could happen early in the mornings, with planes often flying in the area for several hours. 

SPLAT GM-O is harmless to humans and animals. All ingredients in SPLAT GM-O are listed by the Environmental Protection Agency (EPA) as safe.

When would spongy moth management happen?

If approved, aerial management activities in southern Minnesota would likely occur mid-June to early July 2026. More specific management dates will be provided closer to the implementation period. However, timing is dependent on weather and insect development. 

What areas of Olmsted County are being proposed for management activity?

The following areas in Olmsted County would be included: 

• Area name: Carly State Park / Acres: 6,492 (1,571 in Olmsted County, the rest are in Wabasha County).
• Area name: Rochester NE / Acres: 8,107
• Area name: Rochester N / Acres: 11,088
• Area name: Rochester SE / Acres: 17,213
• Area name: Stewartville / Acres: 3,241

An interactive map of proposed spongy moth management activity is available on the MDA website. 

Open houses and more information

Informational public open houses are being held on the following dates:

Tuesday, March 31, 2026

• Time: 4:30 – 6 p.m.
• Location: Development Services & Infrastructure Center (DSIC), 4001 West River Parkway NW, Rochester

Wednesday, April 1, 2026

• Time: 4:30 – 6 p.m.
• Location: Stewartville Civic Center, 105 1st St. E, Stewartville

For more details about spongy moth management, visit the Minnesota Department of Agriculture website. You can also sign up for text or email alerts to stay up to date on the management proposal by visiting the MDA website.

Questions? 

Please email reportapest@state.mn.us or call 888-545-6684.