42 Areas in Minnesota Targeted for Spongy Moth Treatments in 2024

Invasive insect continues its push into the state

St. Paul, MN: The Minnesota Department of Agriculture (MDA) and partner organizations are proposing to treat spongy moth (Lymantria dispar) infestations this summer in seven counties across eastern Minnesota.

Spongy moths are ranked among America’s most destructive tree pests. The insect has caused millions of dollars in damage to forests as it has spread from New England westward in recent decades. Spongy moth caterpillars can defoliate large sections of forest. This pest is found in most of Wisconsin and is now establishing itself in northeastern Minnesota.

The MDA monitors for spongy moth each year, surveying for start-up infestations. When an infestation is found, the department conducts aerial treatments and targets the infestation before it can spread. The number of spongy moths detected in Minnesota in recent years has increased, and populations continue to push westward. The increase in moths created the need for more treatment areas in 2024.

Forty-two treatment areas totaling approximately 160,000 acres are proposed in Carlton, Chisago, Filmore, Houston, Isanti, Pine, and St. Louis counties. The areas will be treated with either: Bacillus thuringiensis var. kurstaki (Btk), a biological insecticide that is organically certified for use on food crops, or mating disruption, an organic substance containing pheromones specific to spongy moths that confuses the male moths. Residents can view an interactive map on the MDA website to determine if they’re located within any of the proposed treatment areas. 

The treatments will be conducted from June through July, depending on insect development and weather.

The MDA has successfully treated dozens of spongy moth infestations across eastern Minnesota from Grand Portage to the Twin Cities to Houston County. These successful treatments help postpone the full-scale invasion of spongy moth. They also save local communities and homeowners money and protect the health of the state’s urban and natural forests.

Residents in proposed treatment areas and the public are invited to attend an informational meeting to learn more about the insect and the treatment methods.

To register for virtual meetings, go to www.mda.state.mn.us/smtreatments.

Residents in proposed treatment areas will also be receiving a postcard with more information. Citizens can also find info on spongy moth treatments, sign-up for text or email notifications, and proposed treatment area maps at www.mda.state.mn.us/smtreatments.

Comments on any of the proposed treatments are being accepted through April 15, 2024. Comments should be submitted in writing via mail or email to: Kimberly Thielen Cremers Minnesota Department of Agriculture 625 Robert Street North St. Paul, MN 55155 [email protected]

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