State plans aerial mating-disruption treatments for spongy moth in Houston County this summer

The Minnesota Department of Agriculture plans aerial pheromone ‘mating disruption’ treatments for spongy moth in three Houston County blocks this summer and asked the county to help notify residents.

Matt Gallo, the MDA’s statewide spongy moth treatment coordinator, told the Board the agency has identified treatment sites in Money Creek, Beaver Creek Valley and part of the Yucatan block shared with Fillmore County and expects the work to occur roughly in June or July, timing dependent on weather and caterpillar emergence. "My name is Matt Gallo. I am the, statewide spongy moth treatment coordinator, at the Minnesota Department of Agriculture," Gallo said during the presentation.

The pest, Lymantria dispar, is a defoliating caterpillar the MDA describes as capable of feeding on more than 300 tree and shrub species. Gallo said Minnesota is particularly vulnerable because many of the state’s common trees — aspens, basswoods, birches and oaks — are preferred spongy moth hosts. He said the agency’s goal is to slow the spread of the insect, not to eradicate it.

The county will not receive bacterial Bacillus thuringiensis kurstaki (Btk) treatments in these blocks this year; MDA intends to use only mating disruption in Houston County in 2025. Gallo described mating disruption as an aerial application of a pheromone product branded in the presentation as “Splat GMO.” He said the product is not a genetically modified organism, is registered with the U.S. Environmental Protection Agency, is biodegradable and “nontoxic,” and that the pheromone used is species‑specific to spongy moth.

Gallo described operational details: aircraft typically fly 50 to 100 feet above treetops during spraying and the pheromone is intended to flood treated areas so males cannot find females. He said the MDA uses trap networks — about 20,000 traps statewide — to target management where trap counts are highest and that the state’s Slow the Spread partnership with the U.S. Forest Service and other states aims to reduce the rate at which the insect moves into new counties.

For outreach, Gallo said every parcel in the three treatment blocks will receive a mailed informational postcard, the agency will issue press releases, run an email/text notification system and hold public meetings for Southeast Minnesota. He asked the county to share information through local websites, social media or newsletters. Gallo also said an environmental assessment will be completed and that the current treatment plan is proposed and subject to change based on public comments and the assessment.

Commissioners asked about treatment timing and data; Gallo said Minnesota has trapped and treated spongy moths since the 1970s and that exact spray dates will be provided as operations approach. "We don't have, like, exact set dates. We have time ranges... generally it should be around June or July," he said.

The presentation materials listed the three Houston County blocks and noted the MDA has identified roughly 100,000 acres for action across nine counties this season, concentrated in northern and southeastern Minnesota.

The MDA public meeting for Southeast Minnesota was listed as March 18 (virtual); Gallo said details and a public sign-up will be posted on the MDA website and that comments from public meetings will be incorporated into the environmental assessment.

What happens next: the MDA will complete the environmental assessment, finalize spray dates based on monitoring and weather, and proceed with outreach; the Board did not take formal action during the presentation.