Gypsy moth treatment coming to Winona County

The Minnesota Department of Agriculture (MDA) is preparing to treat approximately 1,751 acres of land in Winona County to slow the spread of a gypsy moth infestation identified last year. Officials will conduct the aerial treatment sometime between June 22 and June 29, beginning as early as 7:00 a.m. This date is dependent on weather conditions in the area leading up to the treatment date.

gypsy moth

The Minnesota Department of Agriculture will be spraying the Pine Creek area of Winona County in Minnesota to slow the spread of the gypsy moth into the state’s tree forests. (photo from

To help area citizens stay informed, the MDA has set up an Arrest the Pest information line at 1-888-545-MOTH (6684). The hotline will offer the latest details about treatment date and time.

The MDA maintains a monitoring program to watch for start-up infestations. When an infestation is found, the department conducts aerial treatments of the infestation before it can spread. In 2016, the MDA found an infestation in New Hartford Township, Winona County (referred to as the Pine Creek block). (SEE MAP) Details of the area can be found at

Map of treatment area in New Hartford Township, Winona County

The MDA will use a method of mating disruption involving the aerial application of a waxy, food-grade substance containing a pheromone that confuses male gypsy moths. This makes it difficult for the male gypsy moths to find females for mating, which means fewer caterpillars hatching and attacking trees next year. The application is timed just as adult moths emerge in mid-summer.

Mating disruption has been widely used for gypsy moth management in Minnesota and across the nation. It is an effective tool that helps slow the spread of the insect as it moves westward across the country. Minnesota has benefited greatly from the use of mating disruption in Wisconsin and other eastern states that have kept new gypsy moth populations at bay.

This work is being coordinated through the national Slow the Spread of Gypsy Moth program directed by the U.S. Forest Service. Minnesota has been part of this program since 2004. These efforts protect forest health, property values, and the state’s tourism industry.

Gypsy moths are among America’s most destructive tree pests, having caused millions of dollars in damage to Eastern forests. If present in large numbers, gypsy moth caterpillars can defoliate large sections of forest.


MDA Weed of the Month: Brown, Meadow, and Diffuse Knapweeds

December’s Weed of the Month is not one, but three species of knapweed: brown knapweed (Centaurea MDA-logojacea), meadow knapweed (C. x moncktonii), and diffuse knapweed (C. diffusa). All three species are native to Eurasia, and it’s thought they were introduced to western North America for forage. In Minnesota, infestations of meadow knapweed have been reported in St. Louis and Koochiching counties, brown knapweed has been reported in Koochiching County, and diffuse knapweed has been found in Duluth.

Several characteristics of these knapweed species have helped them thrive and become a threat to Minnesota. They outcompete pasture grasses and native plants, leading to large bare patches of soil that is more susceptible to erosion and water runoff. Once established, the knapweeds reduce hay quality and pasture productivity. The plants can also hybridize between species, which makes identification difficult and increases the risk for an aggressive plant that can invade many soil types and growing conditions.

Here’s a look at Brown Knapweed, the December weed of the Month from the Minnesota Department of Ag (photo from www.summit

Here’s a look at Brown Knapweed, the December weed of the Month from the Minnesota Department of Ag (photo from www.summit

Knapweeds can be biennial or perennial. They reproduce primarily by seed, which can be spread with infested hay, on equipment, or by wind and water movement. The flowers are tight clusters of individual flowers called florets. The flower color ranges from pink to white. The plants produce a rosette of leaves, which then sends up a flowering stalk in the summer.

To prevent the knapweeds from further spreading throughout Minnesota, several management strategies are available.

  • Make sure to clean equipment, vehicles, and footwear after being in a knapweed infested area.
  • A combination of hand-pulling and digging is an option for small infestations.
    Here’s a look at meadow knapweed, another invasive species seen in farm fields around Minnesota (Photo from

    Here’s a look at meadow knapweed, another invasive species seen in farm fields around Minnesota (Photo from

    Seedlings are tap-rooted and can be hand-pulled; however, the large taproots must be removed or the plant will regenerate from the root.

  • Herbicides are a very effective management tool for meadow knapweed. For specific herbicide recommendations, contact your University of Minnesota Regional Extension Educator.
  • Mowing does not control meadow knapweed and the mower may spread seed.
  • All infestations must be monitored and treated until the seedbank is depleted.

To report infestations of these species of knapweeds or any other noxious weeds on the eradicate list,

please use the Early Detection and Distribution MAPping System at