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Home > Plants, Pests & Pest Control > Pest Management > Gypsy Moth Program > Treatments

Gypsy Moth Treatments


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    • Minnesota's 2017 proposed gypsy moth treatment areas. Maps created by MDA.
    • The Minnesota Department of Agriculture (MDA), in collaboration with federal, state, and local partners, has proposed to slow the spread of gypsy moth populations in Hennepin, Pine, and Winona counties. Surveys in 2016 revealed three distinct areas where monitoring traps caught a high numbers of moths. These results, combined with the trap records of previous years, and follow-up site surveys prompted the MDA and the Minnesota Gypsy Moth Program Advisory Committee to develop a proposed treatment project for 2017.

      In order to reduce current populations of gypsy moths and slow the growth of future generations of this forest pest, the MDA treated a total of about 1,120 acres of land with a biological insecticide called Bacillus thuringiensis var. kurstaki, or Btk, and about 1,751 acres with mating disruption. Three treatment blocks were identified and named for their geographic locations: Richfield in Hennepin County, Hinckley in Pine County, and Pine Creek in Winona County (see maps at bottom of page). Habitat within the proposed treatment areas included many of the trees species considered susceptible to gypsy moth defoliation.

      The Minnesota Department of Agriculture (MDA) and the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) made official environmental review documents available to the public, including a finding of no significant impact (FONSI), and the underlying final environmental assessment entitled Gypsy Moth Cooperative Eradication Program in Hennepin County, Minnesota. The documents are available at USDA APHIS | Gypsy Moth Programs Environmental Assessments, or by contacting Erin Stiers (USDA-APHIS-PPQ, 900 American Blvd East, Suite 101, Bloomington, MN 55420). For general questions concerning the Minnesota Gypsy Moth Eradication Program, please contact  Kimberly Thielen Cremers (kimberly.tcremers@state.mn.us).

    • For the most up-to date information on treatments call 888-545-MOTH (6684).

    • A copy of the Decision Notice and Environmental Assessment may be obtained by emailing a request to Gypsy.Moth@state.mn.us.

    • Proposed Btk Blocks (two blocks, a total of 1,120 acres)

      Hinckley Block (791 acres)

    • Roads:
      The Hinckley treatment block was shaped like a parallelogram. The western edge of the treatment block was approximately 1.25 miles long and ran parallel to Interstate-35. The northern edge was approximately 0.8 miles long and was roughly parallel to Taylor Rd. The north eastern corner of the treatment block was located 0.26 miles north of Taylor Rd. and 0.2 miles west of Old Government Rd. The eastern edge of the block was approximately 1.2 miles and was roughly parallel to Old Government Rd. The southern edge was approximately 1.2 miles long; the southwestern corner was located 440 feet south and 0.2 miles west from the terminus of Taylor Birch Rd. The Hinckley treatment block was roughly centered over the area where Taylor Birch Rd. makes a 90° turn to run in an east-west orientation (approximately 0.37 miles south of the intersection of Taylor Rd. and Taylor Birch Rd.).

      The majority of the block was located in the township of Barry (639 acres), but the northern portion extended into Sandstone Township (152 acres). There are no state, federal, or tribal lands within the Hinckley treatment block

    • 2017 Proposed Hinckley Btk Treatment Block. Map created by MDA.

      Richfield Block (329 acres)

    • Roads:
      The northern edge of the treatment block beagan slightly west of the intersection of W 61st St. and Washburn Ave S and extended 0.68 mi east to Logan Ave. The north eastern corner of the treatment block was 215 feet north from the intersection of W 61st St. and Logan Ave. The eastern edge was 0.74 miles following Logan Ave south to the intersection of Logan Ave and W 67th St. The southern edge was 0.68 miles following W 67th St. from the corner of Logan Ave and extended to Washburn Ave S. The western edge of the treatment block was 0.75 miles following Washburn Av S from the intersection of W 67th St. north to the intersection of W 61st St.

      The treatment block was primarily located in the northeast section of the City of Richfield (275 acres), with the northern edge of the block extending into the southwest corner of Minneapolis (54 acres); State Road 62 was the dividing line between Minneapolis to the north, and the City of Richfield to the south. There were no state, federal, or tribal lands located within the block.

    • 2017 Proposed Richfield Btk Treatment Block. Map created by MDA.

    • Proposed Mating Disruption Blocks (one block, 1,751 acres)

      Pine Creek Block (1,751 acres)

      The Pine Creek treatment block was an irregularly shaped block located approximately 4 miles northwest of La Crescent, MN. The northwestern corner of this treatment block was located 0.2 miles west of County State-Aid Highway (CSAH) 16 (approximately 1 mile north of the intersection for CSAH 16 and Rose Creek Dr.) The northern edge extended approximately 1.7 miles to a point 0.25 miles west of Lanes Valley Rd; it was bisected by Pier Ridge Rd (approximately 0.18 miles north from the intersection of Thicke Dr.). The eastern edge of the block was approximately 1.5 miles. The eastern boundary crossed Lanes Valley Rd approximately 0.5 miles south of the northeastern corner, continued for 0.5 miles where it crosses Lost Valley Dr., and continued for an additional 0.5 miles to a point approximately 0.2 miles east of Lanes Valley Rd where it terminated. The Pine Creek treatment block then turned diagonally southwest and continued for 0.5 miles. This southeastern diagonal border was bisected by Lanes Valley Rd., (approximately 0.2 miles north of the intersection of N Pine Creek Rd.). West of the southeastern diagonal border, there was a 0.8 mile southern border that was approximately parallel to the northern border. This southern border intersected N Pine Creek Rd. 0.26 miles west of the southeastern diagonal segment and terminated at a point 0.15 miles south of N Pine Creek Rd. The western edge of the Pine Creek treatment block consisted of three segments (southern, central, and northern) which formed a dog leg near its midpoint. The southern segment of the western boundary began at the southwestern corner and extended north for approximately 0.8 miles (crossing N Pine Creek Rd approximately 0.15 miles north of the southwestern corner). The western boundary then turned 90° west, where it traveled east-west for 0.36 miles to form the dog leg. The central segment crossed CSAH 16 approximately 245 feet south from the intersection of Rose Creek Dr. The western boundary then turned 90° north to form the northern segment of the western boundary. The northern segment of the western boundary was approximately 1 mile and terminated at a point 0.22 miles west of CSAH 16 to form the northwestern corner of the Pine Creek treatment block.

      The Pine Creek treatment block was located in the New Hartford Township. There were no state, federal, or tribal lands located within this treatment block.

    • 2017 Pine Creek proposed mating disruption block. Map created by MDA.


    • Healthy treeTreatments for gypsy moth in Minnesota can have two different goals. An eradication treatment, in the pre-infested area, is designed to completely eliminate a population of gypsy moths. An STS treatment, in the slow the spread area, is designed to reduce the gypsy moth population by two-thirds.

      To reach these goals, several products are available to program managers to target gypsy moths. Most commonly, Btk and mating disruption are useful for most projects.

      Btk, short for Bacillus thuringiensis var. kurstaki, is a common soil bacterium that has been isolated and mass produced for maximum effectiveness against gypsy moth. Visit the Minnesota Department of Health's webpage for human health risk information about Bacillus thuringiensis.

      Mating disruptants take advantage of the natural pheromone attractant of the female gypsy moth. Flooding the treatment area with the pheromone confuses the male gypsy moth's search for a mate and, if mating success is limited, fewer eggs are laid and fewer caterpillars are expected to hatch the following year.

      The MDA has successfully treated over 827,000 acres since 1980.

    • The MDA's annual trapping program is the first step in determining where a treatment may take place. Our small cardboard traps are baited with a scent that lures in the male gypsy moths, where they become trapped in the sticky coating on the trap's interior. If multiple catches in a single trap are found, more traps in and near that location are set the following year. This helps to outline a possible infestation.

      Once trapping survey data are analyzed, an alternate life stage survey is conducted in area with high numbers of male moths. If a gypsy moth egg mass is found, this confirms that a producing population exists. Finding even one egg mass often leads to proposing the site for treatment, since there are undoubtedly more egg masses – gypsy moths hide their egg masses very well. Moreover, each egg mass contains 500-1,000 eggs, which allows for moth numbers to increase rapidly.

      The next step is to examine egg mass survey results, past history, and survey data from the current year. Habitat suitability for gypsy moth is also taken into consideration. Urban environments with an abundance of oak and other trees, relatively few predators, and lots of sheltered spots for laying egg masses provide ideal gypsy moth habitat. Based on this data, recommended treatment sites are proposed.

    • At this point the local involvement process begins. Before treatments begin, local officials and the media are notified of our proposal, and public meeting are conducted in the treatment areas as part of an environmental assessment process. These public meetings not only allow us to explain what is proposed and why, but allows citizens to have their comments included in the assessment. We emphasize that this is a proposal. The final treatment decision comes at the end of this process, when the environmental assessment is signed by representatives from the U.S. Forest Service, the U.S. Animal & Plant Health Inspection Service, and other cooperating agencies.

      U.S. Postal carrier routes are used to identify residents within the proposed treatment area, and the MDA attempts to notify everyone in the area by mail. Because treatments are weather dependent, exact spray dates are estimated. Exact dates and times will be announced as soon as possible through local media, the MDA's toll-free telephone line and on this website. Once treatments are approved based on caterpillar development, spray locations are determined on a daily basis, based on local weather conditions. Local media will be notified the day before a treatment takes place. People may call the toll-free line to find out the spray schedule. Local law enforcement, health departments, schools, and hospitals will also be notified.

    • Aerial view of damage caused by gypsy moth

      Because of its ability to defoliate trees year after year, the gypsy moth is a significant environmental, economic, and quality-of-life issue, therefore, infestations and the treatments are taken very seriously. This insect pest is not native to North America and has no natural enemies to keep its population in check. Its native range is Europe, Asia, Siberia and northern Africa. Urban neighborhoods in the northeastern United States, much of the Atlantic Seaboard and Lower Michigan have been devastated by repeated defoliation by the gypsy moth.

      If sites are left untreated in Minnesota, here is what residents can expect within 5 to 10 years: in May/June, caterpillar numbers in any single backyard will reach into the thousands or even millions through June. Oak trees and other host trees and shrubs will be bare by the beginning of summer. Trees may grow a second set of leaves if they are healthy, but they will be weakened. If the tree is already stressed, as many urban trees are, they may die. If trees are defoliated for a second year in a row, they could die, falling victim to other pests because of their weakened state.

      Gypsy moth frass and leaf litter covering a picnic tableAs thousands of caterpillars feed, there is an audible sound of caterpillar droppings falling to the ground. Like any other excess nutrient, droppings get into runoff water and into the local watershed. Each caterpillar sheds its bristly skin four or five times as it grows, and the skins pile up. The bristles may become airborne and irritate human eyes, skin and respiratory systems. In fact, many people develop a rash if they come into contact with the bristles. It becomes extremely unpleasant to work or play outdoors; the caterpillars will also crawl on houses and may get inside.

      Caterpillars pupate in July, offering some respite to humans. The adult moths emerge shortly afterwards, and thousands of male moths begin fluttering around during the day, searching for females to mate with (female gypsy moths don't fly). Females lay eggs, resulting in thousands of unsightly egg masses, visible and hidden, reachable and out of reach, waiting through the winter to start the cycle over. Eventually the moth population will crash, but will re-establish over several years and repeat the devastation.

      Treatment at high infestation levels is more costly than the current low level of infestation and is typically funded in part or completely at the local level – often by individual property owners. Homeowners may have the option of not having their property treated once gypsy moth becomes established, but they will be unable to prevent neighbors from participating in local spray programs or using far more toxic pesticides than a public program might use. There is also considerable cost in removing dead trees and a decline in property value because of the loss of mature trees.

      These are the effects of individuals living in a gypsy moth-infested area, but what about the broader implications? When gypsy moth becomes generally established, counties go into quarantine status, meaning that no outdoor household articles may be moved to non-quarantines areas without proof they have been inspected and found free of gypsy moths. Individuals moving to new places, loggers transporting pulp wood, and nursery growers shipping their stock are all covered by the quarantine. Quarantines increase regulations, increasing costs to consumers. Minnesota has a responsibility to neighboring states to slow the spread of this insidious pest. Not treating does not mean that we are letting nature take its course; the gypsy moth is not a part of Minnesota's natural ecosystem, and as such it is a serious threat to our environment.

    • Spray aircraft normally arrive at urban sites at sunrise or shortly after. On average, a 640-acre block (one square mile) takes about a half-hour to spray with a plane or two hours by helicopter. The aircraft flies over the treatment block, making sequential passes. It will be very low (about 50 feet above the treetops), and loud.

      Spray plane Spray helicopter

      The MDA offers the following tips to residents in and around the treatment area:

      • For the moth treatment to work, it must begin early in the morning. Residents may be awakened on that day by the noise of the low-flying airplane. MDA apologizes for any inconvenience;
      • The airplane noise may spook pets, so residents may wish to keep them indoors during the treatment;
      • The treatment product has no known health effects for humans, but to avoid it residents may wish to stay indoors during the treatment and keep windows closed for a half hour after application; and
      • The residue will not damage a vehicle's finish, but residents may wish to park vehicles indoors to avoid having to wash them after the application. Soapy water will remove any residue on outdoor items.
    • Treatment products are determined based on the results of annual survey trapping, alternate life survey results, and size of the treatment area. Depending on the product, treatments are conducted to target either very young caterpillars or adult moths. In areas that have many male moths captured and where egg masses are found during the alternate life stage survey, Btk is used due to the evidence of a reproducing population. In areas with lower male moth captures over a more extensive area and where no egg masses are found during the alternate life stage survey, mating disruption is used.

      • Btk is used against small caterpillars and is applied in May-June. Since insect development is temperature dependent, an unusually cool or warm spring affects this timing. Treatments occur twice, about a week apart, to catch late-hatching caterpillars. Spraying normally takes place early in the day when low winds and high humidity allow the spray droplets to land where they will be the most effective, and also because fewer people are active outside. A site will typically be finished before children are walking to school or people are heading to work. Learn more health risk information about Bacillus thuringiensis from the Minnesota Department of Health and see frequently asked questions.

      • Treatments targeting adult moths will take place in July, just before the male moths emerge from their pupal cases. Aircraft will fly very low (about 50 feet above the treetops) and be loud. There will only be one application over each treatment area. Spray planes will start very early in the morning but are able to fly for most of the day if weather is favorable. People on the ground may or may not detect any product coming out of the airplane, but be assured that it is being distributed in a swath beneath the aircraft.

        Disrupt II pod 

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