Gypsy moth aerial spraying to begin in May

MADISON — Residents of 21 central and western Wisconsin counties can expect to hear and see loud, low-flying planes as early as sunrise, depending on weather conditions, starting in May. Small, yellow planes will be spraying for gypsy moth caterpillars. These invasive pests defoliate trees during their caterpillar stage, causing stress and potentially tree death.

Arial spraying for gypsy moth caterpillars.
Arial spraying for gypsy moth caterpillars.
Photo Credit: DNR

“These aerial treatments are the most efficient and effective method to reduce the spread of gypsy moth,” says Chris Foelker, gypsy moth control program manager. “Where this insect is well established in eastern North America, it has been a periodic public nuisance and damaging forest pest.”

The gypsy moth has a wide range of negative effects on local communities. The cost of removing dead trees around a house can range from several hundred to over one thousand dollars and the loss of mature trees will decrease property values. During the spring and summer, caterpillars shed bristly skin as they grow. Bristles from the cast skins can become airborne and irritate eyes, skin and the respiratory system. People may develop a rash if they come in contact with the bristles.

Gypsy moth caterpillar.
Gypsy moth caterpillar.
Photo Credit: DNR
About the Gypsy Moth Programs

Stay updated

Spray dates and times are weather dependent. People can sign up to receive email notifications about spray plans at gypsymoth.wi.gov (exit DNR). They can listen to a recorded message about spray plans by calling the toll-free Gypsy Moth Information Line at 1-800-642-6684. Press menu option 1 for updates.

Spraying is expected to begin in southern Wisconsin in early May and end in northern Wisconsin during August. Maps of the specific spray areas are available online at gypsymoth.wi.gov (exit DNR).

Spraying will be completed by two programs:

  • The Slow the Spread Program — conducted by the Department of Agriculture, Trade and Consumer Protection, focuses its efforts in western Wisconsin where gypsy moth populations are low or just starting to build for the first time. The objective is to slow the westward spread of gypsy moth. This year’s Slow the Spread treatments are planned in the following 19 counties: Barron, Bayfield, Buffalo, Chippewa, Crawford, Douglas, Dunn, Eau Claire, Grant, Green, La Crosse, Lafayette, Pepin, Richland, Rusk, Saint Croix, Sawyer, Trempealeau and Vernon.
  • The Suppression Program-conducted by the Department of Natural Resources, serves mainly eastern and central Wisconsin where gypsy moth is well established. In these counties, spraying is done to reduce the number of caterpillars and prevent damage from very high populations. This is a voluntary program that works with landowners and local governments. Two Suppression Program treatments are planned this year in Rock and Sauk counties.
Know what to expect

    Timing

  • Spraying depends on calm winds, no precipitation and high humidity. Planes may start spraying as early as 5 a.m. The planes fly very low and loudly over treatment sites and surrounding areas. Planes will continue spraying until the completion of the day’s spray plans and as long as weather conditions remain favorable. Spraying may last into the late morning or afternoon. Spraying could occur any day of the week, including weekends.

    Spray Treatments

  • Most sites will be sprayed with Foray, which contains Bacillus thuringiensis var. kurstaki (Btk). Btk is a naturally-occurring soil bacteria that kills gypsy moth caterpillars when they ingest it.
  • Btk is not toxic to people, bees, pets or other animals. However, some people with severe allergies may wish to stay indoors during nearby spray activities or avoid areas to be sprayed on the day that spraying occurs.
  • The formulation of this bacterial insecticide used by the state’s cooperative gypsy moth program is listed with the Organic Materials Review Institute as acceptable for use in certified organic food production.
  • The Slow the Spread program will also spray a mating disruptor to additional sites between mid-June and mid-August. The pheromone in the mating disruptor makes it difficult for male moths to find female moths in low, isolated populations, preventing reproduction.

For more information about the programs or gypsy moths, visit http://gypsymoth.wi.gov. Or, call the toll-free Gypsy Moth Line at 1-800-642-MOTH (1-800-642-6684) to hear a recording of current spray plans or talk to staff.