Gypsy Moth

Gypsy moth aerial treatments will be done in select sites in Washburn, Douglas, and Sawyer counties on Wednesday, May 31, weather permitting.

A progress chart and maps of treatment sites can be viewed online at

Gypsy moth aerial treatments by the Wisconsin Department of Agriculture, Trade and Consumer Protection’s Gypsy Moth Slow the Spread (STS) Program. The STS aerial program for 2017 consists of 51 treatment sites, involving approximately 170,000 acres in 18 counties, mostly in western Wisconsin.

The treatments are necessary to control the spread of gypsy moth, a destructive and invasive pest that feeds on the leaves of oaks, maples, crabapple, birch, and many other species of trees and shrubs.

The first Btk treatments will begin at four sites. Most sites may have more than one treatment planned and will be treated again on a later date.

Planes will apply Foray 48B, which is approved for use in certified organic production or food processing by the Organic Materials Review Institute. The insecticide contains Bacillus thuringiensis var. kurstaki or Btk. Btk is a naturally occurring soil bacterium that is poisonous to gypsy moth caterpillars when consumed. Btk breaks down in sunlight within a few days.

Applications can start as early as sunrise and will continue until the day’s plan is complete and as weather conditions allow. Treatment applications require calm winds, high humidity, and no precipitation.

The planes will fly low, just above the tree tops. They will be loud.

Spraying does not affect organic certification. The insecticide is not toxic to people, bees, animals, birds, or plants.

People who have allergies may wish to stay indoors or leave the area until treatments are done. Pets or livestock may be frightened by the noise of the low-flying planes, so they may want to stay indoors.


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