The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) plans to treat select areas in nine western Wisconsin counties for spongy moth (Lymantria dispar) starting in May. Residents can expect loud, low-flying planes in the affected areas as early as sunrise. A small yellow plane will be treating for invasive spongy moth caterpillars. These non-native insects defoliate many kinds of trees and plants during their caterpillar stage, causing tree stress and potentially tree death. In an attempt to slow their spread, treatment efforts will be focused in western Wisconsin, where spongy moth populations are limited or beginning to build. In May to early June, planes will spray Bacillus thuringiensis var. kurstaki (Btk), targeting spongy moth caterpillars. Btk is a naturally-occurring soil bacteria that kills spongy moth caterpillars feeding on treated canopy foliage. The following counties are scheduled to receive Btk treatments: Barron, Buffalo, Chippewa, Crawford, Dunn, Grant, Iowa, Lafayette, and Rusk.