The state plans to continue spraying for gypsy moths on Tuesday in three western Wisconsin counties.
Spraying in Dunn, Eau Claire and Pepin counties was to continue as long as winds are calm, there is high humidity and no rain.
The process is loud as single-engine airplanes fly loud, just above the treetops, to do the spraying starting as early as 6 a.m.
The Wisconsin Department of Agriculture, Trade and Consumer Protection says spraying of non-toxic, organic insecticide is needed to control the spread of the destructive and invasive pest that feeds on the leaves of oaks, maples, crabapple, birch and many other trees and shrubs.
The gypsy moth in its caterpillar stage is known to feed on and defoliate more than 300 different species of trees and shrubs.