A comparison of the SPOT and Landsat thematic mapper satellite systems for detecting gypsy moth defoliation in Michigan

The task of monitoring gypsy moth defoliation is becoming more difficult as the area of defoliation increases. The gypsy moth is now established throughout much of the northeastern U.S. and in Michigan, the site of this study. Defoliation in Michigan occurred on over 120,000 hectares in 1989, with a larger area anticipated for 1990. It is imperative that a monitoring system be able to collect information over these increasingly larger areas in a short time period and at relatively frequent intervals. In this aper we examine and compare two satellite systems―SPOT and the Landsat Thematic Mapper―for their efficacy in discriminating two levels of defoliation, moderate and severe, and non-defoliation.