The larch casebearer Coleophora laricella (Hbn.) is now established throughout all western larch stands in Region 1. Population levels have begun to fluctuate in some of the older infested stands; however, it is still on the increase in more recently invaded territory. During the past 2 years work was begun to develop a method to forecast defoliation and tg ollow trends of the larch casebearer (Ciesla and Bousfield 1971).111/ The purpose of these evaluations was to establish the relationship between the overwintering population and subsequent defoliation for prediction purposes.