Aerially visible defoliation by the western spruce budworm, Choristoneura occidentalis Freeman, increased from 149,250 acres in 1973 to 649,319 acres in 1974 on five eastern Montana National Forests. An egg mass survey during the fall of 1974 predicted that additional defoliation will occur in 1975 on 47 of 48 plots located on these Forests. Areas with the highest potential for increasing populations in 1975 are being considered as sites for pilot control projects of several promising chemical and biological insecticides.
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