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Potential for defoliation by western spruce budworm in northern Idaho and Montana, 1977 Public Deposited
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Epidemic populations of the western spruce budworm persist in the Northern Region. Aerial surveys made in August 1976 showed a decline in the acreage of aerially visible defoliation. In northern Idaho, the defoliated area dropped from 831,487 acres in 1975 to 655,711 acres in 1976, down 21 percent. Surveys in Montana found a net decrease in defoliation of 11 percent, down from 2,797,986 in 1975 to 2,496,274 in 1976. Egg mass surveys made in September and October 1976 indicate that defoliation will be light on the Clearwater and Nezperce National Forests and moderate on the Idaho Panhandle National Forests, Idaho, in 1977. Defoliation in Montana during 1977 is expected to be light on the Flathead, moderate on the Kootenai, and heavy on the Beaverhead, Bitterroot, Deerlodge, Gallatin, Helena, Lewis and Clark, and Lolo National Forests and the Flathead Indian Reservation.
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