Outbreaks of the western spruce budworm in the American northern rocky mountain area from 1922-1971
- Johnson, Phillip C.
Forestry Sciences Laboratory, Missoula, Montana
- Denton, Robert E.
Forestry Sciences Laboratory, Moscow, Idaho
The western spruce budworm has severely damaged more than 15 million acres of publicly and privately owned coniferous forests chiefly in the American northern Rocky Mountain area. Abundant information about behavior of the budworm, characteristics of outbreaks of its populations, and kinds and severity of damage is available from National Forest ranger district annual reports of insect conditions, which were started in 1925, and from later re- ports of damage surveys made by forest entomologists since 1948. The first report of an outbreak of this insect appeared in January 1922. Numerous out breaks have appeared since then, chiefly in forests of Montana and Idaho belt also in Utah and Wyoming. In a few ranger districts in Montana infestation has continued until now, but in many locations the budworm outbreaks have continued for less than 5 years.
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