The Effects on Fish, Birds and Mammals of DDT Used in the Control of Forest Insects in Idaho and Wyoming

the eastern United States (Cottam and Higgins, 1946; Nelson and Surber, 1947), but none has been reported in the forested areas of western United States. During May, 1947, 413,500 acres of forest were sprayed with DDT in oil solution to control an epidemic of tussock moth (Hemerocampa pseudotsugata) in northern Idaho. In July and August, four plots were sprayed in northwestern Wyoming in an experimental attempt to control mountain pine beetle (Dendroctonus monticolae). The spraying was done by airplane under the supervision of the Forest Service and the Bureau of Entomology and Plant Quarantine. These projects gave an opportunity to study the effects of DDT on the fish and wildlife. In Idaho, forests in the western foothills of the Bitterroot Mountains near Moscow were sprayed at the rate of one pound of DDT per acre. The trees principally affected by the tussock moths were Douglas fir (Pseudotsuga taxifolia) and grand fir (Abies grandis). The vegetative habitat also included western white pine (Pinus monticola), ponderosa pine (Pinus ponderosa), western red cedar (Thuja plicata), lodgepole pine (Pinus contorta), and associated species. There was generally a heavy understory of several kinds of shrubs such as willow (Salix sp.), snowberry (Symphoricarpos racemosus), Oregon grape (Odostemon aquifolium), serviceberry (Amelanchier alnifolia), and Menziesia (Menziesia ferruginea). There were more than fifty streams in the treated area including the Palouse River, Potlatch Creek, Elk Creek, and their tributaries.