Forest Preserve District of Cook County, Illinois
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Nature Bulletin No. 31  September 8, 1945 - [edited April,1998]
Forest Preserve District of Cook County
Clayton F. Smith, President
Roberts Mann, Superintendent of Conservation

Large scale experiments are being conducted on selected areas scattered all over the United States and Canada. The U, S. Fish and Wildlife Service, the U. S. Forest Service, the Bureau of Entomology and Plant Quarantine of the Department of Agriculture, and the U. S. Public Health Service are among the agencies cooperating in these experiments. DDT is being applied in the form of dust, suspensions, solutions and emulsions, by means of airplanes, high-powered sprayers, knapsack sprayers, and hand atomizers.

It is being tested against leaf-eaters, bark beetles, wood borers, termites, and a number of sucking insects, including mosquitoes and flies. The experiments indicate that DDT far surpasses any previous used substance for control of insects harmful to forests, orchards, gardens and man himself. Its remarkable lasting qualities, even after rains, the small amount required per acre, and its suitability to application by plane, would seem to make it the answer to most problems of control of harmful insects.

BUT, these problems are complex. For instance: what do many birds feed on? Insects and their larvae. What keeps many harmful insects under control? Other insects. We now know that certain concentrations of DDT upon the surface of a pond or lake will kill the mosquito larvae, but they also kill every fish in that body of water, and the aquatic insects upon which fish feed. While it may kill the harmful moths in an orchard, it also kills the bees necessary for the polarizing and fruiting of that orchard. Its toxic effect in various concentrations, on beneficial insects, fish and wildlife is a serious problem which requires thorough investigation. DDT might do more harm than good. Carefully controlled experiments, watched by scientists specializing in the several fields involved, must be made.

Certain large areas of the Forest Preserve District are included within the boundaries of the DesPlaines Valley Mosquito Abatement District and the North Shore Mosquito Abatement District. We have requested the officials of these districts not to use DDT in the forest preserves until more definite knowledge is obtained from the experiments being carried on by the several government agencies. These agencies have been requested to supply us with up-to-the-minute bulletins of the results so obtained.

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