Forest Preserve District of Cook County, Illinois
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Nature Bulletin No. 687   Septe4mber 29, 1962
Forest Preserve District of Cook County 
Seymour Simon, President
David H. Thompson, Senior Naturalist

The use of chemicals for the control of insect pests, rats and mice, weeds, and the fungous diseases of cultivated plants has become an increasingly widespread practice over the past century.

Beginning in 1867, Paris green -- the first successful insecticide -- was used to control the Colorado potato beetle. During the next 75 years other compounds of arsenic were used more and more for the protection of such crops as fruit, vegetables and cotton. These were supplemented by certain plant products -- pyrethrum from a chrysanthemum flower, nicotine from tobacco, and rotenone from a few tropical legumes .

At the height of World War II, after a frantic search, it was found that an obscure synthetic chemical, now nicknamed DDT, was a remarkably powerful, long-lasting insecticide. In the Pacific and other theaters of the war it was used on a large scale to control those insect-borne diseases that have often decided the outcome of wars. It was a top- secret weapon in the Allies' arsenal.

In 1945, DDT was released for agricultural, household and general use. Large numbers of other synthetic insecticides followed in quick succession. One group, the chlorinated hydrocarbons, is chemically similar to DDT. Another main group is known as the organic phosphates. Both proved so effective on insect pests that many older poisons rapidly declined in popularity.

Soon it was discovered that these miracle chemicals were not unmixed blessings. For example, it was found that DDT does not readily break down, evaporate, wear off or wash off. While this is desirable for some uses, there is the disadvantage that it accumulates in the body fat of animals. It also shows up in milk and milk products. As a result, research programs continually study these pesticides to determine how and which ones may be used best.

At first, DDT worked like magic on houseflies. Sprayed lightly on the walls and screens of homes and farm buildings, or added to paint, it promised freedom from this age-old pest. After a few years, however, flies no longer were affected by the poison and began to increase in numbers. The few survivors had bred a race which is able to resist extremely heavy dosages of DDT. Mosquitoes, roaches, lice, fleas and many other pests are becoming resistant to the commonly used insecticides .

Some pesticides set off a chain reaction. Elm trees in cities and towns are often sprayed heavily with DDT to kill the bark beetles that spread the Dutch elm disease. If this is done in summer, the poison clings to the leaves until they fall in autumn. Later, as earthworms feed on these decaying leaves, the DDT accumulates in their bodies. These worms, though not killed themselves, can be deadly to the robins that eat them the following spring.

Wildlife may suffer severely when wide areas are blanketed with heavy dosages of insecticides in attempts to eradicate or control certain invading insect pests. In extreme cases most of the birds, mammals, fish and beneficial insects have been temporarily wiped out. In a few of these instances, the misuse of insecticides has brought discredit on all pesticides. In spite of these blunders in special cases, the wise use of pesticides plays an important part in the production and protection of our food.

In prairies, woodlands, wetlands, stream and lakes the story is entirely different. The less these are disturbed the better. In our ever-growing need for lands offering outdoor recreation, education and enjoyment to the public -- these have their greatest value when allowed to remain as nearly natural as possible.

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