Economic Entomology and Insecticides

Stand dismayed, you farmers
wail, you vinedressers,
for the wheat, for the barley;
the harvest of the field has been ruined.

Joel 1:11

Spray, farmers, spray with care,
Spray the apple, peach and pear;
Spray for scab, and spray for blight
Spray, O spray, and do it right.

E.G. Packard

In order to understand the controversy over DDT, one must first see it in context. In 1945 the "atomic bomb of insecticides" was a novelty, but chemical insecticides were well established, to the point that they were almost synonomous with insect control. Farmers, economic entomologists, and government agencies had had a half-century of experience in using, recommending, and regulating insecticides. They had a frame of reference into which they would easily fit the new chemical and others like it. It was this frame of reference, a set of unspoken and almost unconscious assumptions about the need for, and the uses, disadvantages, and possible dangers of chemical insecticides, that accounts for the enthusiastic and almost uncritical acceptance DDT found in 1945, and that helps explain both the wide use and the passionate defense conducted later.

The frame was assembled in the late nineteenth and early twentieth century, as economic entomology and chemical insecticides grew out of efforts to meet the problems of insect infestation that plagued the American farmers in this period. Although these were years of enormous agricultural expansion, they were troubled times. Falling crop prices, high railroad rates, and natural disasters made farming an often frustrating business. Among the difficulties was an increase in insect damage to crops, a problem one historian has labeled the "insect emergency." So it must have seemed to the inhabitants of the Great Plains and, to a lesser extent, to the rest of the country. In the 1870s a series of grasshopper swarms ate up the crops. They were followed by the chinch bugs, which ruined farming in the eastern edge of the Plains. The army worm, the cotton worm, the codling moth (apple worm), Hessian fly, Colorado potato beetle, and a host of other pests devoured the crops. Even in Golden California various scale insects threatened to wipe out the young citrus fruit industry.

The insect emergency was in large part due to the progress of the period: the spread of commercial agriculture across the continent, the regional specialization that was coming to mark production for a national market, and the increased speed and volume of transportation meant that diverse ecosystems were being replaced by simpler ones, by continuous areas of food and shelter for the insects that ate the crops, and that railroads and wagons were busily (if unintentionally) spreading pests to these new and attractive homes. An excellent case in point is the Colorado potato beetle. In the early 1860s wagons returning from the Colorado Rockies brought the beetle from its native habitat, where it lived on a variety of plants, to Illinois. There it found ideal conditions, enormous supplies of food (it quickly came to favor the potato vine), few natural enemies adapted to prey on it, and relatively continuous cultivation. It spread from patch to patch, flying or traveling on wagons.

Native insects that developed a fondness for crops were only part of the farmers' problems. There were other insects that normally preyed on the crops and, in addition, many European pests accidentally introduced into the United States by steamship and clipper. These posed a particularly serious danger. Most American crops were native to Europe or Asia, where their pests had developed along with enemies to prey on them. Settlers had brought the crops and commerce seemed, inadvertently, to be bringing the pests, but there was no one to fetch the parasites and predators. As a result, insects that were not important problems in their homelands caused enormous damage here. The fluted, or cottony-cushion, scale, which threatened the California orchards in the late nineteenth century, was native to Australia. The gypsy moth came from Europe, the boll weevil from Central America (via Mexico). In 1897 the head of the USDA's Division of Entomology, Leland 0. Howard, found that thirty-six of the seventy-two most dangerous insect pests in the country were of foreign origin and another six were suspected of being aliens. Worse, Howard warned, there were others, such as the Mediterranean fruit fly, which might enter at any time. He ended with a plea for an adequate quarantine inspection service.

The transportation of insects around the world and their adaptation to new areas was a significant part of the breakdown of isolated floras and faunas that took place in the nineteenth century. American farmers, though, if one may judge from the literature, cared little about the biological significance of their problems. They just wanted to get rid of the pests, and in their desperation they turned to all kinds of remedies, from patent bug-killing machines and days of prayer and fasting (declared by the governor of Missouri during the "hopper" epidemics of the 1870s) to a bewildering variety of washes, emulsions, baits, and sprays. The favorite remedy, which gained in popularity during this period, was chemical poison. The first chemical used on a large scale was paris green — a common pigment for paints and wallpaper — and its first target was the Colorado potato beetle. Beyond these few facts, it is difficult to trace the early history of insecticide use. There were several claimants to the honor of inventor of the beetle poison. In 1868 a farmer in Fond du Lac, Wisconsin, said that an Iowa man had told him that paris green mixed with ashes and sprinkled on the vines would poison beetles. The same year J. P. Wilson patented a solution of one part paris green to two parts mineral oil for the same purpose. Other stories circulated through the rural press, along with recipes. It is probable that several people independently made the discovery. Paris green was, after all, copper aceto-arsenite, and everyone knew, if he knew nothing else about it, that arsenic was a deadly poison. What more natural than to put it on the vines and see what happened?

The use of chemicals increased, slowly at first,...