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PEST CONTROL IN AGRICULTURE George C. Decker Illinois Natural History Survey Nature recognizes no such categories as pests or wildlife and these man-conceived terms have vastly different meanings to many people. It makes little difference whether we regard wildlife as embracing all non-domesticated plant and animal life or accept a more limited definition. In either case, pests are living organ- isms distinguished from many other forms of wildlife only by the fact they have acquired the great displeasure of one of their chief competitors, man. In nature, from time immemorial every living organism has been engaged in relentless competition with every other organ- ism upon which its interests impinge. Man is a part of that en- vironment. By virtue of a unique attribute called intellect which enabled him to develop powerful tools capable of changing physical and ecological environments to suit his needs and whims, he has risen to a position of dominance. In his ascent man selected, pro- tected, propagated, and husbanded certain plants and animals most desired by him. Other species detrimental to man or to the organ- isms he has chosen to husband he regards as pests to be suppressed or, if possible, exterminated. Man's success is evidenced by the fact the human population of this country has risen from less than one million to over 170 mil- lion in some fifteen to twenty generations. To clothe and feed this vastly increased population, a high level of agricultural production must be maintained. While America is presently blessed, or, as some say, plagued, by overproduction, with populations increasing and the area of farm land decreasing, it is only a matter of a few years until agricultural scientists and farmers will have to make ever-increasing use of agricultural technology, including even greater efficiency in pest control, to meet the nation's food and fiber requirements.
Cultivated crops grown in North America are attacked by over 3,000 economically important species of insects, as many plant disease agents, and unestimated numbers of nematodes, ro- dents, weeds, and other competitors. In 1954, the United States Department of Agriculture estimated that to offset the pest losses in agricultural production, an extra 88 million acres must be culti- vated, and that losses subsequent to harvest equal the production of an additional 32 million acres. Estimates of the destruction caused by agricultural pests made independently by several other agencies range somewhere between 8 and 15 billion dollars annuallyâa quarter of our annual productionâand this despite the widespread use of the best control practices now available. One must recall also Section 402 of the Food, Drug and Cos- metic Act clearly indicates that food contaminants may be either biological or chemical in nature. Thus, each year the Food and Drug Administration seizes as unfit for human consumption literally thousands of tons of food. Roughly three-fourths of all these sei- zures are attributable to filth or decomposition, which of course includes the presence of insects, insect fragments, molds, fungi, bacteria, and other undesirable organisms. In the light of these facts the Food Protection Committee has repeatedly said: "Plant and animal pests rank among the foremost causes of food destruction, food deterioration, and food contamination. Hence, the absolute necessity of protecting growing crops and products from serious attack by insects, plant diseases, and other pests is recognized as essential from the standpoint of both quantity and quality of the food produced. " There seems to be general agreement that pest control is es- sential. The area of disagreement seems to involve the procedures to be followed. Since nature does such an excellent job of establish- ing and maintaining balances between species and establishing limi- tations on species, it would seem logical that man, to be most successful in influencing plant or animal populations, should thor- oughly study and then attempt to emulate nature. Our highly successful agriculture of today reflects and is a tribute to man's success in modifying the forces of nature to pro- vide a suitable environment for the production of his crops and 4
livestock. Likewise biologists are attaining considerable success by making rather minor changes in an established environment to provide additional food and cover favoring the reproduction and sur- vival of selected species such as pheasant, quail, and game fish. Conversely entomologists and plant pathologists have through ma- nipulation of the environment, attained considerable success in con- trolling a number of agricultural pests. Pursuing this concept, pest control should be largely bio- logical and ecological in nature. But some home philosopher has said, "You can't have your cake and eat it too. " By modifying the environment in his own favor, man provided an abundant food supply and other environmental conditions highly favorable to many species of insects and other pests; thus he inadvertently created many of his most important pest problems. To reverse the procedure might well nullify some essential production gains. Actually, in years gone by, biologists generally did devote most of their research time to biological and ecological studies, and for many years ecological, cultural, and mechanical control measures dominated all pest con- trol activities. It was only after such methods alone proved to be inadequate and the needs for better pest control became imperative that the farmers themselves turned to the use of chemicals which showed promise. Scientists more or less reluctantly followed their lead, and thus we entered an age of chemical pest control. The rise in pesticide usage has been closely associated with and has run parallel to the advances in farm mechanization. Thus, in these days of automation and labor-saving devices, pesticides are regarded as chemical tools which are just as indispensable as mechanical tools in the production of agricultural crops. It would be economically impossible for farmers to abandon the use of pesti- cides. Capital investments in farms today are such that occasional complete or even partial crop failures cannot be tolerated. If the use of chemical pesticides were to be prohibited or abandoned, it is safe to say most fruits and vegetables would totally disappear from the market or the price of the meager quantities produced would be prohibitive. We know from valid studies con- ducted over the years that apples produced without pesticides will be 40 to 80 per cent damaged by codling moth and 60 to 80 per cent damaged by apple scab, plus an equal or even greater degree of damage caused by other insects or diseases. To this we must add the destruction that would be wrought by wood borers, scale insects, and other pests of the trees themselves.
Without the benefit of pesticides, the yield of staple fiber, cereal, and forage crops could be expected to drop by from 10 to as muchas25 per cent. Careful studies have shown that the omission of insecticide treatments resulted in reduction of cotton yields 25 to 40 per cent. Agronomists have demonstrated quite conclusively that a given acre of land is able to produce just so much dry matter in any given season. With weeds partially uncontrolled, crop yields would be proportionately reduced, and with weeds completely uncontrol- led, yields would be practically nothing. With the advent of DDT for agricultural use in 1945 and the large array of cholorinated hydrocarbon and organophosphate in- secticides that followed in quick succession, a number of indi- viduals, including some distinguished scientists expressed concern lest the widespread use of these materials might create a public health problem. This aspect of the problem was reviewed by sev- eral scientific bodies, notably the World Health Organization, the U. S. Public Health Service, and the Food Protection Committee of the National Research Council. The general conclusions drawn in each instance were: (a) The large scale usage of pesticides in the manner recommended by manufacturers or competent authorities and consistent with the rules and regulations promulgated under existing laws would not be inconsistent with sound public health pro- grams, and (b) although the careless or unauthorized use of pesti- cidal chemicals mightpose potential hazards requiring further con- sideration and study, there was no cause for alarm. However, the very fact insecticides may and no doubt will be misused still remains a matter of some concern to a considerable segment of the American public. This is true particularly of con- servationists and wildlife enthusiasts who quite correctly insist that many forms of wildlife are subjected to certain potential hazards not shared by man and his domestic animals. Many pesticides are admittedly highly toxic to a wide variety of plants and animals. Unquestionably under certain conditions of use they could and do cause some damage to certain species of wild- life. However, a survey of the literature quickly reveals that prac- tically all of the unfortunate incidents recorded to date have involved non-agricultural uses of pesticides such as outright experimenta- tion, eradication programs, excessive rates of treatment in non- agricultural habitats, etc. While there have been numerous minor
incidents involving carelessness, misuse, and accidents, the num- ber of such incidents in agriculture have been amazingly few and far between. In general, agricultural lands present simplified ecosystems with minimal wildlife populations. Pesticide dosage rates are relatively low, and residue dissipation is often so rapid as to neces- sitate frequent retreatment in order to hold even highly susceptible pests in check. Thus, despite the use of billions of pounds of pesti- cides on millions of acres of cropland, damage to wildlife attribut- able to these treatments has been relatively insignificant and in the vast majority of cases undetectable. To quote from the most com- prehensive and complete study of the problem, "Considered in its broadest scope, at the present time pesticides seem to be only minor influents in nature compared to other factors in land and water development and use. " Not infrequently pesticides are accused of upsetting the balance of nature, when insofar as agriculture is concerned it would be more accurate to say they were used to suppress an organ- ism already out of balance. Actually, man himself has been the primary factor in upsetting the so-called natural balance. When he cleared the forest, plowed the prairies, drained a marsh, or dammed a stream, he altered an entire environmental complex and set up an entirely new set of opposing forces which if left unin- hibited would establish an entirely new biotic equilibrium. When those who oppose the use of pesticides propose the substitution of unevaluated, untested non-chemical procedures, they might do well to recall that any change in the environment produces almost endless chain reactions and a realignment of all the forces operating in an ecosystem. Thus, it is possible such measures might have even greater repercussions. Fortunately, most exaggerated differences of opinion emanate from individuals of limited experience or interest who are apparently unable or unwilling to visualize the problem in its full perspective. Now, as never before, scientists in the various disciplines are working together in a common effort to evaluate and solve a mutual problem.
