Popular Science Monthly/Volume 72/February 1908/The Future of Economic Entomology
|THE FUTURE OF ECONOMIC ENTOMOLOGY|
IT is now about three quarters of a century since the economic aspect of entomology was first presented for consideration in America, and this is perhaps an opportune time to survey the progress which thus far has been made, and in some degree to consider its future possibilities.
A careful examination of the writings of T. W. Harris, who may be termed the father of economic entomology in this country, shows several suggestive points. In his day the modern methods of using insecticides had not been discovered, and most of the treatments he suggested are included in the phrases hand-picking, whitewashing, cold water, fall plowing, cutting out borers and burning stubble for grain insects. Even in the cases where he advised the use of red pepper and tobacco, and soap or potash washes, the underlying thought seems to have been as much along the line of repelling as of destroying pests, and the idea of compelling insects to consume poisoned food appears to be entirely absent from his writings. Fumigation, too, though suggested in one instance, seems hardly to have had its possibilities appreciated, and it is probable that the most valuable contribution he made to the subject was the thought, quite new in this country, that insect depredations need not necessarily be accepted as in accordance with the will of God, but that active measures to prevent or reduce loss were possible.
Much has been learned since the days of Harris and new methods of control have replaced some of those he suggested. But it is discouraging to note that with many of our insect pests we stand to-day where we did then, and hand-picking, whitewashing, cutting out borers and fall plowing still occupy a prominent place in the entomological pharmocopœia.
Probably the most potent influence in the development of modern economic entomology was the spreading of the Colorado potato beetle to the east, and the resulting discovery that this pest could be controlled by the use of Paris green. That any insect consuming leaf tissues could be destroyed by applying a poison to be taken into its body along with its food was a discovery the credit for which will never perhaps be correctly assigned, but which marks the beginning of a new era in economic entomology, and rapid developments along this line followed, resulting in the formulation of the general principle of the utility of stomach poisons. This has led to the investigation of many materials from the standpoint of their value as insecticides, together with determinations of their relative efficiency in different cases, how to control their effects and how they may best be applied, resulting in the development of spray pumps, nozzles and spraying apparatus in general.
Closely following the discovery of stomach poisons as insecticides came that of contact poisons for sucking insects, for though Harris had suggested soap solutions in one or two instances the general principle had until this time failed to be formulated. Here, too, investigation progressed rapidly, developing different materials as contact insecticides varying in strength and in their range of application until this field may now be considered to have been well explored.
Fumigation, as a method of control, during all this time remained almost unnoticed, its limitations being apparently so great, and the fumigants themselves being so mild as to give little promise of results of value. But during the last twenty years the utilization of gas-tight tents, and of hydrocyanic acid gas and carbon disulfid has shown that this method of control has a far wider range of applicability than was formerly supposed, and fumigation is now perhaps as well developed and its possibilities as thoroughly understood as is the case with stomach and contact poisons.
During the last three quarters of a century the ravages of insects have so greatly increased as to attract much attention to the subject, and many persons have become specialists in economic entomology. Numbering less than half a dozen in 1850, we now find more than five hundred workers, each year publishing thousands of pages on the results of their investigations. Large societies now hold regular meetings at which the problems of economic entomology are discussed; and the subject, once of little importance and of which almost nothing was known, has now become a large and important branch of applied science, with more positions waiting than there are competent persons to fill them.
The rapid increase in the losses caused by destructive insects, which has focussed so much attention on economic entomology is difficult to state accurately in figures, but was estimated in the report of the U.S. Commissioner of Patents (then in charge of the agricultural work of the government) in 1850, to be at least twenty millions of dollars, while other estimates of that period made in terms of the total crop value placed the loss at about ten per cent. Since that date conditions have changed materially and are continuing to change for the worse. The development of speedy commerce has enabled many of the most serious pests of foreign lands to reach and establish themselves here, till in addition to our own native insects we have also one hundred or more from abroad, many of them developing destructive powers greater than in their native lands. The intensive agriculture and continuous acreage methods of recent years directly favor their rapid increase, and with the gradual reduction in numbers of our insectivorous birds one great check to their increase has been removed.
The result has been what might be expected. Estimates of the average annual loss by insects calculated at eighteen per cent., are now considered as about correct, and this loss on the basis of the United States government crop estimates for 1906 would be considerably over a billion dollars each year.
Nor is the end in sight. The pests of other lands are not yet all represented in the United States, though new ones arrive nearly every year. Agriculture is becoming more intensive, larger areas are being tilled, furnishing a more abundant and easily discovered food supply, and in spite of a healthy growth of interest in preserving our insectivorous birds, it is questionable if the developments connected with an increasing density of population will permit their preservation in any great numbers for more than another century.
This increase of loss has also occurred in spite of all the efforts of the economic entomologists, each one of whom can but acknowledge that while his efforts have not been in vain, the battle is nevertheless going against him, for in spite of all his efforts losses are becoming greater, insects more abundant and ultimate defeat seems certain, unless new and more effective methods can be brought into use in the struggle.
At the present time the economic entomologist is much in the same position as that of a physician who gives his prescriptions, but finds that many are never even taken to the druggist to be put up, while others, though prepared, are never taken and still others are taken but once. Many a crop is entirely lost by the neglect of its owner to apply the proper treatment and the value of many others is lessened one half or even three fourths by careless, shiftless work generally followed by entire failure to apply farther treatment because the first one being improperly or poorly made did not give the anticipated results.
If such are the existing conditions, what of the outlook? How long can this continue before greater crop destruction by insects and fungi, and an increasing population produce famine?
To these questions it is impossible to give decisive answers, though it is probable that many years are still between us and famine caused by insect ravages. But if an improvement of present conditions is desired, it would seem that it must come through the adoption of means by which spraying can be made more acceptable, or by the development of new methods of control.
The remarkable apathy of the crop producers of this country toward their insect foes, and their pronounced disinclination to carry out methods of treatment is an attitude which should be reversed as quickly and vigorously as possible. Much of this change must wait for a new and more intelligent generation, better educated by our colleges and by training in agriculture in the elementary schools. Many a farmer today, however, would gladly spray or otherwise treat his crops if he knew how, but the details of the processes as usually printed serve only to confuse him, and the necessity for handling and mixing chemicals accurately he feels to be beyond his powers. To help this large class it would seem desirable for each state to organize a traveling force which should go from place to place and at each show how to prepare and apply the different materials most commonly used, together with the different kinds of apparatus for different purposes, thus enabling any one to see for himself how to make and apply the treatments needed.
It is very possible that this plan may fail to accomplish the desired results, for farmers as a class are notoriously slow to accept new ideas and new methods. Still it is one which has many elements of promise and should receive a thorough trial in all parts of the country before being rejected.
But where does the economic entomologist stand if this plan fails? For years he has urged, taught and demonstrated spraying methods as effective, and he knows that he is correct. But when his advice is for years persistently rejected by a large proportion of the people, as is still the case, it is certain that the time has now come to place economic entomology on a broader and more scientific foundation.
To accomplish this other lines of work are possible, none of which have as yet been given sufficient consideration. The entomologist who would be successful must soon study more fundamental problems rather than questions of petty detail, for if the fundamental principles are once correctly enunciated the details will then become merely individual examples and can be quickly and easily solved.
If man can not be relied upon to combat his insect foes, it is not improbable that nature may be induced to take up the warfare. In some cases it seems probable that careful plant breeding will result in the production of varieties resistant to the attacks of insects, and along this line experimental research promises much. The development of new plant forms which has been made so prominent recently by the experiments of Burbank and others is very suggestive, and the possibility of producing varieties not attacked by insects seems to have already been demonstrated in one or two cases to some extent.
In the case of insects having numerous food plants this method becomes less feasible, and here a scientific study of what may be termed entomological parasitology may prove useful. We must recognize that parasitic protection is never more than partial, but even a partial destruction of insect pests is of great value. The problem is beset with difficulties because of the existence of parasites on the parasites and by many other factors, and a single wrong conclusion such as the recent statement that the Ceratitis on peach was effectually controlled by parasites in Brazil would be sufficient to discredit this entire method of investigation. For this reason only the best trained scientists especially educated for this line of work should attempt it and it would seem in many ways an appropriate work for the government to take up as it would necessitate much travel and expense, and its benefits would not be restricted to any one state.
If economic entomology is to attain success during the present century then it will be by inducing a more general adoption of the methods of treatment now known but not used generally enough; by the production of new, pest-resistant varieties of plants by experimental plant breeding; and by utilization of all the parasitic forces the world has available, establishing the parasites where their services are most needed and as free as possible from their own enemies. The old methods have proved too nearly useless because they have been so little adopted. A new departure must be taken and the world is waiting for a new Moses to lead the way out of the wilderness.