Integrated Pest Control - Theory And Practice

Everett J. Dietrick, 1976

The purpose of this paper is to define the practice of integrated pest control. For this definition I have drawn largely from papers and reviews, and from conversations with insect ecologists of the Department of Biological Control of the University of California, where I was employed for 15 years. I have had years of experience in practical application of integrated pest control techniques in the field, in my work as a professional insect ecologist representing Rincon-Vitova Insectaries, producers of beneficial insects. My experience also includes association with several well-established supervised control entomologists who are independent of any company affiliations: we are supervising integrated pest control programs on cotton, citrus, apples, pears, tomatoes, corn, potatoes, avocados, olives, grapes, eggplant, lettuce, geraniums, stone fruits and nuts, artichokes, strawberries, and others.

The increasing ineffectiveness of chemical pesticides and the farmer's narrowing profit margins have stimulated the search for more economic regulation of pests. One of these programs is integrated pest control that is, an insect population management system utilizing all suitable control procedures and agricultural production techniques, blending them into a coordinated pattern aimed at profitable production of quality products.

The philosophy of integrated pest control is based upon (1) the principles of applied ecology, (2) the recognition that 10000 mortality of all pests is not required, and (3) avoidance of disruptive chemicals. Since this philosophy of pest control is more of a system of principles for guidance than a set of rules in a fixed program, it requires more than the usual judgment to make it work on the farm.Integrated pest control is based on the principles of applied ecology. Whatever is done in any field situation is always founded, as far as possible, upon full knowledge of the ecology of the pests. In practice, this is attainable only by continuous sampling of the insects in all parts of the fields where integrated control programs are being applied. By this policy of watching the fields much more closely than usual, all the natural control factors can be exploited. Implementing this policy requires the services of a professional insect ecologist under contract to the farmer. This specialist in integrated pest control is the leader of a team that samples the fields, analyzing the total interacting complex of organisms, including the pests and their biological controls, and the effects of all of the agricultural practices and industrial activities of man. This dynamic consideration of the fields takes into account the evolving patterns of plant growth, seasonal developments, and the ever-changing populations of organisms associated with them. Emphasis is always on the developing insect population levels and the predictions as to the course that the pest populations will take.The supervising insect ecologist implements successful pest management in the fields by applying any or all practical cultural and biological practices known to suppress the pests. To attain a favorable balance in a field, it is necessary to attract, augment, and conserve all possible numbers of beneficial predators, parasites, and disease organisms in the fields. Even low numbers of insectary-grown and/or field harvested beneficial insects can be colonized.

Best results from integrated pest control are obtained when effective natural enemies of most target pests are present in the complex of organisms. Crop rotations to alfalfa, grains, and pasture, along with planned cover crops, bring greater plant diversity to a farming area. This diversity of plants brings greater diversity in both host and prey species, and provides nectar, pollen, and alternate host organisms as food for predators and parasites. Alfalfa, grains, and pasture grasses are normally under such satisfactory biological control that they usually require very little control other than cultural management. Such management programs in alfalfa, using strip harvesting techniques, aids in preventing sudden emigration of pests at cutting time. With less disruptive action to pests and their biological controls, there is greater stability in population interaction, and less chance for one species to dominate and cause damage. Different natural enemies have different efficiency levels related to pest population densities; the above environmental manipulations help provide a complete complex of predators and parasites, at a very low cost.

Field harvesting techniques can selectively remove portions of pest populations and collect many predators, parasites, and disease organisms for use in augmenting the natural controls in other fields. Releases of this material, along with colonizations of insectary-grown beneficial insects, can help bring the field into a favorable balance in time to prevent economic losses.

Every pest spot in a field that is controlled biologically adds to the total number of predators in the field; every biologically controlled field grows more predators for the nearby fields and the agricultural area. The less you spray, the less you need to spray. This complex of beneficial insects is a natural resource that the farmer must protect and conserve by applying pesticides only when absolutely necessary to protect the crop. For certain pests there are no immediate prospects for development of effective pest suppression techniques. Then pest populations increase beyond tolerable limits and there is no predictable chance of obtaining a favorable balance, the crop can always be sprayed.

This leads us to the second principle of integrated pest control; a recognition that l00% mortality of all pests is not required to prevent economic losses. This may seem elementary, but society has been brainwashed into believing that "the only good bug is a dead bug"; it is important to point out that insects, mites, weeds, etc. are pests only when they affect our way of life beyond tolerable limits, It is essential to the concept of integrated control that we live with a few pests in order to obtain and retain a favorable balance.

Strict standardization procedures that do not necessarily give the consumer food of better quality or taste may force the farmer to spray for light infestations of a pest. Often any plant damage that might occur would not be harmful to the crop, except perhaps in appearance. Plants can tolerate low populations of aphids, thrips, and mites with no intolerable damage affecting profitable production of the crop. Instead of spraying, the insect ecologist uses these minor pests as food in colonizing additional insectary-grown or field harvested predators. The challenge for the future is to devise ways to grow and or field harvest sufficient beneficial insects and apply them to the fields by mechanical means; in this way, biological control could be better implemented and guaranteed, and many more fields could be saved from pesticides.

The third principle of integrated pest control is the avoidance of disruptive chemicals. Not all pesticides have adverse effects, and certain dosages of conventional pesticides are less disruptive to the existing biological control. Backup sprays are applied when necessary, but of a kind and in a manner least disruptive. Integrated pest control seeks to suppress target pest populations below tolerable damage levels without destroying their biological controls. The professional insect ecologist must know how to use pesticides in this way in given situations. However, because of the polluting side effects of too much pesticide in the environment, it is even more important that he know when and where not to use them.

There is not time to dwell on all the pest control problems that have developed as a result of complete reliance on chemicals; a short list would include target pest resistance to pesticides, target pest resurgence following treatments, secondary pest outbreaks, pesticide residue problems in the crop, the soil, or drift to nearby areas, or runoff to streams and drainage, and destruction of pollinators and other forms of life beneficial to man. In many instances these side effects have created havoc, and the undesirable results have more than off-set any original benefits. It is becoming more and more difficult to kill the target pests economically.

One often-underestimated side problem is the drift of pesticide residues onto nearby crop areas and the widespread effect of destroying favorable biological balances. Searching predators and parasites moving over the plants in search of prey are exposed to more residue, and are killed in greater numbers than the more sedentary pests. This uncontrollable drift creates new pest situations in nearby fields, that in turn require treatment: the problem is spread further and further. Such drift effects have triggered pest outbreaks over large areas and destroyed many beneficial insects. The more you spray the more you need to spray.

The cost of chemical pest control programs is high when all of these side effects begin to interact. The crops may be saved, but at great cost to society and the farmer (who is stuck with the pesticide bills). The real measure of success in farming is in the profits; the real problem that causes the farmer to look for new answers to pest control is the spiraling cost of repeated and ineffective treatments. This search for new answers has forced farmers and entomologists to modify their pest control practices, so as to avoid disruptive chemicals as much as possible.

How effective is integrated pest control in practice? Experience has shown that this philosophy, when practiced on the farm by competent professional insect ecologist, is the only pest management system dynamic enough to solve the problems and keep up with the changing agricultural problems of the future.The farmer must willingly support a team effort to carry out practical application of integrated pest control. The leader is the insect ecologist, a highly trained specialist who utilizes materials and techniques as complicated as those used by the pharmacist or veterinarian. New, more sophisticated integrated pest control programs of the future will be implemented by these professional insect ecologists. The backup part of the integrated pest control team is the insectary, which grows the predators and parasites, and field harvests other beneficial insects, for use in applying positive biological and environmental pest suppression. Other members of the team are the researchers, specializing in long-term ecological studies and development of integrated pest control techniques. Laboratory research specialists on physiology and behavior can discover much to aid in interpretation of data, but only studies in the fields will reveal the true interplay of all the complex ecological factors. The usual fragmentary short-term experiments, so common in pesticide evaluations, are more than vulnerable to error, when considered in the long-term ecological sense.

It is important to understand that valid scientific discovery can result from careful observations and recordings of recurring natural happenings. In other words, scientific proof can be obtained from a sequence of experiments or experiences. History will repeat itself, provided the same combination of effective conditions recurs. In applying integrated pest control, the insect ecologist frequently samples and assesses the fields in his care, constituting a continuous experiment in applied ecology not duplicated at research level. This experiment is carried out in many different field situations, throughout the season, and often over many years on the same farm. What better proof is there of the success of integrated pest control than the practical experience of profitable production of quality products?

Research specialists in integrated pest control must work closely with the insect ecologist, who is the foreman in charge of pest control. Since a multifactored environment is not easy to understand, the researcher can aid in interpreting the experience of the applied worker. At the same time, the insect ecologist can provide assistance to the researchers economically, gathering samples, etc., because he lives in the area of the field experiment. In this way the practical limitations of time and money can be somewhat overcome, and the work of solving the pressing problem of pest control can continue.The commercial pest control applicators and the producers of chemicals and other pest control products will continue to make an important contribution. The pesticide companies will make new products to answer the needs of integrated pest control, because it is the more selective target pesticides that are least disruptive that the farmers will buy.

Active and aggressive educational programs supporting the ecological approach to pest control can help separate fact from fiction regarding integrated pest management. General recommendations to farmers should be flexible, to allow time for alternative integrated pest control techniques to be exploited. Adjustable economic injury levels, including the assessment of beneficial organisms and suggestions for use of selective pesticides, are advisable.

The combined efforts of all members of the integrated pest control team are needed to insure successful and profitable production of sufficient food and fiber for the future. Successful pest control is relative, but in the final analysis it is measured in the economic sense. High costs of ineffective pesticide programs and their ultimate effects on food and fiber prices concerns farmer and consumer alike. There is no question of the success of integrated control in the minds of farmers who have changed their philosophy of pest control and are "suddenly" not paying excessive pesticide bills. The first year or two of successful integrated pest control is often attributed to "luck" or a "good year" by critics of such programs. After several years of economical pest management with little or no spray bills, the farmer eagerly support their insect ecologist and the insectary that supports him. As food supplies become shorter in the coming decades, and as consumers become more conscious of high food costs and toxic residues in foods and less conscious of appearance only, the artificial standards that pesticides depend on will be relaxed. More sophisticated and safer processing of farm products will be developed to insure removal of insect parts, with the result that the consumer will have bug-free as well as toxicant-free products.