Illinois
Fertilizer Conference Proceedings
January 23-24, 1990
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K.L. Steffey and X.E. Gray1
The risks and benefits associated with all of the different insect management techniques could not be discussed satisfactorily in several volumes of print. The risks and benefits of many pesticides, including insecticides, are being studied in detail by an untold number of different groups, and each group has its own agenda. The risks of pesticides are bandied about in the press to such an extent that the general public has more knowledge about pesticides today than at any time in the past. Whether the public's knowledge is accurate, and whether both risks and benefits have been presented equitably and objectively could be argued to the point of fatigue.
Our task is to present the risks and benefits of agricultural insecticide, use, ranging from no use to intensive use. These risks and benefits must be viewed from the standpoint of both agriculturists and the general public, and they should be examined objectively with both short-term and long-term considerations. As all of these viewpoints are considered, one must take into account the economic, environmental, and human health repercussions of continued or discontinued use of insecticides.
The arguments on either side of the issue of agricultural insecticide use are well-grounded in subjective and objective risk/benefit analysis. Those arguing the "Pro Pesticide" side of the issue point out that U.S. agriculture feeds the world, and pesticides have allowed American farmers to grow more food on less land than ever before. The argument is sound and is supported by a wealth of data. The "Con Pesticide" argument is also supported by ample data regarding residues of pesticides on food, contamination of groundwater with pesticides, and poisoning of birds and other wildlife by pesticides. As a consequence, one can consider the argument as one of "opposing goods" (Nevling 1989).
The production of food and fiber for the world population is good. However, the protection of our food, safety, and environment is also good. No one could successfully deny that both sides of the argument are "goods." Therefore, we must determine a way to maintain the balance between the requirements of agriculture and the protection of our food, health, and environment, a way that will satisfy rational individuals representing both sides of the issue.
The benefits associated with the use of agricultural insecticides are primarily economic in nature. When an insect outbreak occurs, usually the only response mechanism available to reduce the insect population and prevent further damage is the use of insecticides. In general, compared with certain other insect management techniques and other farm inputs, insecticides are also relatively cheap. During years when insect outbreaks occur, the return on investment for the insecticide is tremendous. The return on investment is also significant for insecticides that are typically used to prevent insect damage, a practice not generally subscribed to by many entomologists, but one that is employed by many corn farmers. The best example is the use of soil insecticides to prevent injury caused by subterranean insects that feed on portions of the corn plant below ground (seeds, roots, etc.). Subterranean insects are difficult to monitor, so preventive measures, particularly for corn rootworms, are common practices. For corn planted after corn, preventive soil insecticides are a standard input.
The potential impact of cancellation or non-use of insecticides for corn insect management was recently determined from some data gathered from a recent survey to assess the benefits of carbofuran (Furadan) use in corn. Carbofuran is undergoing a special review by the U.S. Environmental Protection Agency (EPA). The question posed was, "What percentage yield loss would corn producers experience if those acres of corn currently treated with insecticides were not treated?"
The potential impact of cancellation or non-use of insecticides for corn insect management was recently determined from some data gathered from a recent survey to assess the benefits of carbofuran (Furadan) use in corn. Carbofuran is undergoing a special review by the U.S. Environmental Protection Agency (EPA). The question posed was, "What percentage yield loss would corn producers experience if those acres of corn currently treated with insecticides were not treated?"
The states that provided information about the potential average yield loss, if acres currently being treated for European corn borers were not treated with an insecticide, were Colorado, Illinois, Iowa, and Kansas. The potential average yield loss for these four states was judged to be 10.4 percent of an estimated 1,267,038 acres of field corn currently being treated with insecticides for control of European corn borers. This represents a potential yield loss of 15,390,505 bushels of corn at an average price of $2.25 per bushel, or a potential economic loss of $34,628,636 for the four reporting states.
The states that provided information about the potential average yield loss, if acres currently being treated for a combination of pests (soil insects, foliar insects, and nematodes) were not treated with an insecticide, were Florida, Ohio, and South Carolina. The potential average yield loss for these three states was judged to be 23% of an estimated 1,824,200 acres currently being treated with insecticides for control of a combination of pests. This represents a potential yield loss of 22,654,750 bushels of corn at an average price of $2.25 per bushel, or a potential economic loss of $50,973,188 for the three reporting states.
From 13 separate reports regarding the use of insecticides to control the soil insect complex, European corn borers, and a combination of pests in field corn, the estimated potential economic loss of not using insecticides is an estimated $379,303,257.
These rough estimates are economic losses that are absorbed by farmers, because they harvest less crop as a result of the yield reductions caused by the untreated pests. Agricultural industries that support farmers would also suffer considerable economic loss. The general public would also be affected economically because food prices would become higher, an oversimplified supply-and-demand economics principle.
Agricultural insecticides allow us to grow plentiful food and feed, even in the-presence of potential insect depredations. However, insecticides are so easy to use that they also allow us to ignore other beneficial insect management techniques that might reduce or eliminate insect problems. As a consequence, the economic benefits attributed to the use of agricultural insecticides are very likely overstated. For example, corn growers can mange corn rootworms by alternating corn with other nonhost crops like soybeans or alfalfa. However, soil insecticides allow farmers to grow continuous corn even though corn rootworms are a threat only in corn grown after corn. As a result, the economic benefits attributed to soil insecticides that control corn rootworm larvae could be largely eliminated by the use of crop rotation.
The risks of continued use of agricultural insecticides have been enumerated many times. We do not propose to address risk assessment, an issue that is being argued vehemently by numerous people, and an issue that will likely remain unresolved into the foreseeable future. (Different people assess risks differently, and acceptable risk is a relative term for the most part.) Instead, we address some of the different risks associated with the use of agricultural insecticides, so that we may propose some solutions toward reducing or eliminating these risks.
Rachel Carson's book Silent Spring, published in 1962, focused on the risks of agricultural insecticides to birds and other wildlife. In fact, that book was one of the primary forces that lead to the development of the Integrated Pest Management (IPM) concept. Unfortunately, losses of wildlife like fish and birds continue to occur as results of "accidents" of agricultural insecticide use. Some of the granular insecticides are currently undergoing or are awaiting special review by the EPA because of the potential avian toxicity that exists when these insecticides are left exposed on the soil surface. In addition, the protection of threatened and endangered species is a law that is currently being addressed on many insecticide labels.
There is a potential risk to human health associated with the use of agricultural insecticides. The most acute risk to human health befalls the individual who handles and applies the insecticide, so user safety is a current priority among most insecticide manufacturing companies. In addition, the risk of residues of insecticides on agricultural products could threaten human health to some degree. Although most of the attention on food safety has concerned fresh produce or processed foods, agricultural grain and oil commodities should not be excluded. Federal tolerances have been established for all insecticides on all commodities for which they are registered, and excessive residues are illegal and potentially harmful.
Although few insecticides have been involved in incidents of groundwater contamination, traces of insecticides are occasionally found in samples of groundwater. As a consequence, the potential health hazard posed by insecticide contaminants in drinking water has been addressed at length. At least one insecticide, Furadan 15G, currently used in Illinois, has a groundwater warning statement on the label: "Carbofuran is a chemical which can travel (seep or leach) through soil and can contaminate groundwater which may be used as drinking water. Carbofuran has been found in ground water as a result of agricultural use. Users are advised not to apply carbofuran where the water table (groundwater) is close to the surface and where the soils are very permeable, i.e., well-drained soils such as loamy sands. Your local agricultural agencies can provide further information on the type of soil in your area and the location of groundwater."
Other potential risks associated with the use of agricultural insecticides pertain to upsetting the natural ecological balance. Resistance of insects to insecticides, destruction of natural enemies, resurgence of insect pest populations after insecticide application and creation of secondary insect pest species may all be a consequence of agricultural insecticide use. And these risks are shouldered primarily by the farmer, not necessarily by the general public. Every one of these ecological disruptions can create an insect pest outbreak resulting in economic losses of crops due to failures in appropriate insect management.
These risks can be eliminated simply by banning the use of agricultural insecticides. However, the benefits currently derived from the use of agricultural insecticides, addressed in the previous portion of this paper, must also be examined before rash action is taken to ban products based solely on the risks they pose. While these risk/benefit analyses are being conducted, we should make every conceivable effort to reduce significantly or eliminate the risks posed by the use agricultural insecticides.
IPM has been driving educational programs in the Cooperative Extension Service for two decades or more. The risks associated with the use of agricultural insecticides are not new, they are simply being emphasized more now than in the recent past. The risks were recognized by scientists long ago. It is interesting to note that of the 24 papers abstracted in Outlines of Presentations of the Illinois Custom Spray Operators' School, printed in 1949, three of the papers addressed certain risks associated with the use of agricultural insecticides: "Toxicity of Spray Residues," "Effects of Agricultural Chemicals on Aquatic Life," and "Effects of Agricultural Chemicals on Wildlife." However, the advent of the IPM concept in the 1970s helped focus much needed attention on how to control insects and avoid the risks posed by agricultural insecticides.
We should begin managing insect pests within an agricultural system when resource conservation and management, rather than maximum yield, are the top priorities. While optimum yield will and should remain a priority, the concept of maximum yield should be abandoned. So the question becomes, "How can we manage insects and conserve and protect our natural resources?" One fragment of the more complex answer is simple: we continue to urge farmers to understand the principles and implement the techniques of IPM within an integrated crop management system. And while we are urging farmers to do so, we must set the example and adopt this attitude ourselves. New pest management tactics will be discovered and old control tactics will be replaced, but the "intelligent selection and use of pest-control actions that will ensure favorable economic, ecological, and sociological consequences" (Rabb 1972) will remain as the foundation of agricultural pest control for a long time to come. Although the notion is not always stated directly, essentially all definitions of IPM suggest that resources should be conserved and managed.
The long-range goals of resource conservation and management in agriculture are to maintain or improve our competitiveness and profitability and to assure the general public that communal resources are being used wisely and are safe for use for generations to come. Two key elements in these objectives are economics and the environment, both of which are cornerstones of IPM programs.
Definitions of certain terms should aid the discussion. Webster's Ninth New Collegiate Dictionary defines "resource" as (1) a source of supply or support: an available means, and (2) a natural source of wealth or revenue. "Conservation" is defined as a careful preservation and protection of something; especially: planned management of a natural resource to prevent exploitation, destruction, or neglect. "Management" is defined as a judicious use of means to accomplish an end.
With these definitions as guidelines, we will discuss resources, specifically as they relate to agriculture, in two ways. Natural resources include water, soil, air, fossil fuel, wildlife, and natural enemies of pests. By definition, these resources should be conserved so that they are neither exploited nor destroyed. Input resources that signify available means include finances, energy, time, equipment, information, and other inputs, including agricultural insecticides. Again by definition, these resources should be managed so that they can be used judiciously to accomplish an end. A truly integrated crop production/crop protection program involves the conservation of natural resources by managing input resources. Farmers and those who advise them should be acutely aware of the significance of all resources, both to the individual and to the public. Farmers influence natural resources, but the quality, quantity, and price of natural resources also influence farmers' profits and ultimately their ability to continue farming.
Integrating insect pest management strategies into a crop production system that emphasizes resource conservation should be as direct as the step-wise development of an IPM program suggested by Ruesink (1975), which is paraphrased here:
A crop production system designed to conserve natural resources would comprise some, if not all, of the following tactics: conservation tillage practices (including no-till, ridge-till, residue management), soil and water conservation practices (including terraces, fall cover crops, diverse crop rotations, strip cropping), and the use of agricultural insecticides on an as-needed basis. As soon as the ecology of the resource conservation system is understood, an IPM program can be introduced and input resources can be managed.
Managing resources for an insect pest management program begins with management of knowledge or information. For example, entomologists understand that the cropping sequence and the type of vegetation (crop or weed) growing in a field play major roles in determining the potential for and extent of insect pest problems. Availability and use of this information will often ensure the successful beginning of an IPM program.
Following is a very broad outline for implementing insect pest management strategies in a resource conservation system. These considerations, if they are thoroughly examined, should ensure a reasonable beginning to an IPM program that embraces conservation of natural resources and management of input resources.
(1) With the aforementioned information at hand, evaluate all appropriate alternatives for insect pest management that will "fit" into the resource conservation cropping system to be employed. These evaluations should include both short-term and long-term pest management schemes, and how these schemes will, in turn, affect the system.
(2) Where possible, utilize all appropriate nonchemical tactics that will prevent or reduce the impact of insect pests, yet will "fit" into the system. For a farmer, these might include growing crop varieties that are resistant or tolerant to insect feeding injury, practicing certain crop rotations, manipulating planting times, eliminating alternate hosts, conserving natural enemies of pests, etc. For an applicator, this might mean simply that when an insecticide is not needed, don't recommend it.
(3) When all else has failed to prevent an insect pest outbreak, an insecticide may be necessary to avert substantial losses in crop quality and yield. However, insecticides are valuable input resources that must be managed with care in order to extend their effectiveness and to avoid disruption of the environment.
The use of insecticides in crop production will continue well into the foreseeable future. Nevertheless, they must be used wisely, with resource conservation firmly in mind, if they are to continue to provide the relatively cheap, effective results with which we have become accustomed. Certain considerations regarding the management of insecticides are in order.
(1) Base the decision to use an insecticide on information obtained during representative scouting trips. Knowledge of the population level of the pest(s), crop growth stage and condition, and presence or absence of natural control factors is the only way to assess a potential pest situation. Elimination of prophylactic insecticide treatments as a form of insurance against insect damage is a goal toward which we should strive.
(2) If they are available, use dynamic decision-making tools or calculations to determine the need for an insecticide. These equations incorporate values that change from time to time and field to field, like commodity prices, cost of control, expected yield, and percentage control. In the future, these dynamic decision-making tools should also incorporate dollar values for potential environmental disruption or risks to the environment.
(3) When "dynamic thresholds" are unavailable, use the economic thresholds that have been established as guidelines for making appropriate insect control decisions. Although they are not as flexible as the dynamic equations, most of the economic thresholds are based on research data and are reasonably reliable.
(4) If possible under the existing circumstances, use a biological insecticide, like formulations of Bacillus thuringiensis rather than a chemical insecticide. Bt. is effective against only a few pests, primarily caterpillars, but is usually just as effective as the chemical insecticides registered for those pests.
(5) If a chemical insecticide must be used, select one that will cause the least amount of environmental disruption and apply it at the lowest effective rate. Unfortunately, the choice made here depends on a very complex set of decisions. The types of environmental disruption vary from the destruction of natural enemies of pests to contamination of surface or groundwater. Each situation must be analyzed in order to determine the most appropriate chemical to use under the existing circumstances. Insecticides that do not persist for extended periods of time and that are not very soluble in water might be logical choices. Additionally, insecticides that are "soft" on predators and parasitoids and on other beneficial insects, like honey bees, would also be logical choices under certain circumstances.
(6) Apply the insecticide in a manner that will cause the least amount of disruption in the environment. Subsurface applications of certain soil insecticides might reduce the risk of the insecticides being carried off the field in runoff situations, or they might reduce the risk of killing birds that ingest granules exposed on the soil surface. Directed sprays, rather than broadcast sprays, might be more appropriate in some situations. Drift of insecticides into nontarget areas is completely unacceptable.
The debate over agricultural insecticide use will continue throughout the 1990s. And while the debate continues, data supporting both sides of the issue will accumulate and the general public will become even more aware of the risks and benefits of agricultural insecticides. As a direct result, additional legislation and regulations will affect the way we use agricultural insecticides in the future, if we use them at all.
If we are to prevent the legislation from becoming unnecessarily harsh, we must make the commitment now to eliminate misuse and needless use of agricultural insecticides. Employ IPM tactics like scouting and economic thresholds, and apply insecticides only when a need has been established and all other alternatives are exhausted. When making a decision whether an insecticide is appropriate, weigh the economic benefits against the environmental and health risks. Data to help you make this comparison currently is not available, so you will have to assess risks and benefits in your best judgment. Remember, the decision not to use an insecticide, even when insect numbers exceed established economic thresholds, is a valid decision. And finally, after the decision to use an insecticide has been made, do everything possible to avoid insulting the environment. Make informed decisions about which insecticide is best and how much is necessary.
We have the knowledge available to establish very effective IPM programs in any type of resource conservation system. However, everyone must make a commitment to IPM as the most intelligent approach toward managing pests. Improved management of insecticides and other agricultural chemicals is essential if we hope to reduce the impact of these input resources on our natural resources. Everyone involved with agriculture has the right to choose how the land will be farmed, but with that right to choose comes the obligation to choose well.
Carson, R. 1962. Silent spring. Houghton Mifflin Co., Boston, MA. 368 pp.
Nevling, L.I. 1989. Agro-ecology balances agriculture, heritage. Guest editorial. Agro-Ecology - Science and Education for a Sustainable Agriculture 1(3):4-5.
Rabb, R.L. 1972. Principles and concepts of pest management. p. 107-115 In Implementing practical pest management strategies. Proc. of a nation extension pest management workshop. Purdue Univ., Lafayette, IN.
Ruesink, W.G. 1975. Analysis and modeling in pest management. p. 353-376 In Introduction to insect pest management, R.L. Metcalf and W.H. Luckmann, eds. John Wiley & Sons, New York.
1Kevin L. Steffey is Associate Professor of Entomology and Mike E. Gray is Assistant Professor of Entomology, office of Agricultural Entomology, University of Illinois at Urbana-Champaign.
