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Pest Management: An Overview1

EUGENE P. ODUM and GARY W. BARRETT

Institute of Ecology, University of Georgia

As we document and celebrate success stories dealing with pests and diseases using ecologically based integrated pest management (combining the IPM and EBPM acronyms), we might inquire, “Why are we having to deal with an increasing number of pests, exotic species, and new diseases?” Perhaps there are some ecosystem-level approaches or overall management practices that we might undertake that would reduce the need to continue only to deal with pest species one at a time.

An increase in air travel and other intercontinental transportation is certainly a factor, but what makes the local ecosystem susceptible to invasion once a new species is introduced or a resident species suddenly erupts to become a pest? Drake et al. (1989), Elton (1958), Levin (1987), Mooney and Drake (1987), and Vitousek et al. (1987), among others, discussed “the ecology of invasions” with the general conclusion that disturbance and “open niches” contributed to making natural ecosystems vulnerable to invaders. When it comes to crops or other cultivated or domesticated ecosystems, we suggest that there are four related current management practices that encourage pests.

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This commentary is organized as a general response to the basic question “Why are managed ecosystems vulnerable to pests?” which was delivered as a dinner presentation by Dr. Eugene Odum at the Professional Societies and Ecologically Based Pest Management workshop in Raleigh, North Carolina on March 10, 1999.



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PROFESSIONAL SOCIETIES and Ecologically Based Pest Management: Proceedings of a Workshop 1 Pest Management: An Overview1 EUGENE P. ODUM and GARY W. BARRETT Institute of Ecology, University of Georgia As we document and celebrate success stories dealing with pests and diseases using ecologically based integrated pest management (combining the IPM and EBPM acronyms), we might inquire, “Why are we having to deal with an increasing number of pests, exotic species, and new diseases?” Perhaps there are some ecosystem-level approaches or overall management practices that we might undertake that would reduce the need to continue only to deal with pest species one at a time. An increase in air travel and other intercontinental transportation is certainly a factor, but what makes the local ecosystem susceptible to invasion once a new species is introduced or a resident species suddenly erupts to become a pest? Drake et al. (1989), Elton (1958), Levin (1987), Mooney and Drake (1987), and Vitousek et al. (1987), among others, discussed “the ecology of invasions” with the general conclusion that disturbance and “open niches” contributed to making natural ecosystems vulnerable to invaders. When it comes to crops or other cultivated or domesticated ecosystems, we suggest that there are four related current management practices that encourage pests. 1   This commentary is organized as a general response to the basic question “Why are managed ecosystems vulnerable to pests?” which was delivered as a dinner presentation by Dr. Eugene Odum at the Professional Societies and Ecologically Based Pest Management workshop in Raleigh, North Carolina on March 10, 1999.

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PROFESSIONAL SOCIETIES and Ecologically Based Pest Management: Proceedings of a Workshop ECOSYSTEM STRESS AND EXCESSES Humans tend not to be satisfied with a reasonably good yield but always seem to strive for more, even recognizing that it is possible to have “too much of a good thing.” When a crop plant (or the cropland itself for that matter) is forced to produce a maximum possible yield of desired products (e.g., forced increase in the harvest ratio), the plant has very little energy left to defend itself from pests. This is one of the reasons we see an increase in pesticide use. Also, growers seeking the maximum rather than the optimum will often experience overshoot or “boom and bust” crop production patterns, as occurred with cotton in the Canete Valley of Peru in the 1950s (Barducci, 1972) and in Texas in the 1960s (Adkisson et al.,1982). An experimental study of the effect of increased egg production on disease in a small bird, the great tit, provides an analogous example of the trade-off between productivity and defense (Opplinger et al., 1996). Researchers artificially increased clutch size by removing the first two eggs laid in the nest boxes. With an increase in the clutch size by an average of one egg, the researchers observed an increase in prevalence of malarial parasites in the blood stream from 10 percent in the control females to 50 percent in the experimental females. Given this trade-off between productivity and defense, what we should consider doing is using the same biotechnology to reintroduce some of the antiherbivore defensive capabilities that most wild plants have developed through natural selection back into crop plants. This strategy may result in lower but more sustainable yields for the crops in question. EUTROPHICATION Our effort to increase agricultural productivity worldwide, in order to support increasing numbers of people and domestic animals (which, in turn, excrete huge amounts of nutrients to the environment), has caused global eutrophication problems that are perhaps the greatest threat to ecospheric diversity, resilience, and stability. Global warming that results from CO2 enrichment of the atmosphere is just one aspect of this overall perturbation. Nitrogen enrichment is also a serious threat (Henrikson et al., 1997; Vitousek et al., 1997). Excess nitrate fertilizer and other nutrient runoff favor many noxious weeds, exotic pests, and dangerous disease organisms because these organisms are highly adapted to high-nutrient environments. The well-known red tide phenomenon is a good example of how enrichment can create a pest out of normally innocuous organisms. At their typical low densities, the red tide microorganisms in estuaries cause few or no problems. They secrete a toxin as a defense mechanism but not in concentrations that could affect fish. But when the estuary is enriched by nutrient-filled pollution, the organisms can rapidly multiply and reach densities when their defensive toxins can cause massive fish kills.

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PROFESSIONAL SOCIETIES and Ecologically Based Pest Management: Proceedings of a Workshop Another example recently described involves cattle in feedlots. When cows are fed enriched corn in order to increase meat yield, high levels of a virulent strain of Escherichia coli were discovered to persist in the lower pH environment of the cattle 's digestive system. These high levels of pathogens can contaminate feed and other cattle, and can cause food-borne illnesses in humans through the consumption of the contaminated meat. When the cows were put on grass and hay diets, their gut pH levels were elevated and resulted in a 106-fold decrease in the numbers of this virulent strain of E. coli (Diez-Gonzalez et al., 1998). CONTROL VERSUS ERADICATION A common response to the appearance of pest species is an effort to eliminate them completely rather than reducing their numbers to a point where their impact is small. The trouble with the “kill 'em dead ” approach is that it often involves heavy applications of pesticides, which often result in strong selection favoring resistant strains (the few individuals in a given pest population that have some mutation-derived differences in their metabolic pathways that confer resistance against the pesticide). More moderate measures that control but do not eliminate pest species appear to alter the relative frequency of these resistant mutations and slow the development of resistance in the pest populations. An example is the development of a rust-resistant strain of wheat accomplished by introducing a “slow rust” gene that keeps the disease at a low level, so that there is less selection pressure on the rust fungus to mutate (see Holden, 1992, for details). Therefore, reducing the overuse of a pesticide may help reduce the development of particularly challenging resistant pests. MONOCULTURE VULNERABILITY TO PEST INVASION For decades the goal of agriculture and agribusiness governmental departments has been to increase crop yields per unit of land by promoting industrial agriculture that involves large-scale monocultures, the use of fossil-fuel-powered machinery, and very heavy applications of chemical subsidies. One result, as documented in numerous papers, reports, and books, is the rapid increase and spread of pests (see, e.g., two reports: NRC, 1989, 1996; and two agroecology books: Altieri, 1987; Gliessman, 1998). Fortunately, new agricultural practices involving reduced tillage, cover crops, crop rotations, strip cropping, trap crop buffers, and other diversifications that are coming into greater use do reduce pests and decrease the need for heavy pesticide use. We cite two field studies that demonstrate that “not putting all the eggs in one basket” does indeed reduce pests. Kemp and Barrett (1989) and Holmes and Barrett (1997) demonstrated that the establishment of grassy corridors in soybeans and strip cropping soybeans with sorghum repeatedly reduced the abundance of insect pests such as potato leafhoppers and Japanese beetles, respectively. Thies and Tscharntke (1999)

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PROFESSIONAL SOCIETIES and Ecologically Based Pest Management: Proceedings of a Workshop compared two different landscapes; one with large monocultures and one with crop fields interspersed with fallow habitat. Crop damage to oilseed rape by the rape pollen beetle was much less in the more structurally diverse landscape due to greater parasitism by parasitoids coming in from the fallow areas. Thus, the practice of crop diversification, within and among crop types, has led to the reduction of insect pests, but also has benefited wildlife, increased soil quality, and increased net economic profits across spatial scales. REFERENCES Adkisson, P.L., G.A. Niles, J.K. Walker, L.S. Bird, and H.B. Scott. 1982. Controlling cotton insects pests: A new system. Science 216:19–22. Altieri, M.A. 1987. Agroecology: The Scientific Basis of Alternative Agriculture. Boulder, Col: Westview Press. Barducci, T.B. 1972. Ecological consequences of pesticide used for the control of cotton insects in Canete Valley, Peru. Pp. 432–438 in The Careless Technology, M.T. Farvar and J.T. Milton, eds. Garden City, NY: Natural History Press. Diez-Gonzalez, F., T.R. Callaway, M.G. Kizoulis, and J.B. Russell. 1998. Grain feeding and the dissemination of acid-resistant Escherichia coli from cattle. Science 281:1666–1668. Drake, J.A., H.A. Mooney, P. di Castri, R.H. Groves, P.J. Kruger, M. Rejmánek, and M. Williamson, eds. 1989. Biological Invasions: A Global Perspective. New York: John Wiley and Sons. Elton, C. 1958. The Ecology of Invasions by Animals and Plants. London: Methuen. Gliessman, S.R. 1998. Agroecology: Ecological Processes in Sustainable Agriculture. Chelsea, Mich: Ann Arbor Press. Henrikson, A., D.O. Hessen, and E. Kessler, eds. 1997. Nitrogen: A present and a future threat to the environment. Ambio 26:253–325. Holden, C. 1992. Hard-won victory over wheat blight. Science 258:551. Holmes, D.M., and G.W. Barrett. 1997. Japanese beetle (Popillia japonica) dispersal behavior in intercropped vs. monoculture soybean agroecosystems . American Midland Naturalist 137:312–319. Kemp, J.C., and G.W. Barrett. 1989. Spatial patterning: Impact of uncultivated corridors on arthropod populations within soybean agroecosystems. Ecology 70:114–128. Levin, S.A. 1987. Ecological and evolutionary aspects of dispersal. Lecture notes. Biomathematics 71:80–87. Mooney, H.A., and J.A. Drake. 1987. The ecology of biological invasions. Environment 29:10–15.,34–37. National Research Council. 1989. Alternative Agriculture. Washington, DC: National Academy Press. National Research Council. 1996. Ecologically Based Pest Management: New Solutions for a New Century . Washington, DC: National Academy Press. Opplinger, A., P. Christe, and H. Richner. 1996. Clutch size and malaria resistance. Nature 381 (6583):565. Thies, C., and T. Tscharntke. 1999. Landscape structure and biological control in agroecosystems. Science 285:893–895. Vitousek, P.M., L.L. Loope, and C.P. Stone. 1987. Introduced species in Hawaii: Biological effects and opportunities for ecological research. Trends in Ecology and Evolution 2:224–227.

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PROFESSIONAL SOCIETIES and Ecologically Based Pest Management: Proceedings of a Workshop Vitousek, P.M., J. Aber, R.W. Howarth, G.E. Likens, P.A. Matson, D.W. Schindler, W.H. Schlesinger, and G.D. Tilman. 1997. Human Alteration of the Global Nitrogen Cycle: Causes and Consequences. Issues in Ecology, Report 1. Washington, DC: Ecological Society of America.