To Provide Our Readers with A Glimpse of What Others Are Saying:
A Few Soundbytes from the Heated Debate on IPM


Sustainable agriculture

by Jos Bijman

...India, in recent decades, adopted chemical-intensive farming techniques in order to achieve self sufficiency in food production. While this goal has been reached, particularly with the help of high yielding wheat and rice varieties, the natural environment has seriously deteriorated, due to heavy use of chemical fertilizers and pesticides. New environmentally friendly technologies, which maintain or increase current levels of productivity, are needed if the use of chemical inputs is to be reduced. Biofertilizers, biopesticides and transgenic pest and disease resistant plants could possibly contribute to solving the environmental problem (and also reduce the concomitant threat to human health).

Problematic alternatives

by Leonard Gianessi

Ironically, the search for nonchemical alternatives to pesticides may be thwarted by many of the same regulatory concerns and public fears that currently surround chemical pesticide use. Although traditionally viewed as environmentally safe, biological control methods -- which include the breeding and releasing of natural enemies, such as parasites, predators, or pathogens, to reduce pest populations -- are being increasingly viewed by entomologists as carrying unrecognized risks. Once released into the environment, these species can multiply, cause unpredictable negative effects, and be impossible to recapture. Biological control activities can even lead to species extinction; Francis G. Howarth of the J. Linsley Grassit Center for Research in Entomology has concluded that species introduced for biological pest control have been strongly implicated in the extinction of nearly 100 species worldwide. Insects or pathogens introduced to control a plant pest may become pests themselves.

There is little regulation of biological control methods and subsequently little analysis of any unintended side effects. Recently, however, the U.S. Department of Agriculture canceled a plan to release a parasitic wasp and a fungus from Australia to control grasshoppers on U.S. rangelands-a project intended to replace synthetic chemical insecticides-for fear that the parasitic wasp might attack some beneficial grasshopper species.

Microbial pesticides, which consist of microscopic living organisms (viruses, bacteria, or fungi) and can be applied like chemical pesticides, are drawing increasing scientific attention as alternatives to chemical pesticides. Since the registration requirements for biological pesticides are essentially the same as those for chemical pesticides, the U.S. Environmental Protection Agency (EPA) will need to anticipate all possible problems. Experiments will have to be designed to show that each virus is not a threat to humans, animals, or the environment. If, as has been pointed out by Louis A. Falcon, an insect pathologist at the University of California at Berkeley, some negative effect were to be caused by a living, replicating virus, it probably could not be controlled or stopped. The public may have considerable apprehension about having their foodstuffs sprayed with viruses.

Another longstanding method of nonchemical pest control is crossbreeding. For example, plants can be bred for increased tissue hardness, so that they are protected by a structural barrier that limits insect damage. Often, crop breeders intentionally alter the chemical profile of the plant. By concentrating naturally occurring chemical repellents, feed deterrents, and toxicants, crop breeders can create cultivars that by themselves can deter or overcome pest attack.

Unfortunately, as Marcus Kogan of the University of Illinois has pointed out, crop breeding has proceeded without great concern for the underlying biochemical mechanisms involved. Some resistance factors may be broadly toxic to beneficial insects, animals, or humans. For example, certain alkaloids of potatoes defend the plant against the Colorado Potato Beetle but are hazardous to humans. So far, traditional cropbreeding methods remain largely unregulated. As riskassessment procedures and toxicity measurements become more refined, however, these altered crop cultivars may become increasingly suspect.

Some researchers are using genetic engineering to find new ways to reduce growers' dependence on chemical pesticides. In most cases, this research is focused on largeacreage crops. Genetically engineered plants may resist certain pests or diseases; some may even release their own insecticides. In addition, viruses may be genetically altered to make them more potent. Already, public concern over the potential risks has blocked the release of a number of biotechnology products. Though the relative risk of most biotechnology products is likely to be low, the public's fear may be high, creating a further obstacle to the development of nonchemical alternatives to pesticides.

The public research agenda should consider the potential risks of the nonchemical alternatives and weigh them against those of the chemical pesticides that they are intended to replace. Otherwise, millions of research dollars may be spent on nonchemical control techniques that prove to be unacceptable.

One other option that deserves mention is the small group of nonsynthetic pesticides. Organic farmers spurn synthetic chemicals, relying instead on natural compounds such as sulfur and copper. But human health and environmental concerns have been raised about several of these natural pesticides, and the use of others has been disruptive to integrated pest management programs because they affect beneficial predators and parasites. In addition, because they are generally less effective in controlling pests, natural compounds must be used in greater amounts than synthetic chemicals.

Pesticide poisons

by Robert J. Spear

By 1980 nearly 500 major insect pests were resistant to pesticides, and at least 20 now are resistant to all widely used insecticides. The National Academy of Sciences reports that resistance to chemicals has developed in 150 plant diseases, 133 species of weeds, 70 species of fungus and 10 species of rats. It expects that by 2000, practically all major insect pests will have gained some form of genetic resistance. This does not sound to me like a situation that Mr. Gianessi and his group have under control.

Mr. Gianessi's contention that we should not continue experiments with natural controls because previous experiments have failed is a rather odd comment. I cannot imagine that he has never learned of the many success stories of natural controls in entomological and agricultural history. His contention that the several thousand insect "crop pests" are best controlled with "about 100 broadspectrum pesticides" rather than with "nature's own controls" that are specific to a single species, is off the mark. From both a scientific and environmental view, if controls must be used, to have an agent that deals with one single "pest" and harms nothing else is exactly what one would want.

Modern pesticides are not necessarily safer: they are more concentrated and potent than ever before. Some remain effective in concentrations as low as a few parts per billion and less. The paradox is that the damages caused by such small amounts become increasingly difficult to discover, and the period of time during which harm may be occurring grows longer as the technology needed for detection and verification lags behind the technology of production.

One must wonder then if the sustained misuse of synthetic chemical poisons on our crops is part of the problem rather than part of the solution.


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