Weaning Farmers From Pest Control Strictly by Pesticides
PESTICIDE pollution has been a concern for decades. Many countries have put more or less strict controls on man-made pesticide use. But we shouldn't let familiarity with this situation breed complacency.
These useful poisons still pose a direct danger to people. Their continued heavy use also interferes with efforts to control crop pests by less harmful methods. That's why pest-control scientists attending last week's annual meeting of the American Association for the Advancement of Science (AAAS) in Atlanta were urging renewed efforts to cut down on pesticide usage.
David Pimentel of Cornell University in Ithaca, N.Y., emphasized this need by citing reports from the American Association of Poison Control Centers, the United Nations Environmental Program, and the World Health Organization. These reports indicate that, globally, about 1 million people are poisoned by pesticides each year, with 20,000 deaths. About 67,000 of those poisonings - all nonfatal - occur in the United States.
Dr. Pimentel further noted that, while insecticide use burgeoned tenfold from 1945 to 1989, annual insect-related crop losses rose from 7 percent to 13 percent of the potential harvest. He blames this seeming paradox on lack of good management practices, such as crop rotation and use of nonpoisonous pest control. Heavy insecticide use wipes out pests' natural enemies as well, and fungicides reduce fungal species that are natural parasites on many insects. This lets the ``bad'' bugs have a field day while the ``good'' bugs disappear.
Clearly, there must be a better way. Entomologists call it integrated pest management. It's a mix of techniques tailored in each case to the needs of individual farmers. The strategy includes growing crops designed to resist pests, making allies of pests' natural enemies, and, where necessary, still using chemicals.
No one technique can do the job alone. As Cornell entomologist Michael Hoffmann acknowledged, ``It is unlikely that biological control will completely replace the use of chemical insecticides.'' But with a mix of tactics, he adds, ``insecticide use can be significantly reduced.''
Many entomologists have preached this integrated strategy for years. But while it has been adopted by some farmers, it has not been pursued aggressively as a new way of agricultural life.
Listening to Pimentel and his colleagues and reading statements presented at AAAS, it became obvious that the basic problem is one of perception. It's easier to reach for the insecticide or fumigant than to learn to use biological controls. And, in spite of welcoming the pollination services of bees, most people don't like insects. ``We must overcome the concept that all insects are pests,'' Hoffmann observed.
Meanwhile, the tools for integrated pest management are improving. Last month, a team from Purdue University in West Lafayette, Indiana, the University of California at San Diego, and Australia's Commonwealth Scientific and Industrial Research Organization reported they have successfully moved a gene that confers resistance to weevil attack from a bean into a variety of garden pea. Moving that gene into other plants may help solve storage problems for major grains such as corn and rice.
Plants such as cotton, potato, and corn have also benefited from addition of a gene, enabling them to produce their own insecticides. Eventually, however, some pests developed resistance to the introduced protein. Robert Fraley, president of the Monsanto New Agricultural Products unit in St. Louis, Mo., reported last week that Monsanto chemists have found genes for ``a number of new proteins'' for insect control.
The bottom line seems to be that scientists now know how to protect crops while drastically reducing pesticide use. Given the strong public demand for pesticide-free food, one would expect the ``better way'' of growing food to become the dominant way. @QUOTE = Heavy insecticide use wipes out pests' natural enemies as well as the pests. This lets the `bad' bugs have a field day while the `good' bugs disappear.