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Lessons from biological pest control.

Lessons from biological pest control

Agriculture's extensive experience with the introduction of biological agents for pest control can offer insight for the safe and effective release of genetically engineered organisms, says David Pimentel, an entomologist at Cornell University in Ithaca, N.Y. Around the world more than 100 programs employing natural, although perhaps foreign, enemies of targeted pests are considered fully effective. On the average, it has taken the introduction of about 20 parasites or predators to find one that is successful for pest control.

Pimentel has surveyed data from 447 attempts at biological control to identify factors that increase the likelihood of success. He finds that although most potential biocontrol agents come from the native habitat of the pest, new associations--for instance, parasites of a related species from a distant location-- tend to be more successful. Examples include the control of prickly pear cactus in Australia by a South American moth that naturally feeds on the tiger pear, and the control of the European rabbit in Australia by a virus introduced from the South American tropical forest rabbit.

The advantage of new associations is that no genetic balance between resistance and virulence factors has evolved between host and parasite. "Changing the genetic makeup of a parasite by genetic engineering should, by a similar principle, make the new parasite genotype a highly effective biocontrol agent,' Pimentel says. "At the same time, when the genetic makeup of an organism is changed, extreme caution must be exercised before it is released to be sure that it will not be a hazard to the ecological system.'

The work with biological control agents offers some guidelines as to when an organism will become established in a new location, Pimentel says. For example, if the conditions of the native habitat and release site are drastically different--say, humid versus arid--the organism probably will not become established. However, when several parastic species are released into a habitat that has a potential host and favorable climate, at least some should become established, Pimentel says.

"Niches are never full,' he says. "Community systems have tremendous flexibility to accommodate new genotypes and species.' There are abundant agricultural examples of native insects extending their diet from native plants to such introduced crops as potato and sugarcane. Pimentel calculates that native insects make up 60 percent of all insect pest species associated with crops introduced into the United States.

Although Pimentel has opposed the proposed field tests of the bacterium genetically engineered to prevent frost damage in crops (SN:3/9/85P.148), he says he supports the environmental release of both natural biological agents for pest control and genetically engineered organisms after they have passed an adequate set of ecological tests. "It must be recognized,' Pimentel says, "that no set of protocols will ever be 100 percent effective in preventing biological catastrophe. However, with a sound basic set of ecological test-protocols, we can greatly reduce the risks of a parasite outbreak and minimize hazards of public health and the environment.'
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Author:Miller, Julie Ann
Publication:Science News
Date:Jun 29, 1985
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