When Mediterranean fruit flies first appeared in California fly traps in June 1980, standard procedure in that heavily agricultural state called for the naming of a Technical Advisory Committee to run an eradication program. A committee of county, state and federal agricultural officials was duly formed. With little or no public attention it launched an attack on the flies, using chemical sprays in the immediate area where the insects were found, stripping fruit in infested areas and releasing large numbers of sterile flies to reduce the likelihood that wild flies would find fertile mates.
By November, no Medflies were being found in Los Angeles County, but the problem was not yet under control in northern Santa Clara County. Nevertheless, the committee was not too worried because winter was approaching, and the Medfly is highly sensitive to cold. Then suddenly, in early December, Washington officials of the Department of Agriculture arrived on the scene with an order to begin blanket aerial spraying of the pesticide malathion over hundreds of square miles. The committee, including its regional USDA members, was flabbergasted. Few adult flies would be around because of the cold weather (most flies would be safely wrapped up for the winter as pupae), those that were around would be unable to fly to the bait pellets on which the spray is dispensed, and the malathion spray would not affect the larvae or pupae. The USDA officials now concede that their order made no sense, though they argue that it did jolt the state into a more serious attack on the flies. It also had this consequence: public opinion was polarized, and groups with a stake in the outcome quickly chose up sides -- to spray or not to spray.
The debate that fllowed appeared to be about malathion's uncertain effects on human health. (Malathion does not appear to cause cancer or acute illness; other possible effects of long-term, low-level exposure have not been fully tested. However, malathion degrades rather quickly and, when sprayed on bait pellets that stick where they fall, seems to be a reasonable health risk.) Lost in the hysterical death-from-the-skies rhetoric was the far more important environmental issue of the process known as IPM--Integrated Pest Management.
IPM is a relatively new approach that emphasizes the use of natural pest controls, such as weather, disease agents and predators, and biological tricks, such as the release of sterile flies, in place of sole reliance on chemical pesticides. IPM uses sophisticated computer modeling of insect life cycles and demands a much greater knowledge of insect biology and behavior on the part of the user--the farmer. But its advocates argue that it can reduce pesticide use by 75 percent, thereby slicing farmers' costs. Even a much smaller reduction would put a big dent in what is now a major market for the chemicals industry.
IPM methods grew out of a concern that excessive use of chemical sprays might be not only dangerous to human health and the environment, but also self-defeating in the long run. The central fact for IPM advocates is this: despite a tenfold increase in the tonnage of chemical pesticides used in recent years, average annual crop loss to pests has not decreased, but has remained constant.
One reason is the appearance of strains genetically resistant to the sprays. In California, three-fourths of the most serious crop pests are now resistant to at least one pesticide. Many are impervious to two or more. Another reason is that sprays commonly kill not only the pest, but its natural predators as well. Thus American agriculture may be running on a chemical treadmill: the more pesticides that are used, the more--and more potent ones--are needed just to achieve the same result.
The committee that was running the Medfly eradication program in California had been using IPM techniques. The USDA's December order convinced many in California that USDA, at least in Washington, was irredeemably committed to a chemicals-or-nothing approach. California Gov. Jerry Brown responded with a bigger IPM program, relying heavily on stripping the fruit, where the fly must lay its eggs. The program appeared to work. All through the winter and into the spring, not a single fertile fly or larva was spotted. By May the Technical Advisory Committee was considering ways to celebrate the success of the largest IPM program ever undertaken. In Washington, USDA wasn't ready to call the program a complete success, but officials remember that "we were feeling pretty good about it."
Then all hell broke loose. In 10 days beginning in late June, larvae were found in 40 different locations. By the middle of July, 110 infestations had been found. Their source remains the central mystery of the Medfly dispute. Some, including prominent entomologists, believe that all these larvae can be traced to the infamous "Peruvians"--a shipment of 10 million supposedly sterile flies, purchased from Peru and released on June 14, many of which were in fact not sterile. Others, including USDA, disagree. Now that the Medfly is spreading again in California and has turned up in Florida, there are even those who claim that if only aerial spraying had been carried out last summer as they recommended, none of this would have happened.
The misfortune is that these claims cannot now be clearly resolved: it may never be known whether the IPM program did control the Medfly until it was wrecked by the fertile flies mistakenly released on June 14, or whether the original infestation was too large to have been stopped by anything short of wholesale aerial spraying. That is a misfortune because, despite the unfounded scare stories of malathion's dangers and Gov. Brown's inexplicably bad judgment that made it appear he had nothing more in mind than gaining political advantage, some thing important was at issue in California's struggle over how to stop the Medfly.