August 03, 1981 12:00 PM

Seldom since the snaillike San Jose scale all but wiped out the state’s fruit crop in the 1880s have Californians been so pestered. The voracious Mediterranean fruit fly, called “the Satan bug ” by farmers, has mounted a frightening attack on California’s $14 billion-a-year farming industry, which produces more than 40 percent of the nation’s fruit and vegetables. The fast-reproducing Medfly, which spoils produce by laying its eggs in the crops, might have been eradicated last year had aerial spraying been undertaken with the pesticide Malathion. Instead, bowing to pressure from environmentalists, California Gov. Jerry Brown chose to rely on less provocative measures, including ground spraying and releasing sterile male flies to cut down on offspring. But this summer, following a massive new Medfly infestation, Agriculture Secretary John Block threatened to quarantine all susceptible California fruit, and Brown finally agreed to aerial spraying. Like many scientists, Perry L. Adkisson and Frank Gilstrap of Texas A&M University are critical of the yearlong delay. Adkisson, 52, the university’s deputy chancellor for agriculture, has advised more than 20 countries on pest control. Gilstrap, 37, an associate professor of entomology, had studied the Medfly in Central America. Recently Gilstrap and Adkisson discussed the destructive pest with Kent Demaret of PEOPLE.

Why has a 13-month campaign failed to bring the Medfly under control?

Gilstrap: California has mishandled the fruit fly problem from the beginning. The Medfly destroys all citrus crops, pitted fruit and many vegetables. Only leafy vegetables and ground crops like carrots and potatoes are safe. The politicians knew that a year ago, but they just dillydallied around.

How did the effort fall short?

Gilstrap: Last summer, after the fly was first discovered, officials established the smallest possible quarantine zone they could—about 600 square miles. They did not regulate private traffic there to make sure no infested produce got out. They didn’t immediately begin stripping fruit off trees to deprive the fly of its egg-laying sites. And they did not immediately go to aerial spraying.

What role has Governor Brown played in this crisis?

Gilstrap: Early this year I was asked to join his California Medfly Technical Advisory Committee, which had been formed last year. After the latest Medfly outbreaks, in late June, we unanimously recommended immediate aerial spraying of Malathion. Called to Sacramento, we sat right across from Governor Brown. Face to face, I personally explained the urgency of the situation. Jerry Brown told us he had already decided to stick with ground spraying. I don’t know why he even called the meeting. It was a charade.

But isn’t ground spraying safer?

Adkisson: We don’t think aerial spraying is riskier in agricultural applications, and it’s the most effective way to treat large and tall crops. In California, however, the affected areas have not been the farms but the suburban residential counties south of San Francisco. So people have a fear. But in my opinion it’s unfounded.

How dangerous is Malathion?

Adkisson: It’s one of the safest and most common insecticides available. In the dosages being used in California it is nontoxic to mammals. And it breaks down in about three days to harmless biodegradable materials. There is nothing better than Malathion right now.

How does it work?

Gilstrap: By blocking the synapses in an insect’s nervous system, it paralyzes the pest’s vital functions. People, however, have in their livers a powerful enzyme that renders it harmless.

Isn’t there some uncertainty, though, about the long-term effects?

Gilstrap: It’s true that definitive research of that kind has not been done, and it’s just good common sense that people with respiratory problems, pregnant women and small children should stay indoors during the spraying, and maybe a day or so after. Unlike DDT, though, Malathion does not get worse and worse as it goes up the food chain, becoming more concentrated in each higher level of animal.

How long has Malathion been in use?

Adkisson: About 30 years. We’ve used it on boll weevils in west Texas for 20 years with no problems. In 1956, to combat a Medfly infestation, it was sprayed repeatedly over the entire city of Miami, and no ill effects have ever been reported.

Then why was there such an outcry among environmental groups?

Gilstrap: Some of these people, though well-meaning, are misguided. They don’t realize how tied they are to the rest of the world and how much a part of their life chemicals of all kinds are. It’s extremely unfortunate that politicians take guidance from people who are unreasonable.

Stripping fruit and ground spraying worked in the Los Angeles area, but not farther north. Why?

Gilstrap: The area to the north is much larger. Also, it’s impossible to track down every last one of those backyard trees: Some are behind locked gates. Bear in mind that each female Medfly can lay up to 800 eggs, producing a new generation in three weeks. That’s 12 generations a year in warm climates. You wouldn’t have to miss many trees to have the flies bounce right back. And for the first six months after the flies were discovered—on June 5, 1980—the major effort in the San Francisco area, along with stripping and ground spraying, was releasing millions of sterile flies. That has never been shown to be an eradication tool anywhere in the world. It’s a control technique and must be combined with other methods.

How does it work ?

Adkisson: The principle is that the female will mate only once, so by releasing thousands of males sterilized by radiation you increase the odds that the female will mate and produce no eggs. It works well when the fly population is very, very low.

You both sound as if you consider pesticides a panacea.

Adkisson: Not at all. We advocate what is called integrated pest management, in which pesticides are a second line of defense. The first involves—among other things—crop rotation so the pests will die when their food is cut off, developing fast-growing and pest-resistant strains of plants that literally outrun pest attacks, and introducing biological control agents.

What are biological control agents?

Gilstrap: A pest’s natural enemies—various kinds of internal parasites, small predators, other insects. The ancient Chinese used to stretch bamboo poles between the branches of citrus trees so that ants could walk from one to another and eat destructive pests.

What is the Medfly’s natural enemy?

Adkisson: A certain kind of wasp. Unfortunately there aren’t any in California, which is why there’s been such a Medfly explosion since the pest was introduced inadvertently, perhaps by a tourist bringing fruit back from Hawaii a couple of years ago.

Where is this wasp found?

Gilstrap: Back where the Medfly hails from—Africa. They are not like our familiar wasps, but tiny things about the size of gnats.

Why doesn’t somebody go to Africa and bring back a batch here?

Gilstrap: That’s exactly what I’m going to do in early 1982. By this time next year, we should have a natural predator for the pest.

Once the Medfly has infested an area, can it ever be entirely eliminated?

Gilstrap: Yes, depending on quick detection and response. In California, the jury is still out on whether the Medfly is now a permanent resident.

You May Like