Go for the Honeydew : Medfly: The sterile-fly theory is cultivated by men who sit in offices and think like industrial engineers. Nature doesn’t work that way.

<i> William Jordan holds a Ph.D</i> .<i> in insect ecology. His book, "Divorce Among the Gulls and Other Essays on Human Nature," will be published by North Point Press next year. </i>

Why has the government claimed so many victories against the Medfly? Because their traps cannot detect the Mediterranean fruit fly at the low levels in which introduction, colonization and naturalization occur. This brings us to the astonishing truth about the state’s eradication weapons.

Eradication depends on early detection. Independent entomologists pretty much agree that the only chance one has of eradicating an insect is soon after arrival, before it spreads. In other words, in Phases 1 or 2. Should an infestation reach Phase 4, the battle is lost. But the state’s traps can barely detect a Phase 4 infestation, much less a Phase 1.

We should know a bit more about trapping. For normal surveillance, the government sets out five traps per square mile. This works out to about one per 116 football fields. When a fly is found, the state wrinkles its brow, rolls up its sleeves and places 100 traps per square mile. This works out to one per nine football fields.

It is hard to convey the enormity of how bad this trap is, especially since all decisions to spray malathion rest on its performance. James Carey, an entomologist at UC Davis, puts it like this: on a scale of 1 (worst) to 100 (best), it would probably rate a 5. Ken Konishiro, an entomologist in Hawaii, conducted a preliminary experiment in which he released 140 wild Medflies within 40 feet of a U.S. Department of Agriculture trap, and not one fly ever went into it. Yet the government has wagered the health of its citizens and the fate of its multibillion-dollar agriculture on the performance of its Medfly traps.


As for the malathion bait, the bottom line is that it has not worked. Here is a likely scenario as to why it has not worked.

Malathion bait is formulated to imitate honeydew, which is the sweet and sticky excrement of aphids, scales, mealybugs and related insects that suck sap. It is a major source of food for hundreds of other insect species and is a primary foodstuff for Medflies. And here is the sweet irony: The malathion bait is killing the predatory insects and the aphids, scales, mealybugs, et. al., are multiplying at Mach velocity and showering the world with honeydew, and the Medflies are saying, “Stuff the bait--go for the honeydew.”

As for that altar of substitute pesticides, the sterile flies, they, too, are highly suspect. Safe, ecologically sound, biodegradable, highly controversial in entomological circles. They seem to have some effect in lowering the level of Medfly populations, but no one knows how they achieve that. The standard line, that wild females mate once and that sterile males get there first because they so outnumber their wild brothers, may be false.

It turns out that wild females are extremely choosy about their mates and must be courted through an elaborate dance. Before that happens, the wild males must undergo intense competition with others to secure an attractive territory, which attracts the female. In nature, only about 15% of the Medfly males account for about 85% of the matings.

But consider the sterile fly. Here is a creature that is raised by the hundreds of millions inside a factory. It eats artificial food, possibly picks up alien body odors as a result, suffers genetic selection so that it’s designed to live in Medfly factories and not the wild and then sterilized.

And how do you sterilize a Medfly? Why, you put it in a radiation chamber and bombard it with cobalt 60. The flies come out of this treatment blinded, crippled, metabolically fried; then they are asked to compete with tough, fit, wild males. For this reason the possibility exists that it is not the sterilized males but the sterilized females that do the damage, because they seem to accept any male that asks--the result, presumably, of being selected for life in factories, where breeding orgies take the place of formal competitions.

By themselves, the sterile flies are defective enough to sabotage the entire eradication program. So, too, are the traps. The malathion bait is nothing but a misguided prayer. But the grossest of all deficiencies is the absence of any outside control. There is no agency that can evaluate the program’s performance, force changes of policy or shut it down completely should it prove ineffectual.

The grand upshot is a program that cannot succeed yet cannot desist. The government warriors have no other weapons, no contingency plans, no long-range strategies, no grasp of Medfly reality. Their only mandate is to succeed. That and the warriors of obdurate pride ensure that the spraying will continue.