Medfly Strategies May Have Masked Problem
Faced with an infestation that won’t go away, the government may have made a critical error in its battle against the Mediterranean fruit fly this summer by ordering aerial pesticide spraying before the true size of the pest population was known, a leading scientist says.
Roy Cunningham, a U.S. Department of Agriculture Medfly expert in Hawaii and chairman of the scientific panel advising the current Medfly eradication program, said the rapidity with which malathion-bearing helicopters were launched may have, ironically, masked the true size of the infestation and provided a false sense of confidence that the problem had been solved.
If the infestation in the Whittier area in October were as large as evidence now seems to indicate, the spray might have killed only 90% of the population. That still would have left enough of the pests alive to spread, Cunningham said.
“We blinded ourselves with the bait spray,” he said. “We must have had a sizable population at the start. We did not appreciate that. Maybe in hindsight it would have been better to wait and evaluate the situation” before going on the attack.
The experts believe there are several reasons that the pest has been found in such diverse locations as Sylmar and Glendora. These reasons include people carrying infested fruit out of the Medfly quarantine zone. But Isi Siddiqui, assistant director of the California Department of Food and Agriculture’s Division of Plant Industry, said much of the spreading infestation in the central Los Angeles area today emerged from the Medfly hot spot in the Whittier area, found on Sept. 26.
That infestation zone was sprayed on Oct. 4, only eight days after the initial find. By that time 61 flies had been found.
“We moved too fast,” said Cunningham. He said the original population in Whittier must have been very large, but no one will ever know how large because of the speed with which treatment was begun. He admitted there is always a danger that the infestation will spread while waiting, but he said it might be better in the future “to take a little time to get a good handle on the situation.”
Cunningham said he now believes it might be important in the future to change the Medfly battle plan, known as the “protocol,” to allow more time to gather intelligence before starting to fight the flies with spraying and by releasing millions of sterile flies. The theory behind releasing sterile flies is that they will breed with the fertile flies, preventing the flies from multiplying.
Los Angeles County Agricultural Commissioner Leon Spaugy in part agreed with Cunningham that the protocol needs revision. But in his view, the particular mistake this time may have been moving in with sterile flies after only a single application of the bait spray.
“If there is a lesson to be learned, perhaps we ought to evaluate the distribution (of flies) very carefully before we rush in with sterile flies,” he said. “Perhaps we should go with multiple bait sprays before the steriles.”
Siddiqui said that, in Florida, the standard procedure for fighting Medfly infestations is to apply four dousings of malathion before bringing in sterile flies. The California protocol allows for that as well, but authorities said they had been able to knock out infestations in 1987 and 1988 in the Los Angeles area with only a single application and, as a result, believed that would work again.
In all, Medfly experts admit the fly’s behavior continues to surprise them. The lessons they thought they learned seven years ago, during the much-publicized Northern California infestation in 1981-82, have not prepared them for what has happened this time.
The frustration of those fighting the crop-destroying pest could be seen Friday at a hearing of the state Senate Committee on Agriculture and Water Resources. “Something is out of kilter,” said Chairman Ruben Ayala (D-Chino).
Pressed for an explanation of why the infestation has spread so far, Siddiqui said, “It’s a good question.” He ticked off a number of possibilities--infested fruit being mailed in, people carrying fruit out of quarantined areas, the arrival of immigrants bearing fruit from infested Central American nations, and others--but finally admitted “there is no pattern” to this outbreak.
