Scientist Says Early State Medfly Attack May Have Lost War

Faced with an infestation that won’t go away, a leading scientist says 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.

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.

Orange County has been doused twice with malathion in the last month. The first aerial spraying on Nov. 30 followed the discovery of a single pregnant Medfly in a guava tree in Brea. On Dec. 6, agricultural officials found three fertile Medflies in La Habra Heights, and on Dec. 12, they resprayed a 26-square-mile area that included parts of Brea, La Habra and Fullerton.

A Medfly was also trapped on Dec. 8 in Westminster, about 10 miles south of the La Habra infestation. But officials decided not to spray Westminster now because the trapped fly, while fertile, was not pregnant. Instead, they tripled the number of traps to see if more flies appear.

The experts believe there are several reasons that the pest has been spreading. 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.