The study, published in the science journal Proceedings of the Royal Society B, found that despite decades of costly eradication efforts by the state, the Mediterranean fruit fly and the Oriental fruit fly have not been eliminated.
The flies' populations are currently low, said study co-author and University of California, Davis entomologist James Carey. But if the state does not change its long-term strategy to control the flies, the future could bring frequent, widespread infestation outbreaks that would devastate California's $43.5 billion agricultural industry, he said.
At least five and as many as nine species of tropical fruit flies are now entrenched in California, the study determined.
The study also found that California's fruit flies are not brought in by visitors or cargo shipments from outside the country, as authorities claim.
"They're here, they're established and lurking," Carey said. "It's like an insidious cancer that's just metastasizing and spreading, and it will eventually develop into a full-fledged cancer."
In addition to current strategies, the state should formulate long-term emergency plans, increase trapping and monitoring of the flies, and create a crop insurance program for farmers, Carey said.
California farmers and packers should also develop crop plans and production strategies based on knowledge of the fly's presence, he added/
State agriculture officials say their methods are effective and their approach would be the same even if the populations were established — though they welcome the input of scientists.
"We believe they come from out of the country. But it's kind of a philosophical discussion with no practical significance," said Dr. Robert Leavitt, director of plant health at the California Department of Food and Agriculture. "Even if they were here permanently, our response would be the same."
The state's current strategies include releasing sterile male flies to break the breeding cycle, squirting bait in trees and bushes to attract and kill male flies, and asking homeowners and growers within a quarter of a mile of the detection area to strip and destroy fruit from trees.
Copyright 2013 The Associated Press.