State Officials Cautiously Claim Victory Over Medfly

After five years of biological warfare, state agriculture officials cautiously declared victory Tuesday over the Mediterranean fruit fly, a persistent pest that could cost California nearly $2 billion a year in crop losses and other damage if it regained a foothold.

According to the California Department of Food and Agriculture, an average of more than seven Medfly infestations were discovered each year from 1987 to 1994, most in Los Angeles, Orange, Ventura and Riverside counties.

But the rate of infestation has dropped dramatically since then.

In 1996, the state began dispatching billions of sterile flies across Southern California, a method that prevents females from laying eggs and effectively eliminates them through attrition. Over those five years, state officials said, just one infestation has been found in the area where the state has used the fight-flies-with-flies technique. That one, in the Walnut Park area of Los Angeles County, was quickly contained without extensive damage to crops.

“We don’t ever want to let our guard down,” Food and Agriculture spokesman Steve Lyle said Tuesday. “But we’re successfully managing the Medfly at this point. This is an excellent program.”

The announcement comes as the state Senate and Assembly are debating how to fund the $15.8-million-per-year program, the cost of which is divided between the state and the U.S. Department of Agriculture.

The Senate has only approved funding for another year, while the Assembly has approved the program as a permanent budget item--the alternative preferred by California pest control officials.

“We want to fund it for the long haul,” said Pat Minyard, the state’s branch chief for pest detection emergency projects. “We think what we’re doing now clearly works.”

Slightly smaller than the housefly, the blue-eyed, droopy-winged Medfly attacks by piercing the skin of fruit and laying eggs inside. The eggs hatch into maggots that feed on the fruit pulp before maturing and launching the cycle again.

Originating in Africa, the Medfly first arrived in the continental United States in 1929, in Florida. Since then, California has seen many outbreaks, including significant populations in the Los Angeles Basin in the late 1980s and early 1990s.

The flies attack more than 250 commercial and backyard crops, and experts estimate that they would cost California $1.9 billion each year in crop loss, job loss, trade embargoes and pesticide use if they established permanent residence.

Borrowing technology developed half a century ago in Texas, where farmers were fighting a worm that bred in the hides of cows, California began using sterile flies to battle Medflies. The method is successful because Medflies mate just once--so when a female mates with a sterile fly, it will never produce eggs.

For years, California had used the sterile flies to fight individual infestations. But in 1996, the state launched a comprehensive program that not only knocks out existing infestations but prevents new ones. Through that campaign, nearly 75 billion sterile Medflies have been released in Southern California.

California has declared victory over the Medfly in the past, amid skepticism from some scientists who pointed out that pest controllers were merely killing off one infestation, then waiting for the next one. The scope of the current program, however, has given agriculture experts new confidence that they have finally won the war.

“Unequivocally, you can say it’s a success,” said USDA spokesman Larry Hawkins.

Another advantage: The program largely replaces air and ground applications of malathion, the sticky insecticide that coated cars, prompted health concerns and roiled Southern California in the late 1980s and early 1990s.

Experts continue to fine-tune the sterile-fly program.

The state’s first target area, for example, wasn’t big enough, and in 1998 the effort failed to halt brief infestations in the Lake Elsinore, Murietta and Lake Forest areas. Those outbreaks have been quelled and those regions added to the program.