State Turns to Guatemala, Mexico as Sterile Medfly Supply Runs Out

A swarm of Mediterranean fruit flies buzz Gary Agosta’s head, but the state entomologist pays no mind: These bugs are harmless, sterile counterparts of California’s most destructive crop pest.

Agosta, working out of a trailer at Van Nuys Airport, is in charge of rearing millions of sterile Medflies, a major weapon in the battle against the fruit-munching pest. Sterile flies are released by the millions in an attempt to breed out of existence any fertile flies that survive aerial pesticide spraying.

Until now, the state has received sterile flies from a California Department of Food and Agriculture laboratory in Hawaii. They are sterilized in Hawaii, where wild Medflies are in abundance, because fertile escapees can cause no greater harm there.

An unprecedented number of infestations in Los Angeles County, however, have exhausted the sterile supply and forced officials to barter with sterile fly factories in Guatemala and Mexico--the only other ones in the world--for more sterile flies.

Without steriles, the only recourse available to the eradication effort is multiple applications of pesticides over residential neighborhoods.

A sense of urgency is evident in the trailers. On a recent workday, Agosta could be heard negotiating furiously with a government official, seeking to book passage on a commercial airline for a batch of Mexican-bred steriles.

The flies, irradiated with cobalt 60 to make them sterile, are shipped to California in their pupae stage in two-foot-long plastic cylinders.

The sterile pupae are stored in trailers at Van Nuys Airport for four days while they incubate and reach maturity. They are kept in the dark, which Agosta says suppresses their sexual appetite.

“They won’t mate in dark, so we want them to be eager” when they are released from airplanes and trucks, he said.

It is the job of one scientist in the trailers to test representative samplings to determine how well they fly and mate--as well as to double-check their sterility.

Sterile flies are dyed red so that agricultural officials checking traps can distinguish the sterile flies from their fertile counterparts.

So far, about 500 million sterile flies have been released in Los Angeles County. And, officials report, they are being found as far away as Sacramento.