The guava fruit fly is back in town.

State agricultural officials say they are treating a 10-square-mile area that includes parts of Garden Grove, Orange and Santa Ana for the pest, which lays eggs in ripening fruit and could have devastating consequences for crops if it gets out of control.

Six of the flies were found in the area this month.

“They attack ripening fruits and vegetables, and the list of those is very extensive — 250 different kinds of fruits and vegetables, including most of the common fruits residents here in Orange County are likely to be growing,” said Nick Nisson, entomologist at the Orange County Agriculture Commissioner’s office who is familiar with the infestation.

They’re fond of tomatoes, for example, as well as citrus trees, peaches, figs, apples, and, of course, guavas.

But unlike the more famous Mediterranean fruit fly, last eradicated in Orange County in 1998, the guava fruit fly has a weakness that makes it relatively easy to control.

Males are powerfully drawn to a chemical released by females during mating time; state technicians are mixing a mimicking chemical with pesticide and spreading it in blotches on street lights, light poles and other surfaces, called “bait stations.”

“I’d say it’s a very effective method, because it’s a very effective lure for the male fly,” Nisson said.

Another guava fruit fly infestation in Orange County was wiped out last year using the same method, said Nisson, who keeps track of invasive pests but is not part of state Food and Agriculture.

So far only adult flies have been found, not maggots in fruit, so experts are hopeful the infestation was caught early enough to be dealt with easily, Nisson said. 

Officials with the California Department of Food and Agriculture have not declared a guava fly quarantine, but they are asking residents not to move backyard fruit out of the area. Residents also can call a toll free hotline at 800-491-1899 to report maggots in fruit or other signs of the fly.

 The fruit fly is native to southeast Asia, Nisson said, from India to Vietnam. They can be reintroduced to the area by hitching rides in the luggage of unwitting travelers.

“This is one that has showed up repeatedly in the L.A. basin for many years,” Nisson said. “It’s always been effectively eradicated with this method.”

(Image courtesy California Department of Food and Agriculture. Register graphic by Brian Moore.)

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