California authorities are starting a treatment program for the guava fruit fly after three of the pests were found in San Jose.

Routine trapping detected a guava fruit fly in the city’s Mayfair area July 3. Since then two more have been found, said Joseph Deviney, Santa Clara County agricultural commissioner.

The flies had infested stone fruit trees. The residential Mayfair neighborhood is about 15 to 20 miles from hundreds of acres of cherries and other commercially grown stone fruit, Deviney said.

“There’s some community gardening going on nearby and some homeowners, but at this moment it doesn’t affect any commercial growers,” he said.

The California Department of Agriculture begins eradication efforts July 17, spokesman Steve Lyle said.

“If we find eight or more, or if we find a mated female or larva in fruit, then we’ll go to a quarantine,” Deviney said. “Hopefully we caught it early on and we’re responding rapidly enough to eliminate the infestation.”

The guava fruit fly has been found before in Santa Clara County, he said, but is less common than an oriental fruit fly.

“I’m pretty sure somebody received contraband fruit,” he said. “It didn’t fly here from Southeast Asia. Somebody brought something in.”

Citrus is the fly’s natural host but not its only one.

“Anywhere you can grow citrus, you can probably grow this fly,” Deviney said. “We don’t have a winter to kill it. If we did nothing it could quickly spread to Monterey and further down. It would have effects on exports.”

There will be a maximum of six treatments, one every two weeks, Lyle said.

An insecticide-laced gelatinous pheromone mix will be placed on fruit trees and telephone poles to attract and kill male flies, leaving any females without mates.