A guava fruit fly infestation has surfaced in Southern California even as the state’s Department of Food and Agriculture was declaring victory over the latest Mexican fruit fly infestation.

The department launched a 10-square-mile guava fruit fly eradication program in Orange County July 14 after six of the pests were discovered in the area earlier in the month, the agency said in a news release. The eradication program covers parts of the cities of Garden Grove, Orange and Santa Ana.

Goodbye Mexican, Oriental fruit flies, hello guava fruit fly

The guava fruit fly can damage a variety of tree fruits, including apples, figs, citrus, peaches and pomegranates, the release said. An agricultural quarantine has not been imposed in Orange County, but residents are asked to contact the Food and Agriculture Department should they find insect larvae in home-grown fruit.

The department lifted a 70-square-mile quarantine in and around the eastern Los Angeles suburb of Azusa July 13 after determining a Mexican fruit fly infestation had been eradicated. The announcement was made less than a week after department officials reported the eradication of the Oriental fruit fly near Long Beach and lifted a similar quarantine.

Quarantines restrict the movement of fresh produce and nursery stock outside of established boundaries. Gardeners also are prohibited from transporting yard waste outside of the quarantine area.

The quarantines had no effect on grower-shippers, because commercial groves and orchards are located many miles from the quarantine areas. 

The method used by the state agency and the U.S. Department of Agriculture to eradicate the Mexican fruit fly was a mixture of a pesticide and a synthetic pheromone that attracts adult males. The mixture is sprayed on fruit trees and utility poles, the release said. The method, which has been used in the state for 30 years, has a 100% success rate and will be the same method used to eradicate the guava fruit fly infestation, the release said.

Most fruit fly infestations in California are caused when international travelers return with infested fruit, or when packages containing infested fruit are shipped illegally into the state, the release said. The vast majority of pest infestations in California occur not on farms, but in urban, residential areas. 

The Mexican fruit fly can infest more than four dozen fruits and vegetables.

There are currently no known Mexican fruit fly infestations in California.