Contra Costa County agriculture officials are waging an extensive eradication campaign against a tiny but destructive winged menace.

The effort comes after seven male oriental fruit flies were discovered recently near Brentwood and Oakley in east Contra Costa County, county officials said.

The county’s agriculture commissioner, in cooperation with the California Department of Food and Agriculture and the U.S. Department of Agriculture, has responded by initiating an extensive survey and eradication plan in response.

Also known as bactrocera dorsalis, the detection of the flies was confirmed Aug. 25 as part of the department’s coordinated pest prevention system that protects the county’s agriculture and natural resources from invasive species before they become established.

The extensive survey, also known as a delimitation survey, consists of multiple oriental fruit fly traps at prescribed densities placed in concentric circles going out 4.5 miles in each direction from the oriental fruit fly detection sites.

The county said in a statement that the discovery of seven oriental fruit flies will trigger a quarantine, which was expected be announced shortly by the California Department of Food and Agriculture.

Fatal attraction

Officials use “male attractant” technique as the mainstay of the eradication effort for this invasive species. The approach has successfully eliminated dozens of fruit fly infestations in California.

Trained workers squirt a small patch of fruit fly attractant mixed with a very small dose of spinosad, a natural pesticide made by soil bacterium that is approved for use on organic crops, approximately 8-10 feet off the ground on street trees and similar surfaces.

Male fruit flies are attracted to the mixture and perish after consuming it. The male attractant treatment program is being carried out over an area that extends 1.5 miles from each site where the oriental fruit flies were trapped.

While fruit flies and other invasive species that threaten California’s crops and natural environment are sometimes detected in agricultural areas, the vast majority are found in urban and suburban communities, the county said.

“These recent detections remind us that we need to remain vigilant in protecting our agricultural and natural resources.”

Matt Slattengren, Contra Costa County Agricultural Commissioner

The most common pathway for these pests to enter the state is by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions of the world or from packages of homegrown produce sent to California.

Agriculture officials ask people to “Don’t Pack a Pest” to help protect California’s agricultural and natural resources when traveling or mailing packages.

“Invasive non-native fruit flies are serious pests for California’s agricultural industry and backyard gardens,” Contra Costa County Agricultural Commissioner Matt Slattengren said in a statement. “These recent detections remind us that we need to remain vigilant in protecting our agricultural and natural resources.

“When traveling abroad or mailing packages to California, we urge the public not to bring back or ship fruits and vegetables as they are pathways for oriental fruit flies and other invasive species entering our state,” Slattengren said.

Voracious diner

The oriental fruit fly is known to target over 230 different fruit, vegetable, and plant commodities. California crops at risk include grapes, pome and stone fruits, citrus, dates, avocados, and many vegetables, particularly tomatoes and peppers.

Damage occurs when the female fruit fly lays her eggs inside the fruit. The eggs hatch into maggots, which tunnel through the flesh of the fruit, making it unfit for consumption. The oriental fruit fly is widespread throughout much of the mainland of southern Asia and neighboring islands, including Sri Lanka and Taiwan, and it has invaded other areas, most notably Africa and Hawaii.

Residents with questions about the project may call the Contra Costa County Agricultural Commissioner’s office at 925-608-6600 or the California Department of Food and Agriculture’s Pest Hotline at 800-491-1899.