Following detection of two male peach fruit flies (PFF) in the city of Palo Alto, staff with the San Mateo County and Santa Clara County Agricultural Commissioners’ offices will place insect detection traps within a 4.5-mile radius including into Menlo Park and East Palo Alto to determine the extent of the infestation.

As early as Thursday, July 11, eradication treatments may begin in hopes of stopping the flies before they become established. PFF, which is widespread through much of mainland southern Asia and neighboring islands, is known to attack more than 50 types of fruits and vegetables. Damage occurs when the female lays eggs in the fruit.  These eggs hatch into larvae, which tunnel through the flesh of the fruit, making it unfit for consumption. 

San Mateo County Agricultural Commissioner Fred Crowder will work with officials from Santa Clara County, the California Department of Food and Agriculture (CDFA) and the United States Department of Agriculture on a delimitation survey to determine the extent of the infestation, and a treatment plan to eradicate PFF. At this time, no treatments will be applied on private property and no quarantines are in place. However, this may change if additional PFF are detected.

The two peach fruit flies prompting this survey were trapped in Palo Alto on June 28 and July 2. The discovery resulted in the placement of additional insect detection traps going out in a 4.5-mile radius from the sites where the fruit flies were found. The CDFA will also begin using the “male attractant” eradication technique in which trained applicators place a small blob of fruit fly attractant containing Spinosad, an organic pesticide, approximately 6 to 8 feet off the ground on street trees, light poles and similar inaccessible elevated locations. Male fruit flies are attracted to the mixture and perish after consuming it.

“These finds are the result of early detection trapping which is key to finding and eradicating exotic pest infestations before they pest can become widely established. This not only protects agricultural interests, but also community and backyard gardens and the environment from destructive invasive species,” Crowder said.

“In San Mateo County, there are over 4,250 exotic pest detection traps placed throughout the county which are checked each week to monitor for the introduction of invasive and impactful insect pests like Gypsy Moth, Japanese Beetle and an assortment of fruit flies such as Mediterranean, Peach, Melon, Guava, Oriental and others.

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 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 home grown produce sent to California. It is important when traveling not to bring home plants, food or other agricultural items that contain harmful pests and diseases.

Learn more about how to help protect California’s agricultural and natural resources when traveling or mailing packages at Don’t Pack a Pest (www.dontpackapest.com).

For questions about the project, please contact the San Mateo County San Mateo County Agricultural Commissioner’s office at 650-363-4700 or the Santa Clara County Agricultural Commissioner’s office at 408-918-4600. Additional information is also available at: https://www.cdfa.ca.gov/plant/PDEP/treatment/peach_ff.html