Oriental Fruit Fly Find

Our Pest Detection staff has found a total of seventeen invasive Oriental Fruit flies, which is one of many invasive pests monitored by Contra Costa County Department of Agriculture. This means that we are now in a quarantine for parts of the Brentwood area.

The first Oriental Fruit Fly (OFF) was found on August 25, 2023 near Lone Tree Way, in Brentwood, California. 

Oriental Fruit Fly (Bactrocera dorsalis)

Oriental Fruit FliesSince the initial detection, 80 additional traps have been deployed in a one mile grid around the original find to determine the extent of the infestation. (See Quarantine Map Boundaries) Our team has trapped sixteen additional OFFs since the initial find. Each of the insects were sent to the California Department of Food and Agriculture's (CDFA) Entomology lab and confirmed as Oriental Fruit Fly (Bactrocera dorsalis). The announcement went out via press release on August 30, 2023. (Press Release Link)

Contra Costa County was placed under quarantine and CDFA issued a Proclamation of an Emergency Program (PEP). This proclamation lined out the threat, the delimitation, sensitive areas, the current work plan, and the findings. CDFA determined that these detections indicate that a breeding population exists in the area. It was also determined "unless emergency action is taken, then there is high potential for sudden future detections in Contra Costa County." Fortunately, the "results of the additional survey also indicated that the local infestation is amenable to CDFA’s OFF response strategies..."

The Oriental Fruit Fly is known to infest over 230 kinds of fruit and vegetables. To view CDFA's official host list, see the Oriental Fruit Fly Interior Quarantine host list.

CDFA has compiled a fact sheet with helpful information found here: Oriental Fruit Fly Fact Sheet.

You may be wondering how this will affect you. Contra Costa County has created a printable pamphlet with examples of the impact this invasive species could have on you. Oriental Fruit Fly Impact Flyer.

There is good news. So far, very few flies have been found since the eradication efforts began. Unfortunately we found two females a week before the end of the first life cycle. This means prior to the eradication efforts, eggs were laid in some fruit in the area and are now hatching. We expect to attract any new flies as they emerge. As we enter the fall and winter and the temperature drops, the cooler weather will slow down the life cycle of the fly. We are hoping the quarantine will be ending sometime in June 2024. (see PEP)

What are some of the ways these flies could have ended up in Contra Costa county?

It was likely brought in by someone shipping fruit from an infested area or bringing infested fruit back with them from a recent trip.

"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." Contra Costa County Agricultural Commissioner Matt Slattengren.