Invasive Fruit Fly Quarantine takes effect in Contra Costa County

CONTRA COSTA COUNTY, CA (Sept. 8, 2023) — The Contra Costa County Department of Agriculture has instituted a quarantine on most fruits throughout much of East Contra Costa County. This comes after the Contra Costa County Dept. of Agriculture found several invasive oriental fruit flies in recent weeks. Communities in Contra Costa and Santa Clara Counties are affected. Here’s what you need to know:

How did these fruit flies arrive in Contra Costa County?

While the exact origin of these oriental fruit flies is unknown, invasive fruit flies are often introduced to an area when someone brings fruit illegally from another state or country against California agricultural controls.

What is the quarantine area?

The 99 square mile area of quarantine includes Brentwood, Oakley, and much of Antioch, Bethel Island, Knightsen and other unincorporated areas. The California Department of Food and Agriculture has an exact map of the area on its web site. You can also use this interactive map to check if a specific address is inside the quarantine area.

What fruits and crops are at risk?

A large number of fruits and other crops attract oriental fruit flies. This includes grapes, tomatoes, squash and walnuts. You can find the abbreviated host list published by the California Department of Food and Agriculture and United States Department of Agriculture in this document.

What will be the impact to our local agriculture?

The quarantine affects some farms, fruit vendors and other businesses. County officials at the Department of Agriculture will proactively reach out to those businesses to help them comply with the quarantine regulations. This may include prescribed spray treatments. It may also require some businesses to process fruit on site instead of off site.

How does this affect fruits I grow in my yard?

Any homegrown fruit must not leave your residence. You may still eat and/or process fruit at home. However, if you throw out the fruit, you must double-bag and sealed it.

What should I do if I spot an oriental fruit fly?

According to the California Department of Food and Agriculture, “The adult oriental fruit fly is somewhat larger than a housefly, about 8 mm in length. The body color is variable. Generally it shows bright yellow with a dark ‘T’ shaped marking on the abdomen. The wings appear clear. The female has a pointed slender ovipositor to deposit eggs under the skin of host fruit.” If you find an oriental fruit fly, call the Pest Hotline at 800-491-1899.