A fruit fly originally dubbed the cherry vinegar fly has shown up in a host of berry crops and cherries in 21 California counties.

The pest, now known as the spotted wing drosophila, is one of only two members of the 3,000-member Drosophila species group known to damage  ripening fruit, according to a North American Plant Protection Organization phytosanitary alert. Most Drosophila fruit flies feed on rotting fruit.

The new pest has been found in cherries, raspberries, blackberries, blueberries and strawberries.

The female damages fruit as she lays her eggs with a serrated ovipositor, according to a blog by University of California Cooperative Extension farm adviser Mark Borda, who's based in Monterey County.

The larvae then develop within the fruit, feeding and damaging it in the process.

The pest is thought to have up to 10 generations per year.

Neither the California Department of Food and Agriculture nor the U.S. Department of Agriculture plan to regulate the pest.

The fly originally is from Asia and is established in Hawaii and Spain, according to the NAPPO report.