In an unusual move, a portion of Los Angeles County has been placed under quarantine after after an invasive species was detected in the area.

More than 20 Tau fruit flies have been detected in the unincorporated area of Stevenson Ranch near Santa Clarita, a city north of Los Angeles, according to the California Department of Food and Agriculture. The quarantine is the first of its kind for Tau fruit flies in the Western Hemisphere and according to the agency, they are a "serious pest for agriculture and natural resources" with a wide host range, including fruits, vegetables and select native plants in California.

The quarantine area is 79 square miles total: bordered by Castaic Junction on the north, Oat Mountain on the south, Del Valle on the west and Honby Avenue on the east.

The California Department of Food and Agriculture said in a release that it is believed the Tau fruit flies were first introduced by travelers bringing uninspected produce into the state, which is a common pathway for invasive species.

In order to eliminate the Tau fruit fly and prevent its spread to new areas, the California Department of Food and Agriculture is working in cooperation with the United States Department of Agriculture and the Los Angeles County Agricultural Commissioner.

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What is the Tau fruit fly?

The Tau fruit fly is an invasive species originating in Asia.

According to a pest profile from the California Department of Food and Agriculture, an adult is approximately 7 millimeters in length, similar to a housefly, with a yellow body with black markings. It has clear wings with two dark stripes. The egg is almost 1 millimeter long, white and cylindrical, and its larvae is creamy-white, legless and may be as long as 9 millimeters.

The species was first detected in California in 2016 in San Bernardino County. Since then, it has been reintroduced and eradicated three times.

California crops at risk with Tau fruit flies in the area include avocado, citrus, tomatoes, peppers and cucurbits.

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What to do if you're under quarantine for the Tau fruit fly

To prevent the spread of Tau fruit flies, the California Department of Food and Agriculture urges residents within the quarantine area to not move any fruits or vegetables from their property.

The fruits and vegetables can be consumed or processed at the property where they are picked. Otherwise, they should be disposed of by double bagging them in plastic and placing them in garbage bins.

On any properties within 200 meters of detections of the flies, staff involved with the containment of the species will cut fruit and vegetables to inspect for any fruit fly larva.

Additionally, properties within 200 meters of any Tau fruit fly detections will be treated with Spinosad, a natural substance, toxic to insects, that will help remove any adult fruit flies and reduce the density of the population.

The agencies involved will also use fly traps with a pheromone lure and a "minute amount of pesticide" that will be used in a wider part of the treatment area, according to a release from the California Department of Food and Agriculture.