SAN DIEGO (FOX 5/KUSI) — A quarantine zone was issued Tuesday in San Diego County after Mexican fruit flies were discovered during a routine inspection, according to the county.

The California Department of Agriculture (CDFA) declared the quarantine after an inspection in La Mesa.

The quarantine zone includes 77 square miles bordered by the San Diego River to the north, Sweetwater Reservoir to the south, the I-15 to the west and the city of El Cajon to the east.

It affects the cities of El Cajon, La Mesa, Lemon Grove, San Diego and Santee, as well as Spring Valley and Bonita.

(California Department of Agriculture)

(California Department of Agriculture)

The quarantine applies to growers, wholesalers, retailers and nurseries handling any fruit or plants in the area.

The county said in a news release that eradication efforts will be done, including the release of sterile male Mexican fruit flies in the area, treatment of properties within 200 meters and fruit removal from areas within 100 meters of where larvae or flies are found.

Home gardeners in the area are urged to avoid moving any homegrown produce off their property.

According to the CDFA, an adult Mexican fruit fly is larger than a house fly and has the potential to destroy a large number of California crops, including peaches, avocados and pears.

The invasive pest usually enters the state by hitchhiking in fruits or vegetables brought back illegally by travelers.

California has different rules and regulations for bringing fresh fruit or veggies into the state, depending on where they are from or the type.

The CDFA also has the website Don’t Pack a Pest that helps to educate travelers on what items are safe to travel with and bring back to the U.S.

San Diego residents who think their fruits or vegetables may be contaminated with the fruit fly are urged to call the state’s toll-free pest hotline at 1-800-491-1899.

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