Five Mexican fruit flies have been found within three miles of each other in La Mesa, prompting the California Department of Food and Agriculture on Tuesday to declare a 77-square-mile quarantine in San Diego County.

The Mexican fruit fly is one of the most destructive agricultural pests and attacks more than 50 different types of fruits and vegetables — from citrus like lemons and oranges to avocados, according to the CDFA. It can grow to be 1 cm in length — about the size of a pea, larger than a common housefly.

“Mexican fruit flies lay their larvae within the fruit, and so the larvae eats the fruit from the inside, making it inedible. If we have inedible fruit, then that increases the cost of fruit and supply reduces the supply," San Diego County Deputy Agricultural Commissioner Jasmine Lopez said.

According to the CDFA, an infestation of the Mexican fruit fly could devastate crops and make it about $124 million more expensive for growers and consumers alike. The county said the Valley Center Mexican fruit fly quarantine of 2022 put $306 million worth of crops at risk.

“Spreading this fly could be very detrimental. It's one of the most invasive species of fruit flies,” Lopez said.

The quarantine affects commercial fruit growers, wholesalers, retailers and home gardeners in portions of the city of San Diego, El Cajon, Santee, Lemon Grove and La Mesa, along with parts of Spring Valley and Bonita, according to the county.

County officials are releasing thousands of sterile males each week to eradicate the problem. The hope is when they mate, no offspring can be produced and the population becomes extinct, the CDFA said. Workers are also setting about 8,000 fruit fly traps and using an organic spray near sites where the flies were found.

Officials expect the quarantine to be over around September. In the case that Mexican fruit fly larvae is found, that property's fruit and all fruit in a 100-meter radius can be ordered for disposal.

To mitigate the spread of the flies, which have geometric-patterned wings that look like stained glass windows, people growing fruit trees and plants are urged to eat what they've grown on their own property.

State health officials will also contact and do checks as needed at retailers and nurseries in the quarantine area.

Pure Fruit Bar and Deli owner Omar Rosales is worried about what the quarantine may do to area businesses. That’s why he’s doing what he can to mitigate any risk at his Lemon Grove business.

“Lucky for me, I don’t worry too much," Rosales said. "I go through procedures for washing fruit right. Using old school tricks of the trade — the vinegar, the water."

The county said these invasive pests often enter the state in fruits and vegetables brought back illegally by travelers from infested areas.

Residents who suspect their fruits or vegetables may be infested should call the state’s toll-free Pest Hotline at 1-800-491-1899.