Invasive flies are once again threatening citrus trees in the Rio Grande Valley, and the federal government is stepping in.

The U.S. Department of Agriculture established quarantine areas in all four Valley counties against Mexican fruit flies.

Female fruit flies deposit eggs beneath the skin of fruits, leaving the fruit decayed and unfit to eat, according to the California Department of Food and Agriculture.

Experts say the biggest attractors of the fruit flies are what’s known as “backyard trees,” or trees that still have fruit on them past April, the end of harvest season.

“There's been estimates of over a million trees in people's yards, that's about seven thousand acres of untreated citrus sitting in folk's backyards,” Texas citrus Mutual President Dale Murden said. “Leave the fruit on the tree, and it's a host for these larvae and these flies that are coming across from Mexico, and it'll jeopardize the commercial industry here in Texas.”

To prevent the flies from spreading further, the USDA is inspecting and putting up traps on people's backyard trees to figure out where they're landing the most.

The USDA is also asking the public to clean up any fruit that's fallen to the ground, and pick all the fruit off your tree before the end of the month. 

The USDA can inspect your citrus trees. 

Residents in Cameron and Willacy counties wanting to get their trees inspected can call the Harlingen USDA office at 956-421-4041.

Residents in Hidalgo and Starr counties wanting to get their trees inspected can call the McAllen USDA office at 956-632-5300.

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