On a warm October morning, in a part of the desert between Hermosillo and Nogales where Gila monsters lumber across sandy dirt roads, a fourth-generation cattle rancher looks on at his herd.
The hard work of ranching has gotten even harder this year in the Mexican state of Sonora. Like most Sonoran ranchers, 71-year-old Jesús Fimbres breeds his cattle to export across the border. But for months, the United States has kept the border closed to cattle, as it seeks to stop the spread of a deadly, flesh-eating parasite called the New World screwworm.
“Right now, the truth is that times have been extremely difficult,” Fimbres said.
There haven’t been any cases of the parasite reported in Sonora, but the sweeping border closure means ranchers like Fimbres are still locked out of a U.S. market offering record-high prices. Fimbres has been forced to sell his cattle domestically for much cheaper, while consumers in the United States pony up for increasingly expensive beef at the supermarket.
But U.S. officials are determined to keep the New World screwworm out of the country. The parasite can be deadly and could spell disaster for ranchers in the United States.
“We have to protect our cattle industry and our beef industry in this country, and in so doing protect our food supply, and in so doing protect our national security for America,” said U.S. Department of Agriculture Secretary Brooke Rollins at a press conference in Texas over the summer on plans to strengthen U.S. defenses against the parasite.
As he heads out for the morning cattle feeding, Fimbres shows off a new tool on his more than 7,000-acre ranch, one his father and grandfather didn’t have in their saddle bags when they crisscrossed their livestock across this same desert. It’s a plastic baggie and a canister — to send any maggots he might come across in his herd to the authorities monitoring the screwworm’s path.
The state of Sonora is beefing up safety protocols like this. That’s created an extra expense for ranchers like Fimbres, who lose money every day the border stays closed. But Sonoran officials and ranchers hope these efforts will convince the United States to reopen the border — at least their section, which borders Arizona.
Mexico has exported 70% fewer head of cattle into Arizona so far this year compared to 2024, according to Russell Tronstad, an agricultural economist at University of Arizona. That steep decline means a reduction of the cattle supply in the United States, as well as less money in Mexican ranchers’ pockets.
“It’s pretty significant,” Tronstad said.
There’s no clear sign, though, that the USDA plans to reopen the border soon.
The United States eradicated the New World screwworm half a century ago. But over the past year, the parasite has breached what was long a containment zone in Central America, and cases have ballooned in southern Mexico.
This fall, a case of the screwworm larva was found less than 100 miles from the Texas-Mexico border.
“We want this border back open, but we have to open the border smartly so we protect our animal agricultural industries,” said Phillip Kaufman, head of the entomology department at Texas A&M University. “Because we stand to lose billions of dollars if this comes in.”
The USDA is seeking to protect the country’s already dwindling domestic cattle supply from the potentially devastating pest, which can burrow into the flesh of warm-blooded animals, including humans. Years of drought have already forced some ranchers in the United States to liquidate their herds, one of the many factors contributing to record high beef prices, livestock economists say. President Donald Trump even said this week the United States would consider lowering beef prices by buying meat from Argentina, whose president is a close Trump ally.
“Closing the borders to Mexican cattle coming to the United States certainly restricts supply, and definitely puts some upward pressure on our beef prices,” American Farm Bureau Federation economist Bernt Nelson said. “There’s just that much fewer cattle that are moving through the supply chain that provide beef for the country.”
Uncooked beef prices in the United States have gone up more than 10% over the past year, according to federal data, far outpacing the overall rate of inflation. But Nelson says if the screwworm were to enter the United States, the effects on the beef market would be much more severe.
So the USDA is investing millions in what experts say is the best-proven method to eliminate the New World screwworm: factory-like facilities that breed and release millions of sterile flies. Those flies produce no offspring when they mate, so overwhelming the population with them can eradicate the pest.
The USDA is spending hundreds of millions of dollars to increase production at an existing sterile fly facility in southern Mexico and plans to build a new one in Texas.
Entomologist Kaufman says it will take time to ramp up sterile fly production enough to completely firewall the United States from the screwworm.
“It is a daunting task, and it’s one we’re going to be working on, my guess is, for well more than a decade we’re going to be in this battle,” Kaufman said.
That means Mexican ranchers like Fimbres will most likely have to adapt and breed cows specifically for a domestic market, says Oklahoma State University livestock economist Derrell Peel. That includes developing more infrastructure like feed lots and changing animals’ genetics to meet consumer demand in Mexico.
“I think Mexico is in a position to have a much more domestically focused system,” Peel said.
At the Hermosillo headquarters for the Unión Ganadera Regional de Sonora, the state’s ranchers’ union, spokesperson and rancher Jesús Ancheta agrees the industry in his state will have to adapt. There are many pressures in addition to the border closure, including a yearslong drought and a younger generation that seems less interested in ranching.
“It’s been very demotivating, every day more so,” Ancheta said.
Back at Rancho Grande, cattle stream toward the bright green grass and alfalfa that blanket geometrical swaths of Fimbres’ land, thanks to the water spraying from giant sloping sprinklers. That water keeps getting harder, and more expensive, to get his hands on, Fimbres says.
Despite the drought, and despite the border shutdown, the circle of life here on the ranch continues.
“It’s satisfying. Mother Nature and God permit us to do all these actions to benefit a living thing,” Fimbres said as dust swirled around the snaking mass of cattle on their way to feed. “Life. That’s life.”
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The complaints come at the same time as Mexican President Claudia Sheinbaum navigates delicate negotiations with the Trump administration, one analyst says. -
U.S. Secretary of Agriculture Brooke Rollins met with Mexico’s president last week to discuss the spread of the parasite. She also led a trade delegation to discuss agribusiness ahead of the 2026 review of USMCA. -
The move comes at the same time as sanctions to individuals and businesses accused of laundering money for criminal organizations. -
The casinos are located across Mexico, including the state of Sonora. -
State officials say a store that caught fire this month in Mexico was operating without state safety protocols in place. The tragedy came 16 years after a day care fire that killed 49 children in Hermosillo.
