Ranchers Rage As Flesh-Eaters March North

A high-tech fly factory on the U.S.–Mexico border is racing to stop a flesh‑eating parasite, while ranchers warn federal science may be moving slower than the screwworm itself.

Story Snapshot

The United States and Mexico are expanding plants that breed sterile flies to crush New World screwworm.
Trump’s USDA backs a Texas facility making up to 100 million sterile flies a week, plus a renovated plant in Mexico.
Texas cattle leaders fear the pest is still spreading despite billions of sterile flies already released.
A fight is brewing over federal “fly factories” versus old‑school kill bait and tougher border controls.

How the U.S. and Mexico Plan to Fight a Flesh‑Eating Parasite

New World screwworm is a deadly fly whose maggots eat living flesh in cattle, pets, wildlife, and even people when not treated fast.^[7] To stop it, the United States and Mexico are leaning on the sterile insect technique, a method that helped wipe screwworm out of the United States in 1966 and beat a Florida Keys flare‑up in 2017.^[7] In this method, labs breed huge numbers of flies, sterilize them with radiation, and release them so sterile males outnumber wild males and crash the population.^[4]

History shows this approach can work when done at massive scale and paired with strong quarantines. Federal records describe past campaigns in Florida, Texas, and Mexico that produced tens or hundreds of millions of sterile flies each week until the parasite was pushed south and eventually fenced off at a “barrier zone” in Panama.^[5]^[8] The sterile males mate with wild females, whose eggs never hatch. Because each female mates only once, the pest slowly dies out if new flies are kept from crossing the border.^[4]^[7]

New Fly Plants on the Border: Big Numbers, Big Questions

To boost capacity inside our own borders, the Trump administration’s Department of Agriculture built a sterile fly production and dispersal facility at Moore Air Base near Edinburg, Texas.^[6] That site is designed to turn out about 100 million sterile flies per week and drop them across a 50‑mile band inside Texas, strengthening the long‑running barrier provided by the Panama plant.^[6]^[9] At the same time, USDA invested $21 million to renovate Mexico’s Metapa facility so it can produce 60 to 100 million sterile flies weekly, instead of relying only on shipments from Panama.^[1]^[6]

For decades, the joint Mexico‑U.S. screwworm program has operated a large fly factory in Chiapas that once sterilized up to 600 million pupae weekly and helped Mexico declare itself screwworm‑free in 1991.^[2]^[8] Today, the smaller Panama plant turns out about 100 million sterile flies per week, which are flown along the Darien Gap to keep the parasite from moving north.^[4]^[9] The new Metapa upgrades and the Texas facility are meant to double up that shield and respond directly inside the United States if the pest crosses the line.^[1]^[6]

Ranchers Push Back: Are Fly Factories Enough?

Texas cattle leaders and Agriculture Commissioner Sid Miller do not fully buy the idea that more sterile flies alone will fix the problem. Miller argues that current fly strains are inefficient because half of the released insects are females that mate with sterile males instead of fertile wild males, wasting precious capacity.^[11] He points to the fact that billions of sterile flies have already been released over months in Mexico and Central America while screwworm still managed to spread more than a thousand miles north and reach Texas and New Mexico.^[1]

Commissioner Miller also blasts USDA for refusing to deploy the Screwworm Adult Suppression System bait, an older fly‑killing formula he says can wipe out up to 95 percent of adult screwworms.^[13] Federal officials worry that bait might harm “good” flies and other insects, but Miller calls that concern out of touch with the economic pain on ranch families.^[13] He warns that producers may underreport cases because they fear harsh quarantines and red tape, which would hide the true scope of the outbreak and slow the response.^[11]

Border Security, Male‑Only Flies, and the Stakes for Rural America

Federal officials admit the parasite’s march north was helped by illicit cattle movement and illegal immigration that bypassed normal inspections.^[6] That reality ties the biology of screwworm directly to long‑standing conservative worries about border security and weak enforcement. If infected animals or pets slip through gaps in the system, no number of sterile flies can fully protect ranchers on our side of the Rio Grande.

Laredo pet and livestock owners are being urged to check their animals daily as the city increases its response to the New World screwworm. https://t.co/WKp5kn9juJ

— KGNS+ News (@KGNSnews) June 27, 2026

USDA scientists are now testing a new male‑only sterile fly strain, often called NovoFly, which is designed so labs can produce almost 100 percent sterile males and no sterile females.^[8]^[9] That shift would double effective output and answer Miller’s complaint that half the flies are “wasted.” At the same time, experts say any real fix must pair these advanced tools with tight animal‑movement rules, rapid treatment for infected herds, and clear communication with ranchers so they report cases without fearing federal overreach.^[6]^[24]