Right now, the Commission for the Eradication and Prevention of Screwworm( COPEG) sterile fly facility in Panama is producing about 100-117 million flies per week, but the industry requires closer to 400-500 million flies per week to fully combat the current outbreak in Mexico and Central America. During the height of screwworm eradication efforts in the 1960s, the U. S. was releasing up to 500-600 million sterile flies per week.
In August 2025, USDA announced a major step in addressing NCBA’ s top priority for combating New World screwworm: the construction of sterile fly production and distribution facilities at Moore Air Base in South Texas. Once operational, these facilities will significantly increase weekly output to more than 300 million flies, strengthen domestic oversight, and address supply challenges in Mexico and Central America— providing critical protection for cattle herds across borders. However, it’ s important to note that bringing these facilities online will take time, and the threat posed by screwworm remains active.
As efforts to ramp up sterile fly production gain momentum, producers can take proactive steps to strengthen their defenses through enhanced biosecurity measures and proven best management practices.
Tools: Best Management Practices
The adult screwworm fly resembles a common housefly but is slightly larger, with distinctive orange eyes, a metallic blue or green body, and three dark stripes along its back. The name " screwworm " comes from the screw-like shape of its larvae, which burrow into wounds to feed on living flesh.
Infestations begin when a female fly lays eggs on an open wound or orifice of a warm-blooded animal. Each female can lay 200 – 300 eggs at a time and up to 3,000 eggs during her lifespan of 10 to 30 days. Within hours, the eggs hatch into larvae that burrow into the wound, causing severe pain and tissue damage. After about a week of feeding, the larvae drop to the ground, pupate in the soil, and emerge as adult flies within 7 to 54 days, depending on environmental conditions.
Transition into pupa and then the fly emerges
Pupae 6-8 Days
L-3 larvae fall from wound & burrow in ground to pupate
Larvae 5-7 Days
L-3
Larval Stage( L-1, L-2, L-3)
L-2
Adult Flies
NWS Life Cycle
L-1
Entire cycle as fast as 21 days
Copulation
Gravid female fly looks for host with a wound or orifice
Gravid female fly lays eggs on wound
Eggs hatch in 12-24 Hours
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DIRECTIONS 2025 NATIONAL CATTLEMEN 7