COPEG
Panama-US Commission producing sterile flies to contain New World screwworm.
COPEG, the Panama-US screwworm Commission, lost its place as the sole source of sterile flies in June 2026, when Mexico's Metapa plant in Chiapas began production, as Mexican human screwworm cases rose fivefold.
Last refreshed: 4 October 2026
Timeline for COPEG
Mentioned in: Screwworm cases in Mexico rise fivefold
Pandemics and BiosecurityBackground
COPEG, the Panama-United States Commission against screwworm, runs the sterile-fly plant at Pacora, near Panama City. The US Department of Agriculture and Panama's agriculture ministry fund and manage it jointly. In 2025 the plant ran at its full capacity of about 100 million sterile flies a week, USDA said.
The same method eradicated screwworm from the United States in the 1960s. Released sterile males mate with wild females, which then lay no viable eggs. COPEG's releases held the line at Panama's Darién Gap from 2006; once flies got past it in 2023, the pest moved north again.
USDA treats sterile-fly supply as the binding constraint on that spread. By mid-September 2026 human infestations in Mexico had reached about five times the whole of 2025's total. COPEG stopped being the region's only producer on 27 June 2026, when Mexico and the US opened a plant at Metapa, Chiapas, rated at up to 100 million flies a week.