Distribution and Persistence of Sterile Screwworms (Diptera: Calliphoridae) Released at the Panama-Colombia Border.

The sterile insect technique is used by the Comision Panama - Estados Unidos para la Erradicacion y Prevencion del Gusano Barrenador del Ganado (COPEG) to maintain a barrier at the border of Panama and Colombia to prevent screwworms, Cochliomyia hominivorax (Coquerel), from South America reinfesting North America. Before studying the distribution and persistence of sterilized, mass-produced screwworms released in the barrier zone, the utility of applying fluorescent dust (similar to 1.0 mg/fly) to pupae and to newly emerged adults was evaluated to determine the potential effect on fly survival. The flight ability of flies collected from two adult emergence/collection systems (enclosed towers and open chambers) and treated with low (similar to 0.20 mg/fly) or high (similar to 1.0 mg/fly) amounts of fluorescent powder was compared. The distribution and persistence of sterile screwworms marked with fluorescent powder (similar to 0.20 mg/fly), after collection from the same two adult emergence/collection systems, was compared after their release in the barrier zone. The results demonstrated that: 1) fluorescent dust did not negatively affect sterile screwworm longevity or flight ability; 2) no differences were detected between sterile flies collected from the two emergence systems; and 3) sterile screwworms distributed evenly in the barrier zone and persisted for > 6 d. This information was useful in implementing the use of a new sterile fly emergence/collection system and deploying a new strain by COPEG for the barrier zone maintenance program; it will be valuable for evaluating alternative release strategies of sterile screwworms by the eradication and barrier maintenance program.