Evaluation of a transient barrier trapping system to manage the canyon fly (Diptera: Muscidae)

ABSTRACT A circular perimeter barrier of CO,-baited Centers for Disease Control and Prevention (CDC) suction traps (without the light) was placed at a hilltop location in southern California known for high "canyon fly" activity, to determine whether a transiently operated barrier trapping system using attractive traps would reduce the number of these nuisance flies to successfully reach a human host within the protected area Preliminary studies demonstrated that the number of flies captured by a human host was reduced when a single CO2 trap was placed < or =20 m from the host, an indication that these traps are attractive enough to reduce fly pressure on nearby human hosts. The use of eight transiently operated CO2 traps placed equidistant along either a 15- or 5-m radius barrier perimeter significantly reduced the number of flies to reach a human host within the protected area Attack rates at the protected human host were reduced by a maximum of 51% in the presence of a protective barrier. However, with attack rates on a human host in the hundreds of flies per minute at the study site, this level of protection was not deemed sufficient for recommendation of this technique to homeowners or others who want temporary suppression of these nuisance flies in a limited area, such as a backyard. Implications of using a transient barrier trapping system to manage canyon flies are discussed.