Evaluation of (Z)-9-tricosene baited targets for control of the housefly (Musca domestica) in outdoor situations

Houseflies (Musca domestica L.) are a major pest species in a variety of outdoor situations, notably on and around livestock farms and landfill used for the disposal of domestic waste. Currently no effective options are available for control of houseflies outdoors, because many populations exhibit at least some resistance to all available synthetic pesticides. (Z)-9-tricosene is the only commercially available pheromone for use in lure-and-kill approaches to housefly control, and it is widely used in indoor livestock units in combination with sugar/insecticide bait. Here we examine the potential of this approach for use outdoors, on a landfill site. We investigate the efficacy of toxic targets painted with a sugar/insecticide/(Z)-9-tricosene mix. The effects of target size and pheromone concentration were examined in two replicate trials, conducted in June and September 2003. As expected, catch consisted largely of males, was consistently higher on larger traps, and generally increased with (Z)-9-tricosene concentration even up to very high levels. However, in repeated trials, and despite mass release of marked flies, catch rates appeared to be insufficient to provide adequate control. We suggest that this is probably because (Z)-9-tricosene is primarily a short-range attractant, and fly populations in outdoor situations are generally distributed over a large area. Catch declined rapidly to zero within 2 weeks, indicating that improved formulation or target design is needed to slow the weathering of active ingredients on the targets. It seems unlikely that (Z)-9-tricosene is sufficiently attractive to houseflies to provide an effective and economic lure in outdoor situations.