Abstract
Filth flies, such as the house fly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.), are globally distributed pests, that cause substantial economic losses in the animal agriculture industry and pose a major health risk to humans. These flies damage livestock and other animals, spoil food, vector disease-causing organisms, and are nuisance pests. Filth flies have a close association with humans and thrive in organic waste materials accumulated in urban and agricultural areas. To combat the risks posed by filth fly pests, management options must be explored. Historically, management practices have relied heavily on insecticide application, although drawbacks such as off-target effects and the evolution of increased resistance to insecticides in these pests remain artifacts of this method. Biological control organisms, such as natural predators, parasitoids, and pathogens, provide a safer alternative to insecticide use. Although biological pest management reduces or eliminates the drawbacks of insecticide use, it is currently not as effective in controlling pests. The parasitoid wasp, Spalangia cameroni Perkins, is a common biological control organism that is commercially-available and released to manage filth flies where they occur, such as livestock facilities. These wasps are obligate pupal parasitoids that utilize filth fly pupae as a host for their developing young. Maximizing the efficacy of parasitoid use in a filth fly management program relies on a more complete understanding of parasitoid-host interactions. Preference for host-containing larval substrates and dispersal patterns have been studied in S. cameroni, but the effects of host-age on parasitism rates is not well understood. Therefore, a study to examine the potential effects of host-age on rates of parasitism and parasitoid induced mortality (PIM) by the parasitoid wasp S. cameroni was conducted. Parasitism was highest when parasitoids were exposed to young pupae (<4 d-old) or pre-pupal life stages and decreased with pupal age. Parasitism was higher when parasitoids were allowed unlimited access to pupae than when restricted to a 24-hour oviposition window. Parasitoid induced mortality was lowest when parasitoids were exposed to young pupae and increased with pupal age. Restriction of the oviposition window did not impact PIM. This study demonstrates the potential impact that release timing may have on parasitoid success. Understanding the interaction of host-age on parasitoid success can inform management decisions and increase the efficacy of this biological control organism.