Evaluation ofParaiotonchium muscadomesticae(Nematoda: Tylenchida: Iotonchiidae), a Potential Biological Control Agent of the Housefly (Diptera:Muscidae)

When housefly eggs were exposed toParaiotonchium muscadomesticaeColer and Nguyen from nematode-infected flies, an IC50(concentration resulting in 50% of the hosts becoming infected) of 23.7 gamogenetic nematodes/fly egg was observed, with an IC90of 183.8. Mortality was low except at high nematode concentrations (LC50 = 4901, LC90 = 102,517). Infected adult flies of both sexes lived about half as long as uninfected flies. Examination of nematode age structure in infected flies revealed that mature gamogenetic females produced about 8 parthenogenetic females each regardless of nematode crowding levels. In contrast, production of new gamogenetic nematodes by parthenogenetic females was density-dependent, with average reproductive rates ranging from 1627 progeny/parthenogenetic female at 8 females/host to 330 progeny at 83 females/host. Infected flies contained 12,000–45,000 new gamogenetic nematodes 10–14 days after fly emergence. The percentage of male flies infected with the nematode was equal to the percentage of females infected with the nematode. Gamogenetic nematodes required 24 h after deposition into fly larval rearing medium before they were capable of infecting new host larvae. Nematodes persisted in rearing medium for 3–5 days after deposition; no infections were observed at 7 and 10 days after deposition.