Seasonal distribution of parasitism of the face fly (Musca autumnalis De Geer) by Paraiotonchium autumnale (Nickle) Slobodyanyuk in Eastern Tennessee

The distribution and prevalence of the nematode Paraiotonchium autumnale in Musca autumnalis was studied at five sites in eastern Tennessee during 1993 and 1994. Paraiotonchium autumnale parasitized face flies at all sites in 1993 with a seasonal prevalence of 1.66%. Parasitized face flies were collected from four of the five study sites in 1994 and had a lower seasonal prevalence of 0.48%. Prevalence at the eastern Tennessee sites during 1993 and 1994 were the lowest reported in the United States, although Ontario had similar levels of parasitism in 1971 of less than 2%. Paraiotonchium autumnale appeared to have no effect on the numbers of face flies collected during 1993 or 1994. Experiments to examine the effects of simulated rainfall on larval mortality in Musca autumnalis were conducted by applying 0, 6, 12, and 24 mm of simulated rainfall to 24, 48, and 96 hr postoviposited larvae in artificial dung pats. Survival of 24 hr postoviposited larvae was significantly affected by simulated rainfall. Unexpected decreases in the numbers of face flies collected were not related to the application of insecticidal eartags. Numbers of face flies were correlated with rainfall of 8 mm or more prior to collections.