Microsporidia (Protozoa: Microspora) in pteromalids (Hymenoptera: Pteromalidae) in broiler-breeder houses of northwest Arkansas

Pteromalid parasitoids were sampled using sentinel bags containing house fly puparia as bait and placed in broiler-breeder houses of northwest Arkansas. Collected pteromalids were examined for occurrence of microsporidian pathogens. Five pteromalid species were collected: Muscidifurax spp. Nasonia vitripennis, Pachycrepoideus vindemiae, Spalangia: cameroni, and S. endius. Relative: wasp abundances were 10.3, 16.6, 32.4, 20.3, and 20.2% in 1994 and 30.7, 7.0, 22.7, 6.0, and 33.5% in 1995 for Muscidifurax spp., N. vitripennis, P. vindemiae, S, cameroni, and S. endius, respectively. Infection prevalences were 13.0, 3.0, 12.0, 21.0, and 31.0% in 1994 and 5.0, 16.0, 50.0, 50.0, and 58.0% in 1995 for Muscidifurax spp., N, vitripennis, P. vindemiae, S. cameroni, and S. endius, respectively. These results are the first known reports of microsporidia from field-collected specimens of N, vitripennis, P, vindemiae, S. cameroni, and S. endius. Though commercially reared pteromalids were released in some houses for fly control, these "release" wasps were not a major source of microsporidia. Spore sizes differed significantly among wasp species but not between the years collected. Microsporidioses in held populations of pteromalids might have negative impacts on the poultry industry; parasitoids infected with the pathogens are less fecund than healthy wasps, potentially leading to reduced filthy fly control. (C) 1999 Academic Press.