Response of soil microarthropods to the application of entomopathogenic nematode–killed insects in crop and refuge habitats

Insects killed by entomopathogenic nematodes and their symbiotic bacteria represent a resource with which soil arthropods can interact. These interactions can be positive for the nematode (e.g., soil arthropods serve as parasitic or phoretic hosts) or negative (e.g., nematodes serve as prey items). Plant diversity and soil disturbance, which alter the physical and biotic environment, may influence these interactions. We investigated the effects of crop and refuge habitats on microarthropod abundance and community composition in soil surrounding wax moth larvae, Galleria mellonella, infected with Steinernema carpocapsae (Sc). Within each habitat, we applied four treatments: 1) burial of Sc-killed insects, 2) burial of freezer-killed insects, 3) sham burial, and 4) no soil disturbance. Soil samples (including G. mellonella) were collected 2 and 20 days (2005) or 2 and 12 days (2006) after application. Samples were placed in Tullgren funnels to extract microarthropods for quantification and identification. In 2005, arthropod abundance and community composition was similar between crop and refuge sites. In 2006, we detected more arthropods, particularly ascid and Eupodes mites, in the crop compared with the refuge. In both years, we observed the greatest difference in community composition between treatments on the final sampling date. Community composition differed between treatments providing resources (Sc-killed and freezer-killed insects) and those without (sham burial and no disturbance). Soil surrounding EPN-killed and freezer-killed insects contained more dipteran larvae, acarid mites, staphylinid beetle larvae, onychiurid and entomobryid collembolans, and mesostigmatid immature and male mites than soil at sham burial and no disturbance sites.