Impacts of disturbance on soil-dwelling microarthropod communities and native entomopathogenic nematodes in winter wheat systems

Soil communities and their relationship to soil quality, pest suppression and nutrient cycling have not been thoroughly explored with respect to agricultural practices. Arthropods and other organisms found in the soil contribute greatly to the soil quality and success of cultivated plants. Disturbance, such as tillage has an effect on the soil-dwelling species complex thus having an effect on the soil quality in that area. The species complex in conventionally tilled versus no-till winter wheat is currently being evaluated to provide information on the effect of decades of tillage in the state of Oklahoma. Impacts of tillage are being evaluated on both decomposer communities and indigenous populations of insect natural enemies, specifically entomopathogenic nemtatodes and entomopathogenic fungi. Decomposer communities were evaluated using Tullgren samples from 36 plots over three sampling dates. Presence of indigenous entomopathogenic nematodes was determined using Galleria mellonella bioassay technique (Kaya, 1997). Three strains of entomopathogenic nematodes were isolated. Steinernema glaseri and Steinernema carapocapsae were isolated from 50 soil samples taken in both conventionally tilled and no till plots (n=108). Infections resulting form conventional till samples are not significantly different from no till samples for either Steinernema sp. Heterorhabditidae bacteriophora was isolated from 5 samples (n=108) and all five samples were taken from no till plots. Confirmation of .nematode species identification is pending molecular analysis.