Assessing entomopathogenic nematodes for western corn rootworm management and non-target effects: A two-year field study

Entomopathogenic nematodes (EPNs) can be used to control several pests, including the western corn rootworm (WCR), Diabrotica virgifera virgifera. However, their persistence, effectiveness and potential impact on non-target organisms remain insufficiently understood. Thus, this study assessed the potential of EPNs for controlling WCR and their impact on non-target organisms over two years. In the first year, approximately 45 million infective juveniles/ha of Heterorhabditis bacteriophora ‘NY 04’ and Steinernema feltiae Oswego, were applied to plots planted with Bt and non-Bt corn. A control and a traditional management treatment using an at-plant insecticide without EPNs, were also included. The treatments were repeated for the second year, with no EPN application, to evaluate their persistence. To assess EPN establishment, pre- and post-inoculation soil samples were collected. Baiting assays were performed and nematodes recovered from White traps were sent for molecular analysis. The emergence and feeding damage of WCR and the diversity and abundance of predatory arthropods were assessed. No EPN samples tested positive for the applied nematodes in the first year, and second-year samples are pending molecular identification. For both years, there was no effect of EPNs on the number of WCR adults or root damage; however, the at-plant insecticide reduced these variables in the second year. Additionally, EPNs did not negatively affect the population of predatory arthropods, although the at-plant insecticide significantly reduced the activity-density of carabid beetles in both year. This research indicates low persistence and establishment of applied EPNs and consequently no reduction in WCR populations or non-target arthropods.