SD75: Impact of high tunnel soil microclimate on commercial entomopathogenic nematode performance

Biological control of insect pests using commercial entomopathogenic nematodes (EPNs) has been evaluated in both field and greenhouse conditions, but little is known of their efficacy in high tunnel soils. Despite this knowledge gap, high tunnel growers apply EPN for biological control of key soil-dwelling insect pests. EPN host seeking and reproduction occur within optimal temperature thresholds, which vary by species. Particularly in shoulder seasons, high tunnels increase air and soil temperatures compared to the field, altering the environment for crop growth and pest-pathogen interactions. However, the impacts of protected culture management on biocontrol services provided by EPN remain unknown. To evaluate commercial EPN performance in the high tunnel environment, formulations of three species, Steinernema feltiae, S. carpocapsae, and Heterorhabditis bacteriophora, were applied to high tunnel and field plots with the same crop composition at the Purdue Student Farm in summer 2025. Soil and air temperatures were taken in the high tunnel and field plots for the duration of the experiment. We quantified and assessed EPN persistence through laboratory waxworm bioassays on soil samples collected from experimental tunnels and plots. Preliminary results suggest that the high tunnel environment positively impacts EPN persistence. Assessing performance of commercial EPN products with high tunnel production will inform recommendations for biological control in this system.