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. The same species were applied under four high tunnel ground cover treatments in a controlled experiment at Meigs Horticultural Farm in Lafayette, IN. We quantified and assessed EPN persistence through laboratory waxworm bioassays on soil samples collected from experimental tunnels and plots. Preliminary results suggest ground cover (i.e. plastic mulch, landscape fabric) used to suppress weeds under high tunnels increase soil temperatures in the active range of EPN, with consequences for EPN persistence that vary by season. Assessing performance of commercial EPN products with high tunnel production will inform recommendations for biological control in this system.