Can entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) function as an indirect plant defense?

Abstract: In a laboratory investigation, we have tested the chemotactic responses of 4 EPN species (Steinernema and Heterorhabditis) to 6 compounds released by insect (wireworms and grubs) damaged and undamaged carrot roots. Our results indicate that all of the tested EPN species exhibited attraction (or repulsion) to volatiles, irrespective of their foraging strategy. Our current results suggest that responses to distinct volatile cues are a species-specific characteristic. Terpinolene (VOC released from undamaged roots) was a repellent for Steinernema and Heterorhabditis species in our investigation. Our results suggest that healthy plant roots release specific VOCs into the soil, which signal to natural insect enemies (EPNs) to keep away.