Chemotactic Responses of Slug-Parasitic Nematodes to Barley Root-Emitted Volatile Organic Compounds

Slug-parasitic nematodes are promising biological control agents against gastropod pests, yet their responses to cereal root volatiles remain poorly understood. We evaluated the chemotactic behavior of Phasmarhabditis papillosa, Oscheius myriophilus, and Oscheius onirici toward synthetic standards of four barley root-derived VOCs—dimethyl sulfide (DMS), hexanal (H), 2-pentylfuran (2PF), and (E)-non-2-enal (N2E)—and their synthetic blends at two temperatures (18 °C and 22 °C). Significant species-specific and temperature-dependent differences were observed. 2PF and DMS consistently elicited the strongest attraction, particularly for O. myriophilus and P. papillosa, while aldehydes produced weaker or reduced-attraction responses. VOC blends often showed masking or antagonistic effects, suggesting complex signal integration. Temperature enhanced overall chemotactic activity, indicating its importance in modulating sensory behavior. These findings provide new insights into the chemical ecology of slug-parasitic nematodes and support the development of semiochemical-based biocontrol strategies tailored to species and environmental conditions.