Entomopathogenic nematodes (EPNs) play a role in indirect defense of plants under attack by root herbivores. Several investigations have shown that EPNs are attracted or repelled by various volatile compounds (VOCs) released from insect damaged plant roots. We hypothesized that the directional responses of EPNs to the VOCs would be affected by foraging strategy and would vary among species, VOC type, and VOC concentrations. We tested the chemotactic responses of four commercial EPN species (Steinernema feltiae, S. carpocapsae, S. kraussei, and Heterorhabditis bacteriophora) to seven compounds released from insect (Melolontha hippocastani)-damaged (decanal, nonanal, octanal, undecane, 6-methyl-5-hepten-2-one, and 1,2,4-trimethylbenzene) and undamaged (2-ethyl-1-hexanol) potato tubers. Our results suggest that EPNs are able to distinguish herbivore-induced VOCs from those that are typical for healthy potato tubers. In our investigation, nonanal, octanal, and decanal had a greater influence on the movement of EPNs than other tested synthetic volatiles. Decanal was an attractant for H. bacteriophora and S. kraussei at both tested concentrations (as a pure compound and at a concentration of 0.03 ppm). The results suggest that the susceptibility to perception of chemical stimuli from the environment is a species-specific characteristic that prevails over the influence of the foraging strategy.
Keywords: 1,2,4-trimethylbenzene; 2-ethyl-1-hexanol; 6-methyl-5-hepten-2-one; Attraction behavior; Decanal; Entomopathogenic nematodes; Nonanal; Octanal; Undecane.