Multi-component trail pheromones of the entomopathogenic nematodes Steinernema diaprepesi and Heterorhabditis...

Entomopathogenic nematodes aggregate in the soil environment to facilitate the location and infection of insect hosts. Significant evidence exists suggesting this aggregated movement is controlled, in part, by pheromones produced by individual nematodes. This aggregated movement is often termed trail following. The investigation of pheromones produced by the nematodes at the point of emergence from the insect cadaver, compared to the pheromones produced while moving through substrates, identified differences in pheromone production during these two behaviors. Additionally, the investigation identified differences in pheromone compositions between species, suggesting species specific ratios of the pheromones. Specifically, Steinernema diaprepesi utilized primarily the ascarosides asc-C4 (ascr#11), asc-C5 (ascr#9), asc-C6 (ascr#12), and asc-C7 (ascr#1), while Heterorhabditis bacteriophora primarily utilized the ascarosides asc-C5 (ascr#9), asc-C6 (ascr#12), asc-C11-EA, and asc-C11 (ascr#18). These results indicate that nematodes release different blends of pheromones when dispersing from the cadaver compared to moving through soil, and the two species of nematodes investigated utilized species-specific pheromone compounds. The understanding of nematode behaviors and the chemicals that govern them could prove to be useful in the improvement of biocontrol programs utilizing entomopathogenic nematodes in agricultural settings.