Comparison of Entomopathogenic Nematode Dispersal from Infected Hosts Versus Aqueous Suspension

Abstract

Dispersal of the entomopathogenic nematodes Heterorhabdidtis bacteriophora Poinar (HP88 strain) and Steinernema carpocapsae (Weiser) (All strain) was measured when nematodes were applied to sand either in Galleria mellonella (L.) cadavers or in aqueous suspension. Dispersal ability was estimated as the percentage of nematodes that migrated through sand or from sand onto an agar surface. Results of overnight assays indicated that the dispersal ability of both species was significantly greater when nematodes were applied in cadavers relative to when they were applied in aqueous suspension. Assays that measured migration onto an agar surface after 1 h also indicated enhanced dispersal of S. carpocapsae when exiting cadavers, but results from H. bacteriophora only weakly supported the trend. The relatively greater movement of nematodes exiting infected hosts was not the result of differences in nematode age or persistence in sand. The enhanced dispersal may have been caused by physiological or behavioral differences between nematodes exiting hosts and those kept in aqueous suspension. Because of the dispersal advantage, application of entomopathogenic nematodes in infected hosts may increase their efficacy in biological control. This study demonstrated a need to further investigate behavior of entomopathogenic nematodes when they exit a host under natural conditions.