Host-finding ability of three entomopathogenic nematode isolates in the presence of plant roots

The effect of plant roots on the host-finding ability of three isolates of entomopathogenic nematodes (EPN), Heterorhabditis bacteriophora D-H-Da1, Steinernema sp. Dongrae and Steinernema sp. BJ was studied. In Petri dish experiments the overall response of the infective juveniles (IJ) of these isolates differed from one another, but all were attracted to a Galleria mellonella larva and to a tomato seedling when either of these targets was presented with a blank control. The BJ and D-H-Da1 IJ aggregated more around a tomato root than a G. mellonella larva when these targets were presented separately, but showed no preference for a G. mellonella-tomato seedling combination over a blank control. Dongrae IJ showed no preference for a G. mellonella larva or tomato seedling when each was presented simultaneously in the same Petri dish. In experiments in pots of soil, plant roots did not affect the host-finding ability of Dongrae IJ. In contrast, compared to control pots with no roots, roots of bean plants hindered the ability of BJ IJ to infect a G. mellonella larva, but tomato roots increased host-finding by D-H-Da1 IJ. Roots of certain plant species modify the host-finding ability of EPN, but the extent and direction of the response varied with the EPN applied.