Role of entomopathogenic nematodes in the management of insect pests

Entomopathogenic nematodes (EPNs) of the genera Heterorhabditis and Steinernema are obligate and lethal insect parasites. They have the greater potential to be developed as a microbial agent for the management of various insect pests of orchard, vegetables, ornamental plants and turf grasses. The third stage juvenile i.e. the infective juvenile along with symbiotic bacteria (Xenorhabdus spp. in Steinernema spp. and Photorhabdus spp. in Heterorhabditis spp.) enters into the insect body through natural openings or sometimes by penetration through intersegmental membrane. The relationship between nematode and bacteria is an example of true mutualism and from this relation both the organisms are benefited. This nematode-bacterium complex causes the death of insect pests within 24–72 hours. Mass rearing of Steinernematid and Heterorhabditid nematodes can be done in vivo in insect hosts and in vitro in solid medium or in liquid medium. For in vivo production Galleria mellonella larvae are used extensively as surrogate host. For large-scale production, in vitro methods using 3-dimensional solid media or liquid fermentation methods have been employed. There is no record of pathogenicity of EPN and their associated bacterial symbionts to warm-blooded vertebrates, including humans. The virulent species of these nematodes are commercially produced as biological control agents all over the world. So the use of EPN can be efficiently incorporated as one of the best microbial control measure in the IPM strategy for many high valued crops.