Beneficial Nematodes: Steinernema and Heterorhabditis species / by Ganpati Jagdale

Entomopathogenic nematodes in the genera Steinernema and Heterorhabditis are recognized as insect-parasitic nematodes, beneficial nematodes, biocontrol agents, biological control agents, biological insecticides or biopesticides. These nematodes are also recognized as pathogens or microbial control agents because of their symbiotic association with bacteria (Xenorhabdus and Photorhabdus spp.) that are mainly pathogenic to insects. Because of mutualistic relationship with pathogenic bacteria these nematodes are named as entomopathogenic nematodes.

These beneficial nematodes contribute to the regulation of natural populations of insects.  However, the population of naturally occurring entomopathogenic nematodes is normally not high enough to manages soil dwelling plant pests. Therefore, during last 3-4 decades, these live nematodes have been commercially mass produced and inundatively applied to control many garden insects, turfgrass insects, nursery insects, greenhouse insects and insects that feed on different field crops.

Use of this natural control of insects is beneficial for both the environment and humans because it reduces use of chemical insecticides/pesticides.

These biopesticides (entomopathogenic nematodes and their symbiotic bacteria) are safe to produce and not harmful to users, application personnel, mammals, most beneficial insects or plants.

Since entomopathogenic nematodes do not cause any health risk to the consumers of nematode treated agricultural produce and damage to the environment, they are exempted from registration requirements in most countries.

These biological control agents have also no detrimental effect on other benefical nematodes including bacterial feeders, some fungal feeders (Aphelenchus sp.), predatory nematodes and other soil microbial communities.

But entomopathogenic nematodes can be detrimental to plant-parasitic nematodes that are responsible for causing a tremendous economic loss to our agriculture industry throughout world. It has been demonstrated that entomopathogenic nematodes can suppress the populations of many economically important plant-parasitic nematodes including foliar nematodes, potato cyst nematodes, ring nematodes, root-knot nematodes,  root lesion nematodes, sting nematodes, stubby root nematodes and stunt nematodes.