Survival of Earthworms Exposed to the Entomopathogenic Nematodes Steinernema carpocapsae and Heterorhabditis indica

Survival and infectivity of entomopathogenic nematodes (EPNs), Steinernema carpocapsae and Heterorhabditis indica were studied after passing the nematodes through the earthworm's, Eudrilus eugeniae gut. Infectivity was evaluated against first instar grubs of rhinoceros beetle, Oryctes rhinoceros. Both the species of EPNs had no deleterious effects on earthworms. S. carpocapsae and H.indica were recovered from the casts of earthworms. Infective juveniles (IJs) of both the EPNs species were successfully transmitted by young and adults of E. eugeniae. More than 50% of IJs recovered from the earthworm casts were viable and pathogenic to first instar grubs of O. rhinoceros. Although entomopathogenic nematodes had no deleterious effects on earthworms, their passage through E. eugeniae gut affected their mobility but not their virulence. Combined application of earthworms with entomopathogenic nematodes may enhance levels of inundative or inoculative biocontrol.