Compatibility of Steinernema carpocapsae and Heterorhabditis indica with insecticides registered against Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract

The gram pod borer, Helicoverpa armigera (Lepidoptera: Noctuidae) is considered as a key pest of pigeonpea and is also a major polyphagous pest of several agricultural and horticultural crops in India. Combining chemical insecticides with Entomopathogenic Nematodes (EPNs) could be an effective alternative to reduce the use of harmful chemicals. Experiments were conducted to determine the compatibility of Steinernema carpocapsae and Heterorhabditis indica with registered insecticides used for H. armigera control in pigeon pea, under laboratory conditions. Compatibility of the insecticides with EPNs was evaluated by observing infective juveniles (IJs) survival and virulence of Galleria mellonella at 24 and 48 h after dipping in insecticide solutions. It was observed that, insecticides showed moderate effect on IJs survival. IJs were able to infect G. mellonella larvae after exposure to these chemicals, but their progeny production was significantly (P < 0.05) reduced. Both nematode species showed differential sensitivity to the tested insecticides, with H. indica exhibiting better tolerance than S. carpocapsae. The studies revealed that the chemicals showed a strong sub lethal effect on the nematode reproductive potential, limiting seriously their possible recycling in the field.