Efficacy of indigenous Steinernema abbasi and Heterorhabditis indica isolates as potential biocontrol agent against Holotrichia consanguinea Blanch. (Coleoptera: Scarabaeidae)

Holotrichia consanguinea is a serious pest of peanut and sugarcane that attacks other commercial crops in India. The efficacy of two species of entomopathogenic nematodes (EPN), Steinernema abbasi and Heterorhabditis indica , against H. consanguinea was tested under laboratory and field conditions. In a laboratory assay, H. indica caused significantly greater mortality (25-100%) than S. abbasi (20-80%) against second instars and H. indica caused 17.5-82.5% mortality in third-instar grub larvae, while S. abbasi caused (10-60%) mortality. These results revealed that second-instar grubs were more susceptible than third-instar grubs and efficacy of EPN against H. consanguinea varies with nematode species. The penetration and multiplication rate for H. indica was significantly higher than those of S. abbasi . Infective juveniles (IJ) of both nematode species and a commonly used insecticide (phorate) were tested against this insect in a field experiment. Field trail data showed that the percentage reduction in H. consanguinea grub population was significantly higher using H. indica at a dose of 2.5 × 10 9  IJ ha −1 than S. abbasi and phorate application. Phorate application was more efficient in reducing the grub population than both nematode species at the lower application rate (1.25 × 10 9  IJ ha −1 ). Overall, these experiments suggest that H. indica may be a promising biocontrol agent against H. consanguinea .