Efficacy of Photorhabdus as a Promising Entomopathogenic Bacteria in the Eco-Friendly Biocontrol of White Grub Larvae

Abstract

White grubs are a major polyphagous pest that imposes damage upon several plant species, mostly by feeding their roots. White grub larvae are one of the hazardous pests found in sugarcane. This problem causes a substantial drop in sugarcane crop productivity every year in India. In this research, white grub larvae were subjected to biocontrol using developed formulations of Photorhabdus bacteria, symbiotically associated with entomopathogenic nematodes under laboratory conditions. The Photorhabdus bacteria isolated from entomopathogenic nematode- Heterorhabditis indica have insecticidal activity towards insect pests by exerting an array of toxic effects. The main insecticidal activity, i.e., chitinase enzyme production by these bacteria, was associated with mortality of insect pests. In the present investigation, chitinase production by Photorhabdus bacteria was determined by DEAE column chromatography. The various bacterial formulations of Photorhabdus were examined for their insecticidal activity against the white grub larvae under laboratory conditions. Mortality of the white grub larvae was observed after 24–48 hours of exposure. The formulations of Photorhabdus showed statistically significant effects on mortality of larvae. The percent mortality of larvae after treatment with formulation 3 was highly significant compared to those treated with formulation 1 and 2. Formulation 3 expressed a significantly lower LD50 value, i.e., 121.31 CFU/mL, over formulations 1 and 2, i.e., 127.34 & 133.56 CFU/mL, respectively. Formulation 3 showed greater efficacy in killing white grub larvae at lower concentrations. The formulation 3 of Photorhabdus bacteria has great potential to kill white grub larvae under laboratory conditions and requires further evaluation for its promising use as a biocontrol agent by pot and field studies.