Potentiation of entomopathogenic fungi with low doses of insecticides for managing Himalayan white grubs

The potential of entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae was studied in combination with the commonly used insecticides, viz. clothianidin 50 WDG, imidacloprid 17.8 SL and chlor­pyriphos 20 EC, against grubs of Brahmina coriacea (Hope) and Holotrichia longipennis (Blanchard). Clothi­anidin, imidacloprid and chlorpyriphos were applied at 50, 75 and 100 ppm respectively, and both the fungi were applied at 10⁷ conidia/ml. Synergistic interactions were consistent across all the combinations and calculated values of χ² ranged from 4.2 to 5.73 in both the species of white grubs. The grubs of H. longipennis exhibited a higher degree of synergism than B. coriacea as obser­ved from the mortality data. Among entomopathogenic fungi, M. anisopliae showed more synergism than B. bassiana against both species. This study will also help reduce insecticidal pollution and the cost of interventions for the management of white grubs in a sense that application rates of chemical insecticides and synergists will be reduced. This practice may be incorporated in integrated pest management, and further study of the synergistic interactions will guide how entomopathogenic fungi and insecticides can be combined to combat environmental pollution effectively.