Potential of entomopathogens in integrated control of whitegrubs in Himachal Pradesh

Abstract

newline The bioassay studies of five entomopathogens viz. Beauveria bassiana, Metarhizium anisopliae, Heterorhabditis indica, Steinernema carpocapsae and Bacillus cereus were conducted against grubs of Holotrichia longipennis and Brahmina coriacea. The entomopathogenic fungi revealed decrease in susceptibility with increase in age. The LC50 values of B. bassiana for I to III instar grubs of H. longipennis ranged from 7.28 x 107 to 1.6 x 108 conidia/ml. In case of B. coriacea, the LC50 values for I to III instars were determined from 5.04x 107 to 1.17x 108 conidia/ml. In H. longipennis and B. coriacea, first instar grubs were 1.12 to 2.43 and 2.85 to 3.84 times more susceptible than second and third instar grubs, respectively. The LC50 values of M. anisopliae for I to III instars of H. longipennis were calculated from 4.36 x 107 to 1.3 x 108 conidia/ml. In case of B. coriacea, M. anisopliae produced 50 per cent kill at a concentration range of 4.9 x 109 to 3.2 x 108 conidia/ml in I to III instar grubs. In H. longipennis, first instar grubs were 2.06 and 2.98 times more susceptible than second and third instar. In case of B. coriacea, the increase in LC50 for second and third instar in comparison to first instar was 2.24 to 3.67 times. The grubs of H. longipennis were found comparatively more susceptible to both entomopathogenic fungi and B. bassiana was found to be less virulent as compared to M. anisopliae. Two entomopathogenic nematodes viz. H. indica and S. carpocapsae were evaluated by soil inoculation method. Against H. longipennis, the LC50 values of H. indica for I to III instars ranged between 324.15 to 796.18 IJs/ml. In case of B. coriacea, the LC50 values of H. indica against I to III instars were calculated from 444.84 to 845.18 IJs/ml. S. carpocapasae produced 50 per cent kill in respective instars of H. longipennis at concentrations ranging from 408.63 to 910.67 IJs/ml. In B.coriacea, a dose of 474.26 to 1620.34 IJs/ml of S. carpocapsae is required to produce 50% kill. There was 1.70 and 2.4 ti