Susceptibility of white grub, Brahmina coriacea (Hope) infesting potato to local strains of Beauveria brongniartii (Saccardo) in Himachal Pradesh

Abstract

Brahmina coriacea (Hope) is the most widely distributed and destructive species of white grubs having potential to inflict 40-50 per cent yield losses to potato in Himachal Pradesh. The efficacy of two local isolates of Beauveria brongniartii (KH I and KH II) was evaluated against grubs of B. coriacea by dip treatment and oral feeding methods. Against first and second instar grubs, KH I in dip treatment proved to be highly effective, whereas for third instar grubs, KH I through oral feeding showed higher virulence. The LC 50 values for first instar grubs for KH I and KH II were 2.55×10 5 conidia/ml and 2.80×10 5 conidia/ml in dip treatment, whereas in oral feeding method, the LC 50 values were 7.27×10 5 conidia/ml and 9.69×10 5 conidia/ml, respectively. Against second instar grubs, LC 50 values calculated were 2.91×10 5 conidia/ml and 3.98×10 5 conidia/ml for KH I and KH II in dip treatment, whereas corresponding values through oral feeding method were 5.36×10 5 conidia/ml and 8.82×10 5 conidia/ml. LC 50 values for third instar grubs were 4.47×10 5 conidia/ ml and 4.88×10 5 conidia/ml for KH I and KH II in dip treatment, whereas through oral feeding, LC 50 values were 3.03×105 conidia/ml and 5.14×10 5 conidia/ml for KH I and KH II, respectively.