Efficacy of Geographical Isolates of Helicoverpa armigera Nucleopolyhedrovirus (HaNPV) Against H. armigera

The Helicoverpa armigera micleopolyhedrovirus (HaNPV) is widely distributed across the geographical regions of Indian subcontinent. Nine geographical isolates of HaNPV were compared by dose and time-mortality assays against second instar Helicoverpa armigera (Hübner) lairae. The results of the study showed distinct variation in biological activity of these isolates. Of the isolates tested, CBE 1, BAN 1, NEC. OOT, HYD and CTR showed higher virulence against second instar with LC₅₀ values ranging from 0.012 - 0.059 poly ocular bodies (POB) /mm² than MAH 1 and RHI with LC₅₀ values 0.343 and 0.415 POB/mm², respectively. Considering the time mortality response, isolate CBE I had the shortest LT₅₀ of 93.77 h that was comparable to NEG and OOT (98.30 - 101.62 h). RAJ isolate recorded the highest LC₅₀ values of 0.864 and 5.225 POB/mm² and LT₅₀ value of 130.89 and 132.81 h, respectively for both second and third instar H. armigera larvae and was significantly inferior to other isolates tested.