Susceptibility of Helkoverpa armigera Hubner to Bacillus thuringiensis, Beauveria bassina and NPV

Mortality of Helicoverpa armigera in all age group larvae (2, 4, 6, 8 & 12 day old) was recorded with four dose concentrations (1x109, 1x108, 1x107 & 1x106) of Bacillus thuringiensis, NPV and B. bassiana. Maximum mortility was observed with B. thuringiensis followed by NPV and B. bassiana was found least effective in reducing larval population of H. armigera in laboratory conditions. The overall mean mortality of different concentrations of three experimented pathogens were 91.0, 76.3, 64.4, 56.0 and 49.9 in 2, 4, 6, 8 and 12 days old larvae, respectively. It was revealed that susceptibility of larvae was negatively associated with age of larvae. The mean mortality achieved in all age group larvae (2, 4, 6, 8 & 12 day old) with 1 x 109, 1 x 108, 1 x 106 also showed decreasing trend. The incubation period recorded for B. thuringiensis, NPV and B. bassiana depending upon the larval age and concentration of the pathogen were 2–8, 2–12 and 3–11, respectively. It may be concluded that larval susceptibility was observed to be positively associated with doses.