Pathogenicity of entomopathogens, Bacillus thuringiensis subsp Kurstaki and Beauveria bassiana, to the larvae of Spodoptera litura (F.) and Pericallia ricini (F.)

Pathogenicity of two entomopathogenic microbes. Beauveria bassicana (Balsam o) and Bacillus thuringiensis subsp. Kurstaki, was tested on different larv al stages of Spodoptera litura and Pericallia ricini. Laboratory studies sh owed that the early instars of both pests were susceptible to B. bassiana a nd B. thuringiensis. Higher doses of entomopathogens were found to be effec tive on late instars. Probit analysis based LC,, values for P. ricini range d from 8.5 to 19.5 log conidia ml(-1) for B. bassiana and 10.1-18.8 log cel ls ml(-1) for B, thuringiensis. The LC50 values for S. litura ranged from 1 1.6 to 12.9 log conidia ml(-1) for B. bassiana and 14.8-17.3 log cells ml(- 1) for B. thuringiensis. with variation among instars. Probit regression an alysis was made and lines for the mortality were drawn.