Insecticidal Activity of Bacillus thuringiensis Berliner and Beauveria bassiana (Balsamo) vuillemin Formulations Against Maize Stem Borer, Chilo partellus (Swinhoe)

Among eight different Bacillus thuringiensis (Bt) formulations tested, dipel 8L (based on Bt var. kurstaki) gave more than 80.0 and 95.0% mortality of neonate larvae of Chilo partellus within 2 and 6 days of treatment respectively. The LT50 value of 1.91 days was lowest for dipel 8L compared to other products tested. Dipel 8L was effective up to 3rd instar stage giving 88.4% mortality in net house screening, which was at par with delfin or bio ASP. Testing of Beauveria bassiana Vuillemin formulation (dispel) revealed that the lowest LT50 value was 3.50 days for 1st instar larvae compared to 4.93 - 6.95 days for 2nd to 5th instar larvae. In net house screening, 1st and 2nd instar larvae were most susceptible compared to 3rd to 5th instar larvae of C. partellus.