Insecticidal activity of Bacillus thuringiensis isolates from soil against larvae of Lepidopteran pests
Indigenous isolates 108 of Bacillus thuringiensis (Berliner) were isolated and characterized from the soil samples collected from different habitats of GKVK campus of the University of Agricultural Sciences, Bengaluru, Karnataka. The morphological and biochemical traits were considered as the criteria for authentication of Bacillus thuringeinsis isolates. All the isolates were observed to be rod shaped, gram positive and spore formers. They were also tested for biochemical tests i.e. catalase, starch and casein hydrolysis. As many as 107 isolates were screened for toxicity against lepidopteran larvae, viz., Plutella xylostella (L.), Spodoptera litura (F.) and Amsacta albistriga (W.). Four isolates (SBT-3, SBT-15, SBT-18 and SBT-27) were found to be highly toxic to P. xylostella with mortality ranging between 93% to 100%. Ten isolates viz., SBT-13, SBT-14, SBT-15, SBT-28, SBT-38, SBT-44, SBT-45, SBT-46, SBT-53 and SBT-57 showed mortality of 100% against S. litura. Whereas 8 isolates viz., SBT-11, SBT-13, SBT-14, SBT-15, SBT-24, SBT-41, SBT-42 and SBT-51 showed mortality up to 70-86 % for the test insect A. albistriga.