Cost-effective media for mass production of Bacillus thuringiensis Berliner for the management of taro caterpillar, Spodoptera litura Fabricius

In the present study, we tried to develop cost-effective media based on inexpensive, easily available raw materials. Among various media components explored for bacterial growth, soybean seed-based medium found to be the best followed by the noxious weed, Parthenium hysterophorus L. extract based medium and they were comparable with standard medium (nutrient broth) with spore counts 34.84, 19.09 and 34.13 (x10⁹ mL⁻¹) respectively, 36 h after fermentation. Soybean seed based and parthenium extract based culture media resulted in highest toxicities (LC₅₀ values of 12.59 μg mL⁻¹ and 21.218 μg mL⁻¹ respectively) against ₃rd instar larvae of S. litura. In the nutrient estimation studies, it was observed that; manganese, one of the most important micronutrients for the production of crystal protein (δ- endotoxin) of B. thuringiensis, was absent in nutrient broth and was present abundantly in parthenium (0.205 ppm).