| Abstract: | Survival of the spores of Bacillus thuringiensis in granular formulations has been tested under storage conditions in the laboratory and also outdoor conditions exposed to weather. The granular formulations were prepared with attapulgite and aqueous and non-aqueous carriers. The virulence of the spore formulation was tested on Bombyx mori larvae. A 0.4% spore concentration, with an initial count of 64 × 106, gave ultimately 0.3 to 0.4 × 106 viable spores/g of the granule after 248 days of storage in the room. The viable count of spores in the granules exposed to outdoor weather conditions fell rapidly within two days; at the end of 65 days, it was maintained at between 3 × 104 and 12 × 104/g of the granules. Optimum concentrations required in granules for 100% mortality of the test insect was found to be 0.4 × 106 spores/g, at the rate of 50 mg of granules per 85 cm2 of leaf surface. The granular formulation of B. thuringiensis was found to be more virulent than “Thuricide” formulation on B. mori larva. |
