Development of a self floating slow release formulation of Bacillus thuringiensis var. israelensis and its larvicidal activity.

Alginate encapsulated B. thuringiensis var. israelensis (B. t. i.) self floating type formulations were prepared. Its spore release rate, floating efficacy and larvicidal activity against Culex quinquefasiatus were tested in the laboratory. The larval mortality of 91-100% was induced by the floating formulation with a mean spore release of 3.04 x 10(4)/ml/day from 6th day to 27th day. From day 28 to 33 the mean number of spores released were 1.16 x 10(4)/ml/day which caused 72.2-88.2% mortality. From 34th day to 40th day the mean number of spores released were 4.97 x 10(3)/ml/day which caused 42.2-67.2% mortality. However, the self floating alginate encapsulated beads were intact and found to float upto 40 days.