Spreading of Bacillus thuringiensis var. israelensis over the water surface by a monolayer carrier

Abstract

The self-spreading properties of monolayers, acting as carriers for Bacillus thuringlensis var. israelensis, were examined in the laboratory. Drops of mixtures of 0.5 to 5% B. thuringlensis in a liquid monolayer were placed at one end of a narrow static water course, 2 m long. In less than 2 min, a single layer of molecules spread over the water surface and deposited enough B. thuringiensis over the whole 2 m to kill test mosquito larvae in 24 h. The monolayer alone did not kill larvae in 24 h because no vegetation was present to deoxygenate the water overnight. Accelerated biodegradation was simulated carrying surface water into an overflow tank for 6 h, the surface monolayer being replenished until the mixture was exhausted. B. thuringiensis was deposited in decreasing quantity along the course with much reaching the overflow tank. The monolayer can carry B. thuringiensis more than 15 m in the field from a point application, dispensing with the need for spray equipment, particularly relevant in developing countries.