Production, design, and evaluation of Bacillus thuringiensis serov. israelensis formulations against Aedes aegypti larvae

Abstract

Bacillus thuringiensis israelensis (Bti) was cultured on three culture media: a reference medium and two new media. Then, spore-crystal complexes were recovered and evaluated against Aedes aegypti larvae. After two formulations, tablets and granulates, were prepared, then irradiated with ultraviolet light and evaluated for larval mortality and residual activities. The most toxic extract was obtained in soluble medium 1 showing the lowest LC50 of 0.3748 mg/L. When Bti extract was formulated and tested in the laboratory, the granulated formulations, presented approximately 90%-100% mortality, during the first 3 days post-application, whereas tablets showed <60% mortality. At 14 days post application, only granulates 2 and 3 showed >40%, whereas unformulated extract presented 22% mortality. The formulations showed reduced mortality of 5%-12% (tablets) and granular (6%-11%) after 72 hours of exposure to UV light; otherwise, reductions in the unformulated Bti extract were higher (32%).