Efficacy of granular formulations of Bacillus thuringiensis (H-14) for the control of Anopheles larvae in rice fields.

Three granular formulations of Bacillus thuringiensis (H-14) were applied to dense stands of maturing and mature rice for control of Anopheles crucians and An. quadrimaculatus. Aerial applications of the Vectobac granule (200 ITU/mg) at 5.6, 11.2 and 22.4 kg/ha to 0.4 ha plots resulted in 92, 94 and 96% reduction 48 hr after application, respectively, in populations predominantly consisting of late instars. The Bactimos granule (175 ITU/mg) was applied by aircraft to 0.4 ha plots and by a Cyclone seeder to 100 m2 plots at 2.8, 5.6 and 11.2 kg/ha, resulting in 100% reduction after 48 hr in natural populations of predominantly early instar larvae at all 3 rates with each type of application. Older instars confined to sentinel cages responded with 92, 98 and 100% mortality, respectively. Complete mortality was also observed at the same time in natural populations of predominantly young larvae in similar plots treated with Teknar granules (104 ITU/mg) at 1.7, 3.0 and 7.5 kg/ha. Near complete mortality (98-99%) was also observed in the older larvae used in the sentinel cages.