Effervescent fast-disintegrating bacterial formulation for biological control of rice sheath blight

A lack of effective, easily applied and stable formulation has been a major obstacle to widespread use of biocontrol agents for control of rice sheath blight. In this study, effervescent fast-disintegrating granules containing endospores of Bacillus megaterium were developed for use either by broadcast or spray application. The formulation composed of lactose, polyvinyl pyrrolidone K-30 (PVP, K-30) and effervescent base (citric acid, tartaric acid and sodium bicarbonate). The number of living bacteria in effervescent granules that performed mycelial growth inhibition was in the range of 109 CFU/g after 12 months storage at room temperature. The number of viable bacteria after applying into the water and spraying on the rice seedling for 7 days in the greenhouse tests were also satisfactory high (109 CFU/g of granules and 106 CFU/g of plant, respectively). The scanning electron microscope (SEM) was used to observe bacterial antagonist on the surface of leaf sheath and leaf blade after spraying with formulation. Effervescent formulation applied either broadcasting or spraying reduced incidence of sheath blight disease in the greenhouse experiments.