Microencapsulation of Bacillus subtilis and its control of Rhizoctonia solani damping-off of tomato

In order to develop compatible and stable new biological pesticide, microencapsulation of Bacillus subtilis was prepared by spray-drying method. The optimum spray-drying conditions were determined by orthogonal test, and the biocontrol efficacy against Rhizoctonia solani in tomato under field conditions was studied. The results suggested that the best proportion of maltodextrin and fermentation broth was 1 :1(m :V). The optimum condition of spray-drying was: inlet air temperature 125 ℃, flow rate 750 mL/h, and spray pressure 0.20 MPa. The survival rate of B.subtilis microcapsules was 91.36% after storage for 360 days, which was significantly higher than that of B.subtilis wettable powders. The result of field trial showed that the biocontrol efficacy of B.subtilis microcapsules against tomato R.solani could reach 72.76% when the application dosage was 300 g/hm2.