Dry flowable formulations of antagonistic Bacillus subtilis strain T429 by spray drying to control rice blast disease

•Dry flowable formulations of Bacillus subtilis strain T429 were synthesized by spray drying.•Wetting agents, dispersants, disintegrants, and adhesives that show good biocompatibility with B. subtilis T429 were obtained.•Dry flowable formulations were shelf-stable and effective to control rice blast.

Dry flowable formulations of Bacillus subtilis strain T429 with fungicidal activity against the rice blast fungus Magnaporthe grisea were synthesized by spray drying. Inert ingredients including wetting agents, dispersants, disintegrants, and adhesives that show good biocompatibility with B. subtilis T429 were obtained. The formulations were optimized by a four-factor and three-level orthogonal experiment. The optimal contents of the wetting agent AEO-5, dispersant NNO, disintegrant (NH4)2SO4, and adhesive CMC-Na were 1%, 9%, 5%, and 1% respectively, the filler kaolinite supplemented to 100%. The mixture was suspended in the fermentation broth of T429 at a ratio of 20% (m/v). After being ground in a ball mill for 3 h, the suspension was spray-dried, and the dry flowable formulations were obtained. The formulation showed good physical characteristics, such as high dispersibility and viability. After 12 months of storage at room temperature, it revealed long shelf life and high viability. Field tests in rice crops illustrated that dry flowable formulations at 50 and 75 g/667 m2 concentrations were as effective as a commercial fungicide in controlling rice blast, control efficiency up to 77.6% and 78.5%, respectively. No significant differences in disease control efficiency were observed between the formulations and the chemical pesticide tricyclazole (79.5%). Overall, a new shelf-stable and effective dry flowable formulation of the biocontrol agent B. subtilis T429 was obtained by spray drying to control rice blast.

Graphical abstractAntagonistic B. subtilis strain T429 with fungicidal activity was spray dried to control rice blast under field conditions.Figure optionsDownload full-size imageDownload as PowerPoint slide