Abstract: This article takes Bacillus velezensis XY40-1 suspension as the research object, conduct additive screening and formula optimization, and its control effect on pepper blight was verified through field experiments. The results showed that the optimal formula for the suspension agent was sodium lignosulfonate 1.5%, Tween-80 2.0%, 2% xanthan gum 0.16%, skim milk powder 0.5%, ethylene glycol 4%, isothiazolinone 0.16%, and dimethyl silicone oil 0.2%. Viable bacteria count of B. velezensis XY40-1 suspension agent was 2.5×10⁹ CFU/mL, pH was 7.396, fineness screening was greater than 95%, persistent foam amount was 10 mL, mass fraction of residue after pouring was 1%, and residual mass fraction after washing was less than 0.23%, these indices met the national standards for biopesticide products. The results of field experiments showed that, the control effect of B. velezensis XY40-1 suspension on pepper phytophthora reached 80.47%, significantly higher than the treatment with 25% metalaxyl wettable powder.

Key words: Bacillus velezensis, suspension concentrate, Phytophthora blight, control efficacy, auxiliary screening