Abstract: To develop an efficient biocontrol antimicrobial agent of tobacco brown spot, single factor test and orthogonal test design were used to optimize the fermentation process and wettable powder (WP) was developed, and its control effect was verified. The optimal fermentation medium for antagonistic bacteria was: glucose 10 g/L, tryptone 2.5 g/L, yeast powder 2.5 g/L, NaCl 10 g/L. The optimal fermentation conditions were as follows: pH 8.0, fermentation temperature 35 ℃, inoculation concentration 7%, 125 mL medium in 250 mL flask. The optimal formulation of WP was silica (15%) as carrier, sodium lignosulfonate (1%) as dispersing agent, Tween 80 (10%) as wetting agent, K₂HPO₄ (2%) as stabilizer, carboxymethyl cellulose (0.1%) as protective agent. After 7 d and 14 d treatment in the field, the efficacy of WP against tobacco brown spot disease was 51.58% and 52.81%, respectively, indicating that the WP had certain application prospect in biocontrol.

Key words: antagonistic bacterium, optimization of fermentation condition, wettable powder, tobacco brown spot, control effect