Abstract: Streptomyces tau-ricus JPD-1 and Alternaria alternate f. sp. mali were considered as the research objects and target pathogen, respectively to screen the carriers, dispersants, wetting and ultraviolet protective agents by the mixture design methods. S. tauricus JPD-1 wettable powder was developed according to the following formula. The optimal formulation was listed as carrier-diatomaceous earth and 89% original powder, dispersant-4% carboxymethyl cellulose sodium, wetting agent-6% sodium dodecyl sulfonate, and ultraviolet protective agent-1% carboxymethyl cellulose sodium. The results showed that the spore content, miscellaneous microorganism rate, pH value, purity rate, drying reduction, wetting time and suspension rate of S. tauricus JPD-1 wettable powder were 2.18×108 cfu/g, 2.45%, 5.8, 91.95%, 4.81%, 15.4 s and 79.67%, and the survival rates of its spores were 70.15% and 80.41% at 25 ℃ for 100 days, and 4 ℃ for 100 days, respectively, by determining the quality standard. The minimum inhibitory concentration of S. tauricus JPD-1 wettable powder spore germination was 25-50 mg/mL, and the controlling efficiency on apple Alternaria leaf spot disease was 84.42% in vitro. The results indicate that the S. tauricus JPD-1 wettable powder is a potential biocontrol agent with high efficiency in controlling of apple Alternaria leaf spot disease.

Key words: Streptomyces tauricus JPD-1, apple Alternaria leaf spot, wettable powder, control efficiency