PURPOSE:To control common scab of potato, by producing the title controlling agent containing Pseudomonas fluorescence biovar V, etc., immersing, applying or spraying the controller on seed potato or spraying on potato culture soil. CONSTITUTION:A controller against common scab of potato, comprising a bacterium such as Pseudomonas fluorescence biovar V (e.g., MD-4f strain), Enterobacter agglomerans (e.g., 2-3B strain), Pseudomonas sp (e.g., F13-1 strain), Acinetobacter sp (e. g. M24-1 strain), etc., suppressing multiplication of ray fungus of the genus Streptomyces, pathogenic bacteria of common scab of potato. As a controlling method, a suspension having 10<9>cfu/ml concentration of the bacterium is used, seed potato is immersed in, coated with or sprayed with the suspension or the suspension is applied to culture land. The controller is further mixed preferably with a fixing preservative such as xanthan gum or methyl cellulose.
