Bactericidal composition for preventing and treating tobacco black shank

The invention belongs to the technical field of pesticides, and particularly relates to a bactericidal composition for preventing and treating tobacco black shank. The invention discloses a bactericidal composition for preventing and treating tobacco black shank. Effective components of the bactericidal composition are formed by compounding a first active component and a second active component, wherein the first active component is mustard essential oil; and the second active ingredient is dimethomorph, oxathiapiprolin or pydiflumetofen. When the plant essential oil mustard essential oil is compounded with the dimethomorph, the oxathiapiprolin or the pydiflumetofen, the co-toxicity coefficient for inhibiting the growth of tobacco black shank mycelia is greater than 120 in a certain mass ratio range, and a synergistic effect is shown; especially, when the mustard essential oil and the pydiflumetofen are compounded according to the proportion of 1: 10, the co-toxicity coefficient reaches 603.5398, and the syne