Preliminary Study on the Synergistic Effects of Bacillus subtilis KXZ-33 and Chemical Pesticides against Cotton Fusarium wilt

【Objective】 Through the combination of biocontrol bacteria and chemical fungicides, the formula combination that can effectively control cotton Fusarium wilt was screened out, and the seed treatment was carried out with a view to providing technical support for the green prevention and control of cotton disease. 【Methods】 Fusarium oxysporum, the main pathogen of Fusarium wilt, was selected by indoor plate confrontation test. The virulence of chemical fungicides was tested by the method of toxic media, and the chemical fungicides used in coordination with biocontrol bacteria were screened by compatibility test. The control effect was evaluated by pot experiment. 【Results】 All the six biocontrol bacteria had inhibitory effects on Fusarium oxysporum, with the inhibition rates ranging from 56.69% to 79.53%, and Bacillus subtilis KXZ-33 had the best inhibition rate of 79.53%. The EC₅₀ of Thiobacillam-methyl, Carbendazim and Formetrix were 15.840,1, 18.018,0 and 12.794,0 mg/L, respectively. The maximum compatibility of KXZ-33 with 20 mg/L Thiobacillam-methyl was 90.46%, and the viable bacteria count was 2.18×10⁷ cfu/mL.The control effect of KXZ-33 and 10 mg/L Carbendazim on 7 d was 90.5%, and decreased to 27.0% on 28 d. KXZ-33 combined with 10 mg/L Thiobacillam-methyl was 87.7% for 7 days and 43.7% for 28 days. 【Conclusion】 Bacillus subtilis KXZ-33 seed treatment and spraying 50% methyl Thiobacillam-methyl 10 mg/L to control cotton Fusarium wilt disease can improve the control effect, make up for biocontrol bacteria in agricultural production of unstable control effect and at the same time reduce the use of chemical pesticides, thus further developing service production.