Screening Chemical Agents And Preliminary Research Of Biocontrol Preparation On Alternaria Alternata

Eight fungicides were applied to control the disease of Alternaria alternata (Fries) Keissler. The toxicity of eight fungicides to Alternaria alternata were tested by the mycelium growth rate methods. The results showed that the eight fungicides can inhibit pathogenic mycelium growth of Alternaria alternata at different levels. The inhibit effect of 10% Difenoconazole WP is the best, the EC50 is 7.45μg/mL, followed by 15% Hymexazol WP and 25% Prochlora EC, the EC50 are respectively 16.26μg/mL and 23.57μg/mL; while the inhibit effect of 80% Chlorothalonil WP is the worst, the EC50 islll.71μg/mL. When the ethephon concentration is 100μg/mL,the bacteriostasis rates of 10% Difenoconazole WP,15% Hymexazol WP and 25% Prochlora EC are respectively 86.67%,84.27% and 69.33%. While the inhibition rate of 80% Chlorothalonil WP is only 30.4%. According to the experimental results, with the increase the concentration of various pharmaceutical inhibition rate also increased. That ethephon concertration was positively correlated with inhibition effect.With three fungicides which screens according to the different proportion matches mutually using actinomycete SZF1 fermentation broth, makes has the high inhibitory action biological controls preparation to Alternaria alternata. The results indicated that when the disinfectant and the SZF1 fermentation broth according to the different proportion timing, it gets sick mutually to the Alternaria alternata the inhibitory action ferments the fluid dilution multiple, the fungicide density, the fungicide itself to oppress to the disease germ the anti-function different and matches mutually factor and proportion influences. Will match the fungicides preparation to reduce, the fermentation broth dilution multiple mutually to Alternaria alternata inhibitory action along with the fungicides density to increase weakens. When the 10%Difenoconazole WP and SZF1 fermentation broth mixed according to the ratio of 1:1, the inhibition rate to Alternaria alternata reached 90.2%that is much higher than the 10%Difenoconazole WP or fermentation broth.The results showed that 100μg/mL10%Difenoconazole WP, the fermentation broth and the mixed agents could drop down the disease index of Alternaria alternata (Fries) Keisslerr. The optimum control were 66%,64.3%and 73.3%.