Development of a Biological Complex Seed-Coating Agent to Control Verticillium Wilt

Objective] The aim of this study is to make use of the antagonism and growth promoting ability of Bacillus methylophicus strain LH-L3, and add it into the chemical seed-coating agent as an active ingredient. Method] The optimum formula (agent No.4: 2.5% fludioxonil＋10% thiram＋10% carbofuran＋109 cfu·mL^－1 LH-L3) was obtained based on the sterilization effect of four seed coating agents on infected seed. Then the survival ability of the strain in agent No.4 and its shelf life were identified by plate test. Finally, the disease and pest control effects were tested in the greenhouse pot experiment. Result] The results showed that the agent No. 4 had the best control effect, and 1.1×105 cfu·mL^－1 of LH-L3 after storage at room temperature for 6 months. Compared with the control, the formula No. 4 increased 11.54% emergence rate, 18.74% plant type height and 20.91% leaf width, respectively, in the 15th day after emergence, and decreased 65.42% and 48.56% of Verticillium wilt at day 2 and day 5 after the disease occurred. The cotton seeds coated with formula No. 4 reduced 83.07% of plant and 92.33% of leaf damaged by Sylepta derogata, compared with the negative control without seed coating. Conclusion] Strain LH-L3 and chemical pesticide compound as a seed coat agent is completely feasible. And the developed biological complex seed-coating agent has better control effect on Verticillium wilt and Sylepta derogate.