Inductive Effect and Synergism of Fungicides Against Tobacco Bacterial Wilt Disease

The effects of inducers on the resistence of tobacco plant against tobacco bacterial wilt disease were tested in vitro and in vivo by injecting the suspension of Ralstonia solanacearum into tobacco leaf veins.The results showed that Benzothiadiazole(BTH) was the best among tested inducers with the induced resistance rates of 60.96% and 52.76% in vitro and in vivo,respectively, at the concentration of 50 μg/mL.Of treatments with BTH at the concentrations of 100, 50,25,12.5 and 6.25 μg/mL for 5 to 15 days after injecting,the induced resistance rates in vitro and in vivo were over 50% at the concentration above 50 μg/mL;BTH showed no activity in inhibiting the pathogenic bacteria from growing in in vitro system,however,the mixture of BTH 12.5 μg/mL and agricultural streptomycin sulphate 25 μg/mL showed obviously synergistic activity,the relative control effects reached up to 75.31% and 73.98% in in vitro and in vivo tests,respectively;the synergistic coefficient was over 20.