Biological Activity of the Mixtures of Tebuconazole,Chlorothalonil to Fusarium graminearum

[Aims] The study aims to screen the ratio of the mixture of tebuconazole and chlorothalonil that had best effect on controlling the mycelium growth of Fusarium graminearum.[Methods] The method of mycelium growth rate was used to test the toxicity to F.graminearum of tebuconazole,chlorothalonil and their mixture under the condition of constant temperature in laboratory.The combined effect of the fungicides was evaluated by using methods of Horsfall test design and Wadley synergistic ratio(SR).[Results] The mixtures of tebuconazole with chlorothalonil of 1:1,1:3,1:5,1:7,1:9,1:11,3:1 and 5:1 had synergistic effect.The SR was 1.5915-84.3772.The mixture of the two components at the ratio of 9:1 and 11:1 had additive effect,the SR were 0.5132 and 1.0190,however,the mixture of the two components at the ratio of 7:1 had antagonist effect,the SR was 0.4382.[Conclusions] SR of the mixture of 1:11 was as high as 84.3772.So the rate of 1:11 is the best mixing proportion.This result has established the foundation for controlling the disease in the futher.