Abstract:

The purpose of this study is to determine the highest synergy ratio (SR) of the mixture of fungicide fludioxonil and tebuconazole that inhibited the mycelial growth of Fusarium graminearum. The effective concentration of 50% (EC₅₀) of fludioxonil, tebuconazole and their mixtures against F. graminearum isolates were determined by mycelium growth rate method. The SR of the mixture of the fungicide fludioxonil and tebuconazole was determined by Wadley’s SR method. The synergistic ratio of the mixture of the fungicide fludioxonil and tebuconazole was evaluated. The results showed that the EC₅₀ value of fludioxonil and tebuconazole against F. graminearum was 0.0205 μg/mL and 0.1704 μg/mL, respectively. When the mass ratio of the mixture of fludioxonil and tebuconazole was 40:1, 20:1, 10:1, 5:1, 1:1, 1:5 and 1:40, the SR range was from 0.54 to 1.28, which showed additive inhibition. When the mass ratio of the mixture of fludioxonil and tebuconazole was 1:10 and 1:20, the SR was 1.56 and 1.62, respectively, which showed synergistic inhibition. When the mass ratio of the mixture of fludioxonil and tebuconazole was 1:20, the SR value was the highest, which was the best synergistic ratio. These results could provide a theoretical basis for the control of wheat scab and delaying the development of tebuconazole resistance.

Key words: fludioxonil, tebuconazole, wheat scab, Fusarium graminearum, synergistic effect