Hexaconazole and binary mixtures of it plus fludioxonil efficiently control tomato leaf mold caused by Cladosporium fulvum

Leaf mold caused by Cladosporium fulvum is one of the most severe foliar diseases of tomato. We were interested in whether we could use a binary mixture of hexaconazole and fludioxonil for the management of tomato leaf mold. The results showed that hexaconazole with an EC50 value of 0.30 & mu;g/ml could significantly inhibit the mycelial growth of C. fulvum. A total of 126 isolates collected from Shandong Province were used to determine their sensitivity to hexaconazole, and the data fit a bimodal curve with a mean EC50 value of 4.69 & mu;g/ml. The optimal proportion of the binary mixture of hexaconazole and fludioxonil against C. fulvum was 1:2, and its synergistic ratio (SR) was 2.23. Field trials in 2018 and 2019 indicated that both hexaconazole and the binary mixture of hexaconazole and fludioxonil (1:2) had favorable protective and curative efficacy against tomato leaf mold. Applying hexaconazole at 67.50 g/ha resulted in higher efficacy than did flusilazole at 75.00 g/ha, which had been registered in China to control tomato leaf mold. In addition, a binary mixture of hexaconazole and fludioxonil (1:2) at 60.75 g/ha had an efficacy of 85%, which was significantly higher than that of a commercial binary mixture of fluopyram and trifloxystrobin at 150.00 g/ha. Even when applied at 20.25 g/ha, hexaconazole could also provide better efficacy than thiophanate-methyl could regardless of whether it was applied before or after the occurrence of tomato leaf mold. In summary, hexaconazole and its binary mixture with fludioxonil (1:2) could be favorable candidates for the management of tomato leaf mold.