Screening Effective Fungicides To Control Tomato Leaf Mold Disease And Related Application Performance In Field

Tomato leaf mold caused by Cladosporium fulvum Cooke is one of the most important leaf diseases in tomato. It can occur throughout the growth season and lead to yield losses and quality decreases. At present, thiophanate-methyl, captan and other fungicides were registered for controlling tomato leaf mold in China. However, its pathogen had been different degrees of resistance. There are rarely reports about screening fungicides for controlling tomato leaf mold at home and abroad. In addition, a large degree of blindness are existing in the selection of fungicides for farmers. Therefore, efficient fungicides were urgently screened for controlling tomato leaf mold disease. In this paper, high activity fungicides against the different development stages of Cladosporium fulvum were screened in laboratory. And the safety of triazole fungicides to tomato plants were evaluated in the glasshouse condition. Then the field trials were also conducted to investigate the control efficacies of different fungicides. The main results are as follows:1.The toxicity of 13 fungicides against mycelia growth, spore germination and germ tube elongation exhibited significantly different. And each fungicides had high inhibitory activity on mycelia growth. The order of inhibition virulence of mycelia growth was fuldioxonil, hexaconazole, difenoconazole, tebuconazole, tetramycin, thiophanate-methyl, SYP-Z048, flusilazole, fluazinam, fluopyram, myclobutanil, isopyrazam and tetraconazole. The EC50 values of these fungicides were 0.20, 0.50, 0.55, 0.80, 0.82, 1.79, 2.17, 2.42, 3.41, 4.27, 6.92, 12.68 and 15.08 mg/L.Tetramycin, isopyrazam and fluopyram had high inhibitory activity on spore germination and germ tube elongation. The EC50 values of these three fungicides on spore germination were 0.013, 0.66, and 3.05 mg/L. And the EC50 values of these three fungicides on germ tube lelogation were 0.013, 0.085, and 1.92 mg/L, respectively. The inhibitory activity on spore germination and germ tube elongation of the rest of fungicides were relatively lower. And the inhibitory activity on germ tube elongation were higher than spore germination.2.The safety test of spraying tomato plants with tebuconazole and hexaconazole at the rates of 50, 100 and 200 mg/L, difenoconazole and myclobutanil at the rates of 100, 200 and 400 ml/L were conducted in the greenhouse. Sprayed with hexaconazole and tebuconazole 200 mg/L, the growth of plants were inhibited, but the leaf color and plant morphology of tomato were no significantly effect. So, there was a security risk. The plant height, stem diameter, leaf color and plant morphology with other fungicides and dosages treatments were no significantly effect, which were relative safe.3.The results of field trials indicated that the incidence of tomato leaf mold disease sprayed by all the fungicides significantly decreased. Among them, spraying tetramycin 90 mg/L, hexaconazole and tebuconazole at the rate of 100 and 150 mg/L, myclobutanil and difenoconazole 300 mg/L, the field efficacies against of tomato leaf mold were relatively higher. The protective efficacies reached more than 80.16%, and the curative efficacies reached more than 71.68%. Each fungicides can effectively control the occurrence of tomato leaf mold disease, and the effect of spraying fungicides before the onset were better than the effect after the onset. However, the control efficacies of SYP-Z048 150 mg/L, fluazinam 300 mg/L and fludioxonil 90 mg/L were relatively lower.