The aim of this study was to test the effect of fungicides and potassium silicate sprays on the control of late blight (Phytophthora infestans) of industrial tomato. The fungicides were applied according to the Wallin forecast system (FS) and on the weekly calendar. The experiment was carried out in a completely randomized block design with six treatments and four replications. The treatments (T) were: T1 - control; T2 - dimethomorph + chlorothalonil (disease severity values - DSV = 10) + metiram; T3 - metalaxyl-M + chlorothalonil (DSV = 10) + metiram (metiram was sprayed weekly when the DSV did not reach the required value for the treatment); T4 - calendar: dimethomorph + chlorothalonil, mancozeb, metalaxyl-M + chlorothalonil and chlorothalonil, alternated weekly; T5 and T6 - potassium silicate (5 and 15 g/L), respectively. The severity of late blight was evaluated according to a scale from 0 to 100 %. The final disease severity was 100; 2.6; 12.3; 5.5; 97.6 and 96 %, respectively, on the treatments T1, T2, T3, T4, T5 and T6. Disease severity was 93 %, less on the treatments that received the application of fungicides compared to the control. The FS (treatment 2) showed better results than treatment 3. The treatment 2, based on the FS, showed efficiency comparable to the weekly calendar (treatment 4) with yield of 62.103,73 and 52.473,33 kg/ha, respectively. These yields were superior compared to the other treatments. The applications of potassium silicate did not differ from the control. This indicates the inefficiency of this product in the control of late blight.
integrated disease management; Phytophthora infestans; disease forecast
