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Effect of potassium silicate alone or mixed with fungicides on the control of late blight on potato

This study aimed to investigate the effect of foliar application of potassium silicate, alone or mixed with different rates of fungicides, on the control of late blight, caused by Phytophthora infestans, on potato. The experiment was carried out under field conditions using the completely randomized block design with 8 treatments and 4 replications. The potato cultivar used was Asterix. The fungicide Cimoxanil + Mancozeb (60 + 700 g/Kg i.a.) and potassium silicate at the rate of 60 g/L (pH = 5.5) were used. The treatments (T) were the: T1 - Control; T2 - Cimoxanil + Mancozeb (2.0 Kg/ha); T3 - Cimoxanil + Mancozeb (2.5 Kg/ha); T4 - Cimoxanil + Mancozeb (2.0 Kg/ha) + potassium silicate; T5 - Cimoxanil + Mancozeb (2.5 Kg/ha) + potassium silicate; T6 - Cimoxanil + Mancozeb (3.0 Kg/ha) + potassium silicate; T7 - potassium silicate and T8 - Cimoxanil + Mancozeb (3.0 Kg/ha). Sprays were done weekly. Evaluations of late blight severity were done using a descritive scale ranging from 0 to 100%. Results from late blight severity were used to calculate the area under disease progress curve (AUDPC). The AUDPC was 72.5, 23.8, 18.3, 29.5, 19.7, 17.9, 68.3 and 16.3, respectively, for the treatments T1, T2, T3, T4, T5, T6, T7 and T8. The treatments 3, 5, 6 and 8 were the most efficient (lower values for AUDPC and highest values for yield) on the control of late blight. The potassium silicate was not efficient on disease control and did not show any additional effect when mixed with fungicide.

integrated disease management; Phytophthora infestans; Solanum tuberosum

Grupo Paulista de Fitopatologia FCA/UNESP - Depto. De Produção Vegetal, Caixa Postal 237, 18603-970 - Botucatu, SP Brasil, Tel.: (55 14) 3811 7262, Fax: (55 14) 3811 7206 - Botucatu - SP - Brazil