One of the factors to be managed for maximum vineyard productivity is the downy mildew, disease caused by Plasmopara viticola that affects grape production in many parts of the world. In Brazil, several fungicide applications for its control are necessary. Different active ingredients are available on the market. The influence of climatic factors (air temperature, rainfall and relative humidity) on fungicide efficacy in Vitis vinifera was analyzed using results of fungicide trials for downy mildew control as a base. The experiments were carried out at Embrapa Uva e Vinho with the cv. Tannat conducted on vertical trellis system during 1995 and 1996. The assessment of the environmental factors pointed out primary and secondary infection periods, being the rainfall and high relative humidity responsible for the high severity in the year 1996. The analysis of the incidence and of the disease rate on leaves and bunches, indicated that the most efficient treatments were cymoxanyl + mancozeb, metalaxyl + mancozeb and dithianon, in the two years. The active ingredients copper oxychloride, alone or combined with mancozeb, and copper sulphate were not efficient for downy mildew control on bunches under favorable environmental conditions to this disease.
Vitis vinifera; Plasmopara viticola; chemical control; grape downy mildew
