Agrometeorological and ecophysiological approach to the analysis of grapevine response to downy and powdery mildew infections

Reducing factors are responsible for the final amount of crop production. Among these, foliar diseases can decrease carbon uptake and thus biomass accumulation. The knowledge of these mechanisms can represent the basis for improvement of protection method, also by means of simulation models. The responses of grapevine (Vitis vinifera) to downy (Plasmopara viticola) and powdery mildew (Uncinula necator) infections are analysed in this paper. Natural field infections were studied during 1997 on Sangiovese variety, measuring agrometeorological, ecophysiological and growth variables. Downy mildew was observed at a very low intensity and no effect was determined on infected leaves and plants. Powdery mildew intensity was very high (about 60%) and a significant reduction of gas exchanges was measured throughout the season. However the reduction of biomass accumulation was lower than expected, probably because of a modification of storage organ dry matter.