Impact of "bois noir" disease (BN) on performance of 'Chardonnay' grown in Eger (Hungary) is reported from plant (vegetative and reproductive parameters, fruit composition) to wine (wine quality, sensory analysis). BN-associated chlorophyll degradation and leaf rolling resulted in a loss in functioning surface of the canopy. Lack of lignification and non-viable buds evoked unpredictable crop production. Severity and extent of reduction in production varied between years, but the crop loss was always above 53%. In the case of BN-affected grapevines the reduced quantity resulted in a low quality of grape bunch composition, which enhanced unfavourable outcomes in wines. Differences in fruit composition and wine quality between healthy and BN affected grapevines were most pronounced in years with optimal weather conditions and the negative effect was covered up in poor years. In wine regions where mechanical harvesting is applied, harvesting of phytoplasma diseased vineyards can therefore not be selective and qualitative. According to the three years study presented BN induce severe loss, and BN-affected plants compromise the yield and wine quality, and therefore the overall profitability of a vineyard.< Leer menos