Observation on Black Dead Arm in French Vineyards
causing decline and eventually death. Previously, this disease was confused with esca because of the similarity of the
foliar symptoms. Two forms of black dead arm, a mild and a severe form, were observed in French vineyards on
Cabernet Sauvignon and Sauvignon. Isolations from 23 vines collected from four vineyards located in three viticultural
districts of Bordeaux showed that the main fungi associated with the brown streaks were Botryosphaeria obtusa, B.
dothidea and Trichoderma spp. Pathogenicity tests showed that B. obtusa and B. dothidea caused dark lesions on 1-
year-old canes. Therefore, these two fungi merit further study to determine their role in causing black dead arm.
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