Main symptoms

Symptoms of blackwood can be localized to the vine or generalized to it (Figure 1). They are particularly influenced by climatic conditions and the grape variety: Chardonnay, Cabernet Sauvignon and Sauvignon grape varieties are particularly sensitive. They can appear at several phenological stages of the vine:

• in spring , we can observe a delay in budding, then a wilting of the inflorescences which is the first visible consequence of the disease on the production of the vines.
• at veraison , the leaf blades harden and become brittle, become discolored (white grape varieties turn yellow, red grape varieties turn red) (figures 2 and 3) and curl more or less depending on the grape variety. The bunches may show berry drying out starting from the stalk. If we are interested in the organoleptic quality of the berries produced by the diseased vines, they are fibrous which gives them a bitter and sour taste. It is obvious that the wine produced subsequently is of poor quality and often difficult to market.
• at the end of summer , the most characteristic symptom is the partial or total absence of hardening (lignification) of the woods. The branches which remain green and flexuous can then assume a drooping habit. Brown spots sometimes appear on the bark.
  
  Note that the website http://flavescencedoree.jimdo.com presents many photos of the symptoms of flavescence dorée and black grapevine wood.