CropsMain symptoms
The symptoms induced by Flavescence dorée can be localized (figure 1) on the vine or generalized to the latter (figure 2). They are particularly influenced by the vigor of the plants, the grape variety (chardonnay, cabernet sauvignon and sauvignon are particularly sensitive; merlot and sémillon are much less) and climatic conditions. They can appear at several phenological stages of the vine:
- In spring , we can observe a delay in budding, then the first visible consequence on the production is a wilting of the inflorescences.
- At veraison , the leaf blades harden and become brittle, become discolored (white grape varieties turn yellow, red grape varieties turn red) (figures 3 and 4) and exhibit more or less marked curling depending on the grape variety. The bunches may show berry drying 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.
It is only when several of these symptoms are visible on a vine that one can recognize a phytoplasma disease of the vine. The symptoms induced by other phytoplasmas (such as Bois noir) are indistinguishable from those of Flavescence dorée.
It is important to specify that the symptoms of Flavescence dorée are not visible the year of infection, they will appear the following year, or even up to several years later.
Rootstocks (cultivated in mother vines or wild regrowth) show few symptoms although they can be carriers of phytoplasmas.
Note that the website http://flavescencedoree.jimdo.com presents many photos of the symptoms of Flavescence dorée in the vineyard.
Once these symptoms have been observed, the presence of the responsible phytoplasma must be confirmed by tests carried out by an approved laboratory (nested-PCR or real-time PCR).
Note that the website http://flavescencedoree.jimdo.com presents many photos of the symptoms of Flavescence dorée in the vineyard.
Once these symptoms have been observed, the presence of the responsible phytoplasma must be confirmed by tests carried out by an approved laboratory (nested-PCR or real-time PCR).
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