Grape yellow disease (or flavescence dorée) is from North America. That’s a recent plague in southern France that causes devastation that could become as big a problem as Phylloxera. Since 1987, its mandatory in France to fight against that disease, that leads to heavy loss of yields, and eventually and the loss of entire vineyards.
The origine is a phytoplasma. That microorganism is propagated by a leafhopper (Cicadellidae, suborder Homoptera or Scaphoideus titanus) going from vine to vine where it reproduces. That grape yellows disease is to be found everywhere in south of France from Aquitaine, Languedoc-Roussillon, Midi-Pyrénées and Provence. The disease results as wilt of the berries, leaves turn red for red variety and yellow for white’s, a bad lignification process (hardening of the vine wood). The disease impact vary according to the strength of the plant (drought, hydric stress…) and the variety (Cabernet is more fragile). Symptoms are visible on a part of the stump or on the whole vine. They may be visible very late, sometimes 5 years after the first diseas attack. This grape yellow disease can propagate very quickly, the cicadelle has only one generation a year, hivernation is taking place in winter as eggs. From july to september, female lay 20 to 30 eggs on the bark and branches. There’s five larva stadiums, jumper grub, maximum 5 mm long. Female a slightly bigger than male. Long summer favours the insect expansion as well as cool winters. There’s no straigthforward manner to fight against the phytoplasma. Only chemical means are available to keep the cicadelle (that’s a real problem for organic winemakers, chemical products kill predators of the predator of the vine). Abandoned vines acount a dangerous infection reservoir for the neighbouring vineyards. They must be spotted and immediatly grubbed up and burned, in order to destroy the eggs. Cicadelle lay eggs in march, that hatch between may and june. Contamination risk spreads from june to august. Two kinds of treatments exist : one after laying eggs, the second after hatching and development of the larva.