downy and powdery mildews

Grapevine powdery mildew is a disease caused by Erysiphe necator (Schw.) Burr., that causes great financial and harvesting losses in the cultivation of grapevines worldwide. In the early stages of the disease, the harm is not widespread and sometimes difficult to distinguish.

It is an obligatory parasite that has a restricted range of hosts, as it only affects members of the Vitaceae family. The environmental conditions suitable for releasing cleistothecia ascospores are 2.5 mm of rain and temperatures above 4°C, being critical between the green tip and flowering phenological stages (Gadoury and Pearson, 1990) and, for secondary infections, temperatures between 20 and 27°C. These are normal conditions in the Rioja Alavesa area, where it is a common disease, appearing every growing season and being treated periodically to avoid heavy losses both in terms of finances and the quality of the grape. It appears sporadically in Txakoli producing areas, especially in areas which are prone to it developing.

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Powdery mildew on leaves

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Powdery mildew on the stem

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Powdery mildew on vine shoots
Grapevine downy mildew is caused by the oomycete Plasmopara viticola (Berk. Et Curt.) Berl. et De Toni. It is widely distributed worldwide in temperate areas and those where spring times are rainy. It causes losses in crop yield both directly and indirectly, such as inflorescence rot, stem and shoot rot, a reduction in the photosynthesis activity of the affected leaves and premature defoliation of infected plants.

This disease sporadically appears every growing season in the Rioja Alavesa vineyards, but it is recurring in Txakoli areas, where constant humidity and moderate temperatures prevail throughout each growing season.

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Downy mildew on leaves
Downy mildew on stems

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