Code: OIV 456

Name: Cluster: degree of resistance to powdery mildew

Category: , GROUP OF CHARACTERISTICS, ORGAN

Subcategory: POWDERY MILDEW, BIOTIC RESISTANCE - FUNGUS, BUNCH

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Description

The resistance of grapevine varieties to powdery mildew (Erysiphe necator) is to be observed under field trials over several years without the use of chemical plant protection and/or resistance inductors. Evaluation of Oidium attack on all the clusters from 4 – 6 vines at two periods, if possible: before veraison and before vintage. 1 to 3 = A large number of berries of all clusters attacked by powdery mildew (Erysiphe necator ), some however can be attacked moderately. Many cracked berries. 5 = Many attacked berries (up to 30 %), most clusters are moderately attacked, some however, can be attacked severely. Rare cracked berries. 7 to 9 = None or only a few berries out of all clusters are attacked, of which only a few clusters are slightly attacked., No cracked berries. The symptoms should be evaluated considering the climatic conditions, that could influence the evolution of the disease, and, possibly, on plants without any biotic or abiotic stresses.

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