This fungus is recognizable by the appearance of pale yellow spots on the leaf, where after on the leaf and on the berries white powdery fungus spots are formed. At first, the growth points and the young leaf are affected, later the mature leaves and the grapes.
The fungus overwinters in the buds or on the old wood, where small yellow or black spots are visible. In spring as the buds will open, the fungus becomes active and touches the growth points. In spring, especially in fairly humid and warm weather and at an average day temperature of 8 °C, an extensive contamination can be expected.
Keeping the plant open ensures that it dries quickly, avoiding the mildew to expand significantly. The newer grape varieties are better resistant to fungi. In case of attack chemical treatment is possible by spraying with an extract of horsetail (Equisetum arvense) or with a sulfur solution.
Prepared slide by Lieder www.lieder.com