Downy Mildew on Grapes
Plasmopara viticola
Grapeoomycete
A rain-driven oomycete disease producing yellow "oil spot" lesions and white downy growth on leaf undersides.
Symptoms
Yellow "oil spot" lesions on the upper leaf surface with white, downy fungal growth on the underside during humid weather, plus berry rot.
Favorable conditions
- •Rain events during the growing season
- •Warm, humid conditions
Management
- 1Apply a fungicide program timed to rain events
- 2Plant resistant varieties where available
- 3Manage the canopy for airflow
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