Powdery Mildew in Zinnia
Zinnias are bright, heat-loving annuals that bloom in vivid colours all summer. A fungal disease that coats leaves, stems, and buds with a white or grey powdery substance. It rarely kills plants but weakens them significantly.
Zinnia care requirements
These care conditions are most relevant to powdery mildew in Zinnia. Check each one as a potential cause.
Symptoms to look for in Zinnia
- fiber_manual_recordWhite or grey powdery coating on leaf surfaces
- fiber_manual_recordAffected leaves yellowing and curling
- fiber_manual_recordDistorted or stunted new growth
- fiber_manual_recordPowdery patches on stems and flower buds
Common causes in Zinnia
- fiber_manual_recordHigh humidity combined with poor air circulation
- fiber_manual_recordOvercrowded planting conditions
- fiber_manual_recordWarm days and cool nights
- fiber_manual_recordExcessive nitrogen fertilisation promoting soft growth
- fiber_manual_recordWater-stressed plants are more susceptible
How to diagnose powdery mildew in Zinnia
The white powdery coating is distinctive — unlike downy mildew, powdery mildew sits on the upper surface of leaves and can be rubbed off with a finger.
How to treat powdery mildew in Zinnia
Remove and dispose of affected leaves. Spray with a diluted solution of baking soda (1 tsp per litre of water) or neem oil. Ensure good air circulation around the plant. In severe cases, use a fungicide labelled for powdery mildew.
Preventing powdery mildew in Zinnia
Space plants adequately for air flow. Avoid overhead watering. Do not over-fertilise with nitrogen. Water in the morning so foliage dries before evening.