Home/Problems/Powdery Mildew
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Powdery Mildew

A fungal disease that coats leaves, stems, and buds with a white or grey powdery substance. It rarely kills plants but weakens them significantly.

Symptoms

  • check_circleWhite or grey powdery coating on leaf surfaces
  • check_circleAffected leaves yellowing and curling
  • check_circleDistorted or stunted new growth
  • check_circlePowdery patches on stems and flower buds

Causes

  • arrow_rightHigh humidity combined with poor air circulation
  • arrow_rightOvercrowded planting conditions
  • arrow_rightWarm days and cool nights
  • arrow_rightExcessive nitrogen fertilisation promoting soft growth
  • arrow_rightWater-stressed plants are more susceptible

How to Diagnose

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.

Treatment

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.

Prevention

Space plants adequately for air flow. Avoid overhead watering. Do not over-fertilise with nitrogen. Water in the morning so foliage dries before evening.