University of Maryland Extension

Powdery Mildew on Houseplants

powdery mildew poinsettia

  • There are several fungal species that cause powdery mildew of house plants, but the symptoms are the same.
  • The most obvious symptom is the white powdery coating on the surfaces of infected leaves and stems.
  • The initial areas of mildew may start out as small spots of powdery white growth before growing together to form a white coating over the entire surface.

Management Strategies

  • Individual infected leaves can be picked off and destroyed.
  • Any method that will lower the humidity, or increase air circulation will help to lessen the chances of infection.
  • Space plants so that air can circulate between them to help reduce moisture.
  • Registered fungicides can be used, but in most home conditions, removal of infected plant parts and adjustment of environmental conditions to promote better air circulation should help.
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