University of Maryland Extension

Gray Mold or Botrytis on Houseplants

botrytis on begonia leaves

  • Gray mold or Botrytis blight often begins with relatively large grayish to tan areas on older leaves or spent flowers.
  • The dusty gray spores of the fungus are easily seen and infected areas can rapidly enlarge and cause tissue collapse.
  • This fungus primarily infects older tissue and generally is not a serious pathogen unless infection conditions are ideal.
  • Optimum infection conditions would include wet leaves, high humidity, cool temperatures and cloudy overcast days.


  • Any method that will lower the humidity, decrease leaf wetness or increase air circulation will help to lessen the chances of infection.
  • Watering should be done early in the day to allow leaf surfaces time to dry quickly.
  • 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 drier conditions should help manage this disease.

 botrytis on orchid
Botrytis on miltonia orchid flower

botrytis on mum
Botrytis on a potted mum

botrytis on orchid flower
Botrytis on disa orchid flower

botrytis on impatiens flower
Infected impatiens flower

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