University of Maryland Extension

Petal Blight - Ovulinia - Shrubs

  Brown diseased flowers
Small black resting structures called sclerotia will develop on the brown
flower remains and will overwinter on the ground
  

Key Points

  • This disease only affects the flower petals.
  • The first symptoms are small water-soaked spots on the petals.
  • The spots rapidly enlarge and cause the flower to collapse and feel slimy.
  • This disease is most severe under warm moist conditions. Flowers blighted by other fungi such as botrytis or those killed by frost will not feel slimy.
  • Flowers affected by petal blight turn brown and remain attached to the plant.
  • Small black resting structures called sclerotia will develop on the brown flower remains and will overwinter on the ground.
  • Sclerotia can survive as long as two years in the soil and will start the infection cycle in the spring.

Management

  • Remove old garden debris and old mulch below plants to reduce the sclerotia (fungal structures) that will cause new spring infections.
  • Add a new layer of mulch.

water soaked spots on azalea flower petals
Small water-soaked spots on petals

azalea flowers collapse and turn brown
Flowers collapse and turn brown

rev. 2020

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