University of Illinois Extension

University of Illinois Extension

Hort Answers

Fungal Disease

Gray Mold [Annuals and Herbaceous Perennials]
Botrytis cinerea & paeoniae

Botrytis blight on rose flowers.
Botrytis blight on rose flowers.
5 (1 = rare 5 = annual)
5 (1 = very little damage 5 = plants killed)
Affects many herbaceous plants including: Achillea sp. (yarrow); Chrysanthemum sp. (shasta daisies and mums); Echinacea sp. (coneflower); Heuchera sp. (coral bells); Paeona sp. (peony); Rosa sp. (rose); Tulipa sp. (tulip); and a wide range of other plants.

Plants Affected
Botrytis (known as gray mold; on tulips it is known as tulip fire.) appears as brown dead areas and under proper moisture may have a gray fuzzy appearance. The pathogen attacks buds, flowers, flower buds, leaves, leaf buds, and stems. It may eventually kill the perennial.

Life Cycle
This pathogen over-winters on dead and live plant material. It grows at temperatures between 32 and 84 F. Botrytis releases spores on rapidly rising and lowering humidity. It needs free standing moisture to infect.

Fungicides and sanitation may be helpful.

Related Resources
Home, Yard & Garden Pest Guide
Illinois Commercial Landscape and Turfgrass Pest Management Handbook
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic