Chicago Botanic Garden

YOUR GARDEN — Plant Information

Pests, Problems, and Diseases

Botrytis Blight on Ornamental Plants

 

Susceptible Plants
Many ornamental plants, including trees, shrubs, annuals, perennials, houseplants and greenhouse plants. Commonly afflicted plants include dogwood (Cornus), lilac (Syringa), peony (Paeonia), rose (Rosa), phlox (Phlox), zinnia (Zinnia) verbena (Verbena) and others.

Description & Symptoms
Botrytis blight is a fungal disease that flourishes in cool, damp conditions and affects many different parts of various plants, particularly tender plant tissue, such as flower petals, seedlings or buds. Botrytis first causes water-soaked brown lesions to form. These are followed by a tan or gray fuzzy mold that grows under conditions of high humidity. Botrytis is often referred to as gray mold.

Damage
Unopened flower buds wither and brown. Lesions appear on stems. Spots form on leaves, often followed by a tan or gray fuzzy growth. In seedlings, botrytis is a cause of damping-off, a condition where young stems rot at soil level.

Treatment & Solutions
Botrytis is controlled best through cultural techniques. Site plants in well-drained soil. Heavy clay soils that drain poorly promote the disease. Since splashed water spreads the fungal spores, overhead watering should be avoided where possible. Aging and dead plant tissue is often attacked by spores, which rapidly multiply and then spread to healthy tissue. Cleaning up fallen debris, deadheading flowers and removing dying leaves is essential to controlling botrytis. Provide good air circulation and avoid overcrowding plants. Also avoid fertilizing plants with high nitrogen fertilizers, which cause a flush of succulent, tender growth vulnerable to infection.

 

For approved chemical treatment of botrytis and a list of disease-resistant crabapple trees, call the Plant Information Hotline at (847) 835-0972.