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 during cool, damp weather and affects various parts of many plants, particularly tender plant tissue, such as flower petals, seedlings, or buds. Botrytis first causes water-soaked brown lesions to form which are followed by a tan or gray fuzzy mold that thrives in 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 best controlled through good cultural techniques. Site plants in well-drained soil. Avoid overhead watering when possible because water splashed onto plants may spread fungal spores. Remove fallen debris, deadhead flowers, and remove dying leaves as aging and dead plant tissue is often attacked by spores which rapidly multiply and spread to healthy tissue. Provide good air circulation and do not overcrowd plants. Avoid fertilizing plants with high nitrogen fertilizers that may cause a flush of succulent, tender growth that is vulnerable to infection.

Please contact Plant Information Service at (847) 835-0972 or via e-mail at plantinfo@chicagobotanic.org for recommended chemical treatments for botrytis.