Watch for Gray Mold in Your Greenhouse

Watch for Gray Mold in Your Greenhouse

Gray Mold on Vinca

Botrytis gray mold on annual vinca stems (NC State PDIC)

Warmer weather means annuals production season, but it also means the potential for Botrytis gray mold. Botrytis gray mold is a fungal disease that can progress rapidly under cool, moist, or humid conditions and has a large host range, including many common ornamentals and vegetables.


Under ideal conditions, gray mold will produce spores that will look like a gray (sometimes light brown), fuzzy mass on foliage, stems, and/or flowers. However, when the fungus is not sporulating, it can easily be confused with other diseases. Symptoms include elongated tan or brown lesions on stems and petioles, irregular shaped lesions on leaves, and small spots on flower petals. In severe cases, it can cause part of or a whole plant to collapse. Foliar infections often start where a spent flower touches a leaf.

Inga Meadows, Extension Associate, Vegetable and Herbaceous Ornamental Pathology at North Carolina State University, offers tips on managing gray mold here.