Learn how to identify and manage Botrytis blight (gray mold) in greenhouse and nursery crops, with tips on sanitation, air circulation, watering practices and fungicide use for commercial growers.
Published January 08, 2024
Editor's Note: This article originally appeared in the November 2025 print edition of Greenhouse Management under the headline “Botrytis blight.”
Botrytis blight on marigold
Mary Ann Hansen, Virginia Polytechnic Institute and State University, Bugwood.org
Botrytis blight, also know as gray mold, is a fungal disease caused by several species in the genus Botrytis. It affects the buds, flowers, leaves and bulbs of many nursery and greenhouse crops. Wounded or weakened plants are particularly susceptible to this disease. The responsible fungi spreads quickly in periods of high humidity or when there is moisture on plant tissue. It can survive year-round in greenhouses due to the relative humidity. Nurseries should be extra vigilant during rainy and drizzly weather conditions.
Source: Missouri Botanical Garden, Michigan State University Extension
