Gray mold, or Botrytis blight, is a common disease of a number of non-woody plants worldwide and causes a greater loss of strawberry flowers and fruit than any other disease. The causal organism, Botrytis cinerea, can live as a parasite as well as a saprophyte on decaying plant debris.

Symptoms and Disease Cycle

Botrytis blight usually starts as a blossom blight that eventually invades the developing fruits, causing them to rot. This rot may first appear at the base of the fruit or when the berry is in contact with the soil, other damp surfaces, or other rotten fruit and can destroy the berry within 48 hours. As ripening increases and humidity remains high, a characteristic gray, fuzzy coating or web, produced by the fruiting of the fungus, covers the strawberry fruit. As the disease progresses, spores are produced and are easily blown or splashed onto healthy foliage. Once the fungus becomes established, it can continuously produce spores throughout the growing season.

Disease Management

Moisture is necessary for the spores to germinate and infect plants. The disease is, therefore, favored by humidity and relatively cool conditions. During a wet bloom season, it is critical to time and apply sprays. This critical timing will prevent the spread of the fungus into the decaying flower parts. Practices that help reduce humidity and increase air movement, such as opening up plants by cultivation and wider spacing of rows and plants, help control gray mold. The fungus thrives on debris, and sanitation is essential for control. Dead plants and fallen leaves should be removed and burned or buried.