As the disease progresses, spores are produced and are easily blown or splashed onto healthy foliage. Once the fungus becomes established, it can produce spores continuously throughout the growing season. The causal organism, Botrytis cinerea , can live as a parasite as well as a saprophyte on decaying plant debris. Under favorable conditions, the fungus produces spores that are spread by air currents and rain. The flower parts become infected first, and the disease spreads to developing fruit.
Gray mold is favored by cold temperatures and high humidity.
Practices that help reduce humidity and increase air movement, such as opening up plants by cultivation and spacing rows and plants farther apart, 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. Some strawberry cul-tivars are less susceptible to gray mold than others. A wide array of leaf spots infect cultivated and wild strawberry species, including birds-eye leaf spot, black leaf spot, Septoria leaf spot, Cercospora leaf spot, Alternaria leaf spot, red spot, and Angular leaf spot.