Disease of the Month: Botrytis spp. (Grey Mold)
by Emily Gatch

Purpose: To acknowledge the dim, soggy days of late winter and to herald our new introduction of four varieties of strawberries, a coveted crop that is particularly susceptible to this month's disease.

Botrytis is a saprophytic fungus that attacks most species of vegetables, fruits, and bulbs, both in the field and in storage. A saprophyte feeds on dead tissue and hastens the normal decay process, so Botrytis tends to thrive later in the season when harvest injuries and other pathogens have already compromised plants. The disease is characterized by a rapidly-progressing decay that quickly invades plant tissue and produces a grayish, velvety/powdery mold on the surface of the lesions. Gray mold is most severe in cool, humid temperatures and is thus a challenge for many winter greenhouse crops. Botrytis may form storage structures called sclerotia that can survive in the soil for several years.

Basic recommendations for all Botrytis control include avoiding damage, such as topping of onions, maintaining proper drying techniques for vegetable and fruit storage, reducing nitrogen fertilization to avoid lush leaf canopies, increasing plant spacing to facilitate air movement, ensuring burial of plant residues, and maintaining a minimum three year crop rotation.

Primary crops affected by Botrytis:

Onion:
B. allii: neck rot (primarily a storage disease)
B. squamosa: Botrytis leaf blight or Botrytis blast

Basil, Lettuce, Bean, Pepper, Tomato, Cabbage, Stawberry:
B. cinerea: gray mold

Emily Gatch
Greenhouse and Pathology Coordinator

Photo Caption: Emily patrols the greenhouse monitoring plant health