Botrytis blight and stem canker is caused by Botrytis cinera. Wilted branches and darkened, woody stem seen in this photo are common symptoms. This pathogen is ubiquitous in the environment, has an extremely wide host range, and prefers to attack senescent and/or injured tissue. Botrytis can be controlled by management of environmental conditions, sound cultural practices and fungicide applications. Control weeds and remove plant debris. Space plants to allow good air circulation, reduce humidity within the canopy, and minimize leaf wetness. Improve horizontal air flow with fans. Reduce humidity by a combination of heating and venting in the evening, particularly when warm days are followed by cool nights. Water in the morning if practical.
See fact sheet: Botrytis Blight of Greenhouse Crops