Botrytis (Gray Mold) can occur on spent blossoms and cause a flower blight. Infected flowers can spread the disease by dropping onto leaves of healthy plants.
Botrytis blight and stem canker is caused by Botrytis cinera. 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. Fungicides appropriate for Botrytis include 26 GT, 26/36, Compass, Cleary's 3336, Botran, Decree, Daconil, Dithane, Heritage, Exotherm Termil, Sextant, Protect DF, and Medallion. Check label for host appropriateness. Resistance to Cleary's 3336, 26 GT, and Sextant has been reported in Botrytis populations. Always alternate fungicide applications between materials with different modes of action to prevent resistance development.
See Fact Sheets:
Gray Mold on the UConn IPM Web site.