Warm, gray and fuzzy?
Don’t allow Botrytis to flourish in your greenhouse.
Botrytis cinerea is a fungus that causes disease on greenhouse ornamentals including leaf spots, blighting, stem cankers, and damping-off of young seedlings (Photos A-C). Blighting is the most common symptom and affects leaves, petioles, blossoms and stems. Botrytis produces large masses of gray conidia or spores (Photo D) – hence the name “gray mold” – that are carried on air currents to healthy plants where blight can become established. On bedding and stock plants, Botrytis typically becomes established and produces conidia on older lower leaves that are near the moist soil surface and under the plant canopy. Botrytis also readily infects the broken or cut stem surface of stock plants and progresses downward, causing a dieback of the entire stem.
Watering in the morning so that the foliage can dry rapidly is one way to minimize Botrytis. Practices that reduce the relative humidity are also helpful and include spacing plants further apart and providing good air circulation. Reduce the relative humidity for a minimum of 24 hours immediately following the harvesting of cuttings to help “dry” the wounded stems and thereby limit stem blight.