Closely spaced plants, overcast cloudy weather, and flower drop from overhead hanging baskets encourage Botrytis blight on many greenhouse crops. The fuzzy grayish-brown spores, are easily spread on air currents and by water splash.
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.
Remove and destroy infected plants and plant debris. Control weeds. Water early in the day so foliage dries rapidly. Improve air circulation and light penetration by plant spacing and horizontal air flow (circulating fans). Reduce humidity by heating and venting the greenhouse several times in the evening and in the morning.