Grey mould is a form of botrytis that affects the flowers and foliage of many cultivated plants,particularly those grown under glass where conditions are humid.
It can also attack many types of fruit, particularly as it is ripening, e.g Strawberries.
The disease can be found at any time during the growing season.
The spores unlike powdery mildew spores grow on dead plant material.
It normally infects plants under stress, but will infect healthy plants as well, especially those growing in humid conditions.
It can also infect a plant through a wound in the stem.
These are seen as small spots on the flowers and a grey fuzzy mould on the stems and petioles, usually near the base of the plant/s
Further signs are that flowers stems collapse, and on fruit the disease appears as brown bruises, which turn soft and rot.
As mentioned above the fungus thrives on dead plant material, forming black, tough resting structures called sclerotia in the dead tissue.
Good hygiene around the plants is often the best control i.e. keeps the area around the plant/s free from dead leaves and detritus, particularly if the plants have been affected by powdery mildew.
There are no fungicides available to the amateur gardener to control this disease, but by using the treatment suggested for Powdery mildew, damage can be minimized.
Increasing ventilation will reduce the humidity around plants, which in turn will help to keep the number of spores down.
Preventing plant overcrowding can also improve the air flow around plants.