Gray mold is also known as botrytis blight. It attacks many different flowering plants, fruits and vegetables. It is a fungus that looks like a mold you've seen on old strawberries.
The fungus loves shady, crowded conditions. It is very common in cool and humid climate or seasons. The spores of the fungus are spread by the wind and when water is splashed. The mold usually starts on old fruit or plant tissue and then spreads to healthy tissue. Sometimes the fungus looks slimy when the tissue rots.
Do not overcrowd plants in the garden, and allow good air circulation between the plants. Water early in the morning to allow the plants to dry out during the day. Pick off dead flowers and leaves to get rid of the infection areas. Destroy clippings from infected plants. Dust with sulfur or spray with compost tea to help to control the mold.
Watering is necessary when transplanting, but be careful not to over water.