Botrytis, otherwise known as gray mold, initially occurs as pink spots
on light-colored flowers. These might turn yellow or dark brown with
age. Flowers may fail to open, or may just rot. Leaves also rot. You can
see a grey mold on the plant, and it may also attack the base of the
plant where it contacts soil. Gray mold loves moist and cool
temperatures. As soon as you see grey mold, you must cut all infected
parts off the plant and destroy them.
The fungus Sphaceloma rosarum or Elsinoe rosarum is called Purple
Spotting or Spot Anthracnose fungus. It appears as red, purple, pink or
brown spots on leaves and stems. In advanced condition, the leaves turn
yellow and drop off.
Another fungus is called rose Wilt or Verticillium Wilt. This fungus
lives in soil and prevents the plants from uptaking water from roots
into the plant. During hot conditions, the disease becomes obvious, with
wilting and yellowing of leaves a prevalent symptom. Eventually, the
entire plant is defoliated and dies. Verticillum can get out of control
quickly, and most growers are forced to yank infected plants and destroy
Check out the link here to solve your gray mold and rose wilt problem
'Flower Gardening | Advanced Nutrients Articles'