Armillaria Root Rot

• Armillaria root rot is also known as oak root fungus and roses are very susceptible to it. It lives in the soil and in the fall and winter it appears as honey-colored mushrooms that measure from 2 to 5 inches across near the roots. It not only goes after dead wood but living roots, as well. It will stunt the plant's growth, the leaves will be sparse and the ones that are there will be yellow. There is no fungicide that is effective against Armillaria root rot.
  
  

Common Rose Mosaic

• Common rose mosaic is a viral disease that is seen in roses around the world. Symptoms include yellowing of the leaves, the formation of erratic wavy rings and lines, and puckering of the leaves. The bush can become slightly stunted or severely dwarfed and can become more easily injured by the winter cold.
  
  

Botrytis Blight

• Botrytis blight attacks the flowers themselves in the spring. It flourishes in wet weather, so it can reappear in the fall. The rose petals can become spotted or the edges can become brown and mushy. In some cases, the roses might not open up at all. Twigs may die back and blotches appear on the canes. It is prevalent on bare-root roses that are bought by mail order. Take them out of their shipping containers as soon as they arrive. The fungus grows in warm and humid conditions, but it can lay dormant in a plant, even through cold winters, until the right wet conditions appear. Cut infected flowers off the bush right away and prune off any affected twigs and canes.
  
  

Rose Rust

• Rose rust is a fungal disease that is more prevalent in the western states. It appears on the underside of the leaves as bright orange powdery pustules. It can also attack new stems and can spread to the canes, as well. It will spread during cool moist times of the year. The fungus will winter over in any fallen leaves and stems and make a comeback in the spring.
  
  

Rose Spot Anthracnose

• Rose spot anthracnose is caused by the Sphaceloma rosarum fungus. It can cause a great deal of spotting that starts out as small, round red/purple spots on the leaves. The centers will turn gray or white, rimmed with red. The plant's tissue may fall out of or crack in the center of the spots. The fungus can spread to other parts of the plant and is spread from one plant to another by splashing water.