Colorado's dry climate and high altitude are not conducive to the development of most fungal diseases. Rose mosaic usually shows up as mosaic patterns or splotches of yellow and green on leaves.
Powdery mildew is a common rose disease because it occurs in dry as well as humid weather.
Rust appears on the undersides of leaves and other plant parts as orange, powdery pustules. Anthracnose appears as small, circular leaf spots with dark red margins. Few rose diseases are found under Colorado conditions. The state's dry climate and high altitude are not conducive to the development of most fungal diseases. Viruses commonly associated with roses are not known to be transmitted by Insects.