There is nothing as disheartening as watching your rose plants getting affected by disease or fungus, after all the hard labor that you have put in to see its growth and development. Rose plants weaken during winter dormancy and become more prone to afflictions as soon as the growing season starts.
 
Even after the survival of the winter cold, the rose bush is subjected to spring rains and the heat of summer when it can attract a variety of fungal infections.
 
Here is a brief summary of some of the common ailments affecting rose plants :

Powdery Mildew

A kind of fungal infection which manifests itself  in the form of a powdery substance along the top, bottom of the leaves as well as the stem. If you don’t treat this, the disease retards the plant growth and soon the leaves die and fall off.

Rust

This looks like an orange powder which you can see on the underside of leaves , which soon spreads to other parts of the plant.

Blackspot

While hybrid teas can resist an attack of this disease, other varieties of roses are often victims of blackspot. It shows itself as round black spots on the leaves with a diameter ranging between 1/16 to ½ inch. If you don’t treat this disease, it can destroy the foliage.

Rose Mosaic

While most rose infections are fungal in nature, this is caused by a virus. It manifests itself by discolored mosaic patterns of yellow and green.
 
The only way you can get rid of this disease is to remove the infected plant from your garden, along with any leaf or clippings which may have fallen from the plant.
 
If you find that you are unable to check the fungal infections yourself, you can call a professional garden supply person and ask for various fungal/viral treatment products which are available commercially.
 
Here are some tips which can help you avoid fungal infections :

Remember to water the soil around the rose plant. Never water the plant itself.
 
Rose beds should be cleaned thoroughly and regularly. Do not let clippings and fallen leaves litter the rose bed.
 
If you notice any diseased cane or bloom, remove it immediately and put them away in a trash bin.

Prune your rose bushes regularly. And remember to prune the centre of the bush, whch will allow more fresh air circulation.
 
Remember to seal all the cuts with Elmer’s Glue. It is effective, safe and affordable.
 
Give your roses proper nutrition. Wee-fed roses are more disease-resistant.
 
Last but not least important thing to remember is to choose roses that are resistant to diseases. This is particularly important if your home is in a hot and humid area. Please remember that disease-resistant does not mean that the roses can never contract any ailment. It means that there are less chances of it getting affected by ailments, if you follow the tips provided here.