Rose Bush Leaf Diseases

Rose leaf diseases, in addition to being unsightly, also pose a risk to the health of the rose bush. They are easy to identify, but can be difficult to eradicate. Prevention is the best strategy.

Types of rose leaf diseases

There are three common rose leaf diseases, all of them fungal: powdery mildew (Sphaerotheca pannosa var. rosa), rust (Phragmidium mucronatum), and downy or black spot mildew (Peronospora sparsa).

Identification

The names of the diseases accurately describe their appearance. You'll know your rose is infected if you see powdery, rust-colored or black spots forming on leaves, and spreading across the plant.

Warning

All three diseases can completely defoliate a rose bush, weakening and eventually killing it. Remove infected leaves as soon as you spot them, and burn them to prevent the fungus spores from traveling to other leaves or even other nearby rose bushes.

Prevention/Solution

Rose leaf diseases thrive when nights are damp and days are hot and moist. Avoid overhead watering of roses, which can spread the spores and encourage disease; water instead at the base of the rose, or use an underground soaker hose or other irrigation system. Healthy roses are more resistant, so appropriate feeding, watering and pruning of your roses will also help prevent disease.You can also take care to buy roses varieties that are disease-resistant.

Remedies

Once a rose bush is infected, chemical sprays designed to fight rose fungus diseases can be used. However, these sprays can be more toxic to some roses than the disease itself; this is especially true of some heirloom or old garden roses.

References

• Rose Gardening Made Easy
• The Complete Book of Roses; John Mattock, Sean McCann, Fred Witchell and Peter Wood; 1994