Rose Bush Diseases & Cures

Disease-free rose bushes burst with blooms.

A healthy rose bush is the ideal, but problems sometimes crop up even in the most well-tended gardens. Knowing your rose diseases and how to combat them will help you grow strong and vigorous rose bushes.

Black Spot

Rose bushes defoliate from black spot, a disease caused by the fungus Diplocarpon rosae. Symptoms include circular black spots on the upper side of leaves followed by yellowing. Black spot is spread by splashing water and thrives when leaves remain wet. Clean up diseased leaves on a regular basis, avoid overhead watering and apply a fungicide.

Botrytis Blight

Botrytis blight causes flower buds to droop, brown and decay without opening. Symptoms include a gray lesion below the flower head. Botrytis occurs when water remains on flower buds. Avoid overhead watering, destroy all infected flowers and apply a fungicide.

Powdery Mildew

Powdery mildew causes a damaging white-powdery coating on leaves and buds. The condition comes from the fungus Sphaerotheca pannosa, which is spread by wind. It usually occurs during hot, dry days and humid nights. Destroy spores by rinsing foliage and apply a fungicide.

Rust

Rust creates orange powdery lesions on leaves. It is caused by several rust fungi of the genus Phragmidium that travel by wind. It often occurs when rainfall is followed by sunny conditions. Avoid overhead watering and treat with a fungicide.

References

• University of Minnesota Extension: Rose Diseases
• Oregon State University Extension Service: Controlling Diseases and Aphids on Your Roses

Resources

• North Dakota State University: Roses