Rose Guide
How to Treat Black Spot on Roses
Remove and destroy infected leaves, clean up all fallen debris, water only at the base, and improve airflow. For susceptible roses, apply a fungicide preventively. Long term, switch to resistant varieties.
Black spot is a fungal disease that spreads in wet, still conditions. At the first sign — black, fringed spots with yellowing — pick off affected leaves and clear every fallen leaf from the ground, since the fungus overwinters there.
Prevent its return by watering at the base to keep foliage dry, spacing plants for airflow, and applying a preventive fungicide on prized but susceptible roses. The most durable solution is to grow disease-resistant varieties, which shrug black spot off with no spraying at all.