Black Spot
Diplocarpon rosae
Overview
A serious fungal disease primarily affecting roses, causing circular black spots with fringed margins on leaves. Infected leaves yellow and drop, weakening the plant over successive seasons.
Symptoms
Circular black spots with feathery, fringed margins on upper leaf surfaces. Leaves yellow around spots and drop prematurely. Stems may develop dark purple-red blotches. Severe defoliation weakens plants.
Environmental Conditions
Humid
Prevention
Plant resistant rose varieties. Ensure good air circulation. Water at the base, not overhead. Remove fallen leaves promptly. Apply preventive fungicide sprays in spring.
Management
Apply neem oil, sulfur, or copper fungicides every 7-14 days during wet weather. Remove and destroy all infected leaves including fallen ones. Prune to improve airflow.