Symptoms
- check_circleDark black or dark brown circular spots
- check_circleSpots with a yellow halo around them
- check_circleSpots starting on lower leaves and spreading upward
- check_circleMushy black patches (rot-related)
Causes
- arrow_rightBlack spot fungal disease (Diplocarpon rosae) — primarily on roses
- arrow_rightBacterial leaf spot — spreads in wet conditions
- arrow_rightOverwatering causing tissue rot
- arrow_rightCold water splashed on warm leaves
- arrow_rightFrost damage
- arrow_rightAnthracnose fungal infection
How to Diagnose
Roses with circular black spots with feathery edges and yellow halos almost certainly have black spot disease. Other plants with angular spots limited by leaf veins likely have bacterial spot. Soft, sunken, spreading black patches suggest rot from overwatering or fungal rot.
Treatment
Remove all affected leaves immediately. For fungal black spot on roses: spray with a fungicide (copper, sulphur, or specialist rose fungicide) and repeat weekly. For bacterial spot: improve air circulation, reduce overhead watering, apply copper-based spray. For rot: let soil dry and check roots.
Prevention
Water at the base, not overhead. Ensure good air circulation. Remove fallen leaves from around roses. Use resistant varieties where possible. Apply preventative fungicide in spring on susceptible plants.
Affected Plants
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