Rose Black Spot (Diplocarpon rosae)
Rose (Rosa spp.) ยท Black or Dark Spots
Distinct circular or irregular dark blemishes, often surrounded by yellow halos.
Diplocarpon rosae fungus thriving on foliage kept damp for longer than 7 hours by rainfall or overhead sprinklers.
Possible causes
- Overhead watering splashing fungal spores from old leaf litter
- High humidity combined with stagnant air around dense canes
- Susceptible modern hybrid tea rose varieties
Care steps
- Rake up and discard all fallen spotted leaves: Never compost diseased rose foliage.
- Prune overlapping interior branches: Open the center vase structure to maximize breeze and sun penetration.
- Apply organic sulfur or copper spray: Coat both top and underside of remaining healthy canes.
Prevention tips
- Always irrigate roses at soil level in early mornings
- Dormant oil spray in late winter to suppress overwintering spores
- Apply 5cm organic compost mulch to trap spores under soil