Scientific name
Diplocarpon rosae
Common Names
Black Spot, Rose Black Spot
Black Spot is one of the most common fungal diseases affecting roses throughout Australia. It thrives during warm, humid weather and prolonged periods of leaf wetness, particularly where air circulation is poor or overhead irrigation is used. The disease first appears as black, feathery-edged spots on leaves, often surrounded by yellowing tissue. As the disease progresses, infected leaves turn yellow and drop prematurely, weakening the plant and reducing flowering.
Similar Diseases
- Powdery Mildew (Erysiphe spp.)
- Downy Mildew (Peronospora spp.)
- Botrytis Grey Mould (Botrytis cinerea)
- Cercospora Leaf Spot (Cercospora spp.)
SCENARIOS AND SOLUTIONS
At the first signs of black spots on rose leaves: Apply Copper Oxychloride to protect healthy foliage and slow disease spread.
During warm, humid periods favouring Black Spot: Apply Apparent Mancozeb 750 preventatively before extended periods of leaf wetness.
On roses with recurring Black Spot each season: Rotate Copper Oxychloride and Apparent Mancozeb 750 as part of an integrated disease management program.
In densely planted rose gardens: Remove infected leaves, improve airflow, avoid overhead watering and maintain a preventative fungicide program using registered products.
References
https://www.agric.wa.gov.au/plant-diseases/black-spot-roses
https://www.rhs.org.uk/disease/rose-black-spot
