95% confidence
Based on 20,000+ analyzed cases
Black Spot Fungus on rose
What's Happening
Diplocarpon rosae fungus thrives in warm, wet conditions (75°F/24°C). Spores splash from infected fallen leaves onto lower foliage during rain or overhead watering, causing circular black spots with fringed edges followed by rapid yellowing and leaf drop.
How to Fix It
- 1
Remove and destroy all infected leaves immediately (do not compost)
- 2
Rake up and dispose of fallen leaves around the base
- 3
Apply a fungicide containing chlorothalonil, copper soap, or neem oil every 7-14 days
- 4
Prune to open the center of the bush for better air circulation
How to Prevent It
Water at the base of the plant only, keeping foliage dry. Apply fresh mulch in early spring to prevent soil-borne spores from splashing up. Choose disease-resistant varieties.
Related Problems
Frequently Asked Questions
What causes black spot fungus on my plant?
Diplocarpon rosae fungus thrives in warm, wet conditions (75°F/24°C). Spores splash from infected fallen leaves onto lower foliage during rain or overhead watering, causing circular black spots with f...
How do I fix black spot fungus?
Remove and destroy all infected leaves immediately (do not compost). Rake up and dispose of fallen leaves around the base.
How do I prevent black spot fungus from happening again?
Water at the base of the plant only, keeping foliage dry. Apply fresh mulch in early spring to prevent soil-borne spores from splashing up. Choose disease-resistant varieties.