Black Spot
[NOTE: Diplocarpon rosae causes black spot on roses (Rosa spp.); Septoria and...
15 host plants · Fungal
Last updated
Circular black spots with yellow halos develop on leaves. This fungal disease favors wet foliage. Improve air circulation and remove fallen leaves.
Plant cultivars known to be resistant in your area. Note that the cultivar Carefree Spirit was the first landscape shrub to survive for 2 years in AARS tests without any fungicide and voted a winner.
What Should I Do?
- Plant cultivars known to be resistant in your area.
- Note that the cultivar Carefree Spirit was the first landscape shrub to survive for 2 years in AARS tests without any...
- Avoid dense plantings and shaded areas.
Quick Reference
Management
Apply frequently in wet spring weather and occasionally in summer.
Infection occurs when temperatures are 65-75°F (optimum 72°F) with 7+ hours continuous leaf wetness. Spore germination requires free water on leaf surfaces. Disease most severe during warm, humid weather with frequent rain or overhead irrigation. Below 60°F infection slows significantly; above 85°F spore germination is inhibited. In western WA, the spring/fall moisture requirement is frequently met. Source: Horst (1983) Compendium of Rose Diseases; PNW Plant Disease Management Handbook.
Cultural Controls
- Plant cultivars known to be resistant in your area.
- Note that the cultivar Carefree Spirit was the first landscape shrub to survive for 2 years in AARS tests without any fungicide and voted a winner.
- Avoid dense plantings and shaded areas.
- Avoid overhead watering that keeps plants wet for extended period of time.
- Rake up and burn all leaves in a rose planting at season's end.
- Prune canes back to two buds if canes are infected.
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