Treating Black Spot On Roses

Treating Black Spot On Roses

This year we have a lot of ‘black spot’ on the second flush of roses. Is the fungus within the rose itself or just affecting the leaves? I’ve been cutting off infected leaves and keeping them away from the plants, but some new growth still shows signs. Can you help?

Black spot is one of the most prevalent fungal diseases on roses in New Zealand. It must be prevented as once it is in the leaves it cannot be cured and will spread very quickly. 

While some rose varieties are highly resistant, others are particularly vulnerable. Warm, humid midsummer conditions create the perfect environment for black spot to thrive.

Tips for Prevention and Management:

  • End of Growing Season: Remove all old leaves and small twigs from your roses to stop the fungus from overwintering in your garden.
  • Winter Care: Apply copper oxychloride and horticultural oil during the dormant months to ensure clean spring growth.
  • Summer Care: Use Shield fortnightly during summer flowering to help control outbreaks.
  • If a particular rose variety struggles with recurring black spot, consider replacing it with a more resistant type to reduce ongoing issues.
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