Garden Q&A: How should I treat mildew and blight on 'Red Robin' shrubs?

Whether you're a gardening beginner or expert, Irish Examiner columnist Peter Dowdall has the answer to your questions

The red and green leaves of Photinia fraseri 'Red Robin' shrub. File picture

Question

My Photinia 'Red Robin' shrubs have brown spots, powdery mildew and fireblight. Is copper sulphate pentahydrate suitable to treat them?

Answer

Copper sulphate pentahydrate can be used to help manage some of the issues affecting your Photinia 'Red Robin', particularly fungal leaf spot and, to some extent, fireblight — though it’s more of a preventative than a cure.

However, it's not effective against powdery mildew, which is better treated with a sulphur-based spray or potassium bicarbonate. 

If you choose to use copper sulphate, apply it carefully during cooler, overcast periods to avoid leaf burn. 

It’s also most important to prune out infected growth and thus, improve air circulation through the plant. 

I would follow up any treatment with a good quality general-purpose plant food such as Fast Grow mix of seaweed and chicken manure pellets.

• Got a question for Peter Dowdall? Email [e-mail]