Garden Q&A: Could anti-fly spray be causing my lupins to die?

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

Lupins flourishing in summer at Lake Tekapo, New Zealand. Picture: iStock

What has happened to my beautiful lupins? All of a sudden they began to die, about a fortnight ago, and I don’t know why. They were flourishing, with new flowers ready to take over from the ones I needed to cut. I use an anti-fly spray on them to protect them, but it has never adversely affected them before. 

ANSWER 

Firstly, it could well be the spray that you used that has caused this and I would advise disposing of it carefully and using more organic and straightforward ways of dealing with flies and aphids. 

However, it is more likely to be one of two fungal infections — namely either Lupin anthracnose or Lupin root rot, phytophthora.

In any event, the name is incidental as the symptoms and reasons for the infection or similar for both. 

Wet, poor-draining soil is what leads to the development of these fungal infections and so, improving the drainage will help in the long term. 

I always plant lupins a few inches above soil level for this reason so that the crown isn’t sitting in wet soil and whilst we have enjoyed some beautiful sunshine this summer, we have also experienced periods of intense rainfall.

Remove all signs of infected growth now, even if this means removing all foliage and stems to ground level and drench with a solution of copper sulphate and water. 

Unfortunately, I can't promise that the plants will come back — but cross your fingers.

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