By Kris Collins
A former national collection holder will not grow Canna cultivars again because of damage caused by two prolific viruses attacking UK plants.
Nottingham-based Ian Cooke destroyed around 500 cultivars towards the end of last year because Canna yellow mottle virus and bean yellow mosaic virus had spread via aphid infestations.
The situation has got so bad, according to Cooke, that in just four to five years, most stocks in the US and Europe have become infected with one or both of the viruses.
The RHS abandoned trials at Wisley two years ago because the site was hit by the viruses.
Canna yellow mottle virus causes distortion, stunting and chlorosis of the leaves, while bean yellow mosaic virus causes a pale speckling to leaves.
RHS trials recorder Jacquie Gray said: “Unfortunately, we found the two viruses to be endemic to Canna. Without realising it, some of the plants were infected and this spread to other stocks in the trial.
“The only control is to remove infected material and then regularly spray plants to control aphids. I would advise anyone who has bought infected pants to take them back or burn them.”
Cooke’s decision leaves just one national collection of Canna, tended by Hampshire-based Hart Canna owners Keith and Christine Hayward. They have kept on top of the viruses by removing infected leaves and regularly spraying plants to protect against aphid attack.
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