Last year I grew lots of lupins for friends. As they developed I potted them on to larger pots and kept them on capillary matting but this year they were covered in white powdery mildew, I treated them with roseclear. My question is will they continue in the future to suffer from this mould , if that's the case it would be unfair to give them to anyone. Should I destroy them and start again . What can I use to sterilise the matting. All advice greatly appreciated.