Many Thanks for the replies. I’m quite sure it is white rust (Albugo candida) as the leaves are blistered and the new growth is also infected and deformed.
Before I knew what it was we ate the least affected leaves and both times I experienced a low grade allergic reaction – itchy mouth, fatigue – perhaps my system was reacting to the mold? I have bought some hydrogen peroxide and will see if washing the leaves in a dilute solution will help. I have removed all affected leaves and just waiting to see if the plants recover. Other than rotating the crop next year if there any thing I can do to prevent it reoccuring? Cristal
