Foot Rot in Runner Beans
Sorry to hear you are having problems with your runner beans.
I believe it may be something called Foot Rot – this is a fungus that causes plants to rot at ground level, this may occur if runner beans have been planted too often on the same site.
Various books advise to water with a Chestnut Compound, this is available from garden centres but unfortunately it is not organic as it contains a Copper Sulphate & Ammonium carbonate mix. My advice is not to overwater and move your beans to a fresh site next year.
Lynn Burton - Horticultural Advisor