Runner Bean leaf problem ?

Hi Harry, sorry didn't notice your post first of all.

I've never seen this on Runner Beans. There is something similar called Chocolate Spot that is quite common on Broad Beans but I've never seen it on runners (or French in your case). It does look like Chocolate spot, but whatever it is I'm sure the horrid cold wet weather is to blame. Hopefully it's just a few of your lower leaves. If the stems are infected that is bad news.

 

I don't know what it is, either . I'd remove any leaves that look as though they have been affected.

I don't think chocolate spot affects runners. Very few diseases affect them but the commonest one is halo blight - and that doesn't look like it at all. The only other thing I can think of is anthracnose and I can't see any red markings around the pockmarks, so don't think it's that either. Anyway, you couldn't use Bordeaux Mixture (doesn't cure it but prevents it getting worse) as you mustn't use it if there are flowers on the plants.

Did you buy the seed or did you save them from previous years?

Hopefully it isn't either of those and is just a bad reaction to the weather. Remove affected leaves and hope for the best.

 

So it could be the weather causing it. If it is anthracnose (you should be able to see a red border around the pockmarks) then it's likely that the beans you bought came from diseased plants (damp conditions encourage the disease).

Give the plants a little time to see whether they grow OK once you have removed the affected leaves (in which case it's not anthracnose) - make sure you burn them or put them in your green waste bin. If there is a possibility that it's the dreaded lurgy then make sure you don't transfer it to your other beans and don't plant beans in that part of the garden for a couple of years.

Next year, to be on the safe side, you could give them an early dose of Bordeaux Mixture but make sure it's before the flowers start to form.