Sooty mold on runner beans

[Colin Miles]

Although my runner beans have nearly finished a couple of plants have suddenly decided to produce quite a few flowers and as they are self-pollinated they are also starting to produce beans. However, in the last couple of days the leaves of most of the plants which have finished have suddenly become covered with what I assume is sooty mold. Should I just pull them all up? We have had a fantastic crop so I wouldn't be too disappointed to loose those remaining.