These are symptoms of ring spot disease that affects members of the brassica family such as sukuma wiki (collard greens), cabbages and cauliflower. With time, tiny black fruiting bodies containing large numbers of spores develop in concentric circles in the centre of the spots, which give the disease the name ring spot. Ring spot affects young seedlings and it is more severe in mature and old plants. The ring spot lesions are grey and contain black, pinheaded dots in concentric circles. Severe ring spots on leaves can reduce growth, delaying harvest and damaging crops that are harvested in leaf.

Source: Daily Nation May 29, 2020 18:11 UTC