Foliar symptoms of bacterial ring rot gene … Foliar symptoms of bacterial ring rot generally appear at mid-season or later. Yellow areas develop on leaf margins or between veins and later turn brown, giving the leaves a burned appearance. Plants with advanced symptoms show vascular discoloration and milky, viscous bacteria may be forced from cut stems. In tubers, symptoms may occur before harvest or in storage. Rot begins as a brown necrosis in the vascular ring and progresses to surface. Cracks may appear on surfaces of tubers, which are frequently nothing more than hollow shells. requently nothing more than hollow shells.