EARLY DYING (vine) and VASCULAR DISCOLORATION (tuber)

Two species of Verticillium seem to be infective agents, V. dahliae and V. albo-atrum. These cause early dying, or more correctly Verticillium wilt, and vascular discoloration.

I. On vines, this disease is called early dying or Verticillium wilt.

a) Early symptoms start with a wilting appearance on one side of the plant. This can be one or two stems out of several or leaves on one side of a stem and not the other side. When the stem is cross-sectioned, the vascular ring appears dark on one side, semi-circle, as opposed to all the way around as with Fusarium wilt (see description above). This is best observed with a slanting or diagonal stem cut near the soil surface.

b) Later symptoms show the whole plant wilting and the vascular ring is discolored all the way around. Stem decays. At this point, this disease cannot be discerned from Fusarium wilt without microbiological culturing of diseased tissue for fungal growth and identification.

II. On tubers, the disease is called by its principle symptom, vascular discoloration.

The key symptom is the discoloration of the vascular ring starting from the stem end. This may not appear on all tubers from a plant but only on those from the side of the plant first infected. The tuber surface may also show discoloration especially around the eyes. This symptom may be confused with other diseases such as pink eye which does not have vascular discoloration as a symptom. Note some disorders such as too rapid vine desiccation and other diseases may also cause vascular discoloration

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