Pathogen. The viroid persists in infected seed tubers. It is transmitted by direct contact and by any mechanical operation that involves the release of plant sap, such as seed cutting, seed handling and crop cultivation.
Symptoms. High temperatures early in the growing season promote the development of symptoms. This disease has been eliminated from Canadian potato stocks.

and have fewer stems than healthy
plants. Leaves are smaller than normal
and are folded upward with wavy
margins. Leaves are attached to the
stem at acute angles.

pointed at the stem end than normal. The eyes
are more numerous and may protrude or be
shallower than those of healthy tubers.