ring spot

any of various plant diseases caused by a virus or fungus and characterized by concentric rings of discoloration or necrosis on the leaves.

Origin of ring spot

First recorded in 1905–10

In this way the first ring-spot probably arose in some species on only one—the penultimate segment.
Studies in the Theory of Descent (Volumes 1 and 2)|August Weismann
The formation of the second ring-spot sometimes takes place in the present stage (Fig. 42).
Studies in the Theory of Descent (Volumes 1 and 2)|August Weismann
At a later period these two222 crescents and also the two primary nuclei coalesce, producing a ring-spot which, as in Fig. 61, Pl.
Studies in the Theory of Descent (Volumes 1 and 2)|August Weismann
On the first segment only there is210 no spot, and here no ring-spot is afterwards formed.
Studies in the Theory of Descent (Volumes 1 and 2)|August Weismann