Black Ring, a Virus Disease of Cabbage and Other Crucifers'

A virus disease of cabbage (Brassica olerácea Li. var. capitata L.), designated as black ring, is prevalent mainly during the winter and spring seasons near San Pablo and Colma in the San Francisco Bay section and in the Sacramento, Salinas, and Santa Clara Valleys of California (18).^ Other crucifers of more importance ill California, including Brussels sprouts (B. olerácea L. var. gemmijera DC.) and cauliflower {B. olerácea L. var. botrytis L.) are also highly susceptible to infection. The results of field and greenhouse studies of this disease, in progress since 1932, are presented in this paper.