The susceptibility of perennial delphiniums to six viruses

Abstract does not appear. First page follows.

Perennial delphiniums (hybrid and horticultural varieties of several species of Delphinium) have been found to be naturally infected with several virus diseases. Three such diseases—California aster yellows, celery calico, and delphinium ringspot—have been reported in previous papers ⁽⁵⁾, ⁽⁶⁾, ⁽⁷⁾.3 A fourth—tomato spotted wilt—is reported in this paper. Also, included herein are the results of experimental infection of delphiniums with five other viruses—common cucumber mosaic,4 western cucumber mosaic, tobacco ringspot, ordinary tobacco mosaic, and curly top. None of these five has been found on delphinium in California under natural conditions up to the present time, but the first has been reported by other investigators to occur naturally on this host plant in England.

Tomato Spotted Wilt

Spotted wilt on perennial delphinium has been reported in California by Gardner, Tompkins, and Whipple ⁽²⁾. Smith ⁽⁸⁾, ⁽⁹⁾ reported that considerable damage may be caused to delphinium by the spotted—wilt virus in England and he described the symptoms of the disease as follows: black rings, or numerous double concentric rings, or patches of dead tissue appear on the older leaves. The younger leaves are malformed with edges yellow, necrotic, and inwardly curled. Necrotic patches may develop on the stems and older leaves.

Spotted wilt ranks next to aster yellows ⁽⁶⁾ in seriousness as a disease of delphinium in the coastal regions of California. Entire fields of delphiniums have been observed to be infected with spotted wilt near San Leandro, San Bruno, and Berkeley.