University of California

Additional ornamental flowering plants naturally infected with California aster yellows


Henry H. P. Severin
Julius H. Freitag

Authors Affiliations

Henry H. P. Severin was Entomologist in the Experiment Station; Julius H. Freitag was Assistant Professor of Entomology and Assistant Entomologist in the Experiment Station.

Publication Information

Hilgardia 16(12):597-618. DOI:10.3733/hilg.v16n12p597. June 1945.

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The natural infection of some ornamental flowering plants with California aster yellows has already been reported (Severin and Freitag, 1934).4 In California, such infection was found on 8 species in 7 genera belonging to 4 families.

(Severin (1942a), (Severin 1942b) described the symptoms, determined the incubation period of the disease, and reported on vectors of the aster-yellows virus on perennial delphinium and annual larkspur. A later paper (Severin, 1943) dealt with the disease on annual phlox (Phlox Drummondii), apparently the first case of a leafhopper-transmitted virus inducing breaking in color of flowers. In a companion paper the symptoms of this disease on vegetable and seed crops have been described (Severin and Frazier, 1945).

Surveys were made from 1934 to 1943 to determine additional host plants. Field investigations were conducted on the ranches of seed companies; on the University Farm at Davis; and in the canyons of the Montara Mountains, where the production of cut flowers is an important industry.


A detailed account on methods is given in the third paper of this series (Frazier and Severin, 1944).

Host Range of Virus

The host range of the aster-yellows virus among ornamental flowering plants naturally infected includes 45 species and 1 interspecific hybrid in 38 genera belonging to 17 families, including those previously reported (Severin, 1929), (Severin 1942a), (1942b), (1943), (Severin and Freitag, 1934). The season’s duration of each plant is given in the following list:


Myosotis scorpioides L.,*5 true forget-me-not; annual or perennial


Dianthus borbatus L., sweet william; perennial

Gypsophila paniculata L.,* baby’s-breath; perennial

Literature Cited

Frazier Norman W., Severin H. H. P. Weed-host range of California aster yellows. Hilgardia. 1944. 16(12):621-50. DOI: 10.3733/hilg.v16n12p619 [CrossRef]

Kunkel L. O. Studies on aster yellows. Amer. Jour. Bot. 1926. 13:646-705. DOI: 10.2307/2435474 [CrossRef]

Kunkel L. O. Studies on aster yellows. Boyce Thompson Inst. Contrib. 1926. 1:181-240.

Kunkel L. O. Studies on aster yellows in some new host plants. Boyce Thompson Inst. Contrib. 1931. 3:85-125.

Severin H. H. P. Yellows disease of celery, lettuce, and other plants, transmitted by Cicadula sexnotata (Fall.). Hilgardia. 1929. 3(18):543-83. DOI: 10.3733/hilg.v03n18p543 [CrossRef]

Severin H. H. P. Transmission of carrot, parsley, and parsnip yellows by Cicadula divisa. Hilgardia. 1932. 7(3):163-79. DOI: 10.3733/hilg.v07n03p163 [CrossRef]

Severin H. H. P. Potato naturally infected with California aster yellows. Phytopathology. 1940. 30(12):1049-51.

Severin H. H. P. Infection of perennial delphiniums by California aster-yellows virus. Hilgardia. 1942a. 14(8):411-40. DOI: 10.3733/hilg.v14n08p411 [CrossRef]

Severin H. H. P. Viroses of annual larkspurs. Hilgardia. 1942b. 14(10):549-61. DOI: 10.3733/hilg.v14n10p549 [CrossRef]

Severin H. H. P. Breaking in color of flowers of annual phlox caused by the aster-yellows virus. Phytopathology. 1943. 33(8):741-43.

Severin H. H. P., Freitag J. H. Ornamental flowering plants naturally infected with curly-top and aster-yellows viruses. Hilgardia. 1934. 8(8):233-60. DOI: 10.3733/hilg.v08n08p233 [CrossRef]

Severin H. H. P., Frazier Norman W. California aster yellows of vegetables and seed crops. Hilgardia. 1944. 16(12):573-96. DOI: 10.3733/hilg.v16n12p573 [CrossRef]

Severin H, Freitag J. 1945. Additional ornamental flowering plants naturally infected with California aster yellows. Hilgardia 16(12):597-618. DOI:10.3733/hilg.v16n12p597
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