Additional ornamental flowering plants naturally infected with California aster yellows

Abstract does not appear. First page follows.

Introduction

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.

Methods

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:

Boraginaceae:

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

Caryophyllaceae:

Dianthus borbatus L., sweet william; perennial

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