A MOSAIC DISEASE of PRIMULA OBCONICA and ITS CONTROL' a Mosaic Disease of Primula Obconica Hance, Grown Extensively As a Potted
A MOSAIC DISEASE OF PRIMULA OBCONICA AND ITS CONTROL' By C. M. ToMPKiNS, assistant plant pathologist, and JOHN T. MIDDLETON, junior plant pathologist, California Agricultural Experiment Station ^ INTRODUCTION A mosaic disease of Primula obconica Hance, grown extensively as a potted ornamental plant in commercial greenhouses in San Fran- cisco, was first observed in August 1937. The incidence of the disease on very young to older seedling plants ranged from 5 to 25 percent and, because infected plants could not be marketed, serious financial losses were incurred. The results of studies on transmission, experimental host range, and properties of the virus, as well as control of the disease, are presented in this paper. REVIEW OF LITERATURE That many cultivated species of the genus Primula are generally susceptible to virus infection is indicated in the literature. In addi- tion to the mosaic diseases, the aster yellows, curly top, spotted wilt, and certain tobacco viruses may cause infection. Since this paper deals with a mosaic disease, only pertinent references are listed. In Japan, Fukushi (4.y in 1932 and Hino (6) in 1933 recorded the occurrence of a mosaic disease on Primula obconica. The latter also observed a similar disease on P. denticulata Sm. Smith (13) in England, in 1935, described a virus disease of the mosaic type on Primula obconica caused by cucumber virus 1. Later, Smith (14) stated that Cucumis virus 1 sometimes caused color break- ing of the fiowers and that other species of Primula were susceptible. Cucumis virus IB, a strain, induced '^a pronounced yellow and green mottling.'' In Germany, Ludwigs (7) and Pape {8) described very briefly a virus disease of Primula obconica without apparently establishing the identity of the virus.
[Show full text]