Additional virus diseases of spinach in California

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Summary

Spinach was demonstrated to be naturally infected in California with sugar-beet mosaic and two cucumber mosaics—western cucumber mosaic and celery calico. Nine varieties of spinach were experimentally infected with the two cucumber mosaic viruses, five with sugar-beet mosaic. The three viruses were recovered from naturally infected spinach and transferred by mechanical inoculation to White Spine cucumber (Cucumis sativus), Turkish tobacco (Nicotiana tabacum), N. glutinosa, or sugar beet (Beta vulgaris).

The symptoms of these three diseases on spinach are similar. Filamentous leaves occur only in western cucumber mosaic. But cleared venation, chlorotic spotting, blisterlike elevations, and necrosis occur in all three. The viruses can be distinguished by transferring them to sugar beets; on that host the symptoms are sufficiently distinctive to permit identification.

New Zealand spinach (Tetragonia expansa) was experimentally infected with western cucumber mosaic, and the virus was recovered and transferred to White Spine cucumber and sugar beet.

The green peach aphid, Myzus persicae (Sulzer), is the most important vector of the western-cucumber-mosaic, celery-calico, and sugar-beet-mosaic viruses to spinach under natural conditions. The bean or dock aphid, Aphis rumicis Linnaeus, rarely transmits these viruses.

Introduction

Five virus diseases have been reported to occur on spinach (Spinacia oleracea, family Chenopodiaceae) under natural conditions in California; namely, aster yellows (Severin, 1934); (Severin and Frazier, 1945),3 sugarbeet curly top (Severin and Henderson, 1928); (Scott, 1935), sugar-beet mosaic (Severin and Drake, 1948), spinach yellow dwarf (Severin and Little, 1947), and spotted wilt (Gardner, Tompkins, and Thomas, 1937)

This paper deals with two additional naturally occurring virus diseases of spinach—western cucumber mosaic and celery calico—and with sugar-beet mosaic on this host. Studies were made of the succession of symptoms on naturally and experimentally infected spinach caused by the three viruses. The symptoms of western cucumber mosaic were also studied on New Zealand spinach, Tetragonia expansa, which belongs to the family Aizoaceae. No insect-transmission tests are reported here. But previous reports on aphid transmission and on the aphid species naturally occurring on spinach are reviewed to determine which species are important vectors of the viruses.