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Etiology

Aphid- and Whitefly-Transmitted Cucurbit Viruses in Imperial County, California. J. A. Dodds, Associate professor, Department of Plant Pathology, University of California, Riverside 92521; J. G. Lee(2), S. T. Nameth(3), and F. F. Laemmlen(4). (2)(3)Laboratory assistant, and graduate research assistant, Department of Plant Pathology, University of California, Riverside 92521; (4)Farm advisor, University of California, Cooperative Extension, El Centro 92243. Phytopathology 74:221-225. Accepted for publication 7 September 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-221.

A survey of cantaloupe virus diseases in the Imperial Valley in 1981 detected watermelon mosaic virus-2 (WMV-2) and squash mosaic virus (SqMV), but not WMV-1 or cucumber mosaic virus (CMV). A total of 920 samples were collected from 10 cantaloupe fields between May and June 1981. The most common virus detected was WMV-2, which was present in all samples from plants with mosaic symptoms in eight fields. Two fields had a low incidence of SqMV. WMV-1 and CMV were not detected. Squash leaf curl (SLC) disease, which was observed in melons and squashes and associated with the whitefly, Bemisia tabaci, reached epidemic levels in cucurbit crops in late summer 1981. Symptoms in cantaloupe were less severe than in watermelons and squashes. WMV-1, WMV-2, CMV, and SqMV were not detected in symptomatic plants. Geminate virus particles were associated with field-collected plants of these cucurbit crops. Geminate virus particles were also detected in squash plants experimentally infected with the SLC agent by inoculation with whiteflies. Mechanical transmission of SLC was also achieved, but efficiency was poor. A strong cross-reaction between sap from SLC-infected squash and bean golden mosaic virus antiserum was detected by ELISA. Results of this study show that whitefly-transmitted geminiviruses cause serious field diseases of vegetable crops in Imperial County, California.