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Disease Note.

Outbreak of Sorghum Stunt Mosaic Virus in Corn in California and Arizona. D. E. Mayhew, California Department of Food and Agriculture, 1220 N Street, P.O. Box 942871, Sacramento 94271-0001. . Plant Dis. 73:444. Accepted for publication 20 February 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0444A.

Sorghum stunt mosaic virus (SSMV) is a rhabdovirus previously reported as a minor disease of sorghum in the Imperial Valley of California (1). A severe outbreak of this virus occured in the fall of 1988 in late-planted commercial sweet and hybrid seed corn (Zea mays L.) in Imperial and Riverside countie, California, and Yuma County, Arizona. All 19 fields (2,500 acres) in the Imperial Valley had a high incidence(60%) of infection. Identification of SSMV was based on symptoms, particle morphology, and cytopathology. The leafhopper vector Graminella sonora (Ball) was present in and around affected fields. Symptoms included stunting, mosaic, yellowing and poor seed set. None of the known hosts of this virus is normally grown in the fall in the Imperial Valley. A late crop of corn was planted in the desert southwest in response to the shortage of seed corn following a severe summer drought in the midwestern United States. The late cropping, coupled with unseasonably warm fall weather, may account for the severe outbreak of SSMV that year. This is the first report of a natural infection of corn with SSMV and the first find of the virus in Arizona.

Reference: (1) D.E. Mayhew and R.A. Flock. Plant Dis. 65:84, 1981.