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Disease Note. Sorghum Downy Mildew on Sweet Corn in Central Illinois. J. K. Pataky, Department of Plant Pathology, University of Illinois, Urbana 61801. N. R. Pataky, and D. E. Fisher. Department of Plant Pathology, University of Illinois, Urbana 61801, and Del Monte Research Center, P.O. Box 9004, Walnut Creek, CA 94598. Plant Dis. 74:183. Accepted for publication 7 November 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0183E. Sorghum downy mildew, caused by Peronosclerospora sorghi
Weston & Uppal, was found in Fulton County, Illinois, in an 80-
ha field of sweet corn (Zea mays L. 'Excellency' and Del Monte variety
20-35) that had been double-cropped after wheat. "Half-leaf" and
"strap-leaf" symptoms and conidia on the underside of leaves were
observed. Incidence of systemically infected plants varied in the field
from 0.5 to 90% and averaged 10-15% for the entire 80 ha. Oospores
were found in leaves that were soaked in water for 48 hr. Sorghum
downy mildew also was found on a wild species of sorghum growing
as a weed in adjacent fields, 50-80 m from the sweet corn. The infected
Sorghum sp. may have been a source of conidia that caused systemic
infection of sweet corn seedlings, or soilborne inoculum (oospores)
may have increased on the weed host when the 80-ha field was planted
to soybeans the previous year. P. sorghi occurs on corn in southern
regions of the United States (1,2), but this report is the first of which
we are aware of P. sorghi causing a significant amount of disease
on sweet corn in central Illinois. |