Scout Info Kentucky IPM Pest Information Pages Virus Complex Symptoms Corn plants affected with the virus complex generally lack vigor, have an off-green to yellowish color, may be stunted and may develop reddening of leaves in mid to late season. Closer examination of leaves may reveal mottling, yellow to dark-green mosaic patterns or light green to yellow streaks and stripes in leaves. Nutrient problems can sometimes be confused with the virus complex. However, nutrient problems generally affect plants in an area whereas viruses often, but not always, appear to strike individual plants or small clusters of plants, which may or may not be surrounded by healthy plants. Cause Viruses are often found in fields with a rhizome johnsongrass problem and where susceptible corn hybrids are grown. The photograph at left shows johnsongrass that is infected with a virus and shows the typical streaking in the leaves. IPM Techniques Examine the field once per month in June, July and August. Observe two rows of plants 10 feet in length at several representative locations. Report severity of the disease according to the following rating scale: 0 = no virus symptoms observed 1 = 1-4% of plants showing symptoms, plants have an off-green color, little or no stunting 2 = 5-20% of plants showing symptoms, definite off-green color, some plants stunted 3 = greater than 20% of plants showing symptoms, definite stunting in many of the plants, some plants have reddish leaves, ears are absent or small and poorly developed Plant non-susceptible hybrids. Eliminate johnsongrass rhizomes in and around the field. References and Additional Information IPM-2 Kentucky Corn Manual PPA-10a Kentucky Plant Disease Management Guide for Corn and Sorghum, P. Vincelli and D.E. Hershman, Extension Plant Pathology, University of Kentucky Compendium of Corn Diseases. M. C. Shurtleff. American Phytopathological Society. 1980.

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