Effect of Maize Dwarf Mosaic Virus Infection on Yield and Stalk Strength of Corn in the Field in South Carolina. Graydon C. Kingsland, Associate Professor, Department of Plant Pathology and Physiology, Clemson University, Clemson, SC 29631. Plant Dis. 64:271-273. Accepted for publication 26 November 1979. Copyright 1980 American Phytopathological Society. DOI: 10.1094/PD-64-271.

Infection of two cultivars of corn (Zea mays) in the field by maize dwarf mosaic virus (MDMV) resulted in statistically significant reductions in yield and fewer kernels per ear when diseased plants were tagged for identification at harvest and yields and kernel numbers were compared with those obtained from adjacent “nearest neighbor” symptomless plants. All diseased plants were rated 1.4 for severity of infection; 5% of the plants of both cultivars were diseased. Yields of individual diseased plants varied widely. The severity index did not provide an accurate indication of yield. Extrapolation of yield data from individual plants indicated that an average yield reduction of 62% could occur under circumstances of 100% disease incidence. Each 1% increase in disease incidence was responsible for a loss of an average of 63 kg/ha of grain. Infection by MDMV also resulted in statistically significant reduction in stalk strength, as determined by the kilograms of force required to exceed the resistance of the stalks to bending. Stalks from diseased plants were smaller in diameter than those from symptomless adjacent plants. Stalk diameter appeared to be one factor that determined stalk strength. No stalk lodging occurred in the field.