Effect of Field Distribution of Maize Dwarf Mosaic-Diseased Corn Plants on Yield. Gene E. Scott, Research Agronomist, Agricultural Research Service, U.S. Department of Agriculture, and Professor, Department of Agronomy, Mississippi State University. Eugen E. Rosenkranz, Research Plant Pathologist, Agricultural Research Service, U.S. Department of Agriculture, and Professor, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762. Plant Dis. 65:802-803. Accepted for publication 10 February 1981. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1981. DOI: 10.1094/PD-65-802.

The grain yields of healthy corn (Zea mays L.) plants bordered by healthy or by maize dwarf mosaic (MDM)-diseased plants and of MDM-diseased plants bordered by healthy or by MDM-diseased plants were determined in order to separate the total yield loss caused by maize dwarf mosaic virus into two components, the direct effect on the yielding ability of diseased plants and the indirect effect of the reduced competitiveness of MDM-diseased plants growing next to healthy plants. In the experimental hybrid Mp490 × Mo12, diseased plants bordered by diseased plants yielded 11 and 27% less than healthy plants bordered by healthy plants in 1978 and 1979, respectively. Yields from diseased plants bordered by healthy plants were reduced an additional 16% in each year. Healthy plants flanked by diseased plants did not show compensating yield increases from the reduced competitiveness of the adjacent diseased plants. Our results indicate that in fields with comparable MDM incidence, yield reductions would be greater when diseased plants are randomly distributed than when they are concentrated in pockets in the field.

Keyword(s): maize, maize dwarf mosaic virus strain A, plant-to-plant competition.