One plant may show symptoms early in the season, while another not until after pollination. Diseased plants are often found in spots or centers within a field. First symptoms of MDMV appear in younger leaves as indistinct light and dark green mottling between the veins, or as elongated pale green blotches and interrupted stripes. The blotches and stripes often merge, and the leaves become quite yellow, giving plants a pronounced yellowish cast. Corn plants showing this mosaic pattern are often dwarfed or stunted due to a shortening of the upper internodes.
Some plants show only moderate stunting.
Reduced ear size, barrenness and poor seed set may be involved in very susceptible strains of corn. Diseased plants may have none to several ear shoots. In general, ears remain poorly filled on plants infected early in the season. MDMV can be transmitted mechanically by sap from infected plants, using susceptible corn seedlings as assay plants. Under the electron microscope, MDMV is characterized as flexuous, rod-shaped particles.