Description and Symptoms
Maize dwarf mosaic (Maize dwarf mosaic potyvirus) is seldom observed in Iowa. Infected plants have a stippled (small, discolored specks) mottle or mosaic of light and dark green that may develop into narrow streaks on the youngest leaves. There may be a shortening of internodes causing a stunted, bunchy appearance of the plant. As plants mature and temperatures rise, mosaic symptoms often disappear and the young leaves become more yellow. Infected plants are predisposed to root rot and may be barren or have small ears with kernel abortion. The causal virus overwinters in weeds, primarily in johnsongrass, and is transmitted to corn by several species of aphids. Resistant hybrids are available. Weed management will reduce the spread of the disease from grasses.
The best time to scout for mazie dwarf mosaic is after an aphid outbreak, as several aphid species transmit the virus.
This disease is more common in fields with nearby Johnsongrass (virus host located only in southern Iowa) and on late-planted corn. It (mazie dwarf mosaic) rarely occurs in Iowa.
Photo by Grau