Often there is little obvious damage occurring, and the symptoms may become masked or disappear. When both viruses are found in the same plant, however, a bright greenish-yellow mottling develops in the leaves. In contrast tothe single infections where the plants may outgrow the mosaic symptoms, the bright greenish-yellow mottling of CLN persists to the end of the growing season. Toward the end of the season, leaves may die inward from the margins with eventual death of mature plants, usually from the top down. Ears may be small, often distorted, and have limited or no kernel development.
Infected plants are frequently barren, especially if infection is early.
Corn plants are susceptible at all stages of development, from seedling stage to near maturity. The bright greenish-yellow symptoms usually are not seen, however, before late June or early July. Symptoms will only occur on leaves that emerge after infection takes place. A plant infected later in the season may have a poorly filled ear with premature drying of the husks but no leaf mosaic symptoms. An outbreak of MCMV in a Hawaiian breeding nursery has been linked to thrips.