Barley yellow dwarf virus causes extreme stunting and discoloration of leaves. Leaf blotches that are yellow, orange, or red develop until entire leaves are involved. Plants along the edges of fields are usually affected first. Severely affected plants produce little or no grain. The virus is spread by several species of aphids, which are more active under warm conditions in the late spring and summer.
Plants infected in the seedling stage are the most severely damaged.
Early planted oats typically suffer less yield loss, because they are older during the period of the greatest aphid activity. The virus can infect all cereal grains, corn, and grass weeds. Barley yellow dwarf virus is not considered an important corn disease in Iowa. April 20 is the average planting date for oats in Iowa. If oats are planted in cold wet soil, they will be affected by seedling blights, but if the soil is dry enough, earlier planting will help reduce losses to crown rust and barley yellow dwarf.