By Nathan Kleczewski
Extension Specialist- Plant Pathology
Barley yellow dwarf (BYDV) is reported to be the most widely distributed virus in cereals. Under the right conditions, it can substantially reduce yield and grain quality. Losses upwards of 40% in barley and 25% in wheat are not uncommon in some areas where small grains are grown. The amount and type of damage caused by BYDV varies with the viral strain/species, growth stage at which the plant is infected, plant species, cultivar, and environment.
Symptoms of BYDV are highly variable, and range from discolored flag leaves, to stunting and grain reduction. In affected barley, foliage may be more golden yellow whereas whereas in wheat foliage may develop a orange/red/purple color. Foliar discoloration typically develops from the tip downward. Black specks as well as leaf puckering along and erect leaves may accompany foliar discoloration. Typically it takes 2-4 weeks for symptoms to start to develop after infection.
Stunting and reduction in tillering often is a result of Fall infections, whereas discoloration of the flag leaf without stunting indicates infection in the Spring. Plants can be found scattered throughout a field or found in round patches. Distribution of the virus is a result of the activity of aphids, which carry the virus and transmit it to new plants
The most important and common aphids that can carry and transmit the virus include the English grain aphid, the Bird Cherry Oat Aphid, the Corn Leaf Aphid, and the Greenbug. When an aphid acquires BYDV it can transmit it for several weeks. Thus, a single aphid can be responsible for transmitting the disease to several plants within or even between fields. Infections of small grains in the fall, while the plants are small, may be more severe than when compared to infections that occur later in the growing season. Early infections can directly reduce yield by causing stunting and reducing tillering (Figure 2). Where do the aphids pick up the virus between crops? Well, they pick it up in volunteer wheat, oats, and barley. BYDV can also be found in numerous other grass species.
Management of BYDV is geared at limiting aphid activity and the potential for virus transmission. Planting small grains later in the season, after the Hessian fly free date can potentially limit the amount of time the crop may be exposed to aphids early in their development. Good scouting and aphid management should be followed as well as solid weed management. No resistance is available although some varieties are more tolerant than others.