Plant Disease Control No. 42
Revised March 1998
Small Grain Virus Diseases
BARLEY YELLOW DWARF
Hosts: Wheat, barley, oats, corn, and many grasses.
Symptoms: Stunting of the plant accompanied by chlorotic blotches randomly distributed on the leaf blade. Later these blotches may become bright yellow with the leaf tips becoming red or yellow in color. Leaves tend to be erect and pointed.
Barley- Leaves turn yellow beginning at the tip with the midrib last to turn yellow.
Oats- leaves turn red rather than yellow. Severe blasting of the florets may occur.
Wheat- Mild chlorosis, the plants are lighter in color. Depending on the weather conditions, some varieties may show reddening or yellowing of the leave.
Vector: Barley yellow dwarf is vectored by several aphid species. The virus is prevalent in many cultivated and wild grasses which may not show symptoms.
Control:
1. Plant after grain harvest to avoid infection by aphids moving from green, unharvested grain to newly planted grain. Usually late August or September is satisfactory.
2. Aphids may be controlled with applications of systemic insecticides such as Thimet or Di-Syston at seeding.
3. Disease severity may be reduced if adequate nitrogen is provided and the plants are not stressed for moisture.
WHEAT STREAK MOSAIC
Hosts: Wheat, barley, oats, rye, and many wild grasses.
Symptoms: Symptoms are usually first observed on the edge of fields. Parallel mottled stripes occur longitudinally on the leaves. Leaf edges cup upward and roll to the center of the leaf. Infected plants may be stunted and sterile.
Vector: Wheat streak mosaic virus is vectored by the wheat curl mite, an eriophyid mite, Aceria tulipae.
Control:
1. The most effective control is to have a host-free period between each cereal crop. Avoid having newly planted grain emerge while there is still green, unharvested grain in the area. Winter wheat should be planted as late as reasonable; usually late August or September.
2. Destroy all early volunteer wheat and weedy grasses which often harbor the disease and the mite.
BARLEY STRIPE MOSAIC
Hosts: Wheat, barley, and oats.
Symptoms:Linear yellow spots or stripes appear on the leaves. Later these spots or stripes may turn brown. The stripes resemble those found with barley stripe disease, a fungal disease. Minor problem in most years.
Vector: Seed and windblown pollen transmitted.
Control: Use virus free seed.
Sherman V. Thomson/Extension Plant Pathologist
Scott C. Ockey/Plant Disease Diagnostician
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use. Always read and follow the label.