- Washington State University Bulletin
- Diseases of Washington Crops
- Otis C. Maloy and Debra Ann Inglis
Grains Home * Wheat
Diseases * Barley Diseases
- Symptoms and Signs
- Disease Cycle
- Other interesting Barley Yellow Dwarf sites
Barley yellow dwarf, also called yellow dwarf and red leaf
of oat, is a virus disease that frequently occurs in small grains
in Washington, and occasionally causes significant yield reductions.
Disease incidence often is high in irrigated areas that support
aphid populations during summer and where wheat is seeded early.
Use of the enzyme-linked immunosorbent assay (ELISA), a serological
test, has facilitated disease detection and diagnosis.
A virus transmitted only by aphids, not mechanically or by seed,
causes barley yellow dwarf. As many as 20 different aphid species
reportedly transmit the virus, but in Washington, only five-the
bird cherry-oat aphid, the corn leaf aphid, the English grain
aphid, the greenbug, and the rose-grass aphid- are important.
The Russian wheat aphid is reported to be a non-vector.
The virus is persistent and circulative in its aphid vector
but does not pass through the ovaries into eggs. Isolates of
the virus have been grouped according to serological and pathological
relationships: Group I-MAV, PAV and SGV; Group II-RPV and RMV.
Virus isolates are named according to vector specificity, that
is, PAV = Padi-avenae (bird cherry-oat and English grain
aphids) specific. In eastern Washington, the bird cherry-oat
aphid is considered the most abundant and effective vector of
the nonspecific Barley yellow dwarf virus strain (PAV).
Most cereals and many grasses are hosts of barley yellow dwarf
virus. Corn is a symptomless host (at least the symptoms on corn
are not conspicuous). At least 20 grass and cereal genera tested
have carried Washington isolates of the virus.
Symptoms and Signs
Symptoms of barley yellow dwarf vary with hosts and are greatly
influenced by environment. The disease usually appears as patches
of stunted plants in the field. The leaves of affected plants
are stifffly erect, in comparison with the gracefully drooping
leaves of healthy plants; leaf tips are drawn out to a longer
point than normal. Leaf color may vary in wheat from yellow to
red or purple; this apparently depends on the cultivar. In barley
the leaves have a bright golden yellow color (Photo 16); in oats,
the leaves are red or purple. Discoloration often is mottled,
appearing more intense at the leaf tip, then extending along
the leaf margin to give a "chevron effect."
Temperature, nitrogen fertility and light influence leaf symptoms.
Higher temperatures result in more pronounced symptoms; more
nitrogen produces more color; and higher light intensity supports
intense color development. Mottling may occur during intermittent,
sunny weather. Time of infection also influences symptom expression.
Early infections result in stunted plants, reduced tillering,
blasted florets, shriveled grain, and serious losses. Late infections
usually result in only flag leaf discoloration and small yield
reduction (Figure 6).
Aphids acquire the virus by feeding from some source-wheat or
barley (planted or volunteer), wild grasses, corn, etc.-and move
to wheat, barley or oats. Feeding periods of 12-30 hours are
most efficient for virus acquisition. Evidence indicates that
corn constitutes a major reservoir of both the virus and its
aphid vectors, particularly the bird cherry-oat aphid. Surveys
in central Washington have shown that in some years more than
half of the corn fields contain barley yellow dwarf virus. As
the corn matures, aphids that have acquired the virus from corn
move in search of green hosts, often early-seeded winter wheat.
Barley yellow dwarf is most severe in cool (50- 64F), moist
seasons because of continued plant growth and aphid activity.
The disease frequently does the most damage in early- seeded
winter wheat or barley, or in late-seeded spring grains when
aphids are still active and plant tissues are young and succulent.
Chemical. In some areas (irrigated areas with
lighter soils), applying granular systemic insecticides at planting
may help reduce early infection. Opinions vary on the merits
of this method, since aphids may transmit the virus before they
succumb to the insecticide. However, some argue that the treatment
will prevent or retard aphid buildup and secondary spread of
Cultural. Late seeding of fall grain [after
September 15 most years (Table 7)] or early seeding of spring
grains reduces barley yellow dwarf damage, because plants can
emerge and grow through the highly vulnerable seedling stage
while temperatures are too low for aphid activity.
Resistance. No resistant wheat or barley cultivars
are currently adapted or accepted by Northwest growers. Nevertheless,
resistance offers the best possibility for long-term control
of this virus disease.
Table 7. The relationship of planting date to barley yeallo
dwarf incidence in eastern Washington. From Wyatt, S.D., LJ.
Seybert, and G. Mink. 1988 Plant disease 72:110-113.
Before September 15
After September 15
*Plants infected/plants tested.
Bruehl, G.W. 1961. Barley yellow dwarf. American Phytopathological
Society Monograph No. 1.
Rochow, W.F., J.S. Hu, R.L. Forster, and H.T. Hsu. 1987. Parallel
identification of five luteoviruses that cause barley yellow
dwarf. Plant Disease 71 :272-275.
Wyatt, S.D., L.J. Seybert, and G. Mink. 1988. Status of the
barley yellow dwarf problem of winter wheat in eastern Washington.
Plant Disease 72:110-113.
Other Interesting Barley
Yellow Dwarf sites:
Agriculture, Food and Rural Development -- Barley Yellow
Dwarf Virus, Red Leaf of Oats -- description and pictures.
of California Statewide Integrated Pest Management Project
-- description and links to pictures.
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Edited and reviewed by Ed Adams, WSU Extension Plant Pathologist
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