Barley Yellow Dwarf Virus
Confirmed in Some Wheat Fields
The favorable
warm fall weather that allowed for rapid crop maturity and grain dry-down
last fall is indirectly responsible for the presence of Barley Yellow Dwarf
Virus (BYDV) in some wheat fields this spring. The virus is spread
by more than 20 species of aphids and induces what is probably the most
widely distributed and destructive viral disease in the world. When
aphids remain active well into the fall period, the likelihood for infection
increases. That likelihood now appears to be a reality and has been
enhanced where fields were planted before the middle of September.
Typical symptoms of BYDV are stunted and yellowing circular patches in a field. The small patches, up to 30 feet in diameter, correspond to the establishment and reproduction of the aphids. Fall infections are the most severe but symptoms often don't appear until spring.
Yellowing in wheat fields often begins along grassy field margins. As time progresses, diseased areas enlarge and merge. Plants are stunted compared to other healthy, green plants in the field and root systems are often damaged to the same degree as top growth. When inspecting fields, confirm that adequate nitrogen has been applied or is available to the crop before assuming BYDV is the problem. Like BYDV, lack of nitrogen will also cause plants to look chlorotic and yellow.
At this point, there is little that producers can do to prevent or control this disease. Dr. Craig Grau, UW Extension Plant Pathologist, suggests just "riding it out". In Illinois research, netted field plots of winter wheat were 100 percent infected with BYDV. Yield reductions at worst were 25 percent and in many cases were far less. In a field situation, it's highly unlikely that we would have BYDV infections of the magnitude seen in the research plots.
Many plants are hosts to the virus. These include other small grains, corn, and most cool season perennial and annual grasses. Current wheat varieties have little BYDV resistance although some varieties seem to tolerate the effects of BYDV better than others. Planting later in the fall seems to offer the most viable management practice for reducing infection risk. The problem is that we don't always know what long term weather conditions will prevail following seeding.
For next fall's winter wheat planting season we start with a fresh slate. BYDV does not stay in the soil or overwinter on plant residue as a fungal disease does.
For more information contact Mike Rankin
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