Barley Yellow Dwarf Virus, Red Leaf of Oats

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 Biology | Damage description | Diagnosis | Management strategy


The barley yellow dwarf virus (BYDV), also called red leaf in oats, can infect barley, oats, rye and wheat as well as numerous species of grasses. It occurs in most parts of the world and is considered the most common viral disease of cereal crops. BYDV is transmitted by several species of aphids and occurs in many strains or types.

Usually the aphid vectors cannot overwinter in Alberta and they normally drift in every spring from the United States. These aphids may already be infective they but can also pick up the virus from infected perennial grasses in Alberta. As the aphids (winged or wingless) feed on the cereal crop, they transmit the virus through their mouth parts. The aphids can remain infectious for life, which is around 40 days.

Damage Description

Symptoms vary with the host species and the stage of crop development. Infections at the seedling stage may result in death or dwarfing as well as sterile heads.

Leaves turn yellow from the tip down, along the leaf margins or in blotchy patches. Infected barley leaves, particularly flag leaves, turn bright yellow; in oats, the leaves may turn from red to purple. Discolored areas enlarge and progress to the base of the plant. Heads may be wholly or partially sterile. There may also be an increase or decrease of tillers produced by infected plants. Cereal plants infected early in the season may be shaded out by healthy or late infected surrounding plants. Winter wheat seedlings may be 100 per cent infected with BYDV before freeze-up in the fall.

In dry seasons in the Fort McCleod/Claresholm area, barley that is seeded in June may turn yellow in early July. In alkaline soils this symptom indicates a manganese deficiency in the cereal crop.

BYDV affects yields by stunting, reduced tillering, sterility, and failure to fill kernels. However, because the aphids must move in from the United States, they generally arrive too late in the season to cause significant yield loss in Alberta. In some regions in the United States, yield losses reach 30-50 per cent in oats and 5-30 per cent for barley and wheat. On the Prairies, the only crops that are damaged significantly are late sown spring crops and early sown, fall-seeded crops.

Bright yellow flag leaves in barley by late June or early July will indicate little or no yield contribution from those plants. Severe stunting in winter wheat by mid-May could indicate crop failure from one or more strains of BYDV.


Visual symptoms will indicate the presence of the disease. Confirmation of this virus must be carried out at a research facility.

Management Strategy

  • Use resistant varieties.
  • Seed early in the spring. This will allow for maximum growth of the cereal crop before possible infection by migrating aphids.

Barley yellow dwarf field symptoms - bright yellow flag leaves.

Barley yellow dwarf virus on upper leaves - emerging flag leaves will turn bright yellow.

Barley yellow dwarf virus - most affected to least affected (L to R).

Red leaf of oats caused by infection with the aphid-borne barley yellow dwarf virus.

Extensive barley yellow dwarf infection in wheat field - yellow flag leaves.

Barley yellow dwarf in wheat. Bright yellow flag leaves.

Leaf blotch of oats caused by Pyrenophora avenae.

Text and captions courtesy of Dr. Ieuan R. Evans
Images courtesy of I. R. Evans and WCPD
This document is maintained by Shelley Barkley.
This information published to the web on November 9, 2001.
Last Reviewed/Revised on November 18, 2011.