Cause Barley yellow dwarf virus (BYDV) is present in many cultivated and wild grasses, which may or may not show symptoms of infection. Many grassy species in non-managed grasslands present in the Pacific Northwest are susceptible to BYDV, including: Achnatherum lettermanii, A. occidentale, A. thurberianum, Alopecurus pratensis, Bromus inermis, Danthonia intermedia, Elymus elymoides, Poa bulbosa, P. fendleriana, P. secunda, Sporobolus airoides, and S. cryptandrus. Field and sweet corn can be symptomless reservoirs of the virus. There are virus strains; based on the aphid species vectoring the disease. One strain (RPV) is now known as Cereal yellow dwarf virus. A number of aphid species can vector Barley yellow dwarf, including the English grain aphid, bird cherry-oat aphid, corn leaf aphid, English grain aphid, and green bug aphid. Disease is more severe in cool, moist weather.
Symptoms Symptoms can be variable and may be confused with nutrient deficiencies or stress. Early symptoms of fall infection of barley may first appear in spring as yellowish leaf tips. Oats tend to have reddish leaf tips. Affected leaves may have yellowish, uneven blotches on leaves. Later, blotches may become reddish or purplish. Tissues next to midribs retain their green color longer than the rest of the leaf. The youngest leaves may not have an unusual color.
Damage may not be severe, depending on growth stage at infection, virulence of the viral strain, susceptibility of the cultivar, temperature, and light intensity. Severely affected plants may be stunted and may not head.
- Plant tolerant or resistant varieties. 'Orca' is resistant but will not yield as high as 'Baroness' unless under heavy disease pressure. 'Cayuse' and 'Kanota' have fair tolerance. 'Montezuma' is also resistant.
- Plant in late fall or early spring so the susceptible seedling stage is before or after peak flights of the insect vectors during warm summer months.
Chemical control Apply granular systemic insecticides in-furrow at planting or as a seed treatment to reduce aphid numbers. (For materials, rates, and procedures, consult the PNW Insect Management Handbook.)
References Ingwell, L.L., and N. A. Bosque-Perez, N.A. 2015. New experimental hosts of Barley yellow dwarf virus among wild grasses, with implica-tions for grassland habitats. Plant Pathology 64:1300-1307.
Mathre, D.E. 1997. Compendium of Barley Diseases. St. Paul, MN: APS Press.