Barley Yellow Dwarf Virus (BYD):
Oat Disease of Major Significance to Jackson County

Barley Yellow Dwarf VirusA number oat and other small grain pastures in Jackson County were hit hard by barley yellow dwarf virus (BYDV) in the fall and winter of 2001 and we are beginning to see the effects again in 2002. Barley yellow dwarf virus is the most widely distributed and destructive viral disease that affect small grains. Yield losses of up to 60% have been attributed to this disease.

Symptoms of the disease include leaf discoloration, which begins at the tip and progresses downward. Leaf discoloration can range from yellow to orange to purple. These diseased plants often occur in circular patches within the field. Symptoms of BYDV are often confused with various nutritional disorders or cold damage. Unfortunately, by the time the symptoms are visible it is too late to take action.

BYDV is spread by aphids. Epidemics occur when aphids carry the virus from wild and cultivated hosts. Seedling infections reduce yields the most. Plants infected as seedlings in the fall of the year may not survive the winter, or are severely stunted and discolored when growth resumes in the spring.

The virus persists in small grains (oats, rye and wheat), in corn, and in over 80 species of perennial and annual grass species. Late-season infections occur as the aphids migrate from early-planted small grains, as well as wild grasses. Oats are particularly susceptible to BYDV. Early-planted oats often are heavily infected and serve as a source for migration of aphids carrying the virus into adjacent wheat.

Aphids acquire BYDV by feeding on infected plants. It normally takes 24 to 48 hours of feeding to acquire the virus but, once done, the aphid remains a carrier for life. Spread of BYDV depends entirely on aphid movement. Damaging outbreaks of BYDV are most likely if hosts are exposed to migrating aphids over extended periods of cool weather that favor small grain growth and aphid development. Infections can occur throughout the season and are most abundant where high populations of aphids survive the winter. Barley yellow dwarf virus is specialized in its relationship with the aphid carriers and is not transmissible through seed, plant sap, or by other insects.

There are three ways to reduce yield losses due to BYDV. The first method is to delay planting. Since oats are generally planted early in the fall to provide winter grazing ahead of ryegrass, planting at a later may defeat the purpose of using oats. The second method is to apply the insecticide Gaucho (imidacloprid) as a seed treatment. This systemic insecticide does not necessarily kill the aphids, but does alter their feeding habits and has been shown to be effective up to 90 days after planting. The draw back is the $12-14 per acre additional cost. Insecticide treatment of spring grains to control BYDV is rarely justified. The third approach is to control the grassy weeds within and near small grain fields, to reduce the potential for virus introduction. Currently, there are no small grain varieties with resistance to this disease available, but researchers are attempting to select for this trait.

Georgia Oat Variety Disease Ratings
Oat Variety Barley Yellow Dwarf Crown Rust Cold Hardiness
Harrison poor good fair
Arkansas Co. 604 fair excellent good
Horizon 314 fair good good
NK-Coker 227 poor poor good
Chapman fair good fair
NC Rogers poor poor good

For more information, see Auburn University's Fact Sheet on Barley Yellow Dwarf in Small Grains.