Many native grass species have grown next to wheat and oats in Nebraska for many years without causing serious outbreaks of barley yellow dwarf. Oats and barley are very susceptible to barley yellow dwarf virus. Where these crops are planted late for soil cover, for wind erosion control, for forage, or are volunteer, they often are heavily infected. Therefore, they can be an important local source for migration of aphids and virus into adjacent fall planted wheat. If these crops are still green when winter wheat emerges in the fall, virus infection can produce severe epidemics.
Aphids acquire barley yellow dwarf virus 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 barley yellow dwarf virus depends entirely on aphid movement. One very active aphid feeding for short periods on different plants is a more important carrier than several stationary aphids. In the spring, aphids overwintering as adults on winter wheat or perennial grasses immediately are active as carriers. Aphids do not overwinter in Nebraska, but are blown north on low-level jet winds from overwintering sites to the south.