Symptoms and signs
The viruses that cause BYD infect over 150 species of cultivated, lawn, weed, pasture and range grasses. Some infected hosts display no obvious symptoms. However, in many hosts the most common symptom is stunting due to reduced internode length. The stunting may be so severe that heads fail to emerge or so mild that it is overlooked unless infected plants are carefully compared with uninfected plants. Root mass of infected plants is also often reduced. The most conspicuous symptom on infected hosts, loss of green color in leaves, is often more prominent on older leaves. Discoloration typically begins 1 to 3 weeks after infection and may be preceded by the development of water-soaked areas on the leaves. Barley leaves often turn bright yellow; oat leaves may become tan, orange, red, or purple; wheat leaves typically turn yellow or red; tips or edges of corn (maize) leaves turn red, purple or yellow; and rice leaves typically turn yellow or orange. Symptoms may be affected by the genotype, age and physiological condition of the host plant, as well as by the strain of the virus and the environmental conditions. Other symptoms of infection may include upright and stiff leaves and serrated leaf borders, reduced tillering and flowering, sterility and failure to fill kernels, which results in fewer and smaller kernels and corresponding yield losses.