Wheat is the only cereal that is seriously affected by Wheat Streak Mosaic Virus (WSMV). It causes stunted growth in wheat plants and lower seed production.
WSMV is transmitted by the wheat curl mite and by leaf rubbing. Mites can be blown from field to field by the wind and can overwinter on winter wheat. Its development depends on the population of mites, virus-infected wheat plants, and sufficient moisture for good plant growth and rapid mite reproduction. A severe outbreak can occur when there is an abundance of mites in a spring wheat field and a field of winter wheat is planted early next to it.
Winter wheat will rarely show symptoms of WSMV until spring. Symptoms become more pronounced when temperatures rise above 10°C in the spring. Dashes, streaks, and yellow stripes will appear on leaves parallel to the veins and will become increasingly mottled until the leaves die. Infected plants have stunted growth from the time the infection took place. If the infection took place during the early tillering stage the plant will stop growing and produce few to no heads. If the plant gets infected in the late tillering to early jointing stages there can be head formation, but the flowers may be sterile. With a late-season infection, flowers can be fertile but kernels will be reduced in size. Fall-infected plants will not produce grain the following spring.
WSMV can be controlled by preventing transmission by eliminating the “green bridge.” The green bridge is when a maturing spring crop is close enough in proximity to allow the transfer and survival of viruliferous mites. The green bridge can be eradicated with a seven to ten day break between the drydown of the spring wheat crop and the emergence of the winter wheat crop.