Severe outbreaks occur when there is a build-up of mites and virus on volunteer spring wheats in fields next to winter wheat that was planted early. Symptoms of the disease become more pronounced when temperatures climb above 100C in the spring. Damage Description Mites usually first appear at the edges of fields and under favorable conditions move throughout the field. Winter wheat, although infected in the fall, rarely shows symptoms until spring. These symptoms appear on the leaves as dashes, streaks or yellow stripes parallel to the veins.
Leaves become increasingly mottled until the green areas disappear and the plant dies.
Wheat spot mosaic virus, which is similar to wheat streak mosaic virus, is spread by mites, has a comparable life cycle, and may sometimes be present in winter wheat. Wheat infected in the fall or at an early tillering stage stops growing and produces few to no heads. Infection at late tillering to early jointing stages results in head formation but the flowers may be sterile. With late season infection during jointing to boot stage, the flowers are fertile but kernels are reduced in size. Fall-infected plants do not produce grain the following season.