Symptoms: Infected plants are stunted with mottled green and yellow-streaked leaves. Streaks are parallel, but often discontinuous. Isolates give a symptom range from mild mosaic to severe chlorosis. Symptoms vary with wheat cultivar, strain of the virus, time of infection, and environmental conditions. Heads may be sterile. Leaves can become necrotic.
Development: Often, infections appear at the margins of a field first because of the movement of the virus' mite vector. Infections may occur in the winter, but symptoms often do not appear until the spring temperatures rise to above 10°C.
Vectors/Hosts/Distribution: The wheat curl mite, Aceria tulipae (syn Eriophytes tulipae) and E. tosichella (in the former Yugoslavia) are the only known vectors of WSMV. WSMV is carried in the mid- and hind-gut of the mite, but is not passed through the egg. The virus and the mite vectors persist in wheat, maize, millet, and some grasses. The virus occurs in the United States, Canada, Jordan, eastern Europe, and Russia.
Importance: The virus is most prevalent in the United States, where in the Great Plains it at times can cause complete losses. The incidence can be quite variable, from a few fields to large affected areas.
