Erik L. Stromberg

Wheat Streak Mosaic

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Description:

Wheat streak mosaic virus (WSMV) infection have been found in Virginia the spring of 2000.  The incidence and severity of this disease depends on the environment, vector survival, distribution and frequency of volunteer wheat plants which serve as a source of virus and haven for vector, and wheat cultivar susceptibility.

 Symptoms: Symptoms of with wheat streak mosaic virus typically appear in the spring (image). These symptoms can look very similar to WSSMV, caused by wheat spindle streak mosaic virus, which is vectored by the soil-borne fungus, Polymyxa graminis.   However, the field pattern of wheat streak mosaic is related to the distribution and activity of the vector, the wheat curl mite, Aceria tulipae.   As the wheat crop develops, plants affected with WSMV are typically severely stunted (image) with yellow mottled and streaked leaves.  These yellow streaks are often seen as discontinuous dashes running parallel to the leaf veins (image).

 As the season progresses, plants affected and colonized by the curl mites may develop "leaf rolling".  Leaves appear upright while the margins roll inward.  This symptom of mite feeding looks like drought stress in the affected plants (image).  Wheat streak mosaic symptoms tend to become more severe as the weather warms, and severely affected plants may produce sterile heads or die prematurely.

 Vector:  The wheat curl mite, Aceria tulipae, is the only means by which the virus is transmitted in nature.  This mite thrives in lush young growth of wheat and other grasses.  Thus, volunteer wheat in soybean fields harvested in the fall is a particularly good breeding ground for this mite and the virus.

 The wheat curl mite is approximately 0.03 mm long.  It is invisible to the unaided eye.  It is easily dispersed by winds.  The mite can develop from egg to adult in 8 to 10 days.  It produces rapidly at temperatures ranging from 75-80^oF.   Dry conditions also favor the mite's development.  It can over-winter as an egg, nymph, or adult either in the crowns of wheat plants or other host grasses.   This enables the mite to survive freezing temperatures for several months.  Survival is even greater in mild winters.

 Hosts:  Although wheat is the preferred host for Aceria tulipae, many other species of grasses are hosts for both the mite and the virus.  These include corn, oats, foxtail, barnyardgrass, and others.  Volunteer wheat is the primary means by which the wheat curl mite populations and the wheat streak mosaic virus are maintained.  In the absence of a host with live green leaves the wheat curl mite will only survive for a few days.

 Disease management: There are no effective chemicals registered for control of wheat curl mite.   Disease management should be directed towards removing host plants during the fall and winter months (e.g. volunteer wheat) to prevent the survival of the mite and the maintenance of virus in or near the field.  Cultivars can very in their susceptibility to the virus.

Last updated on February 04, 2003.