No. 3 Article 9/April 20, 2012

Symptoms of Wheat Viruses Present in Illinois Wheat Fields

Wheat leaves displaying symptoms of virus infection (purple and yellow leaf tips, mosaic symptoms, etc.) have been spotted in fields across Illinois. Viruses of wheat are not uncommon in Illinois, with barley yellow dwarf virus (BYDV) being one of the most frequently observed in past years. BYDV is transmitted by aphids that feed on wheat in fall and spring. Infections that take place in the fall generally cause more severe symptoms, such as stunting, while infections in spring often appear as leaf symptoms (discoloration such as yellow or purple, especially on leaf tips).

Symptoms of barley yellow dwarf virus on wheat leaves.

Other common viruses are wheat soilborne mosaic virus (WSBMV) and wheat spindle streak mosaic virus (WSSMV). Both are transmitted by a soilborne organism that infects wheat roots known as Polymyxa graminis, which can survive in the soil for many years. Symptoms of the two viruses appear as mottling and mosaic yellow patterns on leaves as well as stunting in severe cases. Continued development of symptoms to upper leaves often stops when temperatures warm up. Preliminary results from a wheat virus survey conducted from 2009 to 2011 indicate that other viruses, such as wheat streak mosaic virus and high plains virus, may also be found in Illinois wheat fields.

Symptoms of wheat soilborne mosaic virus on a wheat leaf.

In general, it can be very difficult to diagnose viral diseases. Going by symptoms alone often results in misdiagnosis. To ensure proper diagnosis, affected plant samples need to be sent to a diagnostic lab that runs assays specifically testing for viruses (such as ELISA or PCR). The University of Illinois Plant Clinic does not run these virus-specific tests for wheat, but it can help facilitate testing through Agdia. Wheat samples for virus testing can be sent to the Plant Clinic or directly to Agdia (see Agdia's website for instructions).

There are no in-season control options for wheat viruses once symptoms are observed. For viruses transmitted by aphids, insecticide seed treatments and foliar insecticides can be used to prevent transmission. For the best management of wheat viruses, choose varieties that have high levels of resistance to these diseases.--Carl A. Bradley

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