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Issue No. 2, Article 5/April 8, 2011

Wheat Streak Mosaic Virus, Bacterial Mosaic, and Stripe Rust Update

Wheat streak mosaic virus (see photo) was confirmed in a wheat sample from a southern Illinois field recently, and I have received calls about other fields with similar symptoms. Symptoms of wheat streak mosaic appear on the leaves as mottling or yellow streaks that run parallel with the veins. General yellowing and stunting may also occur in plants affected by wheat streak mosaic. The virus is transmitted by the wheat curl mite, and infection likely occurred last fall.

Symptoms of wheat streak mosaic. (Photo courtesy G. Kelly Robertson.)

Symptoms of wheat streak mosaic could easily be confused with those of the disease known as bacterial mosaic (see photo), caused by the bacterial pathogen Clavibacter michiganense subsp. tessellarius. Bacterial mosaic has been observed in Illinois in past seasons, but no confirmations have yet been reported for 2011 in Illinois. The only way that virus diseases can be properly diagnosed is through a laboratory that can run specific tests using ELISA (enzyme-linked immunosorbent assay) or PCR (polymerase chain reaction). As part of a funded-research project, my laboratory is conducting a wheat virus survey for Illinois. If you wish to take part, you can send symptomatic leaf samples (approximately 30 leaves).

Symptoms of bacterial mosaic on wheat leaves. (Photo courtesy University of Illinois Plant Clinic.)

I must receive the samples no later than the day after they are collected. Package samples in a sealed plastic bag and include the county and date of collection along with the submitter's contact information (name, e-mail address, and phone number). Send samples Monday through Thursday by an overnight delivery method--not by regular mail, as they will go to the central campus mail collection point and not reach me on time--to Dr. Carl Bradley, Department of Crop Sciences, University of Illinois, 1102 S. Goodwin Ave., Urbana, IL 61801 (telephone 217-244-7415). Results regarding submitted samples will not be available immediately.

Stripe rust (see photo) was reported in a wheat field in Christian County, Kentucky (just north of the border with Tennessee) on March 30 by Dr. Don Hershman of the University of Kentucky. He notes that this finding of stripe rust is a little earlier than normal (Kentucky Pest News No. 1262). The implication for Illinois is that the risk that stripe rust will occur earlier than usual has increased. Because of this increased risk, it is important to scout wheat fields for stripe rust. If it is found, several fungicides are available that can provide control.

Symptoms of stripe rust on a wheat leaf.

--Carl A. Bradley

Carl A. Bradley

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