No. 9 Article 5/May 23, 2008

Stripe Rust of Wheat Found in Illinois

Stripe rust of wheat, caused by the fungus Puccinia striiformis, was observed earlier this week in a seed company research plot near Mt. Vernon, Illinois. Cool temperatures in the spring are favorable for stripe rust development, so the weather that much of the state has experienced the last few weeks is conducive for the disease. Stripe rust symptoms are observed as long stripes of yellow- to orange-colored pustules on the leaves. Because the fungus produces spores that can travel through the air, wheat growers in other areas of Illinois should take caution and perhaps management action on susceptible varieties.

Stripe rust of wheat (Photo by C.A. Bradley).

Stripe rust can be managed using resistant varieties and foliar fungicides. Both strobilurin and triazole fungicides have activity against stripe rust (see issue no. 3 of the Bulletin, April 11, 2008, "Fungicide Efficacy Table for Wheat"). In most of southern Illinois, it may be too late to apply fungicides, according to manufacturers' labels. The latest growth stage when many fungicides can be applied is Feekes 10.5 (full head emergence); a few fungicides can be applied slightly later at Feekes 10.5.1 (early anthesis).

Avoid spraying any products that can contain a strobilurin fungicide as an active ingredient (Headline, Quadris, Quilt, Stratego) during the latest stages of development because of the potential to increase deoxynivalenol (DON, or "vomitoxin") in the harvested grain. DON is a mycotoxin produced by Fusarium graminearum, the fungus that causes head scab of wheat. Research studies in the U.S. and other parts of the world have shown that strobilurin fungicides applied during the late heading stages can increase DON levels in grain. For more information about head scab and DON, see issue no. 3 of the Bulletin, April 11, 2008, "Managing Fusarium Head Blight of Wheat."--Carl A. Bradley

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