No. 7 Article 5/May 7, 2004

Stripe Rust of Wheat Reported in Illinois

Stripe rust of wheat is appearing in Illinois wheat fields. Robert Bellm, Extension educator from the Edwardsville Extension Center, observed minor stripe rust in wheat near Lebanon. Stripe rust is one of several foliar fungal diseases to watch for now in wheat fields. Others include Septoria leaf blotch and powdery mildew. As reported in the Bulletin 2 weeks ago (issue no. 5, April 23, 2004), Fusarium head blight is also a problem to watch for when wheat begins to flower.

Stripe rust (also called yellow rust) of wheat often appears earlier in the season than leaf rust. Stripe and leaf rusts are distinguished by the color and pattern of the pustules. The stripe rust pustules are more yellow to orange than rusty brown in color, and they usually appear arranged in yellow stripes parallel to veins on leaves. The pustules of leaf rust are dark to light red/brown in color and are scattered in an arbitrary pattern over the leaves.

Stripe rust of wheat in Illinois (2003). (Photo courtesy of Kevin Black.)

Stripe rust can spread and reach damaging levels quickly when cool and moist weather occurs, which favors development of the disease. Stripe rust of wheat seems to have been spreading north more than usual in the past few years. In 2003, it was fairly common and widespread in Illinois, though mostly at low severity levels. Although stripe rust can reach epidemic levels in wheat fields, it has been limited in spread and development in Illinois, in part by weather that is typically too warm and/or dry for the disease. Stripe rust develops most rapidly when there is frequent dew or rainfall and temperatures are between 50 and 60°F; it slows considerably when temperatures exceed about 60 to 65°F at night and 70 to 75°F in the day. The effect of temperature can vary with race of the stripe rust fungus (Puccinia striiformis) and variety of wheat in a field.

Stripe rust can be managed with fungicides and to some degree with wheat varieties that differ in susceptibility. Some of the fungicides labeled for control of stripe rust include Tilt, PropiMax, Quadris, Quilt, Headline, and Stratego. These products cannot be applied after flowering (Feekes growth stage 10.5), and some cannot be applied after the ligule of the flag leaf emerges (Feekes growth stage 8). If fungicide application may be warranted, consult the product labels prior to selection and application of fungicides.--Dean Malvick

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