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Issue No. 8, Article 3/May 28, 2010

Update on Wheat Rusts in Illinois

Leaf rust and stripe rust have been observed in wheat fields across Illinois. Many fields in the southern half of the state are at the soft dough stage, and the yield impact of these rusts will thus likely be minimal. Observations indicate that in fields where stripe rust is present, it is found at a low to moderate incidence, and at low severity levels on the flag leaves. Hot temperatures this week will slow or stop the development of stripe rust. Leaf rust observations indicate that incidence and severity vary depending on location and variety planted. In field research plots in Urbana, high incidences of leaf rust can be found, with pustules developing on the flag leaf.

Symptoms of leaf rust (left) and stripe rust (right) on wheat leaves.

With the current warm, humid conditions, leaf rust should continue to develop. Growers in the northern half of Illinois with wheat fields that are beginning to flower (Feekes 10.5.1) may want to consider applying a fungicide to protect against leaf rust infection. A fungicide application at Feekes 10.5.1 would also provide some protection against infection by the Fusarium head blight (scab) pathogen (Fusarium graminearum).

The Fusarium head blight risk assessment tool presently indicates low to medium risk of Fusarium head blight in the northern half of Illinois. Only Caramba, Proline, Prosaro, and tebuconazole products can be applied at Feekes 10.5.1, and all provide protection against rust diseases and Fusarium head blight. For more information on wheat fungicides, see the efficacy chart of foliar fungicides registered for control of wheat diseases (Adobe PDF) developed by university plant pathologists.--Carl Bradley

Carl A. Bradley

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