Stripe Rust Confirmed in Wheat in South Central and Southeast Nebraska; Other Diseases Increasing

Wheat field April 27, 2017
Figure 1. A section of a wheat field showing lush green growth at the Eastern Nebraska Research and Extension Center (ARDC) near Mead on April 27.

Stripe Rust Confirmed in Wheat in South Central and Southeast Nebraska; Other Diseases Increasing April 28, 2017

Wheat fields are still looking green (Figure 1).  However, development of several diseases is increasing. On April 26, stripe rust was confirmed in Nuckolls County in south central Nebraska and on April 27, it was found at low to moderate levels in research plots at the University of Nebraska-Lincoln’s Havelock Research Farm near Lincoln in Lancaster County (Figure 2).

Various other diseases were observed during a survey of wheat fields and research plots at UNL’s Agricultural Research and Development Center (ARDC) near Mead on April 27. Among them were Septoria leaf blotch which was present at high incidence (percentage of diseased plants) and low to moderate severity (percentage of diseased plant or leaf area, Figure 3) and powdery mildew which was mostly confined to the lower canopy at moderate to high severity (Figure 4). Barley yellow dwarf, a virus disease (Figures 5 and 6), was also observed at low to moderate incidence.

Wheat diseases

From left: Figure 2. Stripe rust at UNL’s Havelock Research Farm in Lincoln on April 27. Figure 3. Septoria leaf blotch in a research plot at the ARDC on April 27. Figure 4. Powdery mildew in the lower canopy in a research plot at the ARDC on April 27.  Figure 5. Barley yellow dwarf in a research plot at the ARDC on April 27.

Management

Although the current cold temperatures will somewhat slow development of stripe rust, a return to seasonal temperatures coupled with wet weather will favor its rapid development. Growers should scout more frequently to determine the extent of stripe rust in their wheat fields. Most fields are less than two weeks from full flag leaf emergence. 

Timing of a fungicide application to protect the flag leaf from stripe rust and fungal leaf spot diseases is critical. If an application is made too early, the flag leaf will not be protected. On the other hand, waiting too long after flag leaf emergence will give more time for stripe rust to develop, which will reduce fungicide efficacy. Fungicides are most effective when applied preventively, not curatively. Virus diseases cannot be controlled once they occur.

Resource

When selecting a fungicide, consider information in Fungicide Efficacy for Control of Wheat Diseases, a resource from the North Central Committee on Management of Small Grain Diseases (NCERA-184).

barley yellow dwarf in wheat
Figure 6. Stunting of wheat plants caused by barley yellow dwarf at UNL’s Havelock Research Farm in Lincoln on April 27.