Wheat Disease Update: Stripe Rust Confirmed in Nebraska

Green wheat field — **Figure 1.** A grower’s wheat field in Lancaster County in southeast Nebraska with low levels of disease on May 8. (Photos by Stephen Wegulo)

May 10, 2024

Stephen Wegulo - Extension Plant Pathologist

Kyle Broderick - Extension Educator and Coordinator of the UNL Plant and Pest Diagnostic Clinic

As of May 9, the majority of Nebraska wheat fields had trace to low levels of disease (Figure 1). Stripe rust (Figure 2) has been confirmed in eight counties in the southern tier of counties (Figure 3). Leaf rust has not been observed yet (Figure 4).

Wheat leaves with yellow spots — **Figure 2.** Stripe rust in the field shown in Figure 1 on May 8.

Map of highlighted stripe rust counties — **Figure 3.** County map showing distribution of stripe rust in Nebraska as of May 10.

Map of highlighted leaf rust counties — **Figure 4.** County map showing that leaf rust has not been observed in Nebraska as of May 10.

On May 3, severe symptoms of the wheat streak mosaic disease complex were observed in a field in Johnson County in southeast Nebraska (Figures 5 and 6). Some samples submitted to the UNL Plant and Pest Diagnostic Clinic are showing symptoms of the wheat streak mosaic disease complex.

Yellowed wheat field — **Figure 5.** Severe symptoms of the wheat streak mosaic disease complex in a grower’s field in Johnson County in southeast Nebraska on May 3.

Other diseases observed in wheat fields this week at trace to low levels include barley yellow dwarf (Figure 7) and leaf spot diseases (Septoria tritici blotch and tan spot). A few areas in eastern Nebraska are showing a moderate to high risk of Fusarium head blight.

Management

Stripe rust, leaf rust and fungal leaf spot diseases are managed by planting resistant varieties and applying a fungicide to susceptible varieties timed to protect the flag leaf. Fusarium head blight is managed by planting moderately resistant varieties and applying a fungicide at early flowering. The North Central Regional Committee on Management of Small Grain Diseases (NCERA 184) has compiled a table of fungicides used to control wheat diseases, including the efficacy of each fungicide in controlling specific diseases (Table 1).

The return on investment from applying a fungicide to control wheat diseases depends on the specific disease, the level of resistance of the wheat variety planted, disease pressure, efficacy of the fungicide on the specific disease, and fungicide cost. In general, return on investment is higher in high disease pressure growing seasons and when a low-cost fungicide — such as a generic — is used.

Yellowed wheat leaves — **Figure 6.** Close-up of symptoms of the wheat streak mosaic disease complex in the field shown in Figure 5.

The wheat streak mosaic disease complex is managed by controlling volunteer wheat and grasses before planting wheat in the fall. The volunteer wheat should be completely dead at least two weeks before planting. Several varieties have moderate to good resistance to the disease complex and the wheat curl mite vector.