UNL CropWatch May 19, 2010: Stripe Rust Widespread in South Central and Southeast Nebraska

UNL CropWatch May 19, 2010: Stripe Rust Widespread in South Central and Southeast Nebraska

 Photo - Minor Stripe rust in wheat  Photo - Stripe rust in wheat - high severity  Photo - stripe rust
Figure 1. Low severity of stripe rust on a wheat leaf in Nuckolls County on May 18. Figure 2. High severity of stripe rust on a wheat leaf in a Nuckolls County (different field from Figure 1) on May 18. Figure 3. A wheat field that was recently sprayed for stripe rust and is not showing any symptoms.

May 19, 2010

 Photo - Wheat field with severe stripe rust

Figure 4.  A large area in a Nuckolls County wheat field showing signs of rust on May 18.

Photo - Wheat varieties resistant and non resistant to stripe rust

Figure 5.  A stripe rust-susceptible variety (right) and a variety showing some resistance in a wheat field in Nuckolls County on May 18.

As of May 18, stripe rust was widespread in south central and southeast Nebraska based on a survey of wheat fields and phone or e-mailed reports.

A survey of fields in south central Nebraska on May 18 found severity of stripe rust ranging from low (Figure 1) to more than 70% (Figure 2). Field symptoms varied, ranging from no visible symptoms (Figure 3) to isolated spots showing yellow leaves to large affected areas (Figure 4). In one field, there was a sharp contrast between a susceptible variety and one planted next to it that appeared to have some resistance (Figure 5).

Responding to Stripe Rust

Stripe rust can cause 100% loss to a wheat crop. This year’s prolonged cool, wet weather has favored and continues to favor development and spread of this disease.

If you see stripe rust in your field, apply a fungicide to protect the flag leaf. This recommendation extends to varieties known to be resistant. They can still suffer damaging levels if a new race of stripe rust is present. If your wheat is headed and or is beginning to flower, apply a fungicide that has good to excellent efficacy against both stripe rust and Fusarium head blight (scab).

Fungicide Efficacy for Control of Wheat Diseases

The North Central Regional Committee on Management of Small Grain Diseases (NCERA-184) has developed the following information (Table 1) on fungicide efficacy for control of certain foliar diseases of wheat. The table is compiled and continually updated by the committee as new data becomes available.

Efficacy ratings for each fungicide were determined by committee members field testing the materials over multiple years and locations. Efficacy is based on proper application timing to achieve optimum effectiveness of the fungicide as determined by labeled instructions and overall level of disease in the field at the time of application. Differences in efficacy among fungicide products were determined by direct comparisons among products in field tests and are based on a single application of the labeled rate as listed in the table. The table includes the most widely marketed products, and is not intended to be a list of all labeled products.

Stephen Wegulo
Extension Plant Pathologist
Dewey Lienemann
Extension Educator