Wheat Disease Update: Stripe Rust, Leaf Rust, Wheat Streak Mosaic at High Levels

Figure 1. A Wheat Field Day in a grower’s field in Washington County on June 6.

Wheat Disease Update: Stripe Rust, Leaf Rust, Wheat Streak Mosaic at High Levels June 9, 2017

Field surveys June 1-8 in south central, southeast, and northeast Nebraska showed stripe rust and leaf rust have developed to severe levels in fields planted with susceptible varieties that were not sprayed with fungicide to protect the flag leaf.  In a state variety trial in a grower’s field (Figure 1) in Washington County on June 6, stripe rust was the predominant disease.

Severe wheat leaf rust
Figure 2. Severe leaf rust on a flag leaf of a stripe rust-resistant variety in a state variety trial at Havelock Research Farm on June 8.
Severe stripe rust in wheat
Figure 3. Severe stripe rust in a grower’s field in Webster County on June 7. (Photos by Stephen Wegulo)

Further south at the Agricultural Research and Development Center near Mead (Saunders County) and at the Havelock Research Farm near Lincoln (Lancaster County), stripe rust was severe in susceptible lines/varieties and leaf rust was severe (Figure 2) in varieties/lines resistant to stripe rust but susceptible to leaf rust.

On June 7 stripe rust in a grower’s field in Webster County (featured in the May 26 issue of CropWatch) had progressed to 70-100% severity on flag leaves (Figure 3) and had killed all leaves in large sections of the field.

Field with wheat streak mosaic virus
Figure 4. Severe wheat streak mosaic in a grower’s field in Jefferson County on June 1.
Fusarium head blight in wheat
Figure 5. Fusarium head blight in a state variety trial in Jefferson County on June 7.
Wheat stem maggot injury to wheat
Figure 6. A wheat head whitened by stem maggot damage in a grower’s field in Lancaster County on June 1.
Take-all disease in wheat
Figure 7. Stunting and whitening of wheat heads caused by take-all at the Havelock Research Farm on June 8.

On June 1, severe wheat streak mosaic, a virus disease, was observed in a grower’s field in Jefferson County (Figure 4). There are reports of severe and widespread wheat streak mosaic in the southern Panhandle with 100% loss in some fields.

Damage to wheat heads by diseases, insects, or environmental factors has also been observed. Trace to low levels of Fusarium head blight (Figure 5) and trace levels of wheat stem maggot damage (Figure 6) and stunting and whitening of heads caused by take-all (Figure 7) were observed during the disease surveys. Fusarium head blight was observed in Nuckolls and Jefferson counties on June 7, in research plots at the Agricultural Research and Development Center near Mead on June 3, and at the Havelock Research Farm on June 5.

Management

It is too late to spray for stripe rust, leaf rust, or Fusarium head blight. Virus diseases cannot be controlled once they occur. To lessen the risk for wheat streak mosaic in the next cropping cycle, control volunteer wheat this summer before planting in the fall.

Wheat Field Days

Six more Winter Wheat Field Days are scheduled for this month and offer growers the opportunity to compare performance of wheat varieties and resistance traits.
Field Day Schedule