Figure 2. Freeze damage in a wheat field in south central Nebraska. The picture was taken on June 5.
Figure 1. Trace levels of stripe rust at the UNL Agricultural Research and Development Center near Mead on June 6.
Figure 3. Close-up of bleached heads in the field shown in Figure 2.
Figure 4. Rotting of the bases of peduncles in the field shown in Figure 2, initiated by freeze damage.
June 7, 2013
Wheat Disease Update
The risk for rust diseases in wheat remains low in Nebraska. Trace levels of stripe rust (Figure 1) were observed on June 6 at the UNL Agricultural Research and Development Center near Mead. The Fusarium Head Blight Prediction Center is currently showing a low risk for Fusarium head blight (scab) in Nebraska. However, the risk may be elevated in localized areas that received heavy rainfall before and during flowering.
Premature bleaching of wheat heads can be due to causes other than scab. Bleaching of wheat heads in the field shown in Figure 2 was determined to have been caused by freeze injury that occurred earlier in the growing season. In this field located in south central Nebraska, heads were observed to be completely bleached (Figure 3), with the partial bleaching characteristic of scab absent. When heads were pulled, they came off the main stem easily and the base of the peduncle (part of the stem supporting the head) appeared damaged and rotted (Figure 4). Stem maggot damage was ruled out based on the absence of stem maggots in affected plants and the extensive bleaching of heads in the entire field with some large areas of the field more severely affected than others.
Currently the predominant diseases in wheat fields in eastern Nebraska are powdery mildew and fungal leaf spots (mainly Septoria tritici blotch and tan spot).
Extension Plant Pathologist