Wheat Diseases Increase, but Still Low to Moderate - UNL CropWatch, June 14, 2013

Wheat Diseases Increase, but Still Low to Moderate - UNL CropWatch, June 14, 2013

Water-stressed wheat field

Figure 1. Wheat in this field in west central Nebraska appeared stressed from lack of moisture and showed widespread injury from a frost that occurred several weeks ago.

June 14, 2013

   Wheat streak mosaic   Fusarium head blight
   Figure 2. Wheat streak mosaic was found in all fields surveyed, but did not appear severe at the field scale.   Figure 3. A wheat head affected by Fusarium head blight at the UNL ARDC near Mead on June 13.
 
   stripe rust
  

Figure 4. A stripe rust hot spot at the UNL ARDC near Mead on June 13.
 

   stripe rust
  

Figure 5. Close-up of a wheat leaf with stripe rust at the UNL ARDC near Mead on June 13.
 

    Leaf rust
   Figure 6. Leaf rust on wheat leaf at the UNL ARDC near Mead on June 13.

A survey of wheat fields on June 11 in west central and south central Nebraska and June 13 in southeast Nebraska revealed a wide range of diseases occurring at trace to moderate levels.

In the west central part of the state, wheat in many fields looked stressed from lack of moisture. In several fields, frost injury that occurred several weeks ago was still evident (Figure 1). Very trace levels of stripe rust were found in this part of the state and leaf spot diseases were at low levels due to dry conditions.

In south central Nebraska, diseases included wheat streak mosaic (Figure 2) and barley yellow dwarf, both virus diseases. Wheat streak mosaic was more widespread, but did not appear to be severe at the field scale. Other diseases observed included trace levels of stripe rust, leaf spot diseases (mainly Septoria tritici blotch and tan spot), and bacterial streak, also known as black chaff when it affects wheat heads (see CW article).

In southeast Nebraska wheat fields at the UNL Agricultural Research and Development Center (ARDC) near Mead were surveyed. Diseases observed were low levels of Fusarium head blight (Figure 3), hot spots of stripe rust (Figures 4 and 5), trace levels of leaf rust (Figure 6), and moderate levels of powdery mildew and bacterial streak and black chaff.

Wheat in most parts of the state is past the latest growth stage at which it can be sprayed to control fungal diseases. Virus and bacterial diseases cannot be controlled once they occur.

Stephen Wegulo
Extension Plant Pathologist