Stephen Wegulo, Extension Plant Pathologist
Dewey Lienemann, Extension Educator, Webster County
Everlyne Wosula, Post-doctoral Research Associate
Satyanarayana Tatineni, Research Plant Pathologist, USDA-ARS
Figure 1. A healthy wheat field with no visible disease symptoms in central Webster County on June 3.
Figure 2. Wheat stressed from lack of moisture and damaged by freezing temperatures in a wheat field in central Webster County on June 3. Note the brown, desiccated foliage and white heads.
A survey of wheat fields in the southern tier of counties in south central and southeast Nebraska on June 3 revealed very little disease in some fields and no disease in most fields. Wheat was in the soft to hard dough growth stage. A few fields looked healthy (Figure 1) with potential for a good yield.
However, in many fields in the south central counties, the wheat crop looked stressed from lack of moisture (Figure 2), with half to three quarters of the leaves below the flag leaf brown due to desiccation, and plant height reduced by up to 50% in some areas in some fields.
In some fields there was a significant number of white heads that appeared to have resulted from freeze injury. This freeze injury may be due in part to the subfreezing temperatures that occurred in early May. In the field shown in Figure 3, the brown tinge is due to a combination of freeze-damaged white heads and brown, desiccated foliage in the lower canopy.
The diseases observed at trace levels were tan spot and Septoria tritici blotch on lower leaves. These diseases were observed only in a few low-lying spots in a few fields with thick crop stands.
In all fields surveyed, there were low levels of wheat stem maggot damage characterized by white heads that come off the plant easily when pulled (Figure 4). In some fields there were curled heads due to awn trapping (Figure 5) which can result from a variety of causes including freeze injury, hail damage, insect damage, or synthetic auxin herbicide injury.
Figure 3. A brown tinge due to freeze-damaged white heads and brown, desiccated foliage in the field shown in Figure 2.
Figure 4. (left) A head turned white due to wheat stem maggot damage in a field in Saline County on June 3. Unlike freeze-damaged heads, wheat stem maggot damaged heads come off the plant easily when pulled.
Figure 5. A curled head due to awn trapping in a wheat field in Saline County on June 3.
Source : unl.edu