Figure 1. A section of a wheat field showing severe symptoms of wheat streak mosaic virus in Cheyenne County.	Figure 2. Cereal aphids on a wheat leaf in Box Butte County.

July 13, 2007

Figure 3. Barley yellow dwarf virus on a wheat leaf in Box Butte County.

A multi-state survey of wheat conditions conducted in early June provides some insight into the variable yields producers are seeing now at harvest. Following is the report of that survey.

The 2007 winter wheat survey was conducted in western Nebraska and southeastern Wyoming from June 4 to June 6 by a group of crop specialists and educators from the University of Nebraska-Lincoln, the University of Wyoming and Texas A&M University.

Some areas in the Panhandle were severely affected by the presence of wheat streak mosaic virus (Figure 1). The wheat streak severity in these areas could be traced back to inadequately controlled volunteer in areas that had received preharvest hail in 2006. Warm conditions this spring maximized the impact of these wheat streak infestations.

Figure 4. A section of a wheat field with stunted wheat due to take-all in Morrill County.

Figure 5. An unidentified condition on leaves of wheat cultivar Hatcher in Box Butte County.

Spotty infestations of Russian wheat aphid and other cereal aphids (Figure 2) were seen, but none were economic. Barley yellow dwarf virus (Figure 3) resulting from earlier cereal aphid infestations was seen in a few fields but was not significant in any of the fields surveyed.

Other diseases observed were take-all (Figure 4), tan spot, stripe rust, and loose smut. A symptom of an unidentified condition (Figure 5) also was observed and was most pronounced on cultivar Hatcher.

In general, dry and hot conditions in the Nebraska Panhandle posed a greater risk to crop yield than diseases.

In Wyoming, the winter wheat crop in Goshen and Laramie counties was generally healthy with the greatest impacts on yield this season anticipated to be moisture related, including the lack of timely rains. We observed wheat streak mosaic and barley yellow dwarf virus infected plants at various locations with some indications of prior cold-temperature injury and foliar feeding injury, probably resulting from black-bugs. Isolated Russian wheat aphid was observed with none of the infestations deemed to be economic in terms of pest management. Powdery mildew, stripe rust, tan spot and a presumptive bacterial disease were observed under irrigation and/or where moisture levels were elevated. Once again, the major impact on yield this season will be moisture related.

Stephen Wegulo, Extension Plant Pathologist, Lincoln
Gary Hein, Extension Entomologist, Panhandle REC, Scottsbluff
Drew Lyon, Extension Dryland Cropping Specialist, Panhandle REC, Scottsbluff
Robert Harveson, Plant Pathologist, Panhandle REC, Scottsbluff
Gary Franc, Extension Plant Pathologist, University of Wyoming
Ronald French, Extension Specialist, Plant Pathology, Texas A&M University
William Booker, Extension Educator, Alliance
William Stump, Research Scientist, University of Wyoming
Jack Cecil, Research Scientist, University of Wyoming