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Nebraska
In the Nebraska Panhandle the predominant diseases were tan spot (Figure 1) and wheat streak mosaic (Figure 2). Tan spot infections were severe in some fields despite dry weather conditions. High inoculum levels from last year’s tan spot epidemics in the Panhandle likely contributed to the widespread occurrence of the disease this year. Loose smut (Figure 3) was observed at very low levels in the Panhandle. It also has been seen at low levels in wheat fields throughout the state.
Although few fields with major wheat streak mosaic infections were seen, higher than normal background populations of wheat streak mosaic were found in several fields. The warm extended fall in 2005 increased the risk of wheat streak, but mite populations in these areas were likely relatively low last fall. This was interesting in that some of these areas had pre-harvest hail last summer and severely mite infested volunteer, but the growers in these areas must have controlled their volunteer wheat well in order to break the green bridge and eliminate mite populations.
Few serious problems were seen with insects during the survey of Panhandle wheat. The presence of Russian wheat aphids was common in numerous fields, but no economic infestations were seen. Perhaps the most surprising find was the regular presence of greenbugs in the wheat (Figure 4). This insect is not common in western Nebraska at any time, but especially not in the spring. Infestations of 1-5% infested tillers were seen, but again this is well short of any economic levels as infestations of 30-50% would be needed to even consider treatment. Areas that regularly have greenbug infestations in winter wheat (Texas, Oklahoma and southern Kansas) do not consider the greenbug to be a serious issue in headed wheat because natural enemies often affect populations by this time. Perhaps more importantly, the widespread presence of greenbug populations may be more of a threat to newly planted sorghum. Over the next few weeks monitor sorghum fields for greenbugs.
In early May the winter wheat crop in the Nebraska Panhandle looked to be on its way to well above average yields. Wheat stands were generally good and wheat growth was excellent. Few major obstacles to high yields were identified. Unfortunately, Mother Nature had a different script.
May precipitation in the Panhandle averages about three inches, depending on location; however, in 2006 much of the Panhandle received less than one-half inch of precipitation. As cool temperatures in early May gave way to well above average temperatures in mid and late May, and as the winter wheat crop advanced in maturity, the crop deteriorated rapidly. Hopes of well above average yields have disappeared and some growers are merely hoping for a crop that justifies harvest costs.
Wheat growing on deep soils with good stored soil reserves has been able to hang on the longest, but even this wheat has pretty much run out of stored soil water and is in need of rain. Wheat growing on shallow, coarse soils or that was seeded without the benefit of summer fallow, is suffering the most. Many wheat plants in these fields no longer have any functioning leaves. Only the stem and heads are green. With grain fill just beginning, these fields stand little chance for profitable yields. Dry, hot weather at flowering resulted in a very rapid flowering period, which also bodes ill for wheat yield potential.
Having said all this, winter wheat is a resilient crop. You predict its demise at your own peril as a prognosticator. The winter wheat crop in the Nebraska Panhandle will likely be harvested earlier than normal, as hot, dry conditions accelerate wheat development. Significant rain in the next week or two may improve yield slightly, but will probably have a greater beneficial effect on grain quality rather than yield.
Wyoming
Evidence of prior frost was evident in most Wyoming fields with tips of some lower leaves dead. Furthermore, drought stress effects were showing up on plants as considerable leaf death low in the canopy around the base of the stems. There was a lack of tillering and tillers that already formed were drying up and turning brown because the plants were in the process of re-directing water to the heads and (hopefully) eventual grain-fill.
Pine Bluffs-Albin-Hawk Springs-Lingle: The crop in this general area was heading out and showing signs of drought stress. The growth stage of the crop will now require timely rains in order to even approach average yields. Tan spot and wheat streak mosaic virus were only found on the occasional plant, in contrast to Nebraska fields where wheat streak mosaic and tan spot were much more common. In contrast, evidence of Russian wheat aphid was much more common in Wyoming than in Nebraska.
Russian wheat aphid was common in some fields, and several producers west of Hawk Springs had already sprayed earlier in May. One of the fields sprayed earlier with insecticide still had living aphids evident, and living aphids were occasionally found in high numbers scattered along the edges of other fields in the area.
Chugwater Bench: The crop was approximately one week behind that in the southeast corner of Wyoming. Russian wheat aphid evidence was common in some fields and, once again, only a few plants were observed with tan spot or wheat streak mosaic virus. The exception was a single field with extensive widespread symptoms of viral infection that looked somewhat like wheat streak mosaic virus. Plant samples from this field will be tested to determine if another virus is possibly involved. As with most fields visited during the survey, rain in the next two weeks is critical if decent yields are to be obtained. By the way...we saw one too many rattlesnakes!
Wyoming Summary: In Wyoming, water availability (lack of timely and sufficient rain) will limit production this year. Disease or other pests will have relatively little effect on yield.
Other crops visited
Garbonzo beans near Alliance, Nebraska: The crop was just emerging and had been planted into heavy mulch and corn stubble. Although under center pivot, the surface mulch was reported to greatly reduce (at least 50%) the water requirement in this particular field because surface evaporation was greatly reduced.
Canola near Alliance, Nebraska and Lingle, Wyoming): The crop was in flower and generally looked good. No apparent disease problems were observed in these fields.
Alfalfa (west of Hawk Springs, Wyoming): Alfalfa weevil was evident, and the crop suffered greatly from lack of water. Even the weeds were dying. Hopefully irrigation water will become available soon.
(Note: See this week's Field Updates for local reports on wheat crop condition.)
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
William Booker,
Extension Educator, Alliance
Karen DeBoer,
Extension Educator, Sidney
William Stump,
Research Scientist, University of Wyoming
Jack Cecil,
Research Scientist, University of Wyoming
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