A field survey project to inspect wheat and barley fields is underway in Minnesota. The survey program has resumed past efforts where survey scouts visit fields to assess crop progress and pest situations. Inspecting wheat and barley fields for the presence of plant diseases and insects provides a weekly regional snapshot of pest problems present in fields and the status of the infestation levels. The survey project is being coordinated by UMN Extension educators in west central and northwest MN. Funding is being provided through a grant awarded by the Minnesota Association of Wheat Growers.
The program mirrors the North Dakota State University Extension Service IPM survey. Working cooperatively with NDSU and following the same survey protocols provides a regional view of small grain crop conditions extending from Minnesota westward to the North Dakota-Montana state line. The scope of the survey often allows identification of problems as they develop and often the geographic extent of problem. This can alert farmers and crop managers to developing situations close to home.
The program functions by compiling weekly scouting reports from 2 MN and 5 ND field survey scouts. Each surveyed field is geo-referenced using GPS coordinates and mapped with software. The maps are generated and posted on-line for reference. Currently, the maps are archived through the NDSU IPM Survey web site which can be found at https://www.ag.ndsu.edu/ndipm/
Wheat Growth Stage Progress
The region's wheat crop ranges from early leaf stages in the most northern counties to boot stage in southern areas, particularly with winter wheat. Certainly weather has played a big role in crop development. Delayed planting and persistent cool, wet weather has delayed the spring wheat crop.
Wheat Diseases Observed
Tan spot is typically the most prevalent foliar disease found early in the season. It is being found throughout the region as indicated by the Tan Spot Incidence map (Incidence = disease is present; the percent plants infested is reported). Fortunately, the severity of infections trends toward the low end (Severity = indicates the extent of the infection level, such as leaf area affected).
These maps provide a summary of what was observed. You are also interested in forecasting risk of grain disease. So, be sure to keep the disease forecast tool handy and refer to it for planning future management options as the crop develops. You can find the model at:
Wheat Insect Observations
The primary insects of interest are cereal aphids: bird cherry oat, English grain, greenbug, and corn leaf. Bird cherry oat and English grain are the most common in wheat at this time. As you can see from the maps, aphids were first detected from June 6 - 7 in more southern and western areas. Expect aphids to start filling in the areas to the north and east.
One serious aspect of aphids is the transmission of Barley yellow dwarf virus (BYDV) which has already been confirmed by the NDSU Diagnostic Lab in winter wheat samples in ND. In other areas, some symptoms that look like BYDV have been reported. Barley yellow dwarf virus is easily confused with a nutritional disorder or the effects of adverse weather. Visible symptoms depend on the plant's stage at infection. Leaf discoloration in shades of yellow, red (oats), and purple (sometimes) appear starting from the tip to the base and along the leaf margins to the midrib.
Because we're dealing with late planted small grains, and the long term forecast calls for cool weather through June, small grains in the area are at a greater normal risk for BYDV if there is an aphid infestation. As a result, producers/crop consultants should be proactive with their cereal aphid control in late planted wheat.
The typical economic threshold for aphids in wheat is when 85% stems with more than one aphid present, prior to complete heading. However, knowing that most of our late planted wheat is at 'high' risk for aphid infestation and BYDV transmission, we recommend that producers/crop consultants take a more preventative approach against aphid infestations and consider treating earlier than the described threshold in an attempt to reduce the risk of BYDV in 4- to 5-leaf stage wheat, stages when the impact of infection can be much greater. Typically, late planted wheat in the more northern areas is at greater risk to aphid and BYDV, so watch northern fields closely for aphid arrival.
For further discussion, read "Low Densities of Cereal Aphids Present in Both ND and MN this Past Week" in the NDSU Crop and Pest Report from 6/23/2011.