ISSUE 9 July 8, 2010
NORTH CENTRAL ND
The wheat streak mosaic virus cases in northwest Ward and western McHenry Counties were confirmed by the diagnostic lab. Symptoms of this disease were also found in a wheat field in SE McHenry County.
Wheat stem sawfly was caught in sweep net samples taken in Mountrail County. Insecticides do not effectively control this pest because of an adult emergence over six or more weeks and larvae that are protected from insecticides inside the wheat stem. Variety selection and crop rotation are the two most effective methods for long term management of this pest.
A wheat field in the Burlington area had symptoms of powdery mildew. A winter wheat field in the Max area had symptoms of bacterial blight on the leaves and heads. Fungicides are not effective for control of bacterial blight. Crop rotation to a broadleaf crop and use of a clean seed source are the best preventative measures for management of this disease.
A barley field in western Bottineau County that was at heading had high levels of barley thrips (10 or more per plant).
The counties in our area are between 1300 and 1540 midge degree days. Wheat is at greatest risk when it is at heading to early flowering during peak emergence (1475 degree days). For more information on thresholds and risk, see Jan Knodelís article in the June 24th and July 1 Crop and Pest Report or refer to the wheat midge section in the 2010 Field Crop Insect Management Guide http://www.ag.ndsu.edu/pubs/plantsci/pests/e1143w1.htm.
Peas, Lentils, and Chickpeas:
Peas and lentils are in bloom to early pod in the region. Pea aphid numbers are increasing but still below threshold in the fields we have scouted. If pea aphids are above threshold (3 per plant, 12 per sweep) the early pod timing is a good treatment window for control of this pest. Lygus bugs were above threshold (10 per 25 sweeps) in a field at the North Central Research Extension center south of Minot. Ascochyta has been found in commercial pea fields and is best controlled during bloom.
Many of the fields in the area are past the optimal timing for Sclerotinia control in bloom (20 to 50% bloom). Based on the risk maps from July 5th, the highest risk areas are portions of Bottineau, Burke and Mountrail Counties with moderate risk in most of the region. Updates can be found at www.ag.ndsu.edu/sclerotinia/. Diamondback moths and larvae are present in canola fields in the area, but numbers were below threshold in scouted fields.
Soybean aphids were found at very low numbers in a field near Karlsrue (McHenry County).
Small numbers of sunflower moths, banded sunflower moths, and Arthurís sunflower moths were caught in traps in western Bottineau County.
Crop Protection Specialist
North Central Res. Ext. Center