ISSUE 12 July 29, 2010
North Central ND
Wheat scab (Fusarium head blight) risk has increased in the last few days because of recent rains. For susceptible varieties scab risk has been moderate to high in most of the area over the past few days. The exception to this is in western Williams county and most of McKenzie county. These areas have had low scab risk for all varieties.
For up to date information please go to the NDAWN website (Applications, Wheat, Disease Forecaster) and select the closest location and stage of wheat development (flowering is the best timing for scab control). Please refer to the 2010 North Dakota Field Crop Fungicide Guide for scab fungicides.
Ergot was observed in wheat fields in McHenry, Renville, and Mountrail counties. The percentage of the fields affected ranged from 2-6%. Ergot contains an alkaloid that is toxic to humans and animals. Livestock that eat ergot contaminated grain may have convulsions, hyperthermia, loss of milk, and gangrene. Ergot can be managed by using high quality seed and rotating to a non-cereal crop. For more information on ergot, please see http://www.ag.ndsu.edu/pubs/plantsci/crops/pp551w.htm.
Loose smut has been observed in a number of fields in the area. A wheat field in Burke County had 8% of the field infected with loose smut.
We have continued to find symptoms of wheat streak mosaic virus (wsmv) in the area. A spring wheat field in southwest McHenry County that was in the boot stage had a significant wsmv infection. Planting date is a significant factor in the severity of this disease. Late planted spring wheat and early planted winter wheat are at higher risk for severe wsmv infections.
Field Peas and Lentils:
Pea aphids were found at levels approximately 5-fold above the economic threshold in a late planted pea field in northern McLean County. The best timing for pea aphids is when approximately 50% of the peas are at early pod. Late pod applications are less effective and may not be economical.
Field peas in Sheridan County were severely infected with powdery mildew. Powdery mildew is common in warm humid weather. The green pea varieties Majoret, Cruiser, and CDC Striker were severely affected, whereas, the yellow pea varieties DS Admiral, CDC Golden, and Agassiz were relatively unaffected. Multiple fungicides have efficacy against powdery mildew and are most economical when severe infections occur during early pod development.
A lentil field in southern McHenry County was infected with white mold. Crop rotation to non-broadleaf hosts, use of tolerant varieties (e.g., Pennell), and fungicides can be used to manage white mold if applied at early bloom.
Most of the fields in the area are in the R1 to R3 stage. The R5.1 stage (start of bloom) is a good insecticide timing especially for red sunflower seed weevil and banded sunflower moth, two of the most damaging insect pests of sunflower in our area. Wild sunflowers are in the R5.1 to R6 stage in the area and are a good prelude to what insect pests will be a problem in the area. We have been finding a number of red sunflower seed weevils and Lygus bugs on wild and cultivated sunflowers and are catching significant numbers of banded sunflower moths in our traps.
The “mystery bug” was in fact a ragweed plant bug, Chlamydatus associatus. According to information from Manitoba, it is typically not an economic pest. Thanks to Pat Beauzay and Jan Knodel for help with identification.
Ragweed plant bug on sunflower (John Gavloski, MAFRI)
Downy mildew has been found in
sunflower fields in Renville and McHenry Counties.
Foliar fungicides are not effective against this disease.
Soybean aphids continue to be low or absent in fields in the area. Green cloverworms have been found feeding on soybean leaves. Cloverworms and other leaf feeding Lepidoptera have a threshold of 20% leaf loss at bloom, 15% at pod fill and 30% post-pod fill to harvest. For more information on leaf feeding caterpillars in soybeans see the August 16, 2007 issue of the Crop and Pest Report (issue 14).
Crop Protection Specialist
North Central Res. Ext. Center
According to NDAWN (North Dakota Ag Weather Network) data, the region received 0.6 inch (Robinson) to 5.4 inches (Jamestown) of rain during July. The region’s soil moisture is highly variable – some areas would welcome rain for row crops while other areas would benefit from sunshine to dry fields and allow small grain harvest. Hail and high winds damaged crops during the week of July 12 in scattered areas including Dickey, Foster, LaMoure, Logan and Stutsman counties.
Winter wheat harvest is underway throughout the region. Barley is being swathed or harvested. Spring wheat harvest has begun south of I94. Preliminary wheat harvest reports indicate good yield and generally adequate protein. Spring wheat leaf disease significantly increased in recent weeks while scab symptoms are difficult to find. Most corn is in the tassel (VT) to silking (R1) stages, with some fields in southern counties in the blister stage (R2). Accumulated growing-degree day units for April 25 planted corn and for the period up to July 26 ranges from +40 units at Fingal to -90 units at Linton compared to the past 5-year average. Soybean and dry bean are in the full flower (R2)/pod-development (R3-4) stages. Sunflower is nearing bloom. Yield potential for corn and broadleaf crops continues to be very good.
Area Extension Specialist/Cropping Systems
NDSU Carrington Research Extension Center