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July 21, 2010

Small grains:

Wheat scab (Fusarium head blight) has been observed in commercial fields throughout the region.  The following table is a summary from our North Central IPM Scout:



% of Field Affected

Avg. % of Head Affected

Southeast of Kenmare




North of Parshall




Northwest of Velva




East of Velva




Northeast of Karlsruhe




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. 

Symptoms of the wheat streak mosaic virus have been observed this week mainly in McLean and Ward Counties, and the western portion of McHenry County. 

Small grain aphids have generally been low with a couple exceptions.  Two locations south of New Town (Mountrail County) had aphids on 52-56% of tillers.  A wheat field north of Keene (McKenzie County) had 44% of tillers infested with aphids.  The threshold for aphids is 15 per stem or 85% of stems with at least one aphid.  It is generally not economical to control aphids after flowering.      

Wheat midge flight has concluded in most of the counties in our area.  When 80% of the heads are at flowering or later, treatment for wheat midge is not effective and can kill the beneficial parasitic wasp that helps control this pest.

Field Peas and Lentils:

Pea aphid populations have remained approximately 3-fold above threshold levels in our field at the North Central Research Extension Center.  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.  Lygus bug numbers have been low on lentils and near zero on field peas.


In the last couple of weeks large numbers of a Mirid plant bug have been found feeding on sunflowers in the area.  These dark gray insects with yellow legs are about one-third the size of a tarnished plant bug (Lygus lineolaris).  We suspect this may be the ragweed plant bug but should be able to confirm this by next week’s Crop and Pest Report.

Sunflower seed maggots have also been prevalent in the area.  Research is being conducted to determine economic injury levels and how to best control this pest.


Soybean aphids have been low or absent in fields in the area.  Several green cloverworms were found feeding on soybean leaves at the North Central Research Extension center.  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).

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