Cropping questions and answers for April
Should I spray for powdery mildew when wheat is in the tillering stage? According to Mary Burrows (MSU Extension Plant Pathology Specialist), the winter wheat plant is quite resistant to yield damage at the tillering stage. Yield damage is more of a risk during flag leaf development. If you do have powdery mildew, and it looks like free moisture and 80 degree temperatures are not going to shut the disease down, it is feasible to combine a fungicide with your herbicide application. A yield advantage is more likely in high yield potential wheat crops. Please apply full rates, not partial rates, for best efficacy and greatest possibility of a yield advantage. Spraying a fungicide as a separate application is not as cost effective during the tillering stage. Headline is rated as ‘good’ and Tilt is rated ‘very good’ for powdery mildew management; a full list of fungicides and their efficacy can be found at http://www.msuextension.org/plantpath/ under ‘fungicides for cereal disease control’ or via the Montana Ag Alerts system (mtagalaerts.org). There is also an online tool to calculate the cost benefit of a fungicide application at https://www.msuextension.org/econtools/fungicide/pages/graph.html.
What is the economic threshold for pale western and army cutworms in cereal grains? If plants are not drought-stressed and appear healthy and vigorous then insecticide treatment is justified when there are four to five army cutworm larvae per foot of row. Treatment is justified for pale western cutworms when two to three larvae per foot of row are present. However, under drought conditions, treatment may be justified at lower cutworm larvae populations.
Have you had many samples test positive for wheat streak mosaic virus in Chouteau County? Yes, we have had seven samples test positive for wheat streak so far. With widespread hail, an extended fall, and the increasingly common practice of grazing hailed wheat, Mary Burrows suspects this will be a severe year for wheat streak mosaic virus.
I’m seeding malt barley. How much Nitrogen should
See Page 3: Green be available in the soil if my yield goal is a 60-80 bushel per acre? A 60 bushel/ acre yield goal will require 72 pounds of available Nitrogen. A 70 bushel/
See Page 3: Green acre yield goal will require 84 pounds of available Nitrogen. An 80 bushel/acre yield goal will require 96 pounds of available Nitrogen.
I’m worried about my protein being too high with the above fertilizer rate recommendations. Irrigated malt barley will be fine with the above recommendations because high protein results from plant stress. Dryland malt barley will be under more stress because of lack of available water. If protein levels of dryland malt barley have been over acceptable levels, reduce the recommended rates by 20 pounds of Nitrogen/acre.
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