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Small Grains Disease Update

The Minnesota Wheat Research and Promotion Council funded a disease survey in small grains in 2012. This is a summary of what the scouts have found in the past few days:

The winter wheat is mostly at or just past anthesis is looking very good overall. The spring wheat is not far behind and is more variable. Drought stress is evident in the central and northern portions of the Red River Valley with the area around Crookston being the hardest hit by drought. Available soil moisture at the NWROC is between ~ 2.7 to 3.3 inches in the top 5 ft of three soils series that were sampled last week (or less than 25% of field capacity), with less than 0.5 inch in the top two feet of two of the three samples.

As far as diseases is concerned:
  1. Scattered incidence of powdery mildew in winter wheat throughout the state. Incidence and severity generally pretty low except for one particular field where is was quite high.
  2. Tan spot can pretty readily found in the middle and lower portions of the canopy of winter wheat and initial infections are starting to show in spring wheat. Incidence in spring wheat is very low. This is likely a function of the fact that most growers now routinely use half a labeled rate of a fungicide at F5 in a tank mix combination with the weed control program. Likewise initial infections of net blotch in barley and Septoria spot blotch in spring wheat can be found.
  3. BYDV like symptomology can be readily found in oat and winter wheat across the state. Foci tend to be small (couple of plants) to medium sized (several feet in diameter) circular patches throughout the field. Aphids (bird cherry oat and English grain) can be found but are generally not at threshold. Some stunting evident, something we rarely see.
  4. No confirmed cases of aster yellows to date, but the first few cases have been submitted for diagnosis.
  5. Stripe rust is now common in the southern portion of the state with incidence nearing 100% in 'Faller' spring wheat (Faller is readily identified because of the rather distinct purple auricles - click here for more details). Severity is approaching 10% on the penultimate and/or flag leaf is some fields.
  6. Leaf rust has been confirmed is a spring wheat field near Barrett, MN (west central MN). The variety was unknown but the incidence was low. The reaction type, however, was S.

There is a fair amount of herbicide injury also showing up in spring wheat that may be mistaken for disease symptoms. The drought stress and a couple of cool nights following the herbicide application is causing this increase in the incidence and severity of the herbicide injury.

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