NDSU Extension - Ramsey County


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June 27, 2011 Agriculture Column

Howdy!!!  Rain, Rain go away for awhile.  I do guess that we may have lucked out over the weekend as the weatherman made mention that the weather could have been worse.  A couple of comments were: the storms were going to merge in the Devils Lake area and get stronger and secondly they talked about upgrading the hail from ¼ inch to tennis size.  Boy would have that done some damage.  I was at the lake and we did receive a little hail but very little and did no damage.

Correct Stage for Applying Fungicides for Scab Control in Wheat and Barley

Early planted winter wheat in southern North Dakota is at or near flowering, the critical stage for Fusarium Head Blight (FHB or Scab) infection.  With the recent rains, the risk of Scab being problematic on winter wheat fields flowering this week is quite high.  Several fungicides and fungicide combinations have been shown to be effective in reducing Scab development and DON levels in wheat and barley when applied at the appropriate growth stage. 


Timing in wheat

Early flowering is the optimum growth stage for applying fungicide for scab control in all classes of wheat (winter, spring and durum).  Applying fungicide during early flowering helps to protect vulnerable florets during fertilization and early grain-filling.  The center spike in the accompanying photo is at the ideal stage for applying fungicide.  The spike on the left has emerged from the boot, but has not yet started to flower (there are no visible anthers extruded from the glumes) and will likely be at the optimum stage in about two days.  The spike on the right is past the optimum stage; the anthers are bleached and dried, unlike the turgid, yellow anthers in the center spike.  The length of time from head emergence to the beginning of flowering usually takes about three days.  Experience has shown that it is better to apply fungicide too early rather than too late. 


Timing in barley

Flowering in barley begins just before head emergence, so barley florets are not overly susceptible to scab infection.  Therefore, Scab infections do not generally impact yield in barley.  The scab fungus, however, is able to infect the glumes of barley and produce DON which impacts its market value, particularly if it is being sold for malt.  The optimum stage for applying fungicides to protect the glumes of barley from infection is when the spike is fully emerged from the boot.  In the accompanying photo, the spike third from the left demonstrates the optimum stage for treating barley with fungicides, with those further to the left too early and the one on the right too late.  With barley the appearance of the first spikelet from the boot is a good indication that the best stage for spraying is only a few days away.



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