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Small Grains Disease and Pest Update 08/10/22

Time flies when you are having fun harvesting the winter wheat and winter rye trials across the state.  It has been three weeks since the last small grains disease and pest update and a lot has happened. Bacterial Leaf Streak (BLS) has maybe stalled out a little, leaf rust made a grand entrance, and it is not hard at all to find Fusarium Head Blight (FHB).  Most surprisingly, however, are the reports/finds of ergot in not just rye but spring and winter wheat across the tri-state region. 

The higher dew points made FHB  rear its ugly head once again.  Many of you heeded Andrew Friskop and my worries and applied fungicides to suppress FHB.  With that fungicide application, you also prevented all leaf diseases, including leaf rust, present in the canopy at the time of application to develop any further.  

Leaf rust did, however, make a grand entrance in the region as was evidenced in the leaf rust nursery at the NWROC.  The disease went from 0-60 in just over two weeks (or two generations) on a very susceptible variety that is seeded in so-called 'spreader rows' throughout the nursery. That had not happened in a few years in Crookston and makes the job of selecting new varieties that are resistant to leaf rust much easier.

The most surprising development, unfortunately, is the reports/finds of ergot in not just winter rye, but both spring and winter wheat across the tri-state region. Ergot is caused by the fungus Claviceps purpurea and the stuff of legends.  Rye is naturally more prone to allow ergot to develop as it is the only cross-pollinating species of the small grains.  If fertilization is successful, ergot seldom has a chance to develop.  Only when a floret opens up after (self) fertilization failed, does the fungus have the opportunity to infect the ovary, ultimately replacing the kernel with an ergot body.

The presence of ergot in the harvested grain is a food and feed safety issue and is, therefore, tightly regulated in the grain grading standards.  One ergot body per two thousand wheat kernels will already result in the 'Ergoty' designation when your grain is graded at the elevator. Ergot bodies, like scabby kernels, are difficult to remove from harvested grain.  It is best to never have them enter the grain tank.

To avoid problems with either scabby kernels or ergot, I suggest the following steps:

  • Scout fields a week before harvest and identify which fields or parts of fields have a higher incidence of ergot and/or FHB.  Edges of fields that are adjacent to grass borders will likely have a higher incidence of ergot as last year's grass crop created the inoculum for this year's problems.  
  • Harvest and store the worst fields or portion of the fields separately. Ergot bodies will eventually drop to the ground as the harvest ripe grain remains standing in the field.  Weigh the risk of leaving the crop stand against weather risks and the risk of sprouting.
  • Turn up the fan speed to remove a greater portion of the lighter, scabby, kernels and smaller ergot bodies from the harvested grain.  Weigh the risk of too much grain being left behind against the risk of discounts and the extra cost of cleaning before delivery of the grain to the elevator.
Finally.  This is also the time to start looking for damages caused by Wheat Stem Sawfly (WSS).

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