Ag Instructor Vic Martin: Wheat Disease Management

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Great Bend Tribune
Published May 16, 2021

As of May 11, the Drought Monitor report is indicating abnormally dry conditions creeping closer to Barton County as it now encompasses almost all of Stafford and Rice Counties. Hopefully, the promised unsettled period will bring rain without too much severe weather. Most of the southern third of the state is still abnormally dry. Moderate drought is still confined to a two-county tier next to the Colorado border and the Dodge/Garden City area did receive some significant rains this past week. The six to ten-day outlook (May 18 to 22) indicates above normal temperatures and precipitation. The eight to 14-day outlook (May 20 to 26) indicates more of the same. If corn and soybeans are in the ground this should help with seedling emergence and establishment. As long as we aren’t too hot, this should help with wheat kernel development. The downside is the wetter conditions will favor diseases, especially rust species.

Our district ANR Extension agents are good about putting press releases from K-State in the paper each Sunday. Without repeating this content, let’s take a peek at the 2021 wheat crop and disease pressure. We will hit the highlights as there are numerous potential diseases.

  • Much potential biological disease pressure may have happened last fall or early this spring. The ones listed here must be prevented since once infected, there is really nothing that can be done. The best options are resistant/tolerant varieties and/or cultural practices. Where volunteer wheat wasn’t adequately controlled, the wheat curl mite aphid could spread WSMV (Wheat Steak Mosaic Virus). This was a large problem several years ago but through concerted efforts has improved, however, infections this year are above average. Another potential problem is Barley Yellow Dwarf (BYD) which is spread by aphids as they feed. Fall infection can cause significant yield losses. Spring infestations, the later the better, will cause yield losses but are typically less severe.
  • Now, what about diseases appearing in the spring that might benefit from a protectant or therapeutic fungicide? The most concern now is rust species – stripe rust, leaf rust, and stem rust. The key with the first two is to keep them off the flag leaf needed to fill the grain. These are favored by warm humid/moist conditions and risk decreases markedly with hot, dry conditions. So this year would seem to favor rust species. As of May 6, leaf rust was only observed in four counties with Pratt the closest but only on lower leaves. That doesn’t mean it’s not there but simply not seen. Stripe rust has been observed in Stafford and most surrounding counties. Our weather pattern would indicate a potentially serious problem for nonresistant varieties. Producers must choose what to do. A preventative fungicide that would have to be reapplied, especially after a good rain or a curative application which buys them more time. The key is to protect the flag leaf and work within the label for the time between application and allowable harvest.
  • One last thing, some abiotic, non-biological, diseases have shown up, especially nitrogen deficiencies in some fields.
  • Having said all this, early indications are for a good wheat crop. Combined with high prices, as of now, there is a decent chance for a good, profitable wheat harvest.
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