Wheat Faces Abnormal Weather, Disease Pressure

May 15, 2011 10:02 PM

An unusually cold, wet spring has added to the many problems that have beset Indiana wheat acreage the past several months, a Purdue Extension wheat specialist says.

"Wheat acres in Indiana have had a challenging season since last fall: bone-dry soils at planting affected stand establishment; the prolonged winter with freezing rain, sleet and snow affected winter survival; and cold, wet soils during green-up affected nitrogen topdressing timings and rates," said Shaun Casteel. "The recent colder temperatures are now causing some abnormal growth of wheat that is near the heading stage."
Many wheat fields in the southern part of the state are into the boot to head growth stages, and the central and northern parts of the state will follow. Cold temperatures will slow growth rate and head emergence, and Casteel said the extended time for head emergence can result in "funny-looking wheat."
The process works like this:
  • The tip of the head will snag at the flag leaf collar and begin to split the leaf sheath at the boot.
  • The plant will continue to push the head, which will begin to extend out of the leaf sheath split.
  • The tip of the head will often stay snagged as the head continues to slowly emerge.
  • The snagged head will eventually pull away from, or push through, the flag leaf collar.
The good news, Casteel said, is that a snagged head will often straighten - depending on how snagged it is.
"Snagged wheat heads should not negatively influence grain yield," he said.
What wheat farmers likely are more concerned with is the potential for Fusarium head blight - especially in the southern parts of the state. While recent rainy weather caused some concern about disease development, cool temperatures have reduced the conditions favorable for fungal infection. With warmer temperatures predicted in the coming week, however, that may be about to change.
If conditions turn wet and warm, this could increase the risk of infection by the fungus that causes Fusarium head blight, said Kiersten Wise, Purdue Extension plant pathologist. The fungus infects wheat during flowering and prefers rainy, warm and humid weather conditions for disease development.
A number of fungicides are available for Fusarium head blight suppression. They are listed in the foliar fungicide efficacy table on the North Central Regional Committee on Management of Small Grain Diseases website.  
"We will need to continue to monitor the level of risk for Fusarium head blight development in wheat in central and northern Indiana as the crop approaches heading in these areas," Wise said.


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