Glume blotch disease affects wheat
There have been many reports this year of glume blotch causing darkened glumes on wheat heads from southeast Kansas through north central Kansas, said Erick DeWolf, K-State Research and Extension plant pathologist.
Initial symptoms of glume blotch are small brown spots on the glumes or awns, DeWolf explained. These expand to dark blotches, darkening the head, he said.
The disease is favored by splashing rain, high humidity and temperatures between 68 and 82 degrees, he said. Where those conditions have occurred over the past month, glume blotch is now being found, he said.
Glume blotch can result in yield losses between 10 and 20 percent, he said. The greatest losses occur when the disease damages both the leaves and the heads, he said. The disease characteristically moves upward from infections on the low leaves to the heads if weather conditions are favorable for the disease, he explained.
The grain produced in heads damaged by glume blotch is often small and shriveled, he added.
Where glume blotch is severe, producers should take some management steps to ensure that the disease doesn't become more of a problem next year, DeWolf said.
"Fields with severe glume blotch disease this year should not be planted to wheat this fall since the fungus that causes this disease can survive in wheat residue," he said.
"The fungus also can survive in grain that is saved for seed. These seed infections can reduce the effectiveness of crop rotations and allow the disease to get established early in the growing season. Growers wanting to save seed from affected fields should have grain cleaned to remove the small heavily infected seeds, and use a fungicide seed treatment such as Dividend or Raxil," the Kansas State University plant pathologist explained.
Infections on volunteer wheat also can serve as the source of inoculum to start off the disease cycle in the new crop of wheat, so controlling volunteer wheat will help control any further spread of the disease, he said.
Other management options include foliar fungicide use and possibly variety selection, he said.
"Foliar fungicides will protect wheat against glume blotch, but must be applied shortly after head emergence. Current fungicide labeling prevents application beginning at flowering or within 30 days of harvest. There are varietal differences in susceptibility to glume blotch; however, high levels of resistance are rare," he said.
For more information and photos of glume blotch, see K-State Research and Extension publication S-84, Diagnosing Wheat Production Problems, at www.ksre.ksu.edu/library/crpsl2/s84.pdf.