Wheat fields in central and western Kansas could use at least one last good rain before harvest.

“Wheat is under stress in much of western Kansas south of I-70 and west of Pratt and Great Bend,” says Kansas State University’s Jim Shroyer. “In areas east of U.S. Highway 281, there are fields where wheat is under stress, especially on terrace tops.”

Shroyer, a crops specialist with K-State Research and Extension, says stressed wheat is generally showing some combination of the following symptoms:

  • White heads, which developed very quickly over a wide area;
  •  Curled and dried up flag leaves;
  •  Tillers that have sloughed;
  •  Loss of one or more small developing kernels in the spikelet;
  •  Poorly developing kernels; and
  •  Chlorotic leaves due to poor root development and nutrient deficiencies.

Shroyer says stress came on quickly this year.

“There were general rains earlier in the spring and topsoil moisture was adequate in most areas until recently. But where subsoils were very dry after last summer’s drought, wheat needed a regular supply of rainfall events this spring to support the top growth. Where that didn’t happen, wheat quickly became stressed, especially during periods of extreme heat this spring – the latest being May 4 and 5.”

During heading and grain fill—a period of high moisture use—wheat uses about 0.25 to 0.30 inches of moisture per day. If moisture isn’t available, wheat will show symptoms, Shroyer says. The combination of dry soils and heat, in particular, will cause heads to turn white quickly, almost overnight. Any additional stress, such as diseases or insects, will add to the stress.

He says although cool weather has returned the crop still needs another rain or two where it is dry.

“If rain comes to stressed wheat while the kernels are still in the milk stage of development or earlier, the wheat may be able to recover some yield and test weight potential as long as the flag leaves are still alive,” Shroyer says. “If the plants are under severe stress and shut down while kernels are in the early dough stage, it is unlikely that any subsequent rain will help the kernels complete their fill. This will result in a loss of yield and low test weight, regardless of the weather during the remainder of the season.”

Other reports indicate that all districts across the state have seen at least some wheatturning color as the crop continues to progress three weeks ahead of normal. Statewide, 98 percent of the wheat crop has headed, well ahead of 55 percent last year and the 5-year average of 46 percent. With the crop in the South Central and Southeast Districts already at 50 percent turned color earlier this week, the state averaged 26 percent turned color.

Since precipitation continued to be scarce in many of the principal wheat growing districts, condition of the wheat crop continued to decline to 5 percent very poor, 11 percent poor, 32 percent fair, 41 percent good, and 11 percent excellent. Insect damage decreased slightly to 18 percent light, 5 percent moderate, and 1 percent severe. Disease damage was nearly unchanged at 28 percent light, 16 percent moderate and 4 percent severe.