About April 25, northwest Oklahoma began to see something strange in the wheat crop.
For the most part, producers have had an extremely good growing season, with slightly above-normal rainfall and very nice temperatures for tillering and flowering of the wheat crop. That was all well and good, but Mother Nature threw producers a curve ball on April 24. That began a stretch of extremely hot temperatures, high wind speeds and little rainfall. In fact, the last rain was around April 14, and that less than 1 inch around the area.
During this time wheat was using 0.3 inches of water per day. Given those parameters, you might be able to select the reason why so many white heads are now appearing in the 2012 harvested wheat crop.
White heads in wheat at this time of the year more than likely can be caused by one of the following four reasons. They can appear as a result of root-rotting diseases, insect damage, heat at the wrong time or moisture stress.
If root rots are the cause of the white heads, you need to follow the white head down to the rooting area of the wheat stool. Gently pull the wheat stool out of the ground and begin to inspect the crown area between the roots and the upright tiller.
If the area is black or brown, more than likely root rots are the cause of the white head. The root-rot disease likely will be from common root rots like bipolaris or fusarium, rhizoctonia sharpe eye, take-all or strawbreaker.
Insect issues that might cause the wheat heads to turn white might include Hessian fly or the wheat stem maggot. If Hessian fly is the issue, the wheat heads will be an off white, but the stems will collapse in a crisscross fashion and the stem will have broken where the Hessian fly had laid their eggs. The stem maggot is limited to individual, scattered heads. These white heads easily can be pulled through the stem. Chewing damage is apparent at the base of the stem, just above the upper most nodes.
If you were not able to explain a reason why a field has white heads at this point, you can now blame Mother Nature for white heads seen in wheat. A more scientific analysis of white heads could be explained as an early senescence or maturity of the head. The cause for this can often be attributed to an excessive number of tillers (heads) produced over the mild winter, then not enough water, and the plants simply ran out of water to fill the grains in the wheat head.
While moisture is now good in these fields, the problem was during the last week of April with above 90 degree temperatures and high, hot southwest winds. These white heads often are mixed in with areas of the field that did have sufficient moisture to sustain the higher tiller count and will fill grain in the normal manners.
Your Oklahoma Cooperative Extension Service ag educators are willing to assess your fields and help identify the causes of concern in your wheat fields.
More information about these white heads can be obtained by attending the Lahoma Wheat Tour on Friday. Call (580) 237-7677 for your lunch reservation.
Gribble is Oklahoma Cooperative Extension Service northwest area agronomist.