Now, temperatures at or near 100 degrees and high winds have come just when the wheat needs cool temperatures and rain to recover lost yield potential, Shroyer said. This heat stress may affect wheat that is flowering or in grain fill.
“If wheat is flowering, you might see some floret abortion and possibly some kernel abortion as a result of temperatures nearing 100 degrees. The plants could recover if they receive some rain and cooler temperatures within the next week, but you won't get any new florets. Once they are gone, they are gone,” Shroyer said.
The high winds accompanying the high temperatures will add to the drought stress of the plants, causing leaves to roll or dry up and turn blue or brown, he added. This will have the same effect on yield as a bad infection of a leaf disease that destroys the flag leaf.
“If the flag leaf is lost at this stage of growth, whether due to diseases or drought stress, the kernels will not be able to fill adequately. This reduces yield potential and test weight,” he said.
If the wheat is still in the flowering or early grain fill stage, it can still fill kernels well if the weather would turn cool and the fields would get some rain, Shroyer added. The later the grain fill stage, the less likely the plants are to recover and the more likely the effect on kernel fill will be irreversible, he said.
Where wheat has not yet headed, the drought and heat will cause plants to be shorter than normal, and tillers will abort, Shroyer said. This wheat is in a precarious position right now.
“If the plants remain alive, they can eventually recover if they get some rain by the boot or early heading stage, but yield potential will be reduced. In severe cases, the plants can turn blue and may die,” Shroyer said.