Daily wilting is taking a toll, primarily by diminishing the energy (sugar) that keeps leaf tissues healthy and repairs damage, but also by causing damage itself. The loss of water vapor through the stomata normally cools the leaf. Leaf temperatures rise above air temperature when the leaves are not getting enough water to keep stomata open. Moreover, sunlight energy that cannot be used in photosynthesis when stomata are closed can damage chlorophyll and the photosynthetic apparatus, leading eventually to loss of leaf color.
Many producers are trying to guess how much corn yield potential has already been lost. In the majority of fields -- those that are pollinating now or that will be pollinating in the next week under conditions of at least moderate stress -- the first yield potential estimates will have to wait until it is possible to count kernel numbers and get some idea of grainfilling conditions at stage R3 (roasting ear) during the last third of July.
“I wish we could be more optimistic,” said Nafziger. “The start to the growing season was outstanding, and most producers ‘did everything right’ to establish good yield potential. There’s not much we can do other than accept that the weather is beyond our control.”