Stress to corn plants during pollination and through grain fill can cause problems with both stalks and ears. The period when stress occurs determines how the plant is affected. Knowledge of ear development helps agronomists and corn producers determine when stress occurred and provides a starting point for developing a management plan to mitigate similar stress in the future.
Drought, heat stress and insect pressure are the three largest stressors, with drought stress being the biggest concern for northern states. Stress can result in a lack of successful pollination, kernel abortion and low starch accumulation.
“Heat stress reduces pollen viability,” said Nick Schimek, Pioneer Field Agronomist. “It can reduce pollen shed and cause silk desiccation. However, drought stress can be more concerning as the silks have a high demand for water. If we have any drought stress, silk growth can be reduced or stopped. This can cause asynchrony between silk emergence and pollen shed.”
Lack of kernel formation means that the stress occurred during pollination. If a portion of the cob shows either very small kernels or kernel dieback, the stress occurred during grain fill. If tip kernels did not abort but their test weight is decreased, the stress occurred during the very latter part of grain fill.
Providing plants with adequate nitrogen, phosphorus and sulfur prior to the vegetative stage can help mitigate issues caused by stress, leading to more completed pollination, better grain fill and higher grain yields. Keeping upper corn plant leaves healthy can also lessen the impact of stress during grain fill. Leaves that are free from insect pressure will photosynthesize better and be able to create more carbohydrates and starch for the kernels.