Physiology

At R1 silks begin to emerge with silks from the base of the ear emerging first. Silks can grow 1-1.5” per day and remain viable for up to 10 days. Depending on hybrid and growing conditions pollen will begin to shed shortly before or shortly after silks begin to emerge and will continue for about 2 weeks. One pollen grain will travel down each silk to pollinate an individual kernel. The silk then detaches from the kernel after the fertilization process completes. Any stress that disrupts this process will cause a kernel to remain unfertilized.

Poor pollination

Weather - Extended periods with temps in the mid 90’s or higher and low relative humidity can affect viability of pollen or cause desiccation of silks; extreme stress can cause asynchrony between pollen shed and silking. Low soil moisture content can also cause poor pollination by affecting emergence of silk and pollen.

Insects – Insects such as corn rootworm beetles and Japanese beetles can clip silks while feeding on pollen thereby preventing kernels from being pollinated. Severity depends on beetle population and timing of clipping.

Aborted Kernels

Any stress substantially limiting photosynthesis can contribute to kernel abortion. Factors such as severe drought stress, high heat stress, nutrient deficiencies, several days in a row of heavily overcast conditions or loss of green tissue from things like foliar diseases, hail or greensnap. Kernels are most susceptible to this during the 2 weeks following pollination.

Herbicides

Herbicides can also affect the pollination and kernel development process depending on growing conditions, timing of application and sensitivity of individual hybrids.