Severe drought and/or heat stress can interfere with the timing of pollen availability and silk emergence. In addition, hot weather can desiccate exposed silks so they cannot receive pollen grains.
Typically, growers would like to determine the success of corn pollination. Once ovules are fertilized, the silks will detach from the immature kernel. This provides a way to determine which kernels are fertilized and those that are not. Silks will continue to elongate and will remain attached even if never fertilized.
The ear shake method is a technique which can be used to check pollination. Take a sharp knife and make a lengthwise cut from the base of the ear shoot to the tip. The knife should penetrate through the husk leaves into the cob. Slowly unwrap the husk leaves so you do not rip any of the silks from the ovules. Then gently shake the ear. Silks of fertilized ovules will drop away and silks from unfertilized ovules will remain attached.
Pollination can be determined by the percentage of silks that fall away from the cob. Be sure to sample ears at random to determine progress. The dry weather has caused different pollination timings within fields. Be sure to check carefully.
For more information, contact Wayne Flanary, Regional Agronomist, University of Missouri Extension at 660-446-3714.