(Excerpted from Extension Educator Nathan Mueller's blog: http://croptechcafe.org/does-high-humidity-and-temperature-disrupt-corn-pollination/)

Will the high temperatures and humidity experienced in the last few weeks impact corn pollination and kernel set?  Here’s a summary from a UNL CropWatch article “How Extended High Heat Disrupts Corn Pollination” written by Tom Hoegemeyer in 2011.

• High humidity helps reduce crop water demand which is helpful for rainfed corn
• Corn heat stress can occur starting at about 92 degrees and higher
• When soil moisture is sufficient, one day of 95-98 degrees has little to not impact on yields.
• Temperatures above 95 degrees several days in a row will decrease the volume of pollen shed and pollen viability (time that pollen remains viable to fertilize silks)
• Higher nighttime temperatures burns more sugars that were produced by the plant during photosynthesis during the day. Not ideal for yield potential.
• Hybrids that silk early compared to pollen shed more at risk of silk desiccation from high temperatures, though less risk with high humidity.
• Dehiscences, releasing of pollen from anthers, is triggered by the drop in humidity and a temperature increase. So with extreme humidity and a lack of drop in humidity in the morning, pollen shed may delay until later in the day.