Does High Humidity and Temperature Disrupt Corn Pollination?

Pollen shed from exserted anthers on a tassel from a corn field in Dodge County.

Does High Humidity and Temperature Disrupt Corn Pollination?

With the high humidity and high temperatures this week, how could this impact corn pollination?  Here is a short summary and highlights 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 (picture above), is triggered by the drop in humidity and a temperature increase. So when extremely humid and lack of drop in humidity in the morning can delay pollen shed until later in the day.

Other facts about corn pollination that are good to remember from Bob Nielsen at Purdue: 

1. It only takes one pollen grain per silk. However, “many pollen grains may germinated on a receptive silk.”
2. “Pollen grain germination occurs within minutes after a pollen grain lands on a receptive silk.”
3. “A pollen tube develops and grows inside the silk, and fertilizes the ovule within 24 hours.”
4. “Majority of successful ovule fertilization occurs during the first 4 to 5 days after silk emergence.”
5. “Silks remain receptive to pollen grain germination up to 10 days after silk emergence,”
6. Elongation of an individual silk stops shortly after germination.

The ear shake test can be done 2 to 3 days after successful ovule fertilization since the silk will detach from the immature kernel by Bob Nielson: