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JenREES 8/21/22

Corn Silage Resources: For those making corn silage this year, hopefully the following resources can be of help. The multiplier for corn silage value from UNL is 7.65 times the market value of corn grain.

Spidermites: I’m hoping that the cooler weather and either rainfall/irrigation are helping a beneficial fungus help us in the battle against spidermites. Last week I was showing growers how to distinguish this via a hand lens. We mostly have two-spotted spidermites in fields, which are yellow with two black spots on them. Anytime they start looking different (darker, cloudy, white) where the spots are no longer visible, it can be an indication that they are infected and will die. Unfortunately I didn’t grab any pics from the field. The economic threshold from Colorado State says spraying is no longer beneficial past hard dough. I can appreciate that’s hard with the severity in some upper canopies, so here’s hoping the cooler weather helped with the battle.

Pollination: I sure appreciated seeing and smelling all the pollen shed in these replant fields last week! It was perfect weather for it, hopefully a bright spot in the midst of a difficult situation. Been hearing and seeing complaints about poor pollination in non to less severely hailed areas. I don’t remember smelling pollen this year like I normally do in July, but I also admit most of my time has been spent in this large replant area this year. The following is about poor pollination, not kernel abortion.

What I’ve learned from Dr. Tom Hoegemeyer and Dr. Roger Elmore about corn pollination through the years: Heat over 95F depresses pollen production with prolonged heat reducing pollen production and viability. When soil moisture is sufficient, one day of 95-98F heat has little or no yield impacts. After four consecutive days, a 1% yield loss can occur for each day above that temperature with greater yield loss by day 5 or 6. High humidity, without a drop in humidity during the day, can delay pollination or prevent pollen from leaving the anther sacs. Pollination mostly occurs between 8:30 a.m. and noon. When the temperature is 90°F to 95°F, the pollen is eventually killed by heat and is seldom viable past 2 p.m. Pollination typically occurs over a span of six to ten days depending on variability of growth stages in the field.

So, I did some digging into weather data. I don’t have all the tools that you may have, so do something similar for your operations based on the timing of when your specific fields were pollinating and where you’re located. First, I did a general map of Nebraska showing the number of days over 95F from July 9-19, 2022. The eastern 1/3 of the State only had 0-1 days that fit this criteria.

Perhaps bigger factors may have been humidity and timing of silk emergence compared to pollen shed? We’ve had high humidity. For pollen shed to occur, relative humidity needs to drop between 50-65% and the pollen is no longer viable at 30%. As I look at weather data for different locations in the area, many places had over 65% relative humidity as an average for the day for at least 5 days in the time period listed above. It really comes down to at what time the relative humidity dropped enough during the day to release viable pollen. It’s possible that for several days, the anther sacs dropped without releasing pollen if the humidity didn’t drop in the morning. I also remember mentioning in July about how extra long the silks seemed this year prior to pollen shed. That can be a problem, particularly for pollination on the lower end of the ear. The first silks that emerge from the husk are attached to kernels at the base of the ear and they begin to form 8-10 days prior to R1. Silks then continue to emerge sequentially up the ear with the ear tip silks emerging last. Silks are receptive to pollen anywhere along the silk, but after 10 days, the silk senesces (and they’re most receptive to pollen in the first 4-5 days of emergence). Some drought tolerant hybrids may have genetic X environmental responses which trigger silks to emerge 4-5 days prior to any pollen shed (which can result in poor pollination). Older silks can also get covered up by newer silks and miss exposure to pollen. Drought stress adds an entire other complexity to this discussion. Japanese beetles clipped silks in some areas, but it sounded like most were sprayed timely or the silk clipping occurred after the silks had pollinated (turned brown). I don’t know the specifics of every individual situation. These are some thoughts to consider if you’re dealing with pollination issues this year.


Days with a high temperature above or equal to 95F during the period of July 9-19, 2022. Data via ACIS.
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