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JenREES 7/18/21

Leaned plants with braceroot growth on leeward side.

Crop Update: Grateful that in general (beyond seed corn), greensnap levels were lower for the widespread area compared to what we saw in 2020. It appears many fields with leaned plants have been working to right themselves with brace roots growing like crazy to help stabilize plants. Ear development on bent plants will be something to watch going forward. With plants bending in the wind instead of breaking, sometimes extra stress occurs where the ear is developing. Sometimes we see ear abnormalities and sometimes the ears are fine. With fields with severe bending, once the plant reaches tassel, it will no longer try to right itself and will switch to putting resources into the ear. For those with storm damaged fields who were originally planning on more nitrogen through the pivot, last year we took tissue samples to assess that need.

For fields with uneven development with plants ranging from vegetative stages to tassel, particularly storm damaged and uneven emerging fields, one needs to be aware that various adjuvants added to an insecticide and/or fungicide application pre-tassel can cause ear abnormalities.

So, the conversation with those at western bean cutworm thresholds with only portions of fields tasseling was to consider not adding the adjuvant (the same applies for those applying fungicide). I wasn’t sure how efficacy would be for different products without them (that would be a conversation for the chemical reps), but we know that adjuvants such as non-ionic surfactants can cause ear abnormalities when applied pre-tassel.

Also had several conversations regarding foliar fungicide applications. Fields have very low disease pressure right now with bacterial leaf streak being the most prevalent, and a fungicide won’t help with it. Gray leaf spot is very low in fields. Southern rust has been found in a few counties in mid- to southern- Kansas. It has not been found in Nebraska. You can view the tracking map at: https://corn.ipmpipe.org/southerncornrust/. Yield increases with automatic VT applications aren’t consistently proven in Nebraska. The following are fungicide timing studies conducted in Nebraska.

Southern rust detected (red counties) as of 7/18/21.

In 2008-2009, a UNL fungicide timing trial was conducted near Clay Center on 2 hybrids (GLS ratings ‘fair’ and ‘(very) good’) with a high clearance applicator. Timing over the two years included: Tassel, Milk, Dough, 25%, 33%, 50%, and 100% Dent comparing the fungicides Headline, Headline AMP, Quilt and Stratego YLD.

  • 2008No yield difference on GLS hybrids rated ‘good’ at any of the timings (Tassel, Milk, 33% and 100% Dent) nor the check when Headline or Stratego YLD were applied. For the ‘fair’ hybrid, no yield difference for any application timing nor the check for the April 30th planting except for Headline applied at milk stage (increased yield). Low gray leaf spot pressure.
  • 2009No yield difference on GLS hybrids rated ‘very good’ or ‘fair’ nor the check on any timings (Tassel, Milk, and Dough) using Headline, Headline AMP, or Quilt. Moderate gray leaf spot disease pressure.

In 2020, Dr. Tamra Jackson-Ziems and her team did another fungicide timing trial at UNL’s South Central Ag Lab near Clay Center. Fungicides were applied at planting, R1, or R3. There were no clear yield differences between applying foliar fungicide at R1 vs. R3 for any of the products except Miravis® Neo. Sometimes a product didn’t show a difference between other products or even the untreated check. There’s a picture of the data at jenreesources.com. Hybrids vary in disease susceptibility (thus response to fungicide application). With last year being a heavy southern rust year, being able to wait till at least R3 (milk) to apply a fungicide provided some additional time for the residual to work when southern really came on. I know some had to apply a second fungicide application when they automatically applied at R1. That’s just tough from an economic and resistance management perspective, in spite of higher corn prices. Thus, why I recommend waiting until disease pressure warrants the application. The main ‘plant health’ benefit observed in Nebraska when disease pressure was low (ex. 2012) was stalk strength.

July 28 South Central Ag Lab Field Day will be held from 8:45 a.m.-4 p.m. (Reg. 8:30 a.m.), near Clay Center. For all those who’ve talked with me about planting green into rye, there’s an excellent study by Dr. Amit Jhala and grad student Trey Stephens. They compare the same herbicide program with rye termination 2 weeks prior to planting or 2 weeks after planting in both corn and soybean. It was really interesting to visualize the differences in May and I’d encourage anyone interested to take a look at this now in July. Additional topics include disease, insect, and nutrient management, cover crops, and irrigation. You can RSVP at https://enrec.unl.edu/2021scalfieldday

Every time a letter is the same, it means there’s 90% confidence that there’s no difference between those treatments. It’s kind of hard to understand this chart with all the letters. The highest yielding group containing “a” also often contain other letters, and those with an “a” occur at both R1 or R3, depending on the product. The only noticeable difference between applying at R1 vs. R3 occurred with the Miravis Neo product. The other noticeable difference was between the Xyway timing of at planting or planting+R1. Any product that does not have a “d” listed above it yielded significantly better than the untreated check in this study in 2020.

JenREES 7-19-20

Crop Update: The smell of pollen is in the air! Did you know each tassel contains around 6000 pollen-producing anthers? Two good articles from Dr. Bob Nielsen, Purdue University at https://go.unl.edu/x5tv.

How does heat impact pollination? Dr. Tom Hoegemeyer, former UNL Professor of Practice, shared that high humidity, without a drop in humidity during the day, can delay pollination or prevent pollen from leaving anther sacs. While heat over 95°F depresses pollen production, one day of 95-98°F has no or little yield impact when soil moisture is sufficient. After 4 consecutive days, there can be a 1% loss in yield for each day above that temperature. Greater yield loss occurs after the fifth or sixth day. Thankfully we’re not in a high heat pattern during this critical time of pollination!

My concerns regarding pollination: bent ear leaves covering silks in wind-damaged fields. Seeing a great deal of this. Also seeing silks continuing to elongate and grow through broken mid-ribs to increase exposure to pollen. Will continue to observe impacts.

Preliminary storm prediction center weather data showed a total of 93 wind, 11 hail, and 13 tornado damage reports on July 8th in Nebraska. Univ. of Wisconsin found lodged plants had yield reductions of 2-6% (V10-12 stage), 5-15% (V13-15 stage), and 12-31% (V17 and after stages). For greensnapped plants (below ear), Iowa State found in the worst case situation, yield reduction may range up to a 1:1 percent broken:yield loss. It’s possible these losses will be as low as 1:0.73 or even 1:0.50. We have an article in this week’s CropWatch (https://go.unl.edu/cwy2) with more detailed information. Recovery pics also at https://jenreesources.com.

Southern Rust was confirmed at low incidence and severity in Fillmore, Nuckolls, and Jefferson county fields this past week (probable for Thayer). Received questions on fungicide applications. In conversations, it seems like there’s fear of making the wrong decision and ultimately pressure to apply them. I realize economically it’s easier to justify adding a fungicide with insecticide when insect thresholds are met to save application costs. Most fungicide studies focus on VT applications; however, yield increases with automatic VT applications aren’t consistently proven in Nebraska.

In fact, in 2008-2009, a UNL fungicide timing trial was conducted near Clay Center on 2 hybrids (GLS ratings ‘fair’ and ‘(very) good’) with a high clearance applicator. Timing over the two years included: Tassel, Milk, Dough, 25%, 33%, 50%, and 100% Dent comparing the fungicides Headline, Headline AMP, Quilt and Stratego YLD.

  • 2008: No yield difference on GLS hybrids rated ‘good’ at any of the timings (Tassel, Milk, 33% and 100% Dent) nor the check when Headline or Stratego YLD were applied. For the ‘fair’ hybrid, no yield difference for any application timing nor the check for the April 30th planting except for Headline applied at milk stage (increased yield). Low gray leaf spot pressure.
  • 2009: No yield difference on GLS hybrids rated ‘very good’ or ‘fair’ nor the check on any timings (Tassel, Milk, and Dough) using Headline, Headline AMP, or Quilt. Moderate gray leaf spot disease pressure.

Thus I’ve recommended waiting till disease pressure warrants the application (have personally recommended apps as late as hard dough in previous years). Hybrids vary in disease susceptibility (thus response to fungicide application). The main ‘plant health’ benefit observed in Nebraska when disease pressure was low (ex. 2012) was stalk strength and that may be something to consider again in this lower disease year. Regarding any improved water use efficiency for drought-stressed plants, the peer-reviewed research published on this was in 2007. The researchers found slightly increased efficiency in well-watered plants, but it was reduced in water-stressed plants. They suggested fungicide use in water-stressed plants could potentially negatively influence water use efficiency and photosynthesis.


 

Same area of a York County Field taken morning of July 9th (left photo) and morning of July 13th (right photo). Grateful to see how plants are re-orienting themselves in many impacted lodged fields!

Leaned plants trying to upright themselves

Plants re-orienting themselves by ‘pushing’ and establishing more brace roots on the leeward (leaned side) helping roots reconnect with soil on the windward side. Notice the additional brace root development within the circled area of this photo.

Plants reorienting themselves at each node at various angles and bends

Plants reorienting themselves at each node at various angles and bends. Nodes become thicker to aid in reorientation.

Splitting open of thickened node

Splitting open of thickened node. Additional cell division and/or elongation occurring at these nodes appears to help ‘push’ the stalk upward (geotrophic response).

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Consistently seeing bent ear leaves covering silks in wind-damaged fields. Will have to watch any impacts to pollination.

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Also seeing how either the ear or silks are working their way through tears in leaves or silks elongating to the side of the plant to try to pollinate.

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Severely greensnapped field of later-planted corn.

Seeing some new growth on some greensnapped plants. Dissecting the growth revealed baby corn ears (they won’t amount to anything). Just shows the resiliency in plants regarding how they’re created to survive and reproduce. I never cease to be amazed by their Creator!

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Seeing this very minor. Ear trapped within thickened husk/stalk tissue so forcing itself through side of plant. Silks visible first.

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Opened this one to see curving of ear and some potential pinching occurring where ear was trapped above where it was forcing out of husk. Will be interesting to see any pollination and ear development impacts on plants like this.

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