Tip Back in Corn
What is Tip Back?
“Tip back” in corn is simply the term used when corn kernels do not form all the way to the tip of the ear.
Tip back made its way into corn discussions this August and September with many commenting that they saw it in more fields this season than in recent years (Figure 1).
Figure 1. Tip back in a corn field in 2024 (photo credit: Josh Kelly).
It can be understandably frustrating to observe tip back when scouting a field during grain fill. One can’t help but feel robbed by lost yield potential when they see part of an ear that has not been filled with kernels, or perhaps feelings of a hybrid or field being too lazy.
What Causes Tip Back?
Tip back is usually caused by some combination of two factors:
- Failed pollination – ovules (female structures of flowers that eventually form the seed) formed on the ear but failed to be fertilized by pollen.
- Kernal abortion – kernels that initiated following successful pollination but later aborted.
Knowing how to diagnose these factors can help provide some understanding as to what has contributed to tip back in a field.
In both cases, it is important to know that the ovules (or kernels following pollination) at the tip-end of corn ears are the most immature. During ear development (starting around V6 or 6 leaf collar stage) ovule initiation and development starts at the base of the ear. Ovules are progressively younger or less developed towards the ear tip. Thus, ovules near the ear tip are the last to form and the last to push out silks from the husks.
What Is Failed Pollination?
Failed pollination is ovules that have not received pollen, and thus do not develop. It is not unusual to find some unfertilized ovules at the ear tip. Fertilization status can be readily confirmed at early grain fill when ovules that have successfully fertilized (received pollen) have silks naturally detach while those that have not fertilized (have not received pollen) will remain attached. Eventually silks for both fertilized and unfertilized ovules will dry and degrade. Unfertilized ovules will remain small and surrounded by glume tissues (the tissues that form red dog or bees’ wings around corn kernels).
What Causes Failed Pollination?
In most cases, these ear tip ovules simply developed too late to have silks emerge in time to intercept viable pollen; they have missed the major pollen shed window. Other silk issues (silk balling, late emergence, insect silk feeding) could cause emergence and pollination issues too (Nielsen, 2003) but these may not be restricted to ear tips.
What Is Kernel Abortion?
Abortion occurs when a kernel that successfully pollinated is later aborted and stops filling grain. Aborted kernels are recognized by their undersized shape or shrunken appearance and translucent or white colouring. On larger aborted kernels, a yellow embryo may be visible inside (Figure 2).
Figure 2. Ear tip with aborted kernels (shrunk and translucent appearance, yellow embryos visible inside).
What Causes Kernel Abortion?
Kernel abortion is usually observed during earlier grain fill and particularly within a couple weeks of fertilization (Nielsen, 2021). Stresses and insufficient supply of plant photosynthates and other nutrients moved in plant sap (also known as assimilates), are often attributed to kernel abortion. This is thought to happen when the source of assimilates cannot meet the demand of the number of fertilized kernels (also known as the sink). When the source and sink demand are not met, the least mature kernels located at the ear tip will start to abort. This is sometimes attributed to the fact they are the smallest sinks (least competitive) and furthest from the source of assimilates.
While it can be difficult to pinpoint the exact causes of kernel abortion in a field, stress, or loss of photosynthetic activity during early grain fill could be driven by factors such as:
- Loss of leaf area from physical damage like hail
- Loss of photosynthetically active leaf area through premature dry down (senescence) of leaves from factors like foliar disease or nutrient deficiencies
- Reduced or impaired photosynthetic output from weather conditions such as overly cloudy weather, drought or extreme high or low temperatures
Know Your Kernel Counts
In his article, Bob Nielsen (Nielsen, 2003) points out that before we get too concerned about tip back and a loss of potential yield, it would be good to take stock of kernel formation in the field. If conditions were excellent during late vegetative stages, it’s possible a much larger than normal ear could have been set, one we might not expect to fill under normal conditions. In this case, some tip back may not be concerning. If number of kernels in length is much lower than normal (for our given number of rows per ear and ears per acre), perhaps there is more reason for concern for yield limitations.
References
Nielsen, R.L. 2003. Tip fill problems in corn. Purdue University. https://www.agry.purdue.edu/ext/corn/news/articles.03/TipFill-0917.html (accessed 23 Aug. 2024).
Nielsen, R.L. 2021. Grain fill stages in corn. Purdue University. https://www.agry.purdue.edu/ext/corn/news/timeless/GrainFill.html (accessed 04 Sep. 2024).
Weather Summary: Thursday, September 26 to Wednesday, October 2, 2024
Location | Highest Temp (°C) | Lowest Temp (°C) | Rain for Week (mm) | Rain Since April 1st (mm) | GDD0C April 1st | GDD5C April 1st | CHU May 1st |
HARROW | |||||||
2024 | 24.0 | 8.3 | 31.5 | 491.7 | 3409 | 2492 | 3767 |
2023 | 24.5 | 11.5 | 15.6 | 601.1 | 3120 | 2216 | 3450 |
2022 | 19.3 | 5.7 | 2.1 | 431.7 | 3257 | 2366 | 3677 |
10 YR Norm (11-20) | 22.5 | 9.7 | 20.6 | 556.0 | 3246 | 2323 | 3699 |
RIDGETOWN | |||||||
2024 | 23.0 | 7.9 | 7.8 | 578.1 | 3233 | 2320 | 3543 |
2023 | 27.3 | 9.1 | 7.3 | 515.2 | 2981 | 2086 | 3237 |
2022 | 20.2 | 2.7 | 9.5 | 309.5 | 3095 | 2211 | 3421 |
10 YR Norm (11-20) | 22.3 | 8.3 | 25.1 | 506.0 | 3063 | 2143 | 3444 |
SARNIA | |||||||
2024 | 25.2 | 10.4 | 11.7 | 491.9 | 3250 | 2339 | 3546 |
2023 | 26.7 | 10.5 | 15.8 | 499.3 | 2954 | 2059 | 3188 |
2022 | 17.8 | 2.9 | 13.0 | 352.9 | 3101 | 2223 | 3402 |
10 YR Norm (11-20) | 21.7 | 9.3 | 23.0 | 502.8 | 3045 | 2128 | 3445 |
LONDON | |||||||
2024 | 24.4 | 7.3 | 6.1 | 591.9 | 3210 | 2294 | 3530 |
2023 | 26.9 | 9.4 | 3.0 | 554.6 | 2962 | 2067 | 3226 |
2022 | 19.2 | 3.1 | 25.4 | 371.4 | 3007 | 2131 | 3327 |
10 YR Norm (11-20) | 21.7 | 8.2 | 22.5 | 533.8 | 3031 | 2115 | 3412 |
BRANTFORD | |||||||
2024 | 24.2 | 7.7 | 6.4 | 492.3 | 3146 | 2236 | 3445 |
2023 | 27.6 | 10.2 | 0.2 | 431.3 | 2936 | 2040 | 3183 |
2022 | 19.6 | 1.7 | 9.5 | 333.0 | 3015 | 2129 | 3266 |
WELLAND | |||||||
2024 | 24.6 | 8.6 | 7.9 | 489.8 | 3231 | 2316 | 3574 |
2023 | 25.3 | 10.0 | 0.9 | 490.7 | 2993 | 2091 | 3271 |
2022 | 17.5 | 2.4 | 4.8 | 400.5 | 3071 | 2177 | 3417 |
10 YR Norm (11-20) | 22.6 | 8.3 | 27.7 | 479.2 | 3053 | 2136 | 3444 |
GODERICH | |||||||
2024 | 27.7 | 6.6 | 5.8 | 380.9 | 2991 | 2084 | 3285 |
2023 | 24.1 | 8.9 | 0.7 | 371.5 | 2771 | 1893 | 3002 |
2022 | 20.2 | 2.1 | 36.0 | 336.6 | 2866 | 1993 | 3169 |
10 YR Norm (11-20) | 20.9 | 8.3 | 17.6 | 462.8 | 2810 | 1903 | 3179 |
ELORA | |||||||
2024 | 25.0 | 5.3 | 7.8 | 456.0 | 2919 | 2016 | 3185 |
2023 | 26.0 | 8.2 | 0.0 | 470.2 | 2722 | 1842 | 2917 |
2022 | 18.5 | 2.4 | 5.8 | 275.7 | 2775 | 1902 | 2997 |
10 YR Norm (11-20) | 20.9 | 6.7 | 22.8 | 522.7 | 2740 | 1837 | 3036 |
MOUNT FOREST | |||||||
2024 | 24.9 | 6.3 | 19.6 | 429.0 | 2921 | 2021 | 3205 |
2023 | 26.0 | 9.2 | 0.0 | 407.8 | 2721 | 1845 | 2927 |
2022 | 18.2 | 1.7 | 29.4 | 415.9 | 2762 | 1895 | 3023 |
10 YR Norm (11-20) | 20.3 | 6.8 | 21.6 | 530.8 | 2733 | 1837 | 3063 |
BARRIE | |||||||
2024 | 23.9 | 5.0 | 10.3 | 578.8 | 2867 | 1967 | 3144 |
2023 | 26.9 | 6.2 | 0.0 | 501.1 | 2721 | 1839 | 2931 |
2022 | 19.2 | 0.3 | 12.8 | 413.1 | 2722 | 1845 | 2971 |
10 YR Norm (11-20) | 20.4 | 6.5 | 16.9 | 468.3 | 2695 | 1802 | 2997 |
PETERBOROUGH | |||||||
2024 | 24.3 | 4.6 | 8.9 | 477.0 | 2895 | 1991 | 3104 |
2023 | 26.9 | 2.2 | 0.0 | 431.0 | 2759 | 1868 | 2916 |
2022 | 19.2 | -2.7 | 12.9 | 363.1 | 2761 | 1874 | 2983 |
10 YR Norm (11-20) | 21.6 | 5.2 | 16.3 | 457.7 | 2765 | 1861 | 3018 |
KEMPTVILLE | |||||||
2024 | 24.4 | 6.6 | 8.8 | 576.5 | 3085 | 2177 | 3405 |
2023 | 25.6 | 4.1 | 0.0 | 508.3 | 2932 | 2045 | 3139 |
2022 | 18.4 | -0.7 | 7.5 | 514.1 | 2922 | 2017 | 3191 |
10 YR Norm (11-20) | 22.9 | 6.8 | 16.9 | 515.9 | 2904 | 2001 | 3231 |
SUDBURY | |||||||
2024 | 23.6 | 2.2 | 10.4 | 556.5 | 2736 | 1854 | 3009 |
2023 | 26.0 | 6.0 | 0.0 | 515.4 | 2573 | 1729 | 2773 |
2022 | 18.2 | -2.7 | 8.4 | 370.0 | 2531 | 1684 | 2798 |
10 YR Norm (11-20) | 19.3 | 4.7 | 22.4 | 508.4 | 2540 | 1697 | 2855 |
EARLTON | |||||||
2024 | 24.0 | 3.7 | 9.9 | 549.7 | 2675 | 1800 | 2895 |
2023 | 24.3 | 1.2 | 0.6 | 404.1 | 2514 | 1670 | 2681 |
2022 | 19.7 | -2.7 | 7.7 | 457.3 | 2467 | 1630 | 2669 |
10 YR Norm (11-20) | 19.6 | 3.0 | 17.9 | 467.9 | 2366 | 1546 | 2627 |
SAULT STE MARIE | |||||||
2024 | 23.4 | 4.4 | 3.3 | 551.0 | 2580 | 1689 | 2802 |
2023 | 26.9 | 8.2 | 7.8 | 386.4 | 2530 | 1684 | 2710 |
2022 | 19.5 | 0.9 | 3.6 | 473.8 | 2313 | 1469 | 2488 |
10 YR Norm (11-20) | 19.9 | 4.3 | 35.2 | 535.8 | 2368 | 1526 | 2599 |
THUNDER BAY | |||||||
2024 | 28.8 | 0.5 | 0.0 | 345.1 | 2485 | 1617 | 2658 |
2023 | 30.0 | 5.5 | 3.9 | 313.9 | 2386 | 1564 | 2593 |
2022 | 19.1 | -4.0 | 0.0 | 563.3 | 2267 | 1458 | 2444 |
10 YR Norm (11-20) | 18.7 | 1.9 | 14.1 | 458.1 | 2279 | 1446 | 2483 |
FORT FRANCES | |||||||
2024 | 27.8 | 2.9 | 0.0 | 490.3 | 2573 | 1694 | 2793 |
2023 | 29.8 | 4.4 | 14.5 | 357.7 | 2549 | 1720 | 2780 |
2022 | 20.3 | -5.2 | 0.0 | 624.7 | 2357 | 1549 | 2620 |
10 YR Norm (11-20) | 18.6 | 1.7 | 15.1 | 463.2 | 2404 | 1553 | 2633 |