Source: Ohio State University Extension
By Peter Thomison, Pierce Paul, Andy Michel
According to the USDA National Agricultural Statistics Service for the week ending May 24, corn was 87% planted, which was 21% ahead of last year and 17% ahead of the 5-year average. Across Ohio, corn is at a range of growth stages. Some of the corn planted in early May is showing up to 3-leaf collars but in later planted fields, corn is still emerging.
Troubleshooting emergence problems early is critical in identifying solutions and developing successful replant plans, if needed. Here's a list of a few common things to look for if you encounter an emergence problem in corn this spring. (Some of this information has been adapted from a newsletter article written by Greg Roth at Penn State several years ago.)
No seed present. May be due to planter malfunction or bird or rodent damage. The latter often will leave some evidence., such as digging or seed or plant parts on the ground.
Coleoptile (shoot) unfurled, leafing-out underground. Could be due to premature exposure to light in cloddy soil, planting too deep, compaction or soil crusting, extended exposure to acetanilide herbicides under cool wet conditions or combinations of several of these factors. It may also be due to extended cool wet conditions alone.
Seed with poorly developed radicle (root) or coleoptile. If the coleoptile tip is brown or yellow, it could be seed rots or seed with low vigor. Although corn has just started to emerge or has not yet emerged in many fields, growers should carefully inspect seedlings for symptoms of disease, especially in lower lying areas of fields where ponding and saturated soils were more likely.
Seeds and seedlings that are brown in color, soft and fall apart easily while digging, are obviously dead or dying. Seeds and seedling roots or shoots with white to pinkish mold growing on them are likely victims of fungal attack and will likely die.
Pythium and Fusarium are common fungi that attack plants and cause these damping-off or seedling blight symptoms under wet, cool conditions. It is more difficult to diagnose disease damage on plants that also show abnormal growth caused by cold soil conditions or by crusting of the soil surface. However, dark, discolored roots and crowns, instead of a healthy creamy white appearance, are typical symptoms of seedling disease problems. So it is best to check these seedlings very closely for dark brown or soft areas on seedling roots and shoots. Any discoloration will indicate a problem that could worsen if the soils remain cold or wet.
Seed has swelled but not sprouted. Often due to poor seed-to-soil contact or shallow planting — the seed swelled then dried out. Check the seed furrow closure in no-till. Seed may also not be viable.
Skips associated with discolored and malformed seedlings. May be herbicide damage. Note the planting depth and which herbicides were applied compared with injury symptoms such as twisted roots, club roots or purple plants.
Seeds hollowed out. Likely seed corn maggot or wireworm. Look for evidence of the pest to confirm.
Uneven emergence. May be due to soil moisture and temperature variability within the seed zone. Poor seed-to-soil contact caused by cloddy soils, soil crusting or shallow planting can also cause this. Other conditions that result in uneven emergence are already noted above, including feeding by various grub species.
Note patterns of poor emergence. At times they are associated with a particular row, spray width, hybrid, field or residue that may provide some additional clues to the cause. Often two or more stress factors interact to reduce emergence where the crop would have emerged well with just one present.
Also, note the population and the variability of the seed spacing. This information will be valuable in the future.
Don’t forget that corn may take up to 3-4 weeks to emerge when soil conditions are not favorable (e.g. temperatures below 55 F, inadequate soil moisture). This was widely observed in many fields in 2005 when corn planted in mid-April did not emerge until the first or second week of May. As long as stands are not seriously reduced, delayed emergence usually does not have a major negative impact on yield. However, when delayed emergence is associated with uneven plant development, yield potential is often reduced.