We have had considerable amounts of replanting going on in the county, mostly due to excess water. However, there are many reasons for delayed emergence in corn and corn stand problems. The following are some possible reasons for stand issues.
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.
-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, combinations of several of these factors, or may be due to extended cool wet conditions alone.
-Seed with poorly developed radicle (root) or coleoptile. Coleoptile tip brown or yellow. Could be seed rots or seed with low vigor. Although corn has just started to emerge or has not yet emerged, 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, are soft and fall apart easily while digging are obviously dead or dying. Seeds and seedling roots or shoots that have a weft of 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 creamish-white appearance, are typical symptoms of seedling diseases 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 poor seed-to-soil contact or shallow planting- seed swelled then dried out. Check seed furrow closure in no-till. Seed may also not be viable.
-Skips associated with discolored and malformed seedlings. May be herbicide damage. Note depth of planting and herbicides applied compared with injury symptoms such as twisted roots, club roots, or purple plants.
-Seeds hollowed out. 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. Other conditions that result in uneven emergence 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 to 4 weeks to emerge when soil conditions are not favorable (e.g. temperatures below 55 degrees F, inadequate soil moisture). 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 can be reduced.
Reprinted in part from “Troubleshooting Miscellaneous Emergence Problems in Corn” by Peter Thomison, Pierce Paul, and Ron Hammond in the May 26, 2009 edition of the Crop Observation and Recommendation Network Newsletter from the Ohio State University.