This article includes comments that should help in diagnosing the source and outcome of corn emergence issues.
- The following are tips that should help in diagnosing the source and outcome of corn emergence issues.
- Scouting fields to check for emergence issues should be done early to allow for ample time to replant, if necessary, without yield impacts.
- Contact our Agronomy Specialist for seed, fertilizer, and expert advice.
Several factors can lead to emergence problems in corn. Here are some examples of what we may see this year:
No Seed
Either the planter was not functioning properly, or something removed the seed. If the planter was not functioning properly, this should occur over much of the field, and/or be limited to specific rows, if the issue was not diagnosed and rectified at planting. Birds, voles, ground squirrels, and raccoons will dig and eat seed. Squirrel and raccoon damage is often along field edges, while birds often eat the seed and leave behind the seed coat and the vegetative portion of the plant. These pests usually leave “divots” where they dug up the seed.
Partial Seed Present
Usually caused by insects or rodents. Seed corn maggots and wireworms are common insect pests. Maggots may not be present when damage is discovered because the life cycle is so short. Brown pupal cases the size of a rice grain are evidence of previous maggot activity. Maggot problems are especially common when manure or decaying plant material is present. Wireworms quickly move from plant to plant and may not be present at the plants you are investigating. Be sure to check several plants. Note that decaying seed often sticks to soil and can be challenging to find when digging.
No seedling / Seed is rotted
Seed quality issues are rare unless the seed has been stored too long, under unfavorable conditions or has been damaged during handling and/or planting. In most cases, germination of affected seed is delayed by adverse soil conditions long enough for seedling pathogens to successfully infect. When corn seed swells with moisture, the seed coat loses some of its ability to protect against pathogens. If germination and emergence are delayed because of cool, wet conditions, the pathogens may gain an advantage.
Seed or Seedling is Present, No Longer Growing
Could be from Imbibitional Injury – A corn seed that absorbs cold water may experience irreversible injury to delicate embryonic tissues. Prolonged exposure of planted corn seed to cold rain, snowmelt, or prolonged soil temperatures below 50 degrees Fahrenheit can result in symptoms ranging from failure to sprout, to death of the germinated seedling.
Seedling Stops Growing / Discoloration or Distorted Growth of Roots, Shoot
Cool growing conditions also may increase the potential for herbicide injury. Review the herbicide program and consider the possibility of this type of injury. Injury symptoms can be uniform over the field or may appear in compacted areas, end rows, and possible sprayer overlaps. Review the herbicides that were sprayed during the previous growing season to analyze potential carryover injury from residual herbicides that were sprayed in a different crop.
Shoot or Seedling is Brown-Tipped, Rotted
Pythium and other pathogens may kill corn seedlings that are delayed in growth by cool, wet conditions. While Seed treatment fungicides reduce risk of infection, the length of their activity is limited. Conditions unconducive to rapid emergence may leave the treated seed vulnerable to disease if the treatment wears off before the seedling is established. Emergence and growth delays caused by cool, wet conditions will favor activity by the pathogens.
Unusual Growth, Leafing Out Underground
When daytime high temperatures are in the upper 60s or higher, and nighttime low temperatures drop into the 40s, the coleoptile shoot may curl around and grow the wrong direction, the coleoptile sheath may rupture and the plant may leaf out underground, the radical or shoot may suddenly cease growing, or combinations of these may occur. This is believed to be related to the production of growth substances (auxins or other hormones) during the warmth of the day, which cannot be properly metabolized during the cold of the night.
Leafing out underground can also be caused by surface compaction of soil, cloddy seedbed, planting too deep (rare), or herbicide (esp. acetamide chemistry) activity. Cloddy soils allow the coleoptile to detect light and unfurl the leaf before the shoot and leaves are clear of the soil clod obstructions.
Brown, Wiry Radical / Seminal Roots / Mesocotyl / Shoot – Ammonia Injury
Corn seed and seedlings planted directly over an anhydrous ammonia knife track may be affected by free ammonia in the soil. This is especially common with spring-applied anhydrous ammonia and where wet soils conditions prevent thorough closure of the knife track and/or the sidewalls of the knife track smear and fail to seal properly. Affected seedlings often have brown, wiry looking radical or seminal roots, or may have brown mesocotyl or coleoptile shoot. Symptoms are sometimes delayed in appearing as soils dry and shrink, allowing ammonia to move upward in the soil along the knife track.
Uneven Emergence
Many Causes – Look for variations in planting depth brought about by challenging soil conditions, cloddy soils, soil crust, and poor seed-to-soil contact. In dry conditions, variations in soil moisture depth may render some seeds unable to absorb sufficient water for germination.
