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.  In addition, seed and seedlings affected in this way are often attacked by fungi and end up rotting.

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 production of growth substances (auxins or hormones) during the warmth of the day, which cannot be properly metabolized during the cold of the night.

Leafing Out Underground – This can 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.

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 or could be limited to specific rows.  Birds may eat the seed.  Look for evidence of bird activity.  Voles or ground squirrels will dig and eat seed.  They usually leave “divots” where they dug up the seed.  Insects may eat the seed.  Insects often leave fragments of the seed.  Look for the insect, itself. (Note: Rotted seeds stick to soil and can be very hard to find when digging.)

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.

Seedling Stops Growing / Discoloration or Distorted Growth of Roots, Shoot – Cool growing conditions may increase the potential for herbicide injury.  Review the herbicide program and consider the possibility of this type of injury.  Injury symptoms are often uniform over the field or appear in compacted areas, end rows, and possible sprayer overlaps.

Shoot or Seedling is Brown-Tipped, Rotted – Pythium and other pathogens may kill corn seedlings that are delayed in growth by cool, wet conditions.  Seed treatment fungicides protect the seed and seedling for only a limited time.  Emergence and growth delays caused by cool, wet conditions will favor activity by the pathogens.

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.  Poor seed-to-soil contact.