Submitted by Wayne Flanary

Most corn fields during emergence looked like a “picket fence.” Spacing and emergence has been excellent in most fields. However, once we reach the V-4 corn growth stage, we find plants missing and stunted when we closely look at corn stands. Now is the time to identify why some stands are fading. Once corn reaches corn growth stage V-6, diagnosis often is more difficult.

During emergence, the mesocotyl may be restricted by soil, residue and temperature swings. This may cause it to break open causing the leaves to corkscrew and hinder emergence. The mesocotyl is a structure that encloses the leaves like they were enclosed in a straw. As the mesocotyl reaches the soil surface under normal conditions, light stops it growth and leaves emerge. Sometimes the plants emerge and are twisted but are stunted.

Insect injury can cause reduction in stands. Looking at individual corn stalks, you may see the center leaves wilting and find the seedling partially fed on below the soil surface by insects. This may happen despite the addition of seed insecticide treatments.

Fungicide seed treatments prevent most seedling diseases for two to three weeks. Once fungicides breakdown, fungal diseases such as Pythium and Fusarium may infect the young corn plant. This may cause death or stunted plants.

There have been a few questions regarding ammonia burn. This is easy to recognize as the roots will be burned off as they enter the ammonia zone. The highest concentration of ammonia is center of the injection and the concentration of ammonia decreases to outside of the band. Initial roots entering zone may be brown in lighter concentrations. Top-growth will take on a wilting appearance. Often the field will have a checker-board appearance if the ammonia was knifed in at an angle and corn planted in normal direction. Each time the planter unit plants into the ammonia zone, plants die or look like they are drought stricken.

Importantly, one should be scouting corn to identify any problems. Emergence problems will soon be difficult to diagnose.

There will be a corn emergence demonstration August 22 at Graves-Chapple  field day. Corn plants are marked on the day they emerged. Many growers are concerned about uniform emergence.

For more information, contact Wayne Flanary, Field Specialist in Agronomy with the University of Missouri Extension Service, at 816-279-1691 (office) or 913-220-3670 (cell phone).