Once corn plants begin emerging, an important step each spring is assessing emergence success. Take note of any abnormalities, missing plants or uneven emergence patterns. One symptom that often occurs each year is referred to as a “corkscrewed” mesocotyl. The mesocotyl is the tissue that connects the base of the corn plant to the seed.

Corkscrew symptoms are usually caused by three main factors: cold injury, soil conditions or herbicide injury. However, these factors can often be confounded with each other, which makes it difficult to diagnose the exact cause of the problem.

Cold injury. Cold soil or wide temperature swings can cause uneven damage to the outer surface layers of the mesocotyl. Areas of the mesocotyl with healthier tissue continue to elongate. However, the damaged layers do not. What you see in this case is the corkscrewing effect. Different sections of the mesocotyl tissue are growing at different rates.

TRACK THE CAUSE: This corn seedling with a corkscrewed mesocotyl was pulled from a field near West Lafayette, Ind., after it turned cold in late April. (Photo by Dan Quinn)

Poor soil conditions. Surface crusting and soil compaction can restrict emergence of corn seedlings. Soils can crust over following planting, or they may be very dense or cloddy. In these conditions, seedlings can bend, twist or even leaf out underground. They sometimes never emerge due to the difficult environment. The seedling just can’t break through the soil surface.

Herbicide injury. Group 15 herbicides such as acetochlor can impact young seedling development if conditions are cool and poor for rapid emergence and growth. However, corkscrew symptoms from herbicide are less common today than in the past due to the use of safeners and current herbicide rates.

Remember, always assess plant stands and check for oddities in development after corn emerges. Also pay attention if you find uneven emergence or missing plants.

Most of the problems you observe occur due to symptoms and developments below ground. Therefore, it is always important to have a shovel or trowel with you as you assess early-season corn emergence. Dig and check overall health and shape of the seed and root system.