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Corn Emergence Concerns

A large weather system moved across the Corn belt this past week and dumped 3-5” of rain in many areas. Temperatures over the past 3-5 days stayed in the mid 50’s. This stretch of weather could pose potential problems for some of the corn that has already been planted. Illinois sits at 34% planted and 5% emerged, Iowa 8% planted, and Indiana 15% planted and 2% emerged. As the seed sits and waits for warmer temperatures, we should be aware of some of the symptoms that may appear.

Imbibitional Chilling

The process known as imbibition occurs when the seed takes its first drink of water to begin the germination process. In the initial 24-36 hours after planting, you risk chilling the seed if soil conditions are below 50°F. The seeds respond to the imbibition of water by swelling. In cold soil temperatures, cell tissues in the seed are at risk of rupturing during the swelling process. Temperatures between April 23rd and April 25th ranged between 70°F and 80°F. Corn planted on or before April 25th had a good chance to get a warm first drink of water before soil temperatures declined from the cool rain. Probability of seedling damage will not be as high as corn planted after April 25th. Some symptoms can include failed germination and a deformed mesocotyl.

Photos courtesy of Purdue University

Insect Damage

Cool and wet soils create ideal conditions for wireworm and seedcorn maggot feeding. As the seedling sits idle in the soil, insect infestations become more widespread. As the soil warms, wireworms move deeper in the soil profile and are no longer an insect of concern. Fields with manure applications are higher risk for seedcorn maggots, as they feed on decaying organic matter.

Figure 1: Wireworm feeding: Photo by J. Obermeyer

Figure 2: Seedcorn maggot: Photo by Purdue Extension Service

Seedling Diseases

Wet and cool soils are going to be the most favorable for seedling diseases. Pythium and Fusarium are the two most common type of fungal pathogens that infect seedlings. These pathogens attack the mesocotyl and it turns brown and begins to rot. A healthy mesocotyl is important as it transports nutrients from the roots to the plant. Saturated soils and extreme ponding will be a major concern in the coming days as plants try to grow in an environment with limited oxygen.

Photos courtesy of Purdue University

As the weather warms, the ground will begin to crust over. It may be necessary to rotary hoe some of these fields to aid in emergence. If the crop is not able to break through the soil surface, damaged or broken coleoptiles may result. In extreme cases a replant may be necessary. If you have any questions, please contact HarvestMax Associates and we would be happy to help you however we can.

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