Watch for seedling blights in corn

By John Brien, AgriGold agronomist

The spring of 2012 is shaping up to be another planting season to remember. Late March was warm and beautiful and got a lot of growers excited about planting corn, then April hit. The first portion of April was decent but after April 10, the temperatures were less than ideal. While the soil conditions were good in most areas, the less than ideal soil temperatures kept most growers wondering when to plant corn. Unfortunately the cool to cold soil temperatures were, in fact, a major hindrance in corn growth.

While most corn planted in Mid-April emerged, that emergence took 2 to 4 weeks and once it emerged, the growth has been less than ideal. The latest concern on the corn planted on April 17 through April 20 is a large and often devastating infestation of seedling blights. Seedling blights is a generic term for soil-borne pathogens such as Pythium and Fusarium attacking the struggling corn plant. The major impact of seedling blights is the loss of corn stands.

Corn stand loss due to seedling blights depends on three factors:

1. The duration of time the soil remains saturated (not just flooded),

2. The growth stage of the corn.

3. The average soil temperature.

Essentially all corn is susceptible to corn seedling blights simply because there is little to no resistance to soil-borne pathogens. The seed treatments, such as Acceleron, provide approximately 10 to 20 days of protection. The only long-term protection the corn plant has against seedling blights is rapid growth. The rapid growth allows the corn plant to outgrow the infection of pathogens. Unfortunately, corn seedling diseases are most severe under cold, wet conditions. The ideal soil temperatures for seedling blights are 50-55 degrees. When temperatures are below 60 degrees, corn is not growing rapidly and is therefore highly susceptible to seedling blights.

With the high potential for seedling blights, field scouting is critical to adequately determine the health of a corn field. When scouting a field for seedling blights examine both the healthy and non-healthy looking plants for signs of brown spots or total death. The seedling relies on the seed for its main nutrient source until V3. After V3, the nodal roots provide the plant with the needed nutrients. Without a seed for nutrition the seedling cannot survive for very long. Therefore if the corn plant is taller than V3 and the mesocotyl is damaged there is a strong likelihood the plant will survive, while corn smaller than V3 will eventually die due to the seedling blights. Examining corn fields now could help eliminate any surprises later in the summer.

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