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Stay on Alert for Seedling Diseases

May 2, 2019

Walking your corn fields within the first few weeks after emergence is crucial to identify any early stand issues that could limit yield potential. Take advantage of a rainy day and scout for these issues by identifying any gaps, damping off, discolored plants or other symptoms potentially caused by seedling disease.

Identifying Disease Pathogens

Corn seedling diseases can be classified in many ways, including:

  • Seed rots
  • Seedling blights
  • Root rots

What causes seedling diseases?

1) Fungi: Seedling diseases of most economic concern are caused by fungi, most of which are inhabitants of the soil or may be seed-borne in corn.

  • Soil-borne fungi that can cause seedling diseases include Fusarium, Penicillium, Pythium, and Rhizoctonia.

2) Nematodes: These are most common in sandy soils. Management guidelines are the same regardless of the attacking species.

Diagnosing Seedling Disease

Knowing the disease pathogen can be useful knowledge for future seed treatment selection.

The most critical time to watch for seedling health issues is during and following wet and cool soil conditions (50-55° F or less). Germination, emergence, and/or early seedling growth are considerably slowed in these conditions, making seedlings vulnerable to various pathogens.

Common above-ground symptoms of seedling disease include:

  • Damping off
  • Yellowing
  • Wilting
  • Death

Common below-ground symptoms of seedling disease include:

  • Brown, decaying tissue in the kernel, seminal roots or mesocotyl.

It is important that all 3 below-ground plant segments remain firm and white from germination through the V6 growth stage, which is typically when the nodal root system becomes established and takes full responsibility for feeding the plant.

Managing Seedling Diseases

Guidelines for managing seedling diseases include:

  • Planting seed treated with top quality seed treatment fungicides.
  • Postponing planting if soil temperature is 50-55° F or cooler, with continued, cold wet weather in the forecast.
  • Planting no deeper than 2.5-3”. Planting too deep places the seed into cooler soil which slows growth. It also makes the plant use up more energy to emerge.
  • Rotating crops, which may help some by reducing disease inoculum, but not for diseases that are found on both soybeans and corn.
  • Tilling wet ground to improve drainage.
  • Avoiding compaction, allowing for better drainage.
  • Planting high-quality seed.

For recommendations specific to your field conditions, speak with your local NK® retailer.

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