The first weeks after corn emergence is a critical time to walk your fields. After a spring rain, take advantage of a break from field work to check your emerged fields for any gaps, damping-off, discolored plants or other issues that could reduce stands. Several factors can decrease stands, including planter problems, planting depth, insect feeding, herbicide injury, environmental stress and seedling disease.
For many of these issues, there is little to nothing you can do to avoid further damage this season. However, you can use this information to avoid similar issues in the future. We are going to focus on diagnosing seedling diseases and how you can reduce future problems.
Diagnosing Seedling DiseaseBe especially watchful for seedling health issues during and following wet and cool soil conditions (50° to 55° F or less). Germination, emergence and/or early seedling growth are considerably slowed in these conditions, making seedlings vulnerable to various pathogens. Be careful not to confuse disease injury with insect injury, herbicide injury, planting issues or environmental stresses.
Above-ground symptoms of seedling disease include damping-off, yellowing, wilting and death. To check for below-ground disease symptoms, dig up a few plants and look for brown, decaying tissue in the kernel, seminal roots or mesocotyl.
While the kernel provides nutrients for the seedling, the seminal roots pull water and nutrients from the soil. As for the mesocotyl, it is the conduit for water and nutrients to reach the stalk and leaf tissues. It is important that all 3 remain firm and white from germination through V6, which is typically when the nodal root system becomes established and takes full responsibility for feeding the plant.
Identifying Disease PathogensCorn seedling diseases are classified as seed rots, seedling blights and/or root rots. Most seedling diseases resulting in economic damage are caused by fungi commonly found in the soil or seed. However, nematodes may also cause seedling disease, especially in sandy soils.
Soil-borne fungi that cause seedling diseases include
Fusarium, Penicillium, Pythium and
Rhizoctonia, which can be difficult to distinguish between and sometimes can be determined by a lab test. Regardless of the attacking species, management guidelines are similar, but it can be good to know which fungus caused the seedling disease in your corn crop so you can select the correct seed treatment next season.
Managing Seedling DiseasesSome guidelines for controlling corn seedling diseases include:
- Planting seed treated with top-quality fungicides
- Postponing planting if soil temperature is 50° to 55° F or lower, and cold, wet weather is in the forecast
- Planting no deeper than 2.5 to 3 inches
- Planting too deep, which can occur as a result of the seed getting placed into cooler soil, therefore slowing growth and requiring the plant to use more energy to emerge
- Rotating crops may help reduce disease inoculum, but not for diseases that are found in both corn and soybeans
- Tiling wet ground to improve drainage
- Avoiding compaction for better drainage
- Planting high-quality seed
The
University of Illinois and
Purdue University outline more detailed seedling disease guidelines that become more important when your field has a history of issues.
Contact your
Golden Harvest Seed Advisor with questions or for additional agronomic insights.
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