Early Yellowing of Young Corn
- At about the V3 stage of growth, corn plants start to rely on the developing nodal root system to acquire the carbohydrates they need to grow.
- If plants are under stress around V3, the seedlings may stall out in growth and appear light green.
- Several factors can result in stalled growth in corn, including temperature changes, cloudy weather, root pests and pathogens and ammonia injury, among others.
At approximately the V2-V3 stage of corn development, the corn plant starts to shift from relying on the seed for nutrients and carbohydrates to the new nodal root system, in conjunction with the photosynthetic capabilities of the leaves. When growing conditions are favorable and the seedling corn plant is healthy, this transition is nearly seamless. However, the impacts of pests, pathogens, poor climate, or other stress factors can result in issues with plant growth.
Results of stress on V2-V3 corn seedlings may appear to stall out in growth, and color may fade from dark green to yellow-green. This growth hesitation normally doesn’t last long, and corn plants quickly resume their normal growth and return to a darker green color. Nonetheless, this delayed growth and resulting aboveground symptomology can be a little disconcerting. If this V3 stall in seedling corn growth shows up in your area, take the opportunity to investigate the possible contributing factors:
- A sudden shift from warm to cool weather
- An extended period of cloudy weather that can reduce photosynthesis and delay growth
- Pests or pathogens that attack the new nodal roots or mesocotyl. Examples include grubs, wireworms, seedling diseases, and nematodes.
- Root injury from free ammonia in the soil. This is more often observed when ammonia is shallow placed, applied near planting, urea placed close to the seed, or soils are dry.
Pest and pathogen related issues are frequently less uniform in their expression across the field. This differs from weather-related issues, which are often evenly distributed across the field.
Be assured that the V3 growth stall rarely lasts long, unless there is a serious underlying problem. Once the nodal roots contact and start taking up soil nutrients, the color and growth rate of the seedling corn will improve.
Reference: Sawyer: J. 2009. Corn seedling injury from Ammonia