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Evaluating crops after hailstorm.

Agronomy Bulletin 68 ─ Corn Hail Damage

Once a plant advances past the V5 growth stage, the growing point rises above the soil, increasing susceptibility to hail damage.

Situation

Hailstorms regularly strike growing corn fields. But not all damage is created equal. Know how to accurately assess yield loss.

Factors to Consider

  • Recovery time
  • Leaf defoliation
  • Leaf counting methods
  • Kernel damage
  • Stand loss
  • Crop insurance

Action Plan

  1. Allow recovery time. Knee-jerk reactions after a hailstorm are often misinformed. Wait three to five days after a hailstorm passes to determine if corn plants will resume normal growth.
  2. Understand different leaf-counting methods. Most agronomy professionals use the leaf collar method. However, crop insurers use the droopy leaf method, which counts all leaves. This begins with the lowermost rounded tip leaf and continues through the stage indicator leaf (refer to Page 12 in the USDA Handbook), which is at least 40 percent to 50 percent exposed and is usually the uppermost leaf pointing downward. Agronomists and insurers each use the same system to measure reproductive stages and kernel development.
  3. Analyze growing point to assess stand loss. Between planting and the three weeks following emergence, the plant’s growing point is still at or below the soil surface. Through the V5 stage, regrowth is expected and yield loss should be considered minimal. Once the corn is in the V6 stage, the growing point has moved above the soil surface. To estimate stand loss, survey three different sections of a field totaling one-one-hundredth of an acre and project the percentage over the entire field. Find the growing point by splitting the stems. A healthy growing point is creamy white in color. If the growing point is watery with a brownish color, the plant is likely dying.
  4. Study leaf defoliation and direct kernel damage. Leaf defoliation due to hail damage limits yield by reducing the amount of leaf area left for photosynthesis. To determine defoliation, survey all leaves on plants in multiple sites throughout the field and then count missing leaf/leaves that are no longer green, not counting torn leaf areas that remain green. Use the resulting percentage of live leaves along with the growth stage classified by the droopy leaf method to determine lost production (refer to Page 70, Table E in the USDA handbook). Hail occurring after ears are formed can damage kernels developing within husks. Harmed kernels should be calculated as a percentage of total kernels per ear and considered a direct yield loss. Finally, fields with stalk damage should be scheduled for early harvest consideration.
  5. Move forward. Before making any decisions, consult with your crop insurance representative to determine the best course of action. Be sure to factor in additional costs such as insect control and the resulting reduction in your existing stand if considering a replant.

Summary

To evaluate corn yield loss due to hail, wait patiently for the plant to have time to exhibit signs of regrowth. Then, identify the growth stage of the plant and estimate yield loss by combining losses from stand reduction, leaf defoliation and direct kernel damage. For more information, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

Resources

Published on Monday, August 05, 2013