Illinois Field Crop Applicators Practice Test

At which life-cycle stage does a corn rootworm primarily damage the roots?

1. Egg

2. Larvae

3. Pupa

4. Adult

The correct answer is: Larvae

The correct answer is the larval stage, during which corn rootworms are particularly destructive to corn plants. After the eggs hatch, the young larvae emerge and begin to burrow into the roots of corn plants, where they feed on the root systems. This feeding can severely disrupt the plant's ability to absorb nutrients and water, leading to stunted growth, reduced yield, and increased susceptibility to other stresses. In the egg stage, which occurs before the actual feeding begins, the potential for damage exists, but damage does not occur until the larvae hatch and start feeding. The pupal stage is a time when the larvae are undergoing transformation and do not feed, thus causing no direct damage to the plant roots. While adult rootworms may cause some harm by feeding on the leaf tissue, their primary impact is not on the root system and occurs mainly through their reproductive activities, which lead to egg-laying, influencing future generations. Therefore, emphasizing the larval stage is crucial for understanding effective management strategies for corn rootworm damage.