At what height of alfalfa do females shift egg laying to growing stems?

The correct height at which female pests shift their egg-laying behavior to growing stems of alfalfa is 6 inches. This shift typically occurs when the plants reach this height, as it provides an ideal environment for the larvae once they hatch. At 6 inches, the plants have sufficiently developed stems that offer both nutritional benefits and shelter for the developing pests. This change in behavior is crucial for the survival of the offspring, as the tender growing stems are typically more conducive to supporting their growth compared to younger, shorter plants.

Understanding this transition point is essential for effective pest management, as monitoring pest activity at this height can inform when to implement control measures. Recognizing the importance of plant height in pest lifecycle timing allows practitioners to strategically manage pest populations before they can significantly impact crop health and yield.