Where do first-generation European corn borers primarily feed?

First-generation European corn borers primarily feed in the whorl of the corn plants. This stage occurs when the young larvae hatch and begin to consume the tender tissue found in the whorl, which is the part of the plant where new leaves are developing. Feeding in the whorl can cause significant damage as it affects leaf development and can stunt plant growth. The impact of first-generation feeding is crucial because it can lead to reduced yields by impairing the plant's ability to photosynthesize effectively and create the structure necessary for proper development.

The other choices represent different parts of the corn plant where damage can occur at various life stages of the pest, but the primary feeding area for first-generation larvae is specifically within the whorl. This understanding is vital for implementing effective pest management strategies that focus on controlling populations before they can cause more extensive damage later in the season.