Illinois Field Crop Applicators Practice Test

At what point during its life cycle does the European corn borer cause significant damage?

1. First generation during whorl damage

2. Only during the adulthood phase

3. Second generation with stalk tunneling

4. Throughout the entire lifecycle

The correct answer is: Second generation with stalk tunneling

The European corn borer primarily causes significant damage during the second generation when it engages in stalk tunneling. At this stage, the larvae have already fed on the plant tissue during their earlier growth phases but reach a critical point of destructiveness when they begin to tunnel into the stalks. This behavior not only weakens the structural integrity of the plant, potentially causing lodging, but also creates entry points for pathogens and moisture, further exacerbating plant health issues. The first generation can inflict some damage through whorl feeding, particularly when larvae attack young plants, but it is the second generation that typically has a more pronounced impact on yield loss due to the severity of stalk tunneling. Tunneling can lead to reduced plant vigor and lower overall quality and quantity of the crop, which is why this stage is crucial for management strategies aimed at minimizing European corn borer-related losses. As for the other choices, the adult phase does not contribute as significantly to crop damage, and while some damage may occur throughout the lifecycle, it is particularly the actions of the second generation that lead to the most pronounced effects on corn plants.