They examined levels of the European corn borer and corn earworm. Tobacco budworm eggs are almost indistinguishable from the eggs of the corn earworm. The corn earworm feeds on every part of corn, including the kernels. On the other hand, corn earworm ridges extend to the rosette. Corn earworm moths regularly migrate from southern regions to northern regions depending on winter conditions. "Helicoverpa zea" earns its nickname the corn earworm for its widely known destruction of cornfields.