Today in our corn efficacy evaluation trial, Ashley and our undergraduate team found small corn earworm caterpillars infesting ears (Figures 1 and 2). Caterpillars have a light-colored head but vary considerably in color from light green, tan, pink, maroon, and nearly black. However, they almost always have alternating dark and light lines running lengthwise down the thorax and abdomen and distinct tubercles (bumps) along the side of the body. They also have many black microspines on the body unlike most caterpillars with “smooth” skin.
Unlike European corn borer and fall armyworm that chew through the side or shank, corn earworm enter corn ears through the ear tip. Mature larvae can eat 8-15 kernels, or the top 2 inches of the ear tip. Feeding injury can provide pathways for fungal pathogens to enter the ear. The caterpillars, frass, and disease can be a contaminant when corn is harvested (especially important for sweet corn).