Which of the following is not listed as a severe corn pest?

Aphids are not typically classified as severe pests of corn. While they can infest corn and cause some damage by feeding on plant sap and potentially transmitting plant diseases, their impact is generally less severe compared to the other pests listed.

Northern and western rootworms are known for their significant detrimental effects on corn, primarily by damaging the roots, which can severely stunt growth and yield. Cutworms also pose a notable threat as they can cut young corn plants at the soil line, leading to plant loss. In contrast, the damage caused by aphids is more frequently associated with vectoring viruses and causing minor stress rather than the catastrophic damage seen with the rootworms and cutworms. Consequently, while aphids can be a concern for corn production, they are not categorized among the most severe corn pests.