More than 300 types of insects are known to damage corn. Among the most important are the European corn borer, the corn ear-worm (bollworm), the corn rootworm, the chinch bug, the fall armyworm. cutworms, wireworms, white grubs, fleabeetles, and grasshoppers. Crop rotation tends to keep some of these pests under control. Insecticides of various types are effective in many cases and certain hybrids have been developed to resist attack.

The principal diseases of corn are corn blight, smut, bacterial wilt, stalk and ear rots, and rusts. Careful control of soil quality and the use of resistant hybrids are methods of control.