Pest Profile

Northern corn rootworm adults are about ¼-inch long with pale green to yellow coloration. Western corn rootworm adults are about the same size as northerns or slightly larger. Overall coloration when viewed from above is yellow with a black stripe around the margin of each wing cover. Westerns frequently have a dark stripe extending part way up the center of the wing covers. Southern corn rootworm adults are about 3/8 inch long and have 12 black spots on a chartreuse background. Mature rootworm larvae are white and slender, about ½ inch long, with brown heads and a dark plate on the top side of the terminal segment. Southern corn rootworms, Diabrotica undecimpunctata howardi, are of little concern, in part because their eggs apparently do not overwinter in Kansas.

Significant production problems in continuous cornfields are most likely caused by western corn rootworms in Kansas. Damage is caused by larvae, which tunnel within corn roots and prune them as they feed. Severe damage causes the plants to “lodge” or lean over, which greatly reduces the ability of the leaves to harvest sunlight and reduces the plant’s ability to tolerate moisture stress, effectively limiting the amount of soil nutrients brought into the plant. Research has concluded that rootworm-infested corn that lodges will yield less than rootworm-infested corn that doesn’t lodge.