Mimeo E-49
January 1964
Purdue University
Cooperative Extension Service
Department of Entomology

SOIL INSECTS AFFECTING CORN
Several kinds of insects live in the soil and feed upon the roots and/or underground parts of corn plants. Some destroy seeds and prevent germination. The number and kind of these soil insects vary greatly from field to field, and there may or may not be enough to cause trouble. Following are the most important soil insects that attack corn in Indiana. The brief description of the pests and their damage should help determine if control measures are needed.

Northern Corn Rootworm: These are small, white, beetle larvae which feed upon the corn roots. Infested plants lack vigor, have poorly developed root systems and are easy to pull from the ground. The corn may also lodge or "gooseneck." Root damage takes place early in the season up to early July.
The worms then start to pupate and emerge from the soil as 1/4 - inch long, green "silk beetles."

This rootworm develops only on the roots of corn, and therefore, the probability of damage increases every year that continuous corn is grown on the same land.

Wireworms: These are hard, slender, brown-colored, wire-like larvae of click beetles, averaging about one inch long. They occur in all soil types but are most destructive in low, poorly-drained areas. Wireworms require from 3 to 5 years to reach maturity. They will feed on germinating seeds, will eat the roots of plants and will even bore upward into the stalks.

White Grubs: These are the familiar large, curved grubs with brown heads. They injure both turf and corn grown in fields that were in sod the previous year. White grubs are the larvae of June beetles.
The clover white grub (grape colaspis) is shaped like the common grub, but is many times smaller. It affects young corn plants by stunting their growth or killing them outright. Purple leaves on corn are a common symptom. This discoloration is actually plant food deficiency resulting from destruction of the corn roots.

Cutworms: The black cutworm, found in heavy dark soils, and the glassy cutworm, in light soils, are two species that feed largely underground and are therefore best controlled with soil insecticides applied broadcast.

Seed Maggots and Beetles: These are tiny maggots and beetles which hollow out and destroy germinating seeds. They are most destructive in high organic matter soil and also in cold soils not conducive to rapid germination.

CORN ROOTWORM