Corn Rootworm Information

Corn Rootworm Information

By Kat Yares, Garden Guides Contributor
adult beetle on corn stalk

About Corn Rootworm

The three varieties of corn rootworms, members of the Diabrotica genus, can cause more devastation to a corn crop than any other corn pest. In some areas, all three, Southern, Western and Northern corn rootworms are a threat; in other,s the concern may be only one or two of the species. Although the beetles lay eggs in the late summer, the eggs will lay dormant until the following spring, at which time they hatch and begin feeding on the roots around them.

Prevention and Control

Corn rootworms are best controlled by the use of hybrid corn seed and the use of special insecticides formulated especially for the pest. Prevention is based on rotation of crops, removal of infected plants and debris where the seeds or larvae can hide.

Affected Plants

Corn and soybeans (for egg laying).


The corn rootworm chews and destroys the root structure of the corn plant. With the loss of root, the plant is less able to obtain water and nutrients from the soil, resulting in lower yields. This weakening of the roots can also lead to stalk and root rot. The adult beetle can devastate the silks on the individual ears causing reduced kernel sets.

Predator Insects

Various Steinernematidae and Heterorhabditidae insect-attacking nematodes (microscopic parasitic worms) are useful for destroying the corn rootworm.

Lacewings and ladybugs will eat the eggs deposited on leaves.

Natural Insecticides

A spray of equal parts wood ash and hydrated lime mixed in 2 gallons of water and sprayed on all areas of the infected plant will deter the adult beetles.

Other Methods of Control

* While rotation of crops is the most common way of controlling the corn rootworm, care must be taken as the adult beetle may have migrated from corn to soybeans for laying eggs and in some cases, the eggs can remain dormant for a full year before hatching.
* Remove all debris from the fields of both soybeans and corn once the crop is harvested.
* Monitor fields weekly for signs of infestation and treat accordingly.

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