NC State Extension Publications

Description and Biology

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The European corn borer adult, Ostrinia nubilalis, is a yellowish brown snout moth that first appears in late spring. Females lay up to 600 eggs in flat masses of 15 to 20 on the underside of host plant leaves. The eggs resemble tiny fish scales in shape and arrangement. The worms hatch and feed on the surface of leaves for a few days. As the borers mature, they bore into the host plant stalk to feed and they eventually pupate inside. Newly hatched larvae are tiny and pale (about 1/16 inch long). Older caterpillars have black heads, five pairs of prolegs, and pale-yellow bodies bearing several rows of small black or brown spots. They develop through five or six instars to become a fully grown larva about an inch long. The brown pupa is about half an inch long with a smooth capsule like body. European corn borer caterpillars are cannibalistic (This explains why only one or two borers are found in a pot of mums even though the moth laid dozens of eggs.). We have four generations per year in North Carolina.

Female European corn borers have a wingspan of about one inch.

Female European corn borers have a wingspan of about one inch.

Male European corn borer moths are smaller and more slender.

Male European corn borer moths are smaller and more slender.

Frass and silk collect at the entrance hole.

Frass and silk collect at the entrance hole.

The European corn borer grows to about one inch long.

The European corn borer grows to about one inch long.

The prepupa tends to be short and stout.

The prepupa tends to be short and stout.

European corn borers pupate inside the host plant stem.

European corn borers pupate inside the host plant stem.

Host Plants

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Although best known as a pest of corn, this worm has been found boring into more than 200 different plants including chrysanthemums, asters, cosmos, dahlia, gladioli, hollyhocks, roses, zinnia and some vegetables as well as corn. barley, beans, millet, oats, and sorghum. Frass and silk collect near the entrance hole. Eventually slender stalks lodge.

Residential Recommendation

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The best pesticide recommendation we can give is to spray with a pyrethroid such as permethrin or bifenthrin every month or so as field crops harden off in mid to late summer. After the borers are in the stalk it is essentially too late to control them other than cutting out and destroying infested stems. This pest overwinters in the stalk, so destroying the stalks of corn, dahlia, mums and weeds in the area should help to suppress next season's population.

References

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For assistance with a specific problem, contact your local Cooperative Extension Center.

This Factsheet has not been peer reviewed.

Author

Professor Emeritus
Entomology and Plant Pathology

Publication date: June 27, 2013
Revised: Sept. 16, 2019

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