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European Corn Borer

Ostrinia nubilalis

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Though named for its impact on corn, the European corn borer will feed on a huge variety of crops, and has a particular preference for peppers.
European corn borer.

European corn borer.

Frank Peairs, Colorado State University, Bugwood.org

Description: European corn borer caterpillars are light pink or gray, with brown head capsules and dark dots down each side of their bodies. The yellow pupae are rarely seen, since metamorphosis occurs within the confines of the larval tunnel. The night-flying moths are somewhat nondescript, with grayish brown wings marked by darker lines and yellow areas. Freshly deposited eggs are cream-colored, but age to a deeper beige or tan.

Life cycle: Late instar caterpillars overwinter in corn stalks or other garden litter, then pupate in early spring. Adult moths emerge in late May or June. Females deposit eggs in clusters of 15-20. The larvae develop, feeding on the host plant, and pupate about a month later. In all but the most northern areas, at least two generations occur during the growing season.

Crops damaged: Primarily corn, snap beans, lima beans, peppers, and potatoes. Less frequently, okra, cabbage, beets, celery, eggplant, tomatoes, and other thick-stemmed herbaceous plants.

Signs and symptoms: In corn, European corn borers feed first on the leaves, then move to the tassels and pollen. Older larvae bore into the stalks and ears. In potato plants, borers tend to penetrate the stem, sometimes causing the plant to topple over. For most other crops, the damage is usually restricted to the fruit.

Control measures:

  • At season's end, clear the garden of all weed debris and plant stalks large enough to shelter overwintering borers.
  • Destroy all corn stalks after harvest. Don't put corn stalks or ears in compost piles, as this may allow borers to overwinter.
  • Attract beneficial insects, especially lacewings, lady beetles, and predatory or parasitic wasps.
  • Plant hot pepper varieties, which are more resistant to European corn borer than bell peppers.
  • In northern areas where only one generation of corn borer occurs, planting corn later in the season may limit infestations.
  • When European corn borer populations are high in corn and peppers crops, a pesticide spray may be warranted. Consult your local extension office for advice.

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