Kentucky IPM Pest Information Pages
European Corn Borer | 
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Adult female moths are a pale yellow/brown with irregular darker bands running in wavy lines across the wings. The male moth is darker. The first generation occurs in late May to late June. Early planted corn has greatest potential for damage. The second generation occurs in late June to August. Late planted corn is most attractive to this generation. A third generation occurs in late July and overwinters in the corn stems. |  |
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Results of feeding by small first generation borers appears as "window pane" or "shot holes" in the whorl leaves. Some borers enter leaf mid-ribs and cause them to break. Second generation damage includes feeding on stalks, tassels, ear shanks, leaf collars and developing kernels. Larvae may be found feeding on pollen and leaf tissue behind the leaf sheath and axil. | 
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Economic Threshold
1st generation: Field corn controls should be considered if 50% of the plants show "shot hole" or "window pane" feeding damage and larvae are present. Treatment may be justified for popcorn and seed corn fields if 25% or more of the plants are infested. Once larvae have bored into the stalks, treatment will not be effective.
2nd generation: Treatment is suggested if egg masses average one per plant and egg hatch has begun or if 50% of the plants inspected have live larvae feeding on the leaves or tassels, in the leaf axils or behind sheaths. If your examination indicates that half of the larvae have entered the stalk, insecticide treatment is not recommended.
NOTE: Refer to the European Corn Borer computer decision management software available in your local (Kentucky) county cooperative extension office and/or ask them for a copy of ENT-49 for further information.
References and Additional Information