The European corn borer, Ostrinia nubilalis (Hübner), is one of the five most important vegetable pests in Pennsylvania. It causes extensive losses in sweet corn and is a major consideration in production of snap beans and sweet peppers. Second generation corn borer injury to peppers is a problem in all areas of the state.

The adult European corn borer overwinters in stalks of corn, weeds, and other herbaceous plants large enough for borers to enter. Borers pupate in April and moths emerge during late May and June. Eggs are laid and borers develop during the summer. The larvae produced by second generation adults overwinter in corn stalks. We typically have a strain with two generations each year; however, in recent years there is an additional single generation strain which produces adults during July.

The full-grown borer is 3/4 to 1 inch long, light brown with two conspicuous, small round, brown spots on the back of each abdominal segment, and the head is dark brown to black. The female moth is pale, yellowish brown with irregular, wavy dark bands across the wing. The male resembles the female but is distinctly darker and smaller. Eggs are small (1 mm) and deposited in irregularly shaped groups in a shingle-like mass of 5 to 50.

The presence of corn borer is often indicated by small egg masses on the leaves and holes in the fruit.

The action threshold for European corn borer is based on blacklight trap catches and field observations for eggs or larval feeding. Control measures are recommended when European corn borer blacklight trap catches average five per night in local traps. In many areas of the state spray applications will be needed from late July through August. As many as eight applications may be necessary.

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