European corn borer

The European corn borer (Ostrinia nubilalis) differs from corn earworm in where it attacks corn -- the borer enters not through the silk tip but through the stalk, leaf axils, and shank (the stem connecting the ear to the stalk). The damage is stalk breakage ("stalk lodging"), ear shank penetration.

The European corn borer (Ostrinia nubilalis) differs from corn earworm in where it attacks corn — the borer enters not through the silk tip but through the stalk, leaf axils, and shank (the stem connecting the ear to the stalk). The damage is stalk breakage ("stalk lodging"), ear shank penetration that disrupts kernel fill, and bore holes in the ear itself. A corn planting with European corn borer pressure looks different from earworm damage: the sign is not a worm at the ear tip but a snapped stalk or a pile of yellow frass at a leaf axil.

I don't grow corn at my Long Island property, so this guide draws on Cornell Cooperative Extension and Penn State Extension research.

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The pest

The European corn borer (Ostrinia nubilalis) is a moth (Lepidoptera: Crambidae) introduced from Europe in the early 1900s. Per Cornell Cooperative Extension, it is now one of the most widespread corn pests in North America, also attacking peppers, potatoes, beans, and other crops.

Adults are:

• Tan to pale yellow-brown moths, wingspan approximately 1 inch
• Female: pale yellow-brown with darker zigzag patterns
• Male: darker olive-brown

Larvae are:

• 0.75–1 inch at maturity; tan-gray with dark spots arranged in rows; brown head capsule
• Bore into plant tissue; produce the characteristic sawdust-like frass at entry holes

Per Penn State Extension, in the mid-Atlantic and Northeast, two generations occur per year:

• First generation: moths active in late May–June; larvae feed in corn whorls
• Second generation: moths active in late July–August; larvae bore into stalks, shanks, and ears