Identification & Incidence: Foliar shot hole injury of mid-whorl corn followed by infestation of larvae in stalks in late June or July is first brood European corn borer (ECB) injury. Second brood ECB larvae infest tassels, ears and stalks in August and early September. In general, 1st brood ECB is more common in early planted corn, and 2nd brood ECB is common in late planted corn.

Egg Mass

"Shot-hole" leaf feeding

"Windopane" leaf feeding

Corn borer frass from stalk entry

larva in damaged ear shank

pupa in stalk

Sampling: To evaluate 1st brood ECB, inspect 20 plants at 5 or more locations weekly during whorl stage. Early detection of 2nd brood ECB is difficult. To evaluate 2nd brood ECB, inspect 20 plants at 5 locations for egg masses or early larva.

Economic Threshold: First Brood: Detection of ECB larvae in 75% or more of stand may warrant treatment if an average of 1 larvae per stalk can be prevented from completing development. Second Brood: Treatment may be warranted if 50% or more of the plants have eggs or early larva. Fields having severe 2nd brood ECB infestations should be harvested early to minimize stalk lodging and ear drop.

Management Options: If significant ECB in-festations are detected prior to stalk boring, chemical treatment may be applied. See chart for insecticides labeled for ECB. Planting of ECB resistant or transgenic Bt-Corn is a preventive option.