European Corn Borer

Ostrinia nubilalis — the European corn borer — is one of the most economically important PESTS OF MAIZE in North America and one of about 1,500 species in family Crambidae (the grass moths and snout moths). The species is native to Europe (where it has been a major maize pest for centuries) and was accidentally introduced to North America in the early 1900s — almost certainly via imported broom corn from Hungary or other parts of Europe in 1909-1917. The species was first detected near Boston in 1917, and rapidly spread across NA over the following 4 decades to become one of the major NA corn pests by the 1950s. The species is now widespread across all of NA corn-growing regions from southern Canada south through the central US to northern Mexico. Adults are 2-3 cm wingspan, pale yellow-tan moths with darker zigzag bands across the wings (males slightly darker overall than females). Larvae are 2-3 cm long when fully grown, light pinkish-brown with darker spots, and tunnel through CORN STALKS, EARS, AND TASSELS. The species' biology: female moths lay eggs on the underside of corn leaves in summer; larvae hatch and initially feed on leaf surfaces (causing 'shot-hole' damage to corn leaves), then BORE INTO THE CORN STALK and tunnel through the inner stalk tissue over 2-3 weeks. Late-instar larvae move into developing corn ears, feed on kernels, and (when the larva is fully grown) tunnel back into the stalk to overwinter. The stalk-tunneling damage WEAKENS the corn plant structurally — wind-broken or 'lodged' corn plants in fields are often the result of stalk tunneling that has weakened the stem to the point of breaking. Yield losses from European corn borer infestation can reach 5-30% of corn yield per generation in unprotected fields, with multiple generations per year compounding the damage. The species and the closely-related CORN EARWORM (Helicoverpa zea) are the TWO PRIMARY TARGETS of GENETICALLY-MODIFIED Bt CORN — engineered varieties expressing Bacillus thuringiensis bacterial endotoxin to provide built-in resistance to lepidopteran larvae. Bt CORN was first commercialized in 1996 and has been one of the most-adopted GMO crops in NA agriculture — currently planted on the majority of US corn acreage. Bt CORN DEPLOYMENT HAS DRAMATICALLY REDUCED EUROPEAN CORN BORER POPULATIONS in NA — a flagship case study of LARGE-SCALE INSECT POPULATION SUPPRESSION by GMO crops. The species' populations in major US corn-growing regions (Iowa, Illinois, Nebraska, Indiana) have declined by 60-90% since Bt corn became dominant — providing a massive 'AREA-WIDE SUPPRESSION' BENEFIT that extends to non-Bt corn fields, organic corn, and alternative crops in the same regions. The Bt-corn-induced area-wide suppression of European corn borer is one of the most-cited examples of GMO benefits beyond direct yield protection in modern agricultural biotechnology. The species is harmless to humans and is a flagship case study in modern textbook discussions of biotechnology-driven pest suppression.