European Corn-borer

• It is the pest against which the first transgenic Bt maize, which produces a bacterial insecticidal protein, was designed; its widespread planting in North America has cut populations so far that growers of conventional maize benefit too.
• There are two races that use different pheromone blends and do not recognise one another, a much-studied case of speciation under way within a single species.
• The larva overwinters inside the stems and crop residues, so shredding and ploughing in the stubble is a basic control measure.
• It is the costliest maize pest of the temperate world: the caterpillar bores through the stalk from within, weakening it until it snaps, and it also attacks the cob.
• It reached the United States around 1917, probably in millet brooms imported from Europe, and within a few decades it had colonised the entire Corn Belt.
• It is the main reason Bt maize exists: the transgenic varieties that produce the Bacillus thuringiensis toxin were developed above all against this species.
• And the result has been measured: a 2010 study calculated that Bt maize in the United States had generated some 6.9 billion dollars in accumulated benefit over fourteen years, and that most of it went to growers of conventional maize, because the reduction of the pest across the landscape benefited them too.
• What is known as Ostrinia nubilalis is in fact two races, separated by the sex pheromone they use, that scarcely interbreed.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

Crops of maize, pepper and other thick-stemmed herbaceous plants

Size at birth

Egg 0.97 mm long by 0.74 mm wide; the mature larva reaches about 25 mm

Gestation / incubation

The eggs hatch in 4-9 days depending on the temperature; the larvae go through five or six instars in more than 30 days and the pupa lasts about 12 days

Litter / clutch size

500 to 600 eggs per female, in flat clutches of 15 to 30 on the underside of the leaves

Sources consulted: Wikipedia (es): Ostrinia nubilalis · Bugwoodwiki · NC State Extension · Bugwoodwiki, Ostrinia nubilalis · University of Illinois IPM · CABI, programas de control biologico en Canada · Clemson University Land-Grant Press · Colorado State University

Best time: It overwinters as a fifth-instar larva in the stems; it pupates when the mean temperature rises above 10 °C and the adults emerge about two weeks later, in late spring