The European corn borer (Ostrinia nubilalis) originated in Europe.

 

 

It causes the most damage to maize, as well as millet, hemp and hops; it is capable of damaging pepper, soybeans and cotton.

 

 

Life cycle

Populations of European corn borer pass through the pupal stage twice, first in May and June, and then again in July and August. During the winter it remains in the larval stage. Temperatures exceeding 10 °C trigger the other developmental stages.

The first generation of the corn stem borer, which develops in late spring, feeds on the leaves and stems of corn plants.

The second and third generations feed on the corn cob, leaf sheath and cob stalk.The European corn borer goes through four developmental stages – egg, larva, pupa and adult. The insect is called a moth in its adult stage.

Adult moths lay their eggs on corn plants. The eggs hatch into larvae.

The larvae have five developmental stages, which are followed by a period of diapause or hibernation.

After this intense period of development, an adult moth emerges from the pupa. The duration of the pupal stage is determined by environmental factors such as temperature, number of hours of light and larval feeding, in addition to genetics.

 

Oviposition

 

Adults are capable of flying tens of kilometers in search of suitable oviposition sites.

 

To begin oviposition, adults need water. The insects’ distribution is therefore dependent on rainfall during the spring and summer period.

 

The female moth lays eggs for the first time in June.

 

The eggs are laid on the underside of the leaves of corn plants near the middle of the panicle. About 90 % of the eggs are laid on the leaf just below the main ear, and an equal number of eggs are laid above and below this leaf, with a slight slope towards the lower leaves.

 

The fecundity of the females varies from 200-700 eggs, up to a maximum of 1250 eggs. Eggs are laid as clutches that include 2 to 70 or more eggs (most commonly between 20 and 40).

 

They are laid in an overlapping configuration and are white-yellow. As the larvae develop in the eggs, they become increasingly transparent and the black heads of the immature caterpillars are visible. The caterpillars hatch by gnawing on the eggs. The eggs hatch within three to seven days.

 


Larva

The fully developed larva is 1.9-2.5 cm long. Larval colour ranges from light brown to pinkish-grey and there are noticeable small, round, brown spots on each body segment. As they grow, they reach between 2 and 20 mm. The larvae feed on corn stalks and bury themselves in the stalk and cob.

 

After they have finished feeding, the larvae overwinter in plant debris. Complete development before pupation lasts an average of 50 days.

 

Adults

The European cornstalk borer is about 2.5 cm long and has a wingspan of 1.9-2.5 cm. The female is yellowish brown with dark, irregular, wavy stripes on the wings. The male is slightly smaller and darker.They are most active before dawn.

 

Life span is between 5 and 20 days.

Diapause

Diapause, also known as hibernation, is induced in the European cornstalk borer by changes in temperature and day length. At higher temperatures, the shorter photo period is sufficient to induce diapause. In 13.5 hours of light followed by 10.5 hours of darkness, 100 % of European corn borer larvae enter diapause irrespective of temperature in the range 18 to 29C.

 

Hibernating larvae can survive long periods of very cold winter temperatures. At high temperatures and long photo periods, fewer larvae enter diapause.