Ostrinia nubilalis

Scientific Name Ostrinia nubilalis (Hübner)
Synonyms Pyrausta nubilalis Meyrick, 1890
Common Names English: European maize/corn borer; Spanish: Barrenador del maiz; German: Maiszünsler; French: Pyrale du mais; Italian: Piralide del mais
Description The adult moth has a wingspan of about 20-30 mm (0.78-1.18 inch), and is yellow to brown in color. The clutches are very distinctive, with their very flat eggs in an imbricated arrangement.

Biology

Damage

The larvae start feeding on the undersides of leaves, but soon move to the spike, where they feed on the male inflorescences and spin them together. Then they bore into the rolled-up leaves, which causes a typical, regular pattern of holes, and later into the stalk, where the holes are about 2-5 mm (0.078-0.197 inch) in diameter and are always found directly above one of the nodes. Inside the stalk, the caterpillars wander downwards during tunneling and feeding. Occasionally, they leave the tunnel to attack another part of the same plant or to migrate to a neighbouring one. Sometimes the larvae (particularly those from a second generation) can be found feeding on the ears, too.

The galleries and holes through the stalk reduce the plant's mechanical stability. The stem may break or the female ear can fall off, especially in years with heavy rain and thunderstorms. The injuries facilitate infection by fungi, e.g. by Fusarium spp. In addition to visible damage, the weakening of the plant due to impeded transport of water and assimilates leads to an additional reduction in grain weight. An infestation becomes apparent even from a distance if many male panicles are broken.

Lifecycle

In late spring, usually a few days before the female inflorescences appear, the moths lay about 500 -1,500 eggs at night in clusters of 10-50 on the undersides of the leaves. Egg development lasts about 1-2 weeks, depending on weather conditions, the most important factor being humidity. The young larvae disperse over several plants; during this phase, mortality is high, especially in cool and wet weather.

After 3-4 weeks, the caterpillars will either pupate, to produce a second generation of moths about three weeks later, or they will start diapause. In both cases, they stay inside the plants. Overwintering caterpillars are very cold-resistant and have often bored so far down within the plant that they are able to survive the winter in the stubble. They pupate in the following spring.

Occurrence

Additional Crop Information

Preferably corn, but sometimes hop, bell pepper, potato, garden beans and many others.

Agricultural Importance

Ostrinia nubilalis is one of the most important pests of corn. It is found in Europe, North America and some areas of northern Africa. In the northern parts of its distribution range, it produces one generation per season; in the southern parts two, or occasionally more, depending on the climatic conditions in spring and summer.

Control

Integrated Crop Management

Destroying harvest residues, if possible by ploughing them in carefully, significantly reduces the number of surviving caterpillars.

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