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Ostrinia nubilalis (Hübner)
Micractis nubilalis, Pyrausta nubilalis

Insecta, Lepidoptera, Pyralidae .

European corn borer, Maize pyralid

Description, Biology, Life Cycle, Damage, Common Names, Images

- Adult: 20 to 30 mm wingspan. The fore wings large and thin are pale yellow with thin brown stripes, dented and transversal in the female. They are darker in the male (*) : ochrous to dark brown. At rest, the last abdominal segments of the male protrude from the side of the folded wings.
- Eggs: clustered in egg-rafts of about 20 eggs deposited on the underside of the leaves (*) .
- Larva: 20 m long when fully developed. It is yellowish grey with, on each segment, 6 plates each bearing a bristle.

- Host plants: maize, possibly hop in the north and the red or green Pepper in meridional regions.
- Egg: embryonic development favoured by high hymidity, lasts 5 to 15 days.
- Larva: when the egg hatches, the young caterpillars spread out over several plants; the mortality is high during these dispersals. They penetrate the maize leaf sheath and feed at its base at the expense of the rolled up leaves; the latter later present characteristic perforations.
Then they feed themselves on the male panicle, inside the sheath. At flowering, they abandon it to penetrate the stem at the level of the leaf axil. They dig galleries there as well as in the peduncle of the ear and in the ear itself (*) . The caterpillars are extremely resistant to cold and spend winter in diapause in the crop debris following harvest.
- Pupa: pupal development lasts about 3 weeks (*) .

[R]Life Cycle
- A single generation in the north, 2 complete generations in the Midi-Mediterranean region. Elsewhere, a varying number of first-generation individuals is susceptible to giving birth to a second generation depending on the climatic conditions in spring and summer.
- Nymphosis occurs in May and June for the first generation and the adults emerge at intervals over about a month, from end of June to mid-July with a maximum towards the 10th July in most regions (in Mediterranean zones, the maximum of second generation flights occurs between mid-June and mid-August).
- Allowing for the earliness of eggs with respect to maize crops, the caterpillars can accomplish all the successive types of attack or only the last: the young second-generation caterpillars are often found on the maize ears.

The attacked fields may contain (especially in meridional regions) many plants whose male panicle is broken at the level of the last leaf (*) . The galleries formed in the stem can lead it to break more or less prematurely; those formed in the peduncle can cause the female ear to drop off.
However, even without any apparent damage, the caterpillar's presence leads to a weakening of the plant which results in a reduction of the weight of grains, the losses reaching up to 30%. Serious damage may occur once the population in a maize field reaches one caterpillar per plant at harvest.
- Biological control employs trichogrammids (*) (*) .

[R]Common Names
DE: Maiszünsler ES: Piral del maíz FR: Pyrale du maïs IT: Piralide del mais PT: Pirale do milho GB: European corn borer, Maize pyralid

[R] Images

  1. Ostrinia nubilalis (Hübner) (BASF)
    Capsule containing trichogrammids and eggs Parasitized eggs of
    Sitotroga cerealella can be seen in the opened capsule. Adults of trichogramids will go out by the aperture existing to that effect. It is possible to see the eggs of O. nubilalis.
  2. Ostrinia nubilalis (Hübner) (Daumal J. / INRA Antibes)
    Female trichogram laying eggs In an egg of corn borer.
  3. Ostrinia nubilalis (Hübner) Adult female on a maize leaf (Coutin R. / OPIE)
  4. Ostrinia nubilalis (Hübner) Male moth on a maize leaf (Coutin R. / OPIE)
  5. Ostrinia nubilalis (Hübner) Egg raft under a maize leaf (Coutin R. / OPIE)
  6. Ostrinia nubilalis (Hübner) Damage on maize The stem is broken at the male ear.
  7. Ostrinia nubilalis (Hübner) Larva in the axix of a female ear of maize (Coutin R. / OPIE)
  8. Ostrinia nubilalis (Hübner) Pupa in a fold in a maize leaf The leaf has been partly folded back to display the cocoon and the pupa.

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