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Curculio nucum (L.)
Balaninus nucum

Insecta, Coleoptera, Curculionidae .

Nut weevil

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

- Adult: 7 to 8 mm long, entirely greyish red and covered with a strong pubescence. Rostrum slender, strongly curved, longer than the body in the female (*) , shorter in the male (*) .
- Larva: 15 mm long, apodous, thick, curved, creamy white; head brown (*) .

- The adult feeds on hazel and on the fruits of various trees such as pear, peach, kaki (Diospyros kaki) and, more rarely, apple, plum and cherry.
The larvae develop exclusively in hazel nuts.
- Adult: it appears before the hazel nuts have formed and feeds on the pulp of pears, peaches, etc, which it punctures with its rostrum. Later, it migrates to hazel and punctures the young hazel nuts as well as the leaf laminae. Attacks are localised in newly invaded places. The females lay eggs in the hazel nuts whose diameter has reached 8 to 12 mm; it perforates them with its rostrum and subsequently introduces an egg which it inserts with its evaginable ovipositor (*) .
- Average fecundity: 25 to 30 eggs.
- Eggs: embryonic development lasts 8 to 10 days.
- Larva: it forms a gallery in the nut; when fully grown (after 40 to 60 days), it emerges, drops to the ground, and then forms a cell amongst the roots of the hostplant, at a depth of 10 to 15 cm, in which it remains in diapause between 1 and 3 winters until pupating (*) .

[R]Life Cycle
- 1 generation every 2, 3 or 4 years.
- The adult arising from a larva which has hibernated for only 1 year overwinters again in the pupal cell in the ground; it emerges only in the spring of the third year.
- The larvae having hibernated for 2 to 3 years pupate; emerging adults will lay eggs only in the spring of the third or fourth year.

- The attacked hazel nuts are ruined (*) . Also, the feeding punctures of the adult on pears or peaches cause deformations; on young hazel nuts, they cause many of them to drop prematurely.

[R]Common Names
DE: Haselnussbohrer, Nussrüssler ES: Gorgojo del avellano FR: Balanin des noisettes IT: Balanino delle nocciole PT: Balanino das avelãs GB: Nut weevil

[R] Images

  1. Curculio nucum (L.) (Coutin R. / OPIE)
    Female pupa In the overwintering cells prepared by the larva in the ground.
  2. Curculio nucum (L.) (Coutin R. / OPIE)
    Egg in contact with the kernel during growth The young hazel nut has been cut open to show the egg.
  3. Curculio nucum (L.) (Coutin R. / OPIE)
    Male under a hazel leaf
  4. Curculio nucum (L.) (Coutin R. / OPIE)
    Female boring an oviposition hole in a hazel nut The egg is generally deposited at the base of the fruit.
  5. Curculio nucum (L.) (Coutin R. / OPIE)
    Larva inside a hazel nut The hazel nut has been broken open to show the larva just before its emergence.
  6. Curculio nucum (L.) (Coutin R. / OPIE)
    Attacked hazel nuts Each fruit shows the emergence hole made by the larva.

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