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Towards solutions to achieve biological control of the hazelnut weevil 

Biocontrol of the hazelnut weevil based on olfaction

Balanin des noisettes ou Curculio nucum. 
Au printemps a lieu l’accouplement. La femelle perce ensuite l’involucre de la noisette avec son rostre et pond à la surface de la coque, un œuf par noisette. Au bout de 5 à 10 jours l’œuf éclot et la larve se développe pendant 40 à 60 jours en se nourrissant de la noisette.. © ANPN & Inra, Rachid Hamidi
Updated on 12/09/2016
Published on 11/24/2016

It is not only squirrels that like hazelnuts! They are the preferred target of the larvae of Curculio nucum, commonly referred to as the hazelnut weevil, as they only develop in this small tree nut.

More prosaically, this small coloepter is the principal pest of hazelnut trees and can cause severe damage to orchards.  At present, the number of plant health products that are effective in controlling this pest is diminishing, in the context of reductions in the use of insecticides.  This situation therefore invites professionals to find more sustainable solutions to control this insect.

Searching for the odour of hazelnut

Communication is vital to the survival and reproduction of insects which use their senses to perceive their environment.  Although they can communicate by sound and visual signals, chemical communication is preponderant in their lives. This therefore constitutes a target of interest for the control of pest insects such as the hazelnut weevil.

Led by the French Association of Hazelnut Producers (Association Nationale des Producteurs de Noisettes, ANPN), in liaison with the UNICOQUE cooperative and in partnership with INRA in Versailles-Grignon, the "Biocontrol of the Hazelnut Weevil” project aims to develop alternative methods for the control of this insect. This three-year project (2015-2017) is being co-funded by the European Union through its European Regional Development Fund, and is accredited by the Agri Sud-Ouest Innovation competitiveness cluster.

Initial findings have shown that the arrival of weevils in orchards is linked to the developmental stage of the plants, and that the insects use odorant compounds to detect the hazelnut trees.

Although encouraging in several respects, these results open promising paths towards identifying the molecules responsible for the weevil’s attraction to hazelnut trees and for them laying their eggs in its fruits.

Contact(s)
Scientific contact(s):

Associated Division(s):
Plant Health and Environment
Associated Centre(s):
Versailles-Grignon

A brief description of the hazelnut weevil

As an adult, the hazelnut weevil, or Curculio nucum, is easily recognisable from its small, round black eyes and particularly elongated snout (or rostrum) that carries the antennae and mouth pieces. Its brownish-yellow body, less than a centimetre long, is covered with small scales that form lighter-coloured flecks.

Mating occurs in the spring, after which the female then bores into the involucre of the nut with its rostrum and oviposits on the surface of the shell, leaving one egg per nut (a female can lay 25 and 30 eggs).

Five to ten days after egg deposition, the larvae hatch and then grow for 40 to 60 days by feeding off the nut. Once fully developed, the larva emerges and falls to the ground where it burrows to form a cell and will then overwinter for 2 to 5 years, before it turns into a pupa.

The adult emerges before nuts appear on the tree, feeding off other plants with fleshy fruits that it pierces with its rostrum. When the nuts start to form, it moves to the hazelnut tree and infests the young nuts.