Nut weevil

Systematic position: The nut weevil (Curculio nucum) is a member of the order Coleoptera and belongs to the family Curculionidae. It is a highly specialized agricultural pest known for its destructive impact on nut-bearing trees across temperate climatic zones.

Host plants: The primary host is the hazelnut (Corylus avellana). However, the pest is also known to infest sweet chestnut and various oak species. The nut weevil is recognized as a major economic threat to hazelnut orchards, as infestations can result in the loss of a significant percentage of the harvest if not managed properly.

Biology and life cycle: The life cycle is univoltine. The larvae overwinter in the soil within earthen cells at depths of 10 to 20 cm. Pupation occurs in the spring, followed by the emergence of adults. Adult weevils feed on the leaves and young nuts before mating. Females utilize their long rostra (snouts) to drill deep holes into the shells of developing nuts to deposit their eggs.

Type of damage: Damage is caused by the larvae, which feed on the developing kernels. A single larva can consume the entire kernel, leaving the nut empty and filled with frass. These damaged nuts usually drop prematurely. The presence of the pest is indicated by small, circular exit holes in the shell, which are characteristic of this species once the mature larva exits the fruit to pupate.

Control measures: Integrated pest management is essential for controlling Curculio nucum. Cultural practices include the regular collection and disposal of fallen nuts to prevent larvae from entering the soil. Soil cultivation around the base of trees in autumn and spring disrupts the larval pupation process. Chemical control involves the application of appropriate insecticides during the emergence period of adult weevils, prior to egg-laying.