Hazelnut weevil

Systematic position: The hazelnut weevil (Curculio obtusus) is a member of the order Coleoptera and the family Curculionidae. It is a highly specialized pest that primarily targets nut-bearing trees, posing a significant economic threat to hazelnut production worldwide.

Host plants: The primary host for Curculio obtusus is the hazelnut (Corylus spp.). The weevils preferentially attack developing nuts, often selecting cultivars with thinner shells, which facilitates the egg-laying process and subsequent larval penetration into the kernel.

Biology and life cycle: The life cycle is synchronized with the development of the host plant. The insects overwinter as larvae or adults in the soil. In spring, adults emerge, feed on leaves and young shoots, and then mate. Females use their elongated snouts to bore into the developing nut and deposit an egg, which later hatches into a larva that consumes the nut meat from within.

Nature of damage and harmfulness: The most visible damage is the presence of small, perfectly round exit holes on the shell of the nut, created by the larvae as they emerge. Infested nuts are hollowed out, leading to premature fruit drop and complete loss of crop value. The damage is often irreversible once the larvae have entered the nut.

Protection measures: Management of the hazelnut weevil requires an integrated strategy:

• Sanitation, including the collection and destruction of fallen infested nuts before larvae exit.
• Cultivation of the soil beneath the canopy in late autumn to expose overwintering stages.
• Application of selective insecticides at the timing of adult emergence based on monitoring data.
• Use of pheromone traps to determine the onset of activity and threshold of infestation.