Acorn weevil

The acorn weevil (Curculio venosus) is a member of the Curculionidae family, widely recognized as a primary pest of oak trees. This insect is highly specialized, and its survival depends entirely on the availability of acorns, which serve as the food source for its larvae.

The host range is essentially limited to the Quercus genus. Adult weevils feed on young leaves and twigs, but their economic impact is greatest during the fruit development stage. By drilling into the acorns, the females ensure that their offspring have a protected and nutrient-rich environment for growth.

The biological cycle is univoltine. Adults emerge in spring, coinciding with the flowering of oak trees. The female uses her long snout to bore into the developing acorn and deposit an egg inside. Once the larva completes its development, it emerges from the acorn, drops to the soil, and digs down to pupate, remaining dormant until the following spring.

Damage caused by this weevil is easily identified by small, round holes on the surface of acorns. These holes are created either by the female during oviposition or by the mature larvae exiting the fruit. Infested acorns are usually hollowed out, filled with frass, and fail to germinate, causing significant losses in oak regeneration areas.

Management of Curculio venosus is challenging and requires integrated pest management (IPM) practices. Key strategies include:

• Mechanical control: Removing and destroying infested acorns early in the season.
• Soil cultivation: Tilling the soil beneath the canopy to disturb or kill overwintering pupae.
• Chemical control: Applying insecticides only if the pest population reaches an economic threshold in nurseries.
• Forest hygiene: Maintaining healthy stands to improve the overall resilience of the oaks.