Walnut weevil

Systematic position: Sternuchopsis juglans belongs to the order Coleoptera and the family Curculionidae. This species is recognized as a significant pest specifically targeting walnut trees, causing economic damage by focusing its lifecycle on the nut development stages.

Host plants and damage: The primary host is the walnut tree (Juglans regia). The larvae cause major economic losses by feeding directly on the kernel. As a result, infested nuts drop prematurely, and the internal quality of the harvest is severely compromised, rendering it unfit for commercial sale or consumption.

Biology and lifecycle: The lifecycle is synchronized with the phenology of the walnut tree. Adults overwinter in soil or leaf litter, emerging in spring to mate. Females lay eggs by boring into the young fruit. The larvae hatch and consume the growing kernel, developing through several instars before either pupating inside the nut or exiting to pupate in the soil.

Nature of damage: Infestation is characterized by visible entrance or exit holes on the husk and shell of the walnut. Internally, the nut exhibits extensive tunneling and contamination with frass, which often leads to secondary fungal rots. Infested nuts are usually hollowed out or significantly decayed by harvest time.

Control measures: Integrated pest management (IPM) is essential for effective control. Key measures include:

• Sanitary removal of all fallen nuts to destroy larvae.
• Application of selective insecticides during the peak emergence of adults.
• Maintaining healthy orchard vigor to withstand minor infestations.
• Using pheromone traps for monitoring and timing treatments.