Rape stem weevil

The rape stem weevil (Ceutorhynchus napi) is a significant beetle species belonging to the order Coleoptera and the family Curculionidae. It is recognized as a major pest of oilseed rape, causing considerable yield losses in many agricultural regions where brassica crops are cultivated on a large scale.

This pest exclusively targets members of the Brassicaceae family. While oilseed rape is its primary commercial host, the weevil also utilizes various cruciferous crops and wild weeds for feeding and oviposition. Its ability to adapt to different host plants makes it a persistent threat in regions with intensive brassica production.

The life cycle of the rape stem weevil involves overwintering in the soil as adults. In early spring, once temperatures rise above 10°C, the weevils emerge and migrate to host plants. Females puncture the stems of young plants to deposit eggs. The larvae then hatch and feed internally, boring through the pith of the stem, which disrupts the plant's nutrient transport system.

Damage symptoms are often visible through the physical deformation of the plant. Infected stems may develop a characteristic S-shaped curve, swell, or even split open as the larvae grow. This structural damage renders the plant susceptible to fungal pathogens like Phoma lingam and severely weakens the plant's overall vigor, often leading to reduced seed production and pod shedding.

Effective management requires a combination of strategies. Crop rotation is essential to prevent the buildup of pest populations in local soil. Monitoring the arrival of adults using yellow pan traps allows for precise timing of chemical control applications. Applying insecticides when the weevils are active but before egg-laying begins is the most effective approach to protect the crop yield.