Beet stem weevil

The beet stem weevil (Conorhynchus conirostris) belongs to the order Coleoptera and the family Curculionidae. This species is recognized as a significant pest of root crops, causing localized but severe outbreaks in commercial beet production areas across its distribution range.

The primary host plants for this pest include members of the Amaranthaceae family, specifically sugar beet, fodder beet, and table beet. While adults feed on the leaves and petioles, the larvae are responsible for deep tissue damage at the crown of the root, which can lead to the total collapse of the plant.

The life cycle of Conorhynchus conirostris is characterized by complete metamorphosis. Adults overwinter in the soil at a depth that protects them from extreme winter temperatures. As the soil warms in the spring, adults emerge, feed on young plant shoots, and initiate reproduction, with females laying eggs near the root collar.

Damage symptoms often start with ragged leaf edges and notched petioles caused by adult feeding. However, the most destructive phase is larval feeding, which creates galleries in the root crown. This leads to weakened plants, secondary infections, reduced nutrient uptake, and a dramatic decline in yield and root quality.

Effective management strategies focus on integrated pest management (IPM) practices. Key tactics include deep autumn tillage to disrupt overwintering sites, proper crop rotation, and the application of systemic insecticides at the time of adult migration. Monitoring of fields during the early stages of plant development is crucial for timely chemical intervention.