Lucerne seed weevil

Systematic position. The lucerne seed weevil (Tychius crassirostris) is a member of the Coleoptera order and the Curculionidae family. It is a specialist pest that has co-evolved with legume plants, primarily focusing on alfalfa (Medicago sativa).

Crops and damage profile. This pest primarily targets alfalfa seed crops. While adult beetles feed on flower buds and foliage, the larval stage is the most destructive. Larvae penetrate the developing seed pods and consume the interior of the seeds, rendering the seed lot useless for commercial or agricultural purposes.

Biology and lifecycle. The weevil typically overwinters as an adult in soil or leaf litter within or near alfalfa fields. As temperatures rise in spring, they emerge and begin feeding on succulent plant tissues. Females lay eggs inside the pods, and the developing larvae remain within the seed pod until they complete their growth, after which they drop to the ground to pupate in the soil.

Economic importance. The lucerne seed weevil is a major limiting factor in alfalfa seed production. Due to its cryptic nature, high infestation rates can cause substantial losses, often exceeding 50% of the potential harvest if left uncontrolled. Proper management is essential for maintaining high-quality seed yields.

Protection measures. Integrated Pest Management (IPM) is crucial for controlling this weevil:

• Implementing crop rotation to break the pest's life cycle.
• Deep autumn plowing to disturb the soil and destroy overwintering sites.
• Monitoring adult populations using sweep nets during the budding phase.
• Applying targeted insecticides during the early blooming stage when threshold levels are exceeded.