Pedrolho

Polydrusus chrysomela

1. Identification

• Common name: Leaf weevil
• Scientific name: Polydrusus chrysomela Olivier
• Order: Coleoptera
• Family: Curculionidae

2. Pest description

• Small adults (4–6 mm), oval body and metallic-green or greenish colouring.
• Covered by fine scales that give them a shiny appearance.
• Short rostrum, typical of weevils.
• Apodous larvae, whitish, develop in the soil.
• Adults feed on young leaves, causing characteristic notches.

3. Main hosts

• Pome fruit: apple tree, pear tree.
• Vine.
• Various tree and shrub species may be occasional hosts.

4. Symptoms and damage

• Semicircular notches on the leaf margins caused by the adults.
• Irregular perforations in young leaves.
• Reduction of the photosynthetic area.
• In intense attacks, delayed vegetative development.
• Damage generally more relevant in young or recently established plants.

5. Biological cycle

• One generation per year.
• Adults emerge in spring and feed on young leaves.
• Oviposition in the soil, where the larvae develop feeding on fine roots.
• Pupation in the soil, with the emergence of the adults the following year.
• Cycle favoured by loose soils and the presence of host vegetation.

6. Monitoring

• Observation of notches in young leaves.
• Visual inspection of adults in the early hours of the morning.
• Regular monitoring in young orchards and vineyards.
• Recording of favourable conditions (humid spring and tender vegetation).
• Assessment of attack intensity to determine the need for intervention.

7. Management measures

• Cultural: surface tillage of the soil to expose larvae and pupae, removal of spontaneous host vegetation and management of plant vigour.
• Biological: conservation of natural enemies present in the soil and use of entomopathogens when authorised.
• Integrated protection: continuous monitoring, interventions targeted only when necessary and integration of cultural practices to reduce the annual population.

Bibliographic references

• EPPO Global Database – Polydrusus spp..
• CABI Invasive Species Compendium – P. chrysomela.
• Cross, J. V. et al. (1999). Pests of pome fruit in temperate regions.
• Alford, D. V. et al. (2007). Pests of fruit crops: identification and management.