Western conifer seed bug

Leptoglossus occidentalis

1. Identification

• Common name: Western conifer seed bug
• Scientific name: Leptoglossus occidentalis Heidemann
• Order: Hemiptera
• Family: Coreidae

2. Pest description

• Adults 15–20 mm, elongated body and reddish-brown coloration.
• Hind tibiae with characteristic leaf-like dilation.
• Nymphs of orange to brown coloration, without developed wings.
• Piercing-sucking mouthpart, feeding on reproductive structures.
• Very mobile species, frequently observed in aggregations.

3. Main hosts

• Stone pine.
• Maritime pine.
• Scots pine.
• Other species of Pinus.
• Cedars and firs as occasional hosts.

4. Symptoms and damage

• Sucking of sap from green cones and forming seeds.
• Reduction of seed viability.
• Deformation and premature drop of cones.
• Significant losses in pine nut production.
• Frequent entry into buildings in autumn for shelter, causing nuisance.

5. Biological cycle

• One generation per year in temperate climate.
• Adults overwinter in natural shelters or human structures.
• Oviposition in spring on needles and young branches.
• Nymphs develop during the summer.
• Adults active until autumn, with high dispersal capacity.

6. Monitoring

• Direct observation of adults and nymphs on green cones.
• Checking for damage to seeds and immature cones.
• Monitoring in stone pine forests during the summer.
• Recording of aggregations in buildings in autumn.
• Assessment of the intensity of attack to determine the need for intervention.

7. Management measures

• Cultural: removal of severely affected cones, management of surrounding vegetation and sealing of entry points in buildings.
• Biological: promotion of natural predators and research into associated parasitoids.
• Integrated protection: continuous monitoring, interventions only when justified, integration of cultural practices and use of authorised products when applicable.

Bibliographic references

• EPPO Global Database – Leptoglossus occidentalis.
• CABI Invasive Species Compendium – L. occidentalis.
• Lesieur, V. et al. (2019). Invasion and impact of the western conifer seed bug in Europe.
• Fusu, L. et al. (2018). Biology and distribution of Leptoglossus occidentalis in forest ecosystems.