Eucalyptus weevil

Gonipterus platensis

1. Identification

• Common name: Eucalyptus weevil
• Scientific name: Gonipterus platensis Marelli
• Order: Coleoptera
• Family: Curculionidae

2. Pest description

• Adults: Weevils 6–8 mm long, oval body, greyish-brown, with fine scales; short rostrum and geniculate antennae; feed on young leaves.
• Larvae: Apodous, whitish to yellowish-green, soft body and dark head; feed intensively on the leaf blade.
• Pupae: Formed in the soil, in earthen chambers.
• Eggs: Laid in oval masses enclosed by a protective capsule attached to the leaves.

3. Main hosts

• Eucalyptus, especially Eucalyptus globulus, E. viminalis, E. maidenii and other widely cultivated species.
• Preference for young leaves and tender shoots.

4. Symptoms and damage

• Partial or total defoliation due to the feeding of adults and larvae.
• Perforations and irregular cuts in the leaves.
• Reduced growth, loss of vigour and delayed development of the stands.
• Frequent secondary resprouting after intense attacks.
• In severe and repeated attacks, mortality of young trees may occur.

5. Biological cycle

• One to several generations per year, depending on temperature.
• Adults active during much of the year, with peaks in spring and summer.
• Eggs laid in protected masses; larvae develop on the leaves for 3–5 weeks.
• Pupation in the soil; adults emerge and restart the cycle.
• Development favoured by mild temperatures and the availability of young leaves.

6. Monitoring

• Observation of egg masses on the leaves.
• Detection of larvae and adults on young leaves and shoots.
• Assessment of the degree of defoliation, especially in young stands.
• Reinforced monitoring in spring and summer, when the main population peaks occur.

7. Management measures

• Cultural: Removal of heavily attacked shoots; promotion of vigorous stands; choice of less susceptible species or provenances when possible; adequate density management to reduce water stress.
• Preventive: Early monitoring; avoiding operations that cause excessive resprouting during periods of high pest activity; maintenance of soils with good water-holding capacity; avoiding mechanical damage that favours tender resprouting.
• Integrated protection: Regular monitoring; intervention only when necessary; practices that reduce the attractiveness of young shoots and the survival of larvae in the soil.

Bibliographic references

• EPPO Global Database – Gonipterus platensis
• CABI Invasive Species Compendium – Gonipterus platensis
• Nahrung, H. F. et al. – Works on the biology and damage of Gonipterus spp.