Eucalyptus weevils
Adult Oxyops species feeding on Melaleuca leaves
© Queensland Government
Eucalyptus weevil larvae feeding; note the trailing excrement strings
© Queensland Government
Damage to leaves caused by eucalyptus weevils
© NSW DPI
Eucalyptus weevils feed on the foliage of some Eucalyptus and Melaleuca species. They can cause stunting and decline in establishing plantations, coppices and naturally regenerating forests. Attacks on mature trees in Australia are not usually of concern; however, the weevils are considered a serious pest in eucalypt-growing regions outside Australia.
Scientific name
Oxyops species
Other names
- Eucalyptus snout beetles
- Australian gum tree weevils
Description
Gonipterus weevils
- Adults:
- grow up to 14mm long
- are brown, dark red-brown or grey-brown, and sometimes striped
- have a smooth dorsal surface
- disperse readily and are active during much of the year.
- Larvae:
- are up to 10mm long and slug-like
- are yellow to orange with small black spots on the back and black stripes on the sides
- may have a thin thread of excrement coiled up or trailing behind them
- are often slimy when older.
Oxyops weevils
- Adults:
- grow up to 14mm long
- are brown or grey-brown, with blotches and mottles
- have a rough dorsal surface.
- Larvae:
- are up to 10mm long and slug-like
- are black
- may have a thin thread of excrement coiled up or trailing behind them
- are often slimy when older.
See additional images of eucalyptus weevils.
Distribution
Widespread across Australia, including temperate and subtropical zones.
Hosts
Gonipterus weevils
- Spotted gum (Corymbia citriodora subspecies variegata)
- Dunn’s white gum (Eucalyptus dunnii)
- Southern blue gum (E. globulus)
- Rose gum (E. grandis)
- Grey gum (E. propinqua, E. punctata)
- Swamp mahogany (E. robusta)
Oxyops weevils
- Broad-leaved paperbark trees, including:
- Melaleuca cajuputi
- M. dealbata
- M. leucadendra
- M. quinquenervia
- M. viridiflora.
Oxyops vitiosa has been used as a biological control agent for M. quinquenervia in Florida, where it is an invasive tree.
Damage
- Larvae feed on the upper surface of emerging leaves, leaving characteristic tracks resembling long, thin windows or holes, which enlarge as the leaf grows.
- Damaged areas turn brown and the leaf falls early.
- Older larvae will consume entire leaves.
- Adults mainly feed on leaf edges, leaving ragged or scalloped patterns.
- Adults can also feed on the soft bark of young shoots.
- Feeding results in retarded growth and shoot dieback.
- Successive defoliation events cause a deformed appearance and the growth of epicormic shoots.
- Sustained attack can reduce tree vigour and cause decline or death in young trees.
- Mature trees are not badly affected.
Biology
- Eggs are laid in batches within a capsule that is attached to leaves.
- Larvae moult several times before falling to the ground to pupate in the soil.
- There are usually 2 or 3 generations per year, depending on the temperature.
Control
- In Australia, natural predators reduce weevil numbers, so control is not usually necessary.
- The Australian parasitic wasp Anaphes nitens has reduced the impacts of weevils in eucalypt plantations overseas.
Resources and research
- Australian Pesticides and Veterinary Medicines Authority (APVMA)
- Carnegie, A, Lawson, SA, Smith, T, Pegg, GS, Stone, C, McDonald, J, 2008, Healthy hardwoods: a field guide to pests, diseases and nutritional disorders in subtropical hardwoods, Forest & Wood Products Australia, Victoria.
- Purcell, MF, Balciunas, JK, 1994, Life history and distribution of the Australian weevil Oxyops vitiosa (Coleoptera: Curculionidae), a potential biological control agent for Melaleuca quinquenervia (Myrtaceae), Annals of the Entomological Society of America, 87:867–873, viewed Aug 2023.