Leafblister sawflies
Symptoms of leafblister sawfly presence; note the larvae visible within the ‘blisters’
© Queensland Government
Leafblister sawfly damage to eucalypt leaves
© Queensland Government
Leafblister sawfly damage to a young plantation tree, with most damage on the lower branches
© Queensland Government
Extensive leafblister sawfly damage in a Dunn's white gum (Eucalyptus dunnii) plantation
© Queensland Government
The leafblister sawfly is a small native wasp. It has a specialised ovipositor that is used to cut slits in the leaf when depositing eggs.
The growing larvae create distinctive blisters on eucalypt leaves. Severe infestations in plantations can cause widespread defoliation and tree death.
Scientific name
Phylacteophaga froggatti, Phylacteophaga species
Other names
- Eucalyptus leaf-mining sawfly
- Leaf-blister sawfly
Description
- These small orange wasps are 4–7mm long at maturity.
- Females have a specialised ovipositor ('sting') that is used to cut slits in the leaf when depositing eggs.
- Larvae feed in groups beneath the upper surface of leaves, mining out sections and creating distinctive blisters. These patches of dead tissue are initially small and enlarge as the larvae grow.
- Larvae are often seen beneath blisters. They mostly occur on older, lower leaves, especially on larger trees.
Distribution
- Leafblister sawflies are widespread in Australia from subtropical to temperate zones.
- Phylacteophaga froggatti is indigenous to coastal eucalypt forests ranging from Brisbane to Adelaide, Western Australia, Tasmania and New Zealand.
Hosts
Leafblister sawflies have a wide host range, including:
- spotted gum (Corymbia citriodora subspecies variegata)
- cadaghi (C. torelliana)
- Dunn's white gum (Eucalyptus dunnii)
- rose gum (E. grandis) and hybrids
- southern blue gum (E. globulus)
- tallowwood (E. microcorys)
- blackbutt (E. pilularis)
- scribbly gum (E. racemose)
- swamp mahogany (E. robusta)
- forest red gum (E. tereticornis)
- brush box (Lophostemon confertus).
Damage
- Leafblister sawflies can cause significant damage in establishing plantations and are considered forestry pests.
- They cause leaf necrosis and inhibit normal leaf function. This leads to premature leaf fall, impedes tree growth and affects overall tree form.
- Mature lower leaves are more often affected.
- Sustained infestations in high numbers can lead to severe defoliation and tree mortality.
- Young eucalypt plantations are most susceptible, especially if already under stress.
Biology
- Eggs are deposited into a slit in the leaf tissue sawn by the female.
- Eggs take around 1 week to hatch.
- Larvae are small and flattish. They feed within the blister on the leaf for the whole feeding period.
- Pupation takes place within the blister, inside a silken cocoon. It lasts 1–2 weeks.
- Adults chew and cut emergence holes to escape.
- There can be several generations per year, depending on conditions.
Control
- Control is not usually necessary. Leafblister sawflies are predated upon by small birds and parasitised by various wasp species.
- Chemical control is difficult.
- Biocontrol methods using an introduced parasitoid have been successful in New Zealand.
Resources and research
- CABI, 2019, Phylacteophaga froggatti (leafblister sawfly), CABI Digital Library, accessed Oct 2023.
- 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.
- Jones, DL, Elliot, WR, Jones, SR, 2015, Pests, diseases, ailments and allies of Australian plants, Reed New Holland Publishers Pty Ltd, Chatswood, NSW.
- Sinclair, RJ, Hughes, L, 2010, Leaf miners: the hidden herbivores, Austral Ecology, 35:300–313, viewed July 2023.