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Eucalypt sawflies | Business Queensland

Eucalypt sawflies

Eucalypt sawflies are also known as clustering sawflies or spitfires. The larvae are often seen in clumps on stems. When disturbed, they raise their tails and regurgitate a yellowish fluid as a defensive mechanism, hence the common name ‘spitfires’.

The adult sawfly is wasp-like in appearance and cannot sting, but is rarely observed. The larvae and the damage they cause are more commonly seen.

Scientific name

Perga species
Pergagrapta species

Other names

  • Clustering sawflies
  • Spitfires

Description

  • Sawfly larvae:
    • are similar to caterpillars with 3 pairs of legs
    • may be covered in short bristles
    • are tan to dark brown or black with a black head and a yellow to orange clasper at the tip of the tail, or light green with a black head and an orange clasper
    • are often seen in clumps of 10 or more on stems during the day
    • disperse and feed at night
    • when disturbed, raise their tails and regurgitate a yellowish fluid as a defensive mechanism.
  • Adults can be up to 60mm long, are wasp-like in appearance and cannot sting, but are rarely observed.

Distribution

Native to Australia and widespread across eucalypt forests and plantations from temperate to subtropical zones.

Hosts

Sawflies have a wide host range including Eucalyptus, Melaleuca and Callistemon species.

Damage

  • Damage to host trees is caused during the larval stage. The adult stage does not feed.
  • Larvae are usually restricted to a small number of trees within a plantation and will often defoliate whole individual trees.
  • Defoliation is common in plantations with establishing trees up to 6 years old. However, widespread defoliation is rarely observed.
  • Single defoliation is unlikely to cause issues in establishing trees.
  • Continued and extensive defoliation may lead to reduced vigour and undesirable form.
  • Sustained defoliation may lead to tree mortality in rare instances.

Biology

  • The adult female sawfly lays eggs in slits made between the upper and lower surface of a leaf or in tree bark. The slits are cut using a specialised ovipositor on the female’s abdomen.
  • Eggs can take up to 2 months to hatch. Adults of some species guard the eggs until hatching.
  • The larvae undergo 6 developmental stages. Each stage lasts 3–4 months.
  • Young larvae graze leaf surfaces at first. When large enough, they eat entire leaves.
  • At maturity, larvae pupate in the soil, or within wood or bark. Adults emerge sporadically.
  • Male sawflies are uncommon; females can produce eggs without mating.
  • Adult sawflies do not feed.

Control

  • Control is not usually necessary.
  • Eggs are preyed on by small birds.
  • Larvae are preyed on by larger birds at all life stages. Larvae are also parasitised by wasp species and tachinid flies.

Resources and research