Environment

Biocontrol agent:
Bracon phylacteophaga  

Target pest:
The leafblister sawfly (Phylacteophaga frogatti), a small Australian wasp whose larvae feed by mining inside the leaves of eucalypts.

What do the Bracon phlacteophaga wasps look like?

Bracon phylacteophaga are small wasps which are ectoparasitoid, meaning they develop outside the body of their host, and are frequently attached to,or embedded in, the host's tissue. If Bracon phylacteophaga are present, the larvae will be seen in the blister on eucalypt leaves feeding on the sawfly larva.

Where are they found?

Bracon phylacteophaga wasps have established throughout Northland.

When and how can they best be harvested for redistribution?

You can tell whether the sawfly larvae in an area are parasitised by opening a sample of the blisters to find the parasitoid larvae feeding on the sawfly larvae. If the parasitoid larvae are seen in the sample, collect intact blistered eucalypt leaves and move them to new sites. Some of them, and in a lot of cases most of them, will contain parasitoids which will emerge to attack sawfly larvae in the area.

What does the target pest look like?

The leafblister sawfly larva has an orange head and a soft yellowish-white, translucent, flattened body. A fully grown larva is about 10mm long. The blister develops from the place where the egg was laid and broadens as the larva grows.

What damage does the target pest do?

Eucalyptus sawfly larva inside a leaf blister.
Source: Ensis The leaf blister sawfly can severely damage the leaves of eucalypts. The lower leaf surface remains intact, but the upper leaf cells are eaten, leaving just a thin, papery blister. Several blisters may join together, destroying much of the leaf which may be shed prematurely, as seen in the picture below. Damage is most common on foliage up to three metres above ground level and small trees can be totally defoliated. In sheltered areas, the damage to large trees can extend high into the canopy.

What about the leafblister sawfly’s life cycle?

Pupation occurs within the blister. Before pupating, the larva spins a silken cocoon which is attached to both leaf surfaces. The newly-formed adult cuts a hole through this to emerge. Larvae can successfully complete their development and pupate in infested leaves which have fallen or been removed from the tree.

The adults live for about five days only, and do not feed. Mating and egg-laying begin soon after emergence. The sawfly has many generations per year, and eggs, larvae, pupae and adults can be found at any time. The life cycle slows down during the winter, but numbers rapidly increase in warm, dry, summer weather.