Leaf cactus

Leaf cactus (Pereskia aculeata), a primitive climbing cactus, is an environmental weed in New South Wales and Queensland. It invades riparian zones, urban bushland, open woodlands, dry forests (including mature native and planted stands), and shrubby rocky areas. Its brightly coloured fruits are bird dispersed and vegetative fragments are often viable.

This sub-project focuses on the stem-wilting bug Catorhintha schaffneri, which attacks the new growth of leaf cactus and as a result reduces flowering and fruiting. In its native range (Brazil) and in South Africa where it has been released as a biocontrol agent against leaf cactus, the stem-wilting bug has been found to damage a significant number of shoot tips (sometimes as much as 90%). Host-specificity tests performed in South Africa showed that this insect is highly specific. Additional host-specificity testing, comprising non-target species relevant to the Australian context, are being performed in quarantine facilities in South Africa and Australia to complement previous results. It is noteworthy that Australia does not have any native species in the Cactaceae family to which leaf cactus belongs. Approval for its release in Australia will be sought from the relevant authorities, pending results indicate that the stem-wilting bug does not pose a threat to non-target species.

Andrew McConnachie of NSW Department of Primary Industries is leading this sub-project.

Damage to a shoot tip caused by the stem-wilting bug Catorhintha schaffneri in the field in South Africa (left) (Photo: A. McConnachie, NSW DPI). Nymph (top right) and adults (bottom right) of the stem-wilting bug (Photos: Iain Paterson, Rhodes University).

The key activities of the sub-project are to:

  1. Prepare and submit to the national Environment and Invasive Committee an information dossier to support the nomination of leaf cactus as a target for biocontrol in Australia.
  2. Undertake in both South Africa and Australia, additional host-specificity testing of C. schaffneri on closely-related plant species to leaf cactus, including selected Australian native species and, pending results indicate that the insect does not pose a threat to non-target species.
  3. Prepare and submit to the relevant authorities an application for its release in Australia for the biocontrol of leaf cactus, pending results indicate that the insect does not pose a threat to non-target species.