Stage 1 and 2

Stage 1

June 2016 to June 2017

Stage 1 (funded under Trust grant 2015/MG/0005) aimed to establish a transparent and robust process for prioritising environmental weed species in NSW for future Stage 2 investment in biocontrol research. The project sought to develop a decision-making framework that would identify which weed species posed the greatest threat to natural ecosystems and were most suitable for biocontrol interventions. This approach was designed to maximise the impact of future research investments by focusing on the most promising targets.

Of the 67 high risk weeds assessed, 49 were excluded as unsuitable for biocontrol, leaving 18 priority species. Subsequently, five weeds were selected for investment in Stage 2 research:

- Balloon vine (Cardiospermum grandiflorum)
- Sea spurge (Euphorbia paralias)
- Leaf cactus (Pereskia aculeata)
- Broadleaved pepper tree (Schinus terebinthifolius)
- Yellow bells (Tecoma stans)

Stage 2

July 2017 to October 2021

Stage 2 (funded under Trust grant 2015/MG/0005) aimed to test and progress the approval of safe and effective biocontrol agents for priority environmental weeds in New South Wales identified during Stage 1 prioritisation. The ultimate goal was to enable the release of suitable agents to support sustainable weed management and protect natural ecosystems.

Sea spurge (Euphorbia paralias)

The fungus Venturia paralias was identified, tested, and approved as a biocontrol agent for sea spurge. Rigorous host-specificity trials confirmed its safety, leading to its release in Australia in late 2020. Mass production and field release methods were developed and trialled at three NSW south coast sites, with initial establishment confirmed.

https://research.csiro.au/sea-spurge/previous-research-2017-2024/

Close-up of sea spurge plants growing on a beach in southern Australia.

Leaf cactus (Pereskia aculeata)

The stem-wilter bug Catorhintha schaffneri was tested as a biocontrol agent. Host-specificity trials in South Africa showed high specificity, and a release application was submitted in 2021. Australian authorities requested further testing on six additional non-target species before approval. An 18-month extension was granted to complete these tests, with future releases dependent on results. This research was delivered by NSW DPIRD’s Weed Research Unit. For further details, contact team leader Andrew McConnachie, andrew.mcconnachie@dpird.nsw.gov.au.

Damage to a shoot tip caused by the stem-wilting bug Catorhintha schaffneri in the field in South Africa Left). Nymph top right) and adults bottom right) of of the stem-wilting bug.

Balloon vine (Cardiospermum grandiflorum)

The rust fungus Puccinia arechavaletae was investigated as a biocontrol agent. While effective against balloon vine, host-specificity testing revealed it could infect several native Australian species, posing unacceptable risks. As a result, the project discontinued further research and did not submit a release application for this agent.

https://research.csiro.au/weed-biocontrol/balloonvine/

Foliage, flowers and fruits of balloon vine. (Photo: John Hosking)

Broadleaved pepper tree (Schinus terebinthifolius)

The leaf-feeding thrips Pseudophilothrips ichini was evaluated. Although it could complete its lifecycle on the target weed, it also developed on native species such as Rhus taitensis, presenting a significant risk. Due to these findings, the project did not proceed with a release application for this agent.

https://research.csiro.au/weed-biocontrol/broad-leaved-pepper-tree-biological-control/