Biocontrol Research for Weed Management (Stage 1 & 2)

Invasive weeds cost the NSW economy approximately $1.8 billion per year and pose a serious threat to biodiversity and ecosystem health. While physical removal and herbicides remain common management tools, they are not always sustainable or cost-effective at scale. Biological control (biocontrol) uses the natural enemies of weeds, such as insects and fungi, to suppress weed populations. It offers an environmentally sustainable alternative that can operate across broad landscapes, often in perpetuity.

The NSW Environmental Trust engaged ACIL Allen to conduct an independent evaluation of Stages 1 and 2 of the Biocontrol Research for Weed Management Project, a CSIRO-led consortium initiative funded at $1 million (ex. GST) from 2016 to 2021. The evaluation assessed project design, implementation and governance, value for money, and lessons for future biocontrol investment.

Stage 1 (completed 2017) developed a prioritisation framework through stakeholder consultation with environmental scientists, ecologists and land managers. CSIRO evaluated 266 weed species using a matrix-based approach, producing a shortlist of 17 species and ultimately selecting five priority targets: balloon vine, sea spurge, leaf cactus, broadleaved pepper tree and yellow bells.

Stage 2 (completed 2021) researched and tested candidate biocontrol agents through laboratory and field studies in Australia and internationally. Of the five agents investigated, only the agent for sea spurge received regulatory approval for release. Agents for balloon vine and broadleaved pepper tree were found to be insufficiently host-specific, the leaf cactus agent ultimately proved unsuitable after additional testing, and yellow bells was not pursued due to budget constraints.

The evaluation found the project was well-designed, delivered on time and within budget, and represented good value for money. CSIRO provided $544,000 in in-kind contributions and regularly secured matched co-funding from research partners, effectively multiplying the initial Trust investment. Total grant expenditure varied from the approved budget by no more than 2% per line item, with administration costs of approximately 5%, well below the 10% cap.

The project directly responded to the 2014 Natural Resources Commission review, which had highlighted alarming declines in biocontrol expertise in NSW. At the time, the state had just three biocontrol scientists, no technical officers and no dedicated biocontrol budget. By focusing on environmental rather than agricultural weeds, the project complemented existing NSW Department of Primary Industries initiatives without duplicating them.

ACIL Allen made three recommendations for future biocontrol research. First, lifecycle planning should be incorporated from the outset, covering integration with existing weed control methods, monitoring protocols and post-control site rehabilitation, even where full implementation funding is not yet secured. Second, flexible funding mechanisms should be retained, supported by clear decision triggers for continuing or terminating specific research pathways. Third, the prioritisation framework developed through this project should be adopted as a model for future initiatives, with ongoing adaptability to incorporate new evidence and support transparent decision-making.