Australia’s national science agency, CSIRO, announced that field trials have confirmed the successful establishment of Venturia paralias, a biocontrol agent for sea spurge.

Sea spurge is a serious environmental weed along the whole of Australia’s southern coastline. It is found from Western Australia all the way around Tasmania to mid-New South Wales. It threatens nesting sites of native shorebirds and little penguins (Edyptula minor), and it displaces native plants and changes natural patterns of sand movement.

CSIRO identified a targeted biological control agent for sea spurge: a fungus called Venturia paralias from France. It infects the leaves and stems of sea spurge, reducing its growth and reproduction.

CSIRO began by commissioning comprehensive host-specificity testing of the biocontrol agent. The purpose was to confirm that the fungus, chosen to combat sea spurge, would not harm native plant species. After confirming the fungus was safe and only targeted sea spurge, it received approval for use in the environment.

Senior research scientist Gavin Hunter was project lead. “We worked with Aboriginal Land Councils, Bushcare, Coastcare and Landcare, state government agencies, and the Sea Spurge Remote Area Teams (SPRATS) volunteer group in Tasmania and Victoria, to release the fungus in areas infested with this weed.” The release program across Tasmania and Victoria was supported by the New South Wales government through its Environmental Trust.

Caroline Delaisse is a research technician with CSIRO. She said it was interesting trying to develop field application methods for the fungus. “In the laboratory, we spread the fungus over a plate of agar to grow a ‘lawn’ of mycelium,” she noted. “We dry this out and package it into plastic tubes to mail out to community partners. They then mix it up in a solution to be sprayed onto sea spurge plants at release sites.”

In total, the biocontrol agent has now been released at 182 sites across 40 locations by 26 registered community groups. So far, data from community participants confirms that the fungus has established at 60 release sites. Field surveys have also confirmed the fungus has established in Tasmania.

The fungus has also been released by Parks Victoria at the London Bridge, a natural offshore arch in Port Campbell National Park. This includes nesting sites for little penguins.

CSIRO conducted initial assessments seven months after the release. They showed the fungus had infected sea spurge plants at six dedicated monitoring spots around Victoria’s coastline. Stem lesions were observed at all six spots and leaf lesions observed at five out of the six sites. The sea spurge plants at most of the plots showed decreased health.

The most recent field data is from October 2023. It confirmed that stem and leaf lesions were affecting sea spurge plants at all six monitoring sites. And surveys showed the biocontrol agent had naturally spread further afield at all of the monitoring sites.