TASMANIAN SEA SPURGE BIOCONTROL RELEASE

DECEMBER 2022 UPDATE BASED ON JON MARSDEN-SMEDLEY’S REPORT

Across southern Australia, the highly invasive weed Sea Spurge (Euphorbia paralias) has formed extensive infestations and is a major environmental threat to coastal values.

Along the southern Tasmanian coastline, south of a line from Bicheno to Macquarie Heads, Sea Spurge is still in its expansion phase In this zone it has either not established large infestations yet, or is being controlled by volunteer groups using intensive weeding.

However, in northern Tasmania, Sea Spurge has established massive ecosystem-transforming infestations, containing 10s to 100s of millions of plants In these very large infestations, spraying and hand weeding are not practical A Sea Spurge biocontrol agent has been developed and tested by the CSIRO and approved for release with the aim of assisting with the control of large infestations The biocontrol consists of a highly specific fungus, Venturia paralias, and it is now being tested on Tasmanian coastlines.

Three initial test sites were established in Tasmania in October 2021 with monitoring conducted in April and November 2022 By November 2022, the biocontrol had established and had started impacting the Sea Spurge Of the tagged trial plants, 100% were killed at the Bakers Beach and Low Head sites, and 66% at the Duck Creek site with all remaining tagged plants infected

There has also been a reduction in Sea Spurge health at the three initial sites along with a moderate reduction in cover. To date, there have not been significant impacts to plant height or reproductive status. The biocontrol has also started to spread from the initial sites and infect new areas.

FOR MORE INFORMATION CONTACT:

JON MARSDEN-SMEDLEY FROM SPRATS

JON.MARSDENSMEDLEY@GMAIL.COM

SPRATS.TAS@GMAIL.COM

Further monitoring and new biocontrol releases will help scientists understand its effectiveness in varying conditions