Department of Primary Industries’ (DPI) biosecurity officers recently inspected eight known Scotch thistle sites, which have now been treated to a high standard by landowners.

DPI Biosecurity Officer Larry Martin said it was great that the infestations at these sites had been treated but suspected there may be more infestations of Scotch thistle which had not yet been detected.

“Scotch thistle is declared a regionally prohibited weed in Port Phillip and Westernport because it’s not yet widely spread and can be contained,” Mr Martin said.

“Unlike spear thistle, which is widely spread throughout the catchment, the infestations of Scotch thistle are limited to Cardinia, Melton, Tarniet and Parwan,” Mr Martin said.

“Due to its limited distribution, we are focussing on containing Scotch thistle and working to ensure landholders treat plants prior to seeding with the aim of working toward eradication at each site.”

Mr Martin said landowners within the Port Phillip catchment had a legal responsibility to take all reasonable steps to eradicate Scotch thistles on their land.

“Scotch thistle is easiest to see and identify during late spring and summer,” he said.

“It has a large pink flower head from two to six centimetres in diameter, and generally one main stem with numerous branches compared to spear thistles, which have smaller pink flowers and several stems forming from the base of the plant.”

Anyone who suspects they may have seen Scotch thistle in this region should contact DPI on 136 186.