Mistaken identity: Urgent appeal to recover invasive weeds sold in Ardrossan

23 March 2020

A highly invasive prohibited weed, mistakenly sold as a plant at Ardrossan’s True Value Hardware during the past three months, must be urgently recovered to avoid an outbreak of this problem aquatic plant.

Salvinia, regarded as one of the worst weeds in Australia and rated a Weed of National Significance (WoNS), was misidentified as the native duckweed until it was recently reported to PIRSA Biosecurity. It had been growing in the local store’s indoor pond and some pieces of the plant were broken off and sold or given away to customers.

This free-floating fern is known to quickly form a thick mass of vegetation in streams and dams that could threaten the state’s primary industries and natural environments. In the right conditions, it can double in size in a couple of days and thrives in nutrient-rich aquatic environments such as agricultural run-off or sewage. Salvinia’s dense matting restricts stock access to watering sites and provides favourable conditions for disease-carrying insects, as well as affecting aquatic habitat for birds and fish.

Natural Resources Northern and Yorke Team Leader Max Barr, who officially identified the pond-growing plant as a weed, said it was crucial to recover all Salvinia sold in the local community and any rogue fragments of the weed that may have gone further afield.

“Salvinia molesta is what is known as an Alert Species and is a huge risk for the whole of South Australia if it became established here,” he said.

“We’re urgently calling on anybody who obtained Salvinia from True Value Hardware in Ardrossan to destroy the plant and also help us track down any that might have been given away. It’s also important for people who have grown Salvinia at home to learn how to decontaminate their garden pond, tank or wherever it was kept.”

True Value Hardware owner Shane Kennedy has joined the campaign to recover the mistaken weed.

“We had duckweed growing in our shop pond but it died during the hot spell leading up to Christmas,” he said. “We were then unknowingly given Salvinia, and while it was never advertised for sale, we have sold or given away small amounts in bags to interested customers. We’re happy to reimburse people and strongly encourage anyone who received fragments of the plant to come into the store where we have photos of the weed for identification, but the most important thing is that it is destroyed.”

Salvinia molesta’s leaves are oval-shaped and lie flat on the water’s surface in the early stages of infestation. The leaves can start to cup due to crowding, before sitting vertically and forming dense mats of floating plants.

People who believe they acquired Salvinia from True Value Hardware in Ardrossan, please contact Natural Resources Northern and Yorke’s Minlaton office on 8853 3880 or the Clare office on 8841 3444.