Seven regions of the state have been infested with rice grass, which severely affects the aquaculture and wild fishing industries.
Little Swanport on the east coast of Tasmania has been hit by the weed, which oyster farmer, Colin Dyke, told ABCHobart was harming the industry.
"It looked as though about a third of the estuary was going to be taken over by rice grass, we had to do something then," he told ABC.
Mr Dyke says volunteers from three oyster farms pitched in to kill the pest with herbicide.
Oyster Farmers Winning Against Water Weeds
AUSTRALIA - Oyster farmers in Tasmania are winning the fight to save their crop from an introduced weed species.