You mightn't have heard of harrisia cactus, but for many communities it's causing hospitalisations, killing animals and gobbling up productive land.

The South American species was introduced to Queensland as a pot plant in the 1890s.

Birds and other animals have since spread it from Charters Towers in North Queensland to Marrar in southern New South Wales.

The numbers are difficult to pin down, but a 2021 study led by Flinders University Professor Corey Bradshaw found it was Queensland’s most costly weed since 1960.