Karamu, a woody shrub native to New Zealand, is a declared weed in a number of locations around Tasmania. The most extensive outbreak occurs in the upper Derwent estuary in the wetlands and along the foreshore between new Norfolk and Dromodary. It thrives in wet environments and has the potential to displace native vegetation and disrupt the normal functioning of the wetland. Healthy wetlands provide breeding areas for fish and birds, help filter pollution and sediment from the water and mitigate floods.
Since 2010 the DEP with support from the Australian Government commenced a control program of karamu. This involved surveying the extent of the infestation and treating outliers to confine its spread and protect the wetlands downriver. In 2011 the treated sites were revisited revealing higher than expected survival. This has prompted a rethink of the methods used and a number of techniques were trialled in 2012 to identify the most effective treatment. The trial included ten different herbicides or mixes, and five different methods of applying it. Karamu found along approximately 8 km of river bank has been treated so far, with follow up treatment required to control emergent seedlings.
The major aim of the three year program is to not only make a start on treatment, but to produce a management plan that outlines best practice for monitoring and control, and the cost effectivness of different on-ground actions. This plan will be available for all land managers, landowners and community groups to encourage a coordinated and strategic approach to manage karamu.