Understanding the distribution
Accurate distribution maps allow targeted control of infestations and provide evidence of where the program has been effective and where it has failed. Knowledge of any nearby infestations, which may reinfect your area, is also useful. It is important to keep taro out of uninfected areas and remove small isolated clumps before they spread. Updating maps regularly provides good feedback to workers on the effectiveness of their efforts.
Physical Control: Mechanical control/slashing does not control taro. Regrowth from corms is rapid. Plants can be grubbed out. Ensure that all corms, corm segments and cormules are removed. Physical removal of plants is the most effective control measure. However, it produces an enormous amount of plant material that requires careful disposal. Because of its rapid growth and spread the entire taro infestation should be removed in one concentrated effort. After this any emerging plants should be pulled out when spotted.
All tubers must be removed from wet or damp areas or they will resprout. The tubers can be composted or rotted down. Be warned, the smell is rather foul.
Chemical control: At present there are no herbicides registered for use in Western Australia on taro. A permit is required for off label use of herbicides except where state 'control of use' laws are in place. A minor off-label-use permit (No. PER4984) covers the control of some environmental weeds in non-crop areas in WA. Herbicide application must comply with all conditions of the permit. A copy of the permit may be obtained from EWAN or the Western Australian Department of Agriculture.
Trial findings: Results from preliminary trials suggest:
Chemical control (continued)
Stems should be cut and swabbed in late summer. In early summer, the copious sap oozing from the cut stems may push the herbicide away. Alternatively, the plants could be slashed and herbicide injected into the bases.
While this method has been found to substantially reduce the population over the short term, its long term success is as yet unknown. Careful follow up is necessary, involving physical removal of isolated plants that survive the initial treatment.
Regeneration of the native plant community:
Our work at Gingin Brook has shown that when small infestations of taro are removed from relatively intact understorey, the space is rapidly recolonised by native species. Some of these, such as the tassel sedge (Carex fasiculata) and the freshwater paperbark come up from seed and some, such as the native fern (Cyclosorus interuptus) and slender knot weed (Persicaria decipiens), move into the site vegetatively. These are all fast growing plants that cover bare ground quickly. Native plants with these attributes are often common in wetland environments with high levels of natural disturbance.
However, regeneration of the native understorey following removal of large infestations may require some assistance. As taro can totally displace the native understorey, removal of large infestations may open up vast areas of bare ground. Erosion of banks and rapid colonisation by other weeds are potentially a serious problem. Careful planning and a long term commitment to site maintenance is required in these situations. Before undertaking such a project you may like to give some thought to the following:
Regeneration of the native plant community once taro has been removed from the site.
Left: In 1999, taro dominated site.
Centre: In 2000, a few small taro plants and little else.
Right: By 2001, Carex fasiculatus and Melaleuca raphiphylla seedlings are emerging through a carpet of Persicaria decipiens, a local colonising species.