Mapping the distribution and spread of Nassella trichotoma (serrated tussock) with a view to improving detectability, containment and eradication

Originating in Argentina, Nassella trichotoma (serrated tussock) infests a considerable area of valuable grazing land in New Zealand, South Africa and Australia. Nassella trichotoma has been the cause of severe losses to farmers as it reduces the productivity of grazing land and livestock, and increases weed control costs. When introduced into a new area that provides a suitable growing environment, it can rapidly dominate the landscape as it produces large amounts of wind-dispersed seed and is highly unpalatable to livestock. Nassella trichotoma has recently colonized the Northern Tablelands of New South Wales, Australia, though most infestations are currently scattered and consist of a small number of individual plants. In 1999/2000 the N. trichotoma infestations in a 20 km×30 km area of the Northern Tablelands were located and recorded using a global positioning system (GPS). The number and maturity of plants were recorded at each GPS site. The process was repeated in 2003/2004. Initial results from the mapping of infestations show a reduction in the maturity and size of infestations but an increase in the number of infestations. These changes may be attributed to the development of improved detection and control of existing infestations as farmers become more aware of N. trichotoma, as well as to the continued spread of the weed. Further work is continuing with the aim of being able to better describe the ecological adaptation of N. trichotoma to this area and its localized distribution, and to improve the ability to detect and manage the weed.