Sparaxis bulbifera (Iridaceae) invading a clay based wetland on the Swan Coastal Plain - control methods and observations on the reproductive biology
Kate Brown and Kris Brooks, Environmental Weeds Action Network, c/- Swan Catchment Centre, PO Box 1906, Midland, Western Australia 6936, Australia
Sparaxis bulbifera, a cormous geophyte from the Cape Region of South Africa, is a serious invasive weed of clay based wetlands on the Swan Coastal Plain. Where it invades these wetlands it forms dense monocultures, displacing much of the rich native herbaceous flora. Herbicide trials were conducted in the Brixton Street Wetlands south east of Perth, where it is invading shrublands and herblands, and impacts of treatments on co-occurring native species recorded. Metsulfuron methyl was trialed at 1.0 g ha-1 and at 2.5 g ha-1 and chlorsulfuron at 2.5 g ha-1. All treatments significantly reduced the number of juvenile and adult plants of S. bulbifera. Metsulfuron methyl at 2.5 g ha-1 was the most effective reducing the number of adult plants per plot from a mean of 25.4 to 0.4 and the number of juvenile plants from a mean of 373.2 to 28.8.
There were 27 species of native taxa scattered across the trial plots and only two taxa, Sowerbaea laxiflora and Philydrella drummondii appeared to have been adversely affected by the herbicide treatments. The results however were compounded by the spatial distribution and the seasonal nature of the native flora. Additional information on the reproductive biology and spread of the weed was also recorded.
Plant Protection Quarterly (2003) 18 (1) 26-29.