Control of bridal creeper Asparagus asparagoides on Kings Park Scarp and limiting factors on its growth and spread

摘要

The dominant weed along the Kings Park limestone escarpment in Perth, Western Australia, is Asparagus asparagoides (L.) Wight (Asparagaceae) a South African rhizomatous geophyte. A three year research program was initiated to establish limiting factors affecting its growth and spread, and to determine control measures. Research indicated that the preferred habitat of bridal creeper is characterised by high soil and litter moisture content and low light intensity, which equates to a longer growing andreproductive season. Disturbed and native habitats with high shade factors are ideal for establishing new populations and subsequent spread. Opening up the canopy to increase light levels above 1000 mu mol sec~(-1) m~(-2) significantly reduces its invasive capacity and assists the establishment of native understorey species. Some knowledge on the control of bridal creeper in Kings Park bushland had been established as early as 1991. Further trials conducted in 1997 in late autumn, winter and early spring were designed to establish if a range of non-selective herbicides at low rates would kill bridal creeper without too much off-target damage to indigenous species. Brush-off (600 g kg~(-1) metsulfuron methyl) achieved the best results overall. When sprayed in July at a rate of 1 or 2.5 g ha~(-1) up to a 100% reduction in above ground biomass of bridal creeper was recorded with little off target damage. The results also indicated a much larger window of opportunity (May to July) when spraying at the higher rate of 2.5 g ha~(-1). Implementing these results on an operational scale has resulted in high death rates and reduced the estimated above ground biomass of bridal creeper on the scarp by 85%.