An eight year removal experiment measuring the impact of bridal creeper (Asparagus asparagoides (L.) Druce) and the potential benefit from its control
Peter J. TurnerA,B,C and John G. VirtueA,D
A CRC for Australian Weed Management.
B School of Animal Biology, University of Western Australia, Stirling Highway, Crawley, Western Australia 6009, Australia.
C CSIRO, Division of Entomology.
D Department of Water, Land and Biodiversity Conservation, GPO Box 2834, Adelaide, South Australia 5001, Australia.
Bridal creeper, Asparagus asparagoides (L.) Druce, is a weed with climbing annual shoot growth and extensive, underground storage tubers, and is capable of dominating native vegetation. While its impacts appear obvious, this has been measured in few quantitative studies. In 1996, forty 3 x 3 m plots were established in a mallee remnant north of Adelaide, South Australia, to investigate this issue. Using glyphosate, bridal creeper was removed from half the plots in 1997, with follow-up treatment for the same plots in 1999.
In 2005 there was still no significant difference in the number of native plant species between plots with or without bridal creeper. There was also no significant difference in abundance of individual native species, except for the saltbush Enchylaena tomentosa (P <0.01). However, there were consistent increases in cover of the chenopod and native grass understorey in the bridal creeper removed plots, even if not significant for some species. The common chenopods E. tomentosa and a combined dataset for Rhagodia parabolica and R. candolleana had greater shoot biomass where bridal creeper had been controlled (P <0.01 and P <0.05 respectively). An exotic plant, Oxalis pes-caprae also had higher cover in plots without bridal creeper compared to untreated plots (P <0.01).
This study has shown that it may take many years for recovery following weed control and additional restoration work may be necessary. Dead tubers were still intact below the surface in the removal plots and their presence may be affecting seedling establishment. Recovery may also have been hindered by higher O.pes-caprae density. A third possibility is a lack of suitable environmental conditions in the eight year period for germination and establishment of indigenous species.
Keywords: Asparagus asparagoides, environmental weeds, succession, weed substitution.
Plant Protection Quarterly (2006) 21 (2) 79-84.