Academic literature on the topic 'Asparagus asparagoides'

Asparagus asparagoides (bridal creeper) is a highly invasive noxious environmental weed in southern Australia. It poses a severe threat to biodiversity and conservation in temperate natural ecosystems. Pterostylis arenicola, a threatened terrestrial orchid endemic to South Australia, is directly imperilled by this weed in most of its remnant populations. The coincident growth phenologies of orchid and weed make for an ecologically sensitive environment when considering methods of weed control or eradication. To minimise impact on the orchid and its ecosystem, this paper examines the efficacy of herbicide application for A. asparagoides control using the weed wiping technique, comparing it to the conventional spray application method. The most prolonged control of A. asparagoides was achieved after a single wipe-application of 1.5 g a.i. (active ingredient) L−1 metsulfuron methyl, either alone or in combination with 120 g a.i. L−1 glyphosate, both treatments giving significantly better weed control five years after treatment than comparable spray applications. An investigation of the effect of glyphosate on cultures of the mycorrhizal fungus isolated from P. arenicola indicated a significant decline in mycelial growth with increasing herbicide concentration over the range 0.5–3.0 kg a.i. ha−1. These results provide further incentive for the use of ecologically sensitive herbicide application techniques, such as weed wiping, in areas of high conservation concern.

Bridal creeper is a weed of natural and productive areas in the northern North Island of New Zealand A classical biocontrol programme was initiated in 20052007 with a survey of invertebrate fauna and pathogens associated with the weed in New Zealand Although bridal creeper was attacked by a wide range of generalist invertebrates their overall damage affected

AbstractBridal creeper has become a serious environmental weed in southern Australia. Historically the invaded areas had low soil nutrient levels. However, our field surveys indicate that soils in bridal creeper–invaded areas have higher phosphorus and iron levels than soils in nearby native reference areas regardless of the proximity to agriculture or other disturbances. A glasshouse experiment was undertaken to determine the influence of increased nutrients on plants that co-occur with bridal creeper in order to (1) assess the impact of changed soil conditions and (2) predict the response of dominant species following the biological control of bridal creeper. The relative growth rate (RGR) of bridal creeper, two native shrubs (narrow-leaved thomasia [Thomasia angustifolia] and bluebell creeper [Billardiera heterophylla]), and an invasive exotic grass (annual veldt grass [Ehrharta longiflora]) were determined in three soil types: soil collected within a bridal creeper stand, soil collected from a nearby reference area, and a potting mix with nutrient levels higher than that recorded in the field. The plant species were chosen due to their association with bridal creeper. For example, the native species narrow-leaved thomasia was identified in a previous survey as the most abundant shrub at the invaded site where the soil was collected. The two other species, bluebell creeper and annual veldt grass, were identified from a previous seedbank trial as being abundant (in the seedbank) and able to readily germinate in invaded areas. When grown in either the bridal creeper–invaded soil or reference soil, bluebell creeper had significantly lower RGRs than narrow-leaved thomasia and annual veldt grass. However, as all these species showed increases in RGRs between reference soil and bridal creeper soil, this study indicates that for at least these three species the impact of increased nutrients may not be a barrier to the recovery of invaded areas following the control of bridal creeper.

This thesis reports on research that examines the early stage invasion process of Asparagus asparagoides (L.) W. Wight (bridal creeper), primarily a bird-dispersed weed, in a remnant vegetation patch. The study site is on Phillip Island, approximately 100 kilometres south east of Melbourne, Victoria. Asparagus asparagoides invasion of the remnant vegetation reserve is a relatively recent phenomenon. Landscape elements that affect bird dispersal and vegetation types that affect seedling establishment may be important factors that limit or enhance the spread of A. asparagoides. A systematic sampling strategy was adopted and data collected for a variety of landscape and vegetative variables including cover and abundance of A. asparagoides and the data were presented in a Geographic Information System (GIS). Preliminary results show that the distribution of A. asparagoides within a remnant vegetation patch is not random. It appears to have entered the reserve from two boundaries, spreading toward the centre, which to date remains sparsely colonised despite the capacity of this weed to spread rapidly over long distances by birds. A number of other outcomes are noted. Asparagus asparagoides establishment is prevented in pasture where sheep and cattle graze, and paddocks subjected to tillage practices. The exclusion of grazing in fenced off vegetation in pastures demonstrates rapid weed establishment and colonisation several hundred metres from main infestation. Field observation and visual inspection of temporal progress of invasion (using above ground weed density with tuber appearance to infer age) appear to suggest that invasion into remnant is associated with the track network. This age/density assumption is strengthened when spatial distribution is examined using a data set where low-density values for A. asparagoides are removed and compared with a data set using all A. asparagoides density values. The mapping of A. asparagoides in fenced off farm remnants suggests that velocity of spread at 191m/yr is a considerable underestimate. Subsequent analysis shows that the spatial distribution of A. asparagoides is not completely spatially random while intensity surface analysis highlights regions of low and high intensity located near track network. Mapping a density surface within GIS provided confirmatory evidence for the establishment of satellite clusters along the track network. The change in the intensity surface observed using the two data sets (lowdensity values and all density values) is also consistent with an expanding invasion occurring between two time periods. Spatial point pattern analysis using K-function statistics shows that xxii the clustering observed using GIS appears to be occurring at two scales or distances (130m- 160m and 195m-205m). The association between tracks and the invasion process observed in the initial stages of the study is examined. There is a change in density as a function of distance from a track where the density of A. asparagoides appears to reduce the further away from the track a site is and this relationship holds regardless of track width. The final stages of the study look at the development of a predictive model. Visual exploration of the data through mapping in a GIS and field observation made during data collection provide the starting point for the development of logistic models to estimate the probability of A. asparagoides presence. Finally the best overall logistic model is applied to a second independent site to determine the general applicability of the model. A number of variables that impact on the presence of A. asparagoides, particularly during the initial stages of the invasion process, are identified. While all the identified variables and the overall model are statistically significant, the model is found to correctly predict presence/absence in only 67% of cases overall. The model however could be expected to correctly predict the presence of A. asparagoides in 74% of cases and has a false positive rate of 40%. The model is applied at a second independent site and found to have an overall percent correct rate of 80% and correctly predicted A. asparagoides presence in 94% of cases. The variables identified as influential in the early stage of invasion are relatively easy to acquire by simple field survey that does not require specialist skills. When considering the model as a tool for the management of remnant vegetation communities, high false positive rates may lead to limited resources being spent on searching sites where there is no weed. However, a high false negative rate would have a larger impact on the management of the weed since the undetected infestations would form sources for new propagules. The model performs well from this point of view in that it provided low false negative rates at both sites. The value of the predictive model is its ability to provide managers with information regarding specific areas to target for weed eradication and management can use the model to assess the effectiveness of any control measures by going back to obtain new cover density data, then using the model to examine the changes over time. The model also provides a starting point for the development of a generic model of A. asparagoides invasion at sites outside of Phillip Island and could also provide the starting point for developing models that could be used for other bird-dispersed fleshy-fruited weed species.

[Truncated abstract] Weeds which invade native communities can have major impacts on biodiversity and ecosystem processes. However, these impacts are rarely quantified, and the mechanisms behind these impacts are rarely investigated. Asparagus asparagoides (L.) Druce (Asparagaceae; common name: bridal creeper), a plant native to southern Africa, is a significant environmental weed in southern Australia. Bridal creeper can invade both disturbed and undisturbed native ecosystems and then dominate native communities. As is the case for many environmental weeds, there has been little work conducted on the impacts of this plant. This lack of knowledge has hampered restoration efforts of invaded areas because very little is known about the potential for invaded communities to recover prior to undertaking weed management. There is a need to improve our understanding of how to manage ecosystem recovery during and after weed control. This can be achieved by (i) determining the impacts caused by the weed; (ii) assessing the condition of invaded communities; and (iii) predicting the impacts that weed management itself will have on the native communities. These three prerequisites to environmental weed control have been determined across sites invaded by bridal creeper in southern Australia. The impacts of this invasive geophyte have been determined through multi-site comparisons, weed removal experiments and controlled glasshouse and laboratory experiments. ... Without additional restoration, we will see those species that readily germinate and those that respond positively to increased soil fertility, replacing bridal creeper after control. This will be dominated by other weeds as the invaded sites have large exotic seed banks that will readily germinate. The tuberous mats of older bridal creeper plants will also leave a legacy as they will remain many years after control and still impact on vegetation, even if control has killed the plant. These impacts will be highest at sites where bridal creeper has dominated over the longer term. Environmental weeds, such as bridal creeper, that are capable of altering ecosystem functions can lead to substantial declines in biodiversity. Therefore, it was fortunate that bridal creeper became a target for biocontrol in Australia even though the impacts of the weed were not quantified when this decision was made. There are areas in southern Australia that are still free of bridal creeper or have sparse populations, and it is highly likely that this biological control programme has lead to the protection of these areas. This protection would not have been possible if other control measures were chosen over biological control, given that biocontrol agents can self-disperse and are able to give continuous control. This means that biological control of weeds in conservation areas can be very effective and is the only economically viable option for the control of widespread environmental weeds such as bridal creeper.

Bibliography: leaves 73-76.
A form of the southern African plant Asparagus asparagoides (Asparagaceae), is a serious environmental week in Australia, where it is known as bridal creeper. Bridal creeper has an extensive underground tuber system and can invade native vegetation, two factors that make chemical and/or mechanical control difficult. The fruit is bird dispersed which facilitates colonisation of new sites. Surveys for potential biological control agents for use against bridal creeper in Australia were initiated in South Africa during 1989. This dissertation describes the identification, distribution and phenology of A. asparagoides in South Africa, as well as the natural enemies associated with the plant and their potential for use as biological control agents in Australia. Potential biological control agents that attack vegetative growth of bridal creeper included an undescribed Zygina sp. (Cicadellidae), two undescribed Crioceris species (Chrysomelidae - Criocerinae) and the rust fungus, Puccinia myrsiphlli DC. (Uredinales). The seeds of bridal creeper are attacked by an undescribed Eurytoma sp. (Eurytomidae) and the fruits by Zalaca snelleni (Wallengren) (Noctuidae). An organism directly attacking the tuber mass of bridal creeper was not found. Experimental results illustrated that herbivore damage to the above ground parts of the plant resulted in reduced tuber mass and also impacted negatively on fruit production.