TASWEEDS Inside…………. Edition 20 September 2003 • Weed Research INCORPORATING • IWM for Ragwort SP TTER • Evidence -Enemy Release and Ecological Resistance From the President… Hypotheses • Phil Watson on Rosaceae Welcome to our Spring edition of Tasweeds and the start of yet another weed season! • Progress on the A number of developments have occurred within and associated with your society at a time when our membership seems to have stabilised at around 65 people and organisations. Very shortly I shall be Ground. forwarding a written invitation to key industries involved in weed management inviting them to join us and • WONS Projects become members of TWS - so hopefully our membership base will continue to grow. on Target If you visit the TWS web site you will see the final copy of our business/strategic plan and formalised position descriptions for members of committee. By the time you read this newsletter, the TWS Executive • Strategies and will have met under the structure of the business plan and will be checking off progress against the plan’s Planning. milestones and initiatives. Remember, if there are any activities or actions you think your society should • Statutory Weed be involved in please contact either myself or any member of committee to get your ideas on the agenda. Management Plans In this newsletter you will read about our next main activity being organised by Karen Stewart with the Approved • Democrats EPBC kind co-operation of Australian Bulk Minerals, namely a visit to one of the company’s rehabilitation sites on the West Coast. This is a rare opportunity to see mine rehabilitation works in-field and the weed Amendment Bill management issues that are dealt with in such an operation. You can also read about the very successful awarding of the TWS sponsored ‘Golden Woodies’ at this year’s State Landcare Awards dinner. This was • Weed Alerts a prelude to 2003 WeedBuster Week activities and the TWS congratulates all the winners. Well done folks! • Spiny emex A number of issues have been on the agenda of the Council of Australian Weed Science Societies (CAWSS) and Dean Zeven, TWS Vice-President and CAWSS delegate has given a run-down of those in • Bumblebees found this edition. in Brisbane and Melbourne Finally the Executive provided some preliminary comment on an early draft of WeedPlan 2, the revised • Red cestrum and updated State weed strategy. In the not too distant future, comment will be sought from the entire • Cape honey flower TWS membership on this very important State strategy. The draft document’s probable method of delivery to you will be via email so if you haven’t already, please forward your email address to the secretary • Education and ([email protected]). Awareness Finally, conferences are in the air. You will note the flyer for the 14th Australian Weed Conference to be • Golden Woody held in New South Wales next year in this newsletter. Keep your eyes and ears open for possible Winners Shine developments through TWS, of a State Weeds Conference to be held in September 2005, in part to • Tas. Herbarium celebrate the TWS’s 10th anniversary. But more about that later. Opens its Doors Until then, happy reading…and weeding! • Ag Contractors’ Weed Workshops Andrew Bishop • Australia’s Virtual President Herbarium [email protected] • TWS News • Physical Weed Control Group • CAWSS Update • TWS Phone Survey • Current Members • TWS FIELD TRIP! TASWEEDS incorporating SPOTTER Edition 20 September 2003 WEED RESEARCH Towards an Integrated Weed Management Plan for Ragwort Karina Potter, University of Tasmania. The first steps toward the production of a comprehensive, integrated weed management plan for ragwort in Australia have already been made in the form of research and publications by John Ireson, David McLaren, Sandy Leighton and their associated co-workers. Many of their recommendations, however, have been based largely on anecdotal evidence and required the support of experimental data. The primary purpose of my postgraduate studies, therefore, was to test experimentally some of the current recommendations, investigate some of the factors affecting the ragwort flea beetle (Longitarsus flavicornis) as a biological control agent for ragwort and provide data to support in the formulation of new recommendations. Here I present some of the outcomes of the study that are relevant to the current strategy, and information that is valuable for the development of new recommendations. Boom sprayed herbicides Experimental evidence is now available that demonstrates that the application of boom sprayed herbicides that achieve a high plant kill have the potential to significantly reduce ragwort flea beetle populations under field conditions. It was predicted that a spring herbicide application would be less detrimental to the survival of the flea beetle than an autumn application as, after a spring application, a food source would remain available for the flea beetle larvae to complete their development. While some variation in the level of flea beetle mortality between the seasons did occur, the application of herbicide in both seasons led to high levels of flea beetle mortality. Wick wiping The wick wiping of herbicides in summer to kill flowering ragwort, whilst leaving rosettes undamaged, is strongly supported by the results of this study. This is primarily due to the negative effects of boom sprayed herbicides on the ragwort flea beetle. No negative impacts of wick wiping on flea beetle populations were identified as flea beetle adults mainly reside and lay eggs on rosettes rather than flowering plants. Sensitivity to desiccation The eggs of the ragwort flea beetle were found to be highly susceptible to desiccation. Summer conditions, particularly in years of drought, are therefore a likely explanation for the low numbers of flea beetles reported in some years and at some locations. Soil type and structure Soil and climate data were collected from a range of sites in an attempt to explain the current pattern of ragwort control by the ragwort flea beetle in Tasmania. These studies were performed with the intention of identifying a variable that could be manipulated to increase the success of the ragwort flea beetle in its control of ragwort at sites where its action is currently restricted. It was concluded, however, that the factor or group of factors that influence flea beetle population dynamics are extremely complex and probably vary considerably between years and locations. Paddock flooding The winter flooding of paddocks, even without the presence of cattle, is likely to be detrimental to ragwort flea beetle populations as high mortality occurred in a pot trial over periods of inundation known to occur in the field. In areas prone to winter flooding, therefore, improved ragwort control could probably be achieved through the release of other biological 2 TASWEEDS incorporating SPOTTER Edition 20 September 2003 control agents such as the ragwort stem and crown boring moth, Cochylis atricapitana, and the ragwort plume moth, Platyptilia isodactyla, both of which are better adapted to survive water logged conditions. Where to from here? The next major step in the development of an Australian integrated management plan for ragwort is to incorporate the other established ragwort biological control agents, the ragwort stem and crown boring moth and the ragwort plume moth into the current management approach. In particular, as both moths are stem borers the impact of the current grazing and mowing recommendations on these agents needs to be assessed and their interactions examined. Funding for this project was provided by Dairy Australia, The University of Tasmania and the Tasmanian Institute of Agricultural Research. For further information on the current recommendations for the integrated management of ragwort please contact Karina Potter ([email protected]) or John Ireson ([email protected]). Enemy Release and Ecological Resistance – Some Evidence for Weeds. The question of why only some but not all plants become invasive when introduced to new areas lies at the heart of weed ecology. A number of explanations have been proposed, among them the enemy release hypothesis. This hypothesis suggests that certain introduced organisms succeed too well in new environments because they are freed from the controls exerted by the predators, pathogens, parasites and competitors with which they coexist in their native range. This freedom supposedly clears the way for the introduced species, allowing it to become invasive. A companion hypothesis that tries to account for the failure of many introduced plants to become invasive in their new environments is that of ecological resistance. This proposes that competition with native species and assaults by native pathogens and predators in the new environment limit would-be invaders to benign population levels that have little demonstrable impact. But what support exists for either hypothesis? Many reviews suggest the evidence is equivocal. The paragraph below describes recent research comparing parasite loads of several hundred plants in both their native and introduced ranges. Release of Invasive Plants from Fungal and Viral Pathogens. (adapted from Charles E. Mitchell and Allison G. Power, Nature, 6 February 2003, pp625-627) Invasive plant species both threaten native biodiversity and are economically costly, but only a few naturalised species become pests. Mitchell and Power report broad, quantitative support for two long-standing hypotheses that explain why only some naturalised species have large impacts. The enemy release hypothesis argues that invaders’ impacts result from reduced natural enemy attack. The biotic resistance hypothesis argues that interactions with native species, including natural enemies, limit invaders’ impacts. Mitchell and Power tested these hypotheses for viruses and for rust, smut and powdery mildew fungi that infect 473 plant species naturalised to the United States from Europe. On average, 84% fewer fungi and 24% fewer virus species infect each plant in its naturalised range than in its native range. In addition, invasive plant species that are more completely released from pathogens are more widely reported as harmful invaders of both agricultural and natural ecosystems. Together, these results strongly support the enemy release hypothesis. Among noxious agricultural weeds, species accumulating more pathogens in their naturalised range are less widely noxious, supporting the ecological resistance hypothesis. The results of Mitchell and Power’s study indicate that invasive plants’ impacts may be a function of both release from and accumulation of natural enemies, including pathogens. 3 TASWEEDS incorporating SPOTTER Edition 20 September 2003 Roses with other names Phil Watson The Rose family (Rosaceae) is a well-known and economically important family incorporating numerous delightful, long established garden favourites (Roses, Spiraeas, Japonicas, and Flowering Cherries), productive fruit trees and shrubs (Pears, Apricots, Apples, Plums, and Loganberries) and notorious weeds. For the native plant enthusiast, the family is represented in bushland communities, by a small group of intriguing but often-overlooked herbs (Native buzzies, Guems, Parsley Piert) as well as scrambling Native Raspberries. Many declared weeds are derived from the Rose family. They were introduced into the native landscape by early European colonists for their important amenity and horticultural values. Within a short period some had escaped the confines of their English style gardens and farms to flourish as aggressive weeds, initiating their invasion and subsequent degradation of vulnerable vegetation communities. Weeds such as briar rose, blackberry, hawthorn, and cotoneaster have now become well known for their abilities to tolerate the toughest environmental conditions and out-compete indigenous flora. Native Rose families members provide tea, bush tucker and delicate flowers Indigenous to Eastern Australia, the Sheep’s Burr, (Acaena echinata and Acaena ovina) and Buzzy or Bidgee Widgee (Acaena novae-zelandiae and Acaena montana) are glossy pinnate leafed ground covers, often proliferating within the inter-tussock spaces of sunny woodlands and coastal sites. The generic name Acaena is Greek for ‘thorn’ referring to their distinctive burr-like seeds, which make up their globose, bristly fruits. Along with the fur of our native marsupials, most bush walkers have inadvertently contributed to the seeds dispersal. The laborious process of removing the balled seed clusters entangled in woolly socks instils in ones memory the need to spot this plant early. No better awareness campaign exists for a native plant! Besides acting as quick growing hardy natural mulch to your native garden patch, the young succulent leaves, once dried, produce a refreshing tea. Remember, only the ‘tiny tips’ will make this a worthy teatime treat! The drought tolerant, thorny, straggling Native Raspberry (Rubus parvifolius) and the more compact Mountain Raspberry (Rubus gunnianus) with its distinctive red blackberry-like fruit, are the only two Tasmanian examples of the twelve native raspberries in Eastern Australia. For optimum development of their tangy sweet fruit, they prefer the moister sections of your bush tucker patch. A quenching and therapeutic tea can also be derived from drying their young leaves or ‘tiny tips’ The Aboriginals were not the only devotees of these fruit. They are cherished by a selection of birds (including the ravenous Currawongs), blue tongue lizards (do you ever wonder where some of your luscious raspberries and strawberries mysteriously disappear to!), the New Holland Mouse and even the tiny Dusky Antechinus. Their resulting deposits (or regurgitations, in the case of the currawong) disperse the seed. Interestingly, the larva of the blue male and green pink female Ghost Moth (Aenetus sp.) are known to bore into and feed within the stems of these native raspberries and other Roseaceae fruit trees (Apples). They have fascinating life cycles, starting out as ‘litter larva’ living under logs and feeding both on the decaying wood and its associated fungi. They then moult into a ‘transfer larva’, which migrates and bores into their host Rosaceae plant stems. A silken wad of excavated fragments acts as the tunnel covering. Here, they moult again transforming into a ‘shrub or tree larva’, which continues to enlarge its tunnel until finally after an exhaustive 5 years, metamorphoses into a beautiful moth. Mountain Geum (Geum talbotianum) has a white chalice-shaped flower with yellow centres and forms small tufts of kidney shaped leaves in sheltered alpine slopes. It is one of only two Tassie representatives (Geum urbanum) of this spectacular cosmopolitan genus cultivated for brightly coloured, long lasting floral displays. The clove-like fragrance in their roots has proved historically popular for flavouring wines and ales. Unless you are happy to experiment, don’t expect to succeed in growing this in your patch,. Instead, it can be cared for as a pot plant, requiring regular potting on to keep it happy. Native and introduced Parsley Pierts (Aphanes australiana and Aphanes arvensis) are small inconspicuous parsley-like annuals with minute flowers that crowd together forming greenish tufts. Its latin name, Aphanes, which means ‘inconspicuous’ is well chosen. However, the significance of Lady’s Mantle (Aphanes vulgaris syn Alchemilla vulgaris) with alchemists cannot be overlooked. By steeping 4 grams of the herb for 5 minutes in one cup of boiling water and straining, a brew was produced for women following childbirth, both for promotion of healing and staunching blood flow. 4 TASWEEDS incorporating SPOTTER Edition 20 September 2003 Its coagulation properties made it a common mouth rinse after teeth extractions. Relief from diarrhoea, menstrual problems and inflamed throats are other proven uses. Rose family environmental weeds By 1820 hawthorn (Crataegus monogynus) proved a godsend for the early settlers as a fashionable hedging and ‘wicker’ style stock fence plant. The fences grew rapidly from hawthorn seedlings (called ‘quicks’) closely planted and woven into wands. Louisa Anne Meredith, a noted author and flower painter of the day, wrote of her admiration for “the anglicised countryside of sober green and white flowering hedgerows”. She loved the “glorious hawthorn hedges in bloom” consisting of the white ‘May’ flowers which she and her fellow Estate owners had gathered as English children. Although it is considered a weed today, its cultural significance should be respected. In an increasingly denuded landscape, its value as a refuge for many of our displaced feathered and furry friends is critical for their survival. Its attributes also extend to craft wood, medicines, food, tea (remember to use those ‘tiny tips’) and a Moorish hawthorn berry wine. Blackberries Rubus fruticosus and Rosehips Rosa rubiginosa (famed for its Vitamin C content) were introduced for their versatile fruits, and hedging abilities. Their aggressive weed status attracts huge resources in an attempt to control their spread. Ironically the botanist Baron Von Mueller (see box below) regarded blackberries as a valuable plant for the colony (hedges with luscious berries, nectar supplies and leaves for herbal tea and medicine). Religiously after boiling the billy, on his botanical sorties, he spread the seeds in the ashes. He mused that “Poor people in times to come will bless me for my thoughtfulness”. Although only touching the surface of the many uses of the Rosaceae (not forgetting the vicar’s rose petal champagne), it is hoped that you a little more inspired to grow and enjoy the lesser-known “Roses” and weed out the odd ‘Rose’ weed. Baron Ferdinand Von Mueller, Victorian Government Botanist. He is credited with discovering and tabulating more flora than any other living person. Born June 30, 1825 in Germany of Danish parents he initially emigrated to Adelaide in 1847 but became the Victorian Government Botanist in 1852. During 1947, nearly all scientific societies urged that a stamp commemorating him be issued. The design comes from a photograph in the National Herbarium, Melbourne with a spray of Yellow String Bark appropriately named Eucalyptus muelleriana. (from http://predecimal.nf/kg6/commems/1948/mueller.htm) 5 TASWEEDS incorporating SPOTTER Edition 20 September 2003 Progress on the Ground Community Support Counts for Weed Control Tanzi Lewis, Greening Australia, Tasmania TIGHT funding and a limited time-frame have not prevented the Weeds of National Significance (WONS) project, administered by Greening Australia (Tasmania), from controlling gorse, willow and blackberry in strategic locations and achieving positive results. Greening Australia (Tasmania)’s Manager of Community Programs, Sebastian Burgess, said the Natural Heritage Trust project had generated a great deal of weed control work across Tasmania for the strategic control of these weeds. Over the past twelve months, the projects have formed partnerships with over 350 land holders to manage these weeds in more than 400 sites. The first stage of control works has been completed in over half of the sites, with land holders committed to long-term follow-up work. “The WONS project has been a real catalyst for engaging the community for a sustained gorse, blackberry and willow control effort,” Mr Burgess said. “Community engagement is vital for weed control projects, particularly when the weeds concerned are like gorse, which require a long-term follow-up and monitoring commitment,” he said. “I believe we have made a very good start at developing community-driven expertise given the high level of interest and participation in this project.” Field days are planned in the regions, including on Bruny Island in the spring to help raise awareness of weed control and to train land holders and community groups in control techniques. “Things are gearing Greening Australia WONS project officer Paul Fazackerley inspects a gorse infestation. up for a lot more work Photo: Greening Australia over the spring and summer as the ground dries out and plant growth becomes more active.” The WONS project has been extended until the end of December 2003, although most of the grant funds are now fully committed. Greening Australia is applying for further funding through the regional call for priority projects to continue the gorse and willow projects for another 12 months. “It’s important to maintain the community momentum generated by the program throughout this period of natural resource management transition, and to continue with the strategic control of these weeds,” Mr Burgess said. 6 TASWEEDS incorporating SPOTTER Edition 20 September 2003 Strategies and Planning The Real Things………. Statutory Weed Management Plans Approved Cindy Hanson, DPIWE Many of you will know something about efforts over the past couple of years to develop statutory weed management plans. Tucked away in the classifieds of Tassie’s three regional papers on Saturday August 30th 2003 was a modest notice announcing the approval of seventy- three statutory weed management plans under the Weed Management Act 1999. This is a small milestone. These plans represent the first time the process for declaring plants under the new Act has proceeded to completion. Each of these plans is now fully enforceable and each provides specific guidance about land owner obligations for managing declared weeds. Importantly, each plan reflects community feeling on what is fair and reasonable in terms of legal requirements for each of the plants concerned. Four weed management plans, drafted with the rest, have been held back from approval pending discussions in relation to their occurrence in imported feed grain. The plants concerned are Carthamus lanatus (saffron thistle), Echium plantagineum (Paterson’s curse) Echium vulgare (viper’s bugloss) and Datura species (thornapples). Copies of the approved plans will be available from the DPIWE website at www.dpiwe.tas.gov.au or you can email [email protected] or call 6336 5414 A Look at the Democrats' Environment Protection and Biodiversity Conservation Amendment (Invasive Species) Bill (2002) Lucy Vaughan (Secretary, Invasive Species Council* and Environmental Lawyer) The Environment Protection and Biodiversity Conservation Amendment (Invasive Species) Bill 2002 ('the Bill') was tabled in Federal Parliament by the Democrats on 19 November 2002. The Bill proposes to introduce a national regulatory structure in order “to prevent the introduction of further species in Australia and to eradicate or control those already here”.i It proposes to do this by amending the Environment Protection and Biodiversity Conservation Act 1999 (Cth) ('EPBC Act') in particular, by inserting a new division called “Listed Invasive Species”. The Bill proposes to define an “invasive species” as a “non-indigenous species” which: “...has been, or may be, introduced into Australia and either, directly or indirectly, threatens, will threaten or is likely to threaten, the survival, abundance or evolutionary development of a native species, ecological community, ecosystem or agricultural commodity or which is “a genetically modified species”.ii The starting point for this national regulatory structure is the establishment of a list of invasive species, categorised as follows: (a) species determined by the relevant agency or Minister to be permitted for import; (b) species determined by the relevant agency or Minister to be prohibited for import; (c) invasive species of the following types currently present in Australia: (i) eradicable; 7 TASWEEDS incorporating SPOTTER Edition 20 September 2003 (ii) substantially containable; (iii) beyond eradication; (iv) controlled; (v) disregarded as an invasive species; (vi) exempt from listing.iii Prohibited Imports In order to prevent the introduction of further invasive species into Australia, the Bill proposes to immediately prohibit the import of the following categories of species: (a) pasture grasses; (b) ornamental plants; (c) aquarium fish; (d) any other species as determined by the Minister, if the Minister is satisfied, on the advice of the Invasive Species Advisory Committee, that a species should be deemed to be a prohibited import.iv Ministerial Permits The Bill establishes a permit system whereby the Minister can issue a permit for the commercial sale, trade or propagation of a non-indigenous species in certain situations, including: • where there is a demonstrated need for the species to be used in food production in Australia; • where there is a low risk that the species will have an impact on listed threatened species or ecological communities; and • where the Minister has approved an invasive species threat abatement plan for the species.v Offences The Bill also creates a number of offences where a person imports or possesses species which are either prohibited or which are categorised as eradicable, substantially containable, or beyond eradication, without a permitvi. Managing Existing Invasive Species The Bill proposes a number of practical management strategies for dealing with invasive species already in Australia, including establishing a process creating an 'invasive species threat abatement plan' in co-operation with relevant States.vii Invasive species threat abatement plans improve on existing 'threat abatement plans' currently provided for under the EPBC Act, in two ways. Firstly, they facilitate a preventative approach to dealing with invasive species. Current 'threat abatement plans' are only triggered at the point when the existence of a threatened species or ecological community hangs in the balance. Secondly, they may, under certain circumstances, be implemented by the Commonwealth outside 'Commonwealth areas'. This is a qualified improvement on current 'threat abatement plans' which can never apply outside 'Commonwealth areas'. However, it should be noted that the Bill appears only to require Commonwealth agencies (i.e. not State agencies) to comply with the invasive species threat abatement planviii. The ultimate effectiveness of this management strategy must therefore be questioned. Discussion The establishment of a national list of invasive species is a constructive beginning to any attempt to provide a national regulatory framework for invasive species. There remain, however, issues with the definition on which the list (and the Bill) rests. The definition of invasive species, whilst fairly broad, nevertheless does not capture those native species which could be considered ‘invasive’ if occurring beyond their accepted normal distribution and which are adversely impacting on local native species and ecosystems. In fairness, Senator Bartlett has acknowledged the difficulties in defining ‘invasive species’. but has stated that it is still necessary to have a workable definition of invasive speciesix. Point taken. 8 TASWEEDS incorporating SPOTTER Edition 20 September 2003 A far more serious weakness of the Bill is that it does not propose to include ‘invasive species’ as a matter of national environmental significancex. Matters of 'national environmental significance'xi operate as the triggers for the environmental impact assessment provisions under the EPBC Act. These environmental impact assessment provisions establish a process for the assessment of proposed 'actions' that have, will have, or are likely to have a 'significant impact' on any of the nominated matters considered to be of 'national environmental significance'. Given that the damage caused by invasive species has largely been attributed to human activity, it is a curious omission. There are plenty of examples where ‘actions’xii have resulted in both native and exotic flora and fauna becoming invasive. Urban development is a case in point. In his book, Feral Future, Tim Low complains of the times when he has served as an expert witness in the Planning and Environment Court “warning that a new housing estate would send waves of new weeds into nearby forests.”xiii This kind of environmental harm could be prevented if proponents of such ‘actions’ were expressly required to consider the threat these pose in relation to the spread of invasive species. An assessment of the impact that the ‘actions’ of private persons and corporations as well as government agencies could have, and do have, in facilitating the introduction or further spread of invasive species is essential if a national regulatory structure for invasive species is to be effective. Conclusion If enacted, there can be little doubt that the Bill would have a dramatic and beneficial impact on the environmental problems created by invasive species. As with the existing EPBC Act, however, it appears to stop short of taking on active regulatory and management roles in relation to the impact of the ‘actions’ of private persons, corporations and the States in facilitating the problems brought about by the introduction and presence of invasive species. In this way, arguably the Bill continues to honour and preserve the articulation of Commonwealth and State roles provided for in the Inter-governmental Agreement on the Environment (IGAE)xiv in much the same way as the existing EPBC Act. The IGAE is perhaps the definitive example of the policy of co-operative federalism (the approach preferred by the current Federal Government) at work. Whilst the IGAE recognises that the Commonwealth has a legitimate role in respect of national environmental issues, it gives the States primary responsibility for environmental management within their respective jurisdictions. This often leads to the 'hands-off' approach taken by the Commonwealth in relation to many national environmental problems, like invasive species. The Democrats should be applauded for introducing the Bill. It is almost certain that Australia is not 'politically' ready to adopt the kind of national regulatory scheme for addressing the problem of invasive species proposed by the Bill. However the Bill presents an excellent opportunity to raise the profile of this issue not only with all levels of Government in Australia, but also with relevant industry and the general community. 9 TASWEEDS incorporating SPOTTER Edition 20 September 2003 WEED ALERTS Spiny Emex Cindy Hanson, DPIWE What is it? Spiny emex (Emex australis) is a semi prostrate annual herb of the Polygonacea family and thus related to docks, wireweed, sorell and Japanese knotweed. Also called three-cornered jack or doublegee, spiny emex originates from southern Africa where it is generally widespread and particularly significant as a weed in cereal crops and grape growing ares. Whilst naturalised in a number of locations around the world it has achieved its worst weedy reputation in Australia. Probably introduced to Western Australia in the 1830s, spiny emex is now found in all States and Territories with Western Australia, New South Wales, northern Victoria, south-eastern Queensland and south-eastern South Australia being its strongholds. It is a major pest of cereal crops and in some fruit growing areas but is also found along roadsides and in stockyards. Of particular concern is the perception that it still appears to be spreading in many areas. Spiny emex is problematic because it is an extremely effective, fast growing competitor with some infestations having densities of up to 900 plants per square metre. Studies in South Australia indicate that infestations are capable of reducing wheat yields by up to 40%. The plant also contains oxalic acid which, following consumption of seedlings by stock, can lead to morbidity and death. The sharply spined fruit also Emex australis. Illustration Dennis Morris creates problems for humans, working dogs and for sheep in which septic wounds progress to a painful condition known as blackleg. 10