Fourteenth Australian Weeds Conference Lippia, Phyla canescens, an increasing threat to agriculture and the environment Mic Julien1,4, Andrew Storrie2,4 and Rob McCosker3 1 CSIRO Entomology, 120 Meiers Road, Indooroopilly, Queensland 4068, Australia 2 NSW Department of Primary Industries, Tamworth Centre for Crop Improvement, RMB 944, Tamworth, New South Wales 2340, Australia 3 Department of Infrastructure, Planning and Natural Resources, PO Box 463, Inverell, New South Wales 2360, Australia 4 CRC for Australian Weed Management Summary Lippia, Phyla canescens (Kunth) Greene BIOLOGY, FORM AND WEEDINESS is a native forb of South America and is now widely Lippia is a prostrate perennial herbaceous plant. It distributed across the world. Lippia is present in all develops a deep tap-root, 50–80 cm deep, extensive mainland states of Australia, except the Northern Terri- fi brous roots, and creeping stems to one metre long tory. It is often confused with P. nodifl ora (L.) Greene, that root at the nodes. Flowers, in spring to autumn, but this species prefers tropical and sub-tropical areas. are small and whitish on dense fl ower heads 5–10 mm Lippia is now a major weed of fl oodplains within the diameter, on an axillary stalk 15–45 mm long. Fruits Murray-Darling Basin (MDB). Recent concern about are 1–1.5 mm diameter and contain two very small lippia led to the formation of the Murray Darling seeds. Reproduction is through seed germination and Lippia Working Group and an assessment of lippia rooting of stem nodes. Dispersal is primarily by water within the MDB that was supported by the MDB Com- for both seed and plant fragments. mission. Lippia currently infests 5.3 million ha of the Lippia favours temperate and sub-tropical areas MDB and this is predicted to increase following recent and occurs over a wide variety of soil types in open fl oods. It is estimated to cost the grazing industry $38 seasonally wet areas and along edges of water bod- million p.a. and have an environmental cost of $1.8 ies (Kennedy 1992). In Australia its distribution is billion p.a. It is a major threat to biodiversity and ripar- New South Wales (NSW), Victoria, southern parts of ian areas. Current pasture management practices fail to Queensland (Qld), South Australia (SA) and Western limit the expansion of lippia. Cultivation is useful, but Australia (WA). It is well adapted to the heavier clay it poses a high erosion risk for fl oodplains. There are soils typical of the upper MDB but not confi ned to no effective management strategies for lippia in ripar- them. ian areas. It is essential that research into biological Lippia seems to have had very limited herbal or control and other management strategies commence medicinal use, and has limited palatability for cat- immediately, in conjunction with awareness and edu- tle. It is used as a lawn species and as an ornamental cation programs, to halt the spread and help manage ground cover. this very aggressive weed. The scrambling growth and deep tap-root pro- Keywords Weed, taxonomy, production costs, vides lippia with a competitive edge. It is drought environmental costs, spread, impacts, distribution, resistant and when favourable growing conditions Murray-Darling Basin. occur its tangled mats of stems and leaves cover the ground smothering or excluding other plant species. INTRODUCTION Allelopathic effects may also be a factor in its apparent Lippia, Phyla canescens (Kunth) Greene, is an intro- dominance (Elakovich 1987, Lucy et al. 1995). duced plant invading fl oodplain plant communities Lippia invades and dominates areas that are not especially in the upper Murray-Darling Basin (MDB). cultivated including perennial pastures, riparian areas, It is an intractable weed that does not generally re- and roadsides. It contributes to deep soil drying leading spond to herbicide or grazing management, though to bank slumping and erosion especially in cracking it is managed by cultivation. Lippia is increasing its clays, resulting in damage to diversion banks, dam distribution, density, and cover, and is having a sig- walls and roads. It is a lowland and wetland plant in its nifi cant impact on conservation and grazing systems, native range. In Australia it is generally regarded as a and rural land values. This paper is intended to raise weed of riparian areas, wetlands and fl oodplains. How- awareness to lippia by describing the weed and key ever, recent observations suggest that it is becoming outcomes from recent studies of its distribution and more prevalent in uplands (Earl 2003). Lippia thrives impact in the MDB. on frequent fl ooding of short duration. 476 Fourteenth Australian Weeds Conference Lippia replaces productive pasture species and re- impacts were becoming more and more signifi cant. duces grazing productivity, in some cases necessitating It was soon realised that an up-to-date study of the total de-stocking. Conventional pasture management distribution and economic impacts of lippia was re- practices do not control this weed. The presence of quired to leverage resources to develop management lippia on a farm reduces the farm’s value because of strategies. the reduced productivity and cost of largely ineffectual A study, commissioned by the MDLWG, funded controls (Lucy et al. 1995, Earl 2003). by the Murray Darling Commission, aimed to: quantify current distribution of the weed, report on economic TAXONOMY AND DISTRIBUTION impacts in the rural sector and evaluate impacts on The naming of lippia in the literature is somewhat the environment. confusing as various combinations of Lippia, Phyla The processes followed in the study were: infor- and Zanpania have been used with various species mation reviews, stakeholder interviews, focus group and sub-species and variety names, some of which meetings, and fi eld assessments. The results, estimates are currently in use for recognised species, e.g. Phyla and conclusions should be of considerable concern to nodifl ora (L.) Greene. agriculturalists, environmentalists, natural resource There are between nine (Kennedy 1992) and 11 managers and politicians, particularly in the MDB. (Munir 1993) species of Phyla recognised worldwide. A precis of the fi ndings is given below. Details are The two species in Australia, Phyla nodifl ora, and in Earl (2003). the weedy, Phyla canescens (lippia), are introduced • Lippia is distributed across at least 5% or 5.3 (Munir 1993). All Phyla appear to be native to the million ha of the MDB. It is present in each of Americas and the Caribbean (Kennedy 1992) and the 19 MDB catchments, some in very low densi- two, P. canescens and P. nodilfora, have been widely ties. The worst affected are upstream catchments. distributed to other continents. Previous estimates of area were 600,000 ha (Lucy Prior to Munir’s (1993) revision P. canescens spec- et al. 1995) or less. Figure 1 shows changes in imens in Australia were identifi ed as Lippia nodifl ora, estimated area of lippia in the Condamine. It was Lippia nodifl ora var. repens, and Phyla nodifl ora. Add- fi rst recorded there in 1953 (Lucy et al. 1995) ing to the confusion, Australian weed texts continue to and the estimates suggest that lippia is in a phase refer to the weed P. canescens as P. nodifl ora. of rapid expansion. Although similar time series Worldwide, lippia is recorded from the United estimates for other catchments are not available, States of America, Mexico, Australia, New Zealand, lippia is much more widely distributed than pre- Guam, India, Afghanistan, South Africa, Algeria, viously thought. This seems due to recent rapid Botswana, Egypt, Senegal, Spain, France and Italy. It expansion, particularly in catchments that were is undoubtedly native to South America where it is re- already signifi cantly infested. This is a warning to corded from southern Ecuador, Peru, Chile, Argentina, other areas where the weed is established or that Uruguay, Paraguay, and Bolivia (Kennedy 1992). it threatens to invade. The distribution of P. nodifl ora and its close phylo- genetic relationships with the other herbaceous Phyla 1200 species (Kennedy 1992) strongly suggests that this species is native to the tropical Americas and Carib- bean. It has also been widely distributed around the world as an ornamental. P. nodifl ora has a different 800 set of requirements for growth than lippia and conse- quently it mainly occurs in the tropics and sub-tropics. In Australia it is found mostly in the Northern Territory and Qld but it also occurs in temperate coastal areas, south to Perth and Sydney (Munir 1993). 400 CURRENT SPREAD AND ESTIMATED COSTS Area of lippia in 1000’s hectares IN THE MDB Concerns about lippia led to a meeting in 2002 hosted 0 by the Cotton CRC and the CRC for Australian Weed 1960 1989 1992 2000 2003 Management, and the formation of the Murray-Dar- ling Lippia Working Group (MDLWG). Anecdotal Figure 1. The estimated distribution of lippia in the evidence suggested that lippia was spreading and its Condamine catchment. 477 Fourteenth Australian Weeds Conference • Lippia has not invaded its full range in the MDB, be used, e.g. riparian zones. Surveys for potential or probably in other parts of Australia. Nor has it agents have never been carried out. Co-investment reached stable densities or biomass in most MDB funding is being sought with Meat and Livestock catchments. Australia (MLA) and the Natural Heritage Trust • Spread, by seed and vegetative propagules, and (NHT)/National Action Plan (NAP) to begin sur- increase in cover is related to fl ood events. veys in South America in mid 2005. A key question • Lippia is spreading into hilly areas above fl ood is: are there suitable and safe biological control levels and onto lighter soils. It remains to be seen agents for lippia? how important it will be as an invader away from 2.