The Distribution and Impact of South/North American Stipoid

Home , Austrostipa flavescens, Jarava, Nassella, Nassella leucotricha, Nassella trichotoma, Poa poiformis

62 Plant Protection Quarterly Vol.13(2) 1998 But through the greater part of Victoria these conditions do not apply, and dense The distribution and impact of South/North American growths of plants formerly unknown or uncommon in an area are cause for con- stipoid grasses (Poaceae: Stipeae) in Australia cern. While there are several introduced D.A. McLarenA, V. StajsicB and M.R. GardenerC, Co-operative Research grass species that form extensive single- Centre for Weed Management Systems species swards, most of these are A Department of Natural Resources and Environment, Keith Turnbull rhizomatous, such as Pennisetum clandestinum (kikuyu) and Cynodon Research Institute, PO Box 48, Frankston, Victoria 3199, Australia. B dactylon (couch), or annuals such as Briza National Herbarium of Victoria, Birdwood Avenue, South Yarra, Victoria species (blowfly grasses), Vulpia species 3141, Australia. (squirrel-tail fescues or silver grasses), C University of New England, Armidale, New South Wales 2351, Australia. Avena species (oat-grasses) and Schismus barbatus (Arabian grass). Abstract these grasses could have on both agricul- Tussock-forming perennials that occur The current and potential distribution of ture and the environment. in dense, uniform stands, readily displac- ten introduced South/North American The Stipeae (Family: Poaceae) is a cos- ing the ‘resident’ species or communities, stipoid grass weeds is documented. The mopolitan tribe of approximately 450 spe- include Phalaris aquatica (canary grass) known ecology and the impacts on agri- cies in 14 genera (Barkworth 1993, Reyna and Lophopyrum elongatum (tall wheat- culture and the indigenous vegetation and Barkworth 1994, Jacobs and Everett grass). Both of these deep-rooted species are presented. Nassella trichotoma has 1996). Including the indigenous genus have been extensively grown in areas significant impacts on both agriculture Austrostipa, there are six stipoid genera in prone to salination. They are both now and the environment. N. neesiana is Australia, five of which are of exotic ori- proving to be a severe threat to native among the most serious environmental gin. These are Achnatherum, Jarava, grassland communities. Both have flattish weeds of grassland and grassy- Nassella, Piptochaetium and Piptatherum. leaf-blades, the former to 20 mm wide, the woodland communities in southeast Achnatherum is the largest and most wide- latter to approximately 6 mm wide. Both Australia. N. leucotricha and especially spread genus. It occurs in Africa, Eurasia, are readily distinguished from stipoid N. hyalina are serious environmental New Zealand and North and South grasses by the absence of awns on the lem- weeds of grassland communities, par- America (Barkworth 1993) but is prima- mas, and by the narrow, more or less cy- ticularly on the Victorian Volcanic rily of Eurasian/North American origin. lindrical inflorescences. Plains. Achnatherum caudatum and A. Jarava, a recently resurrected genus Should Table 1 not provide a satisfac- brachychaetum have the potential to be- (Jacobs and Everett 1997), is endemic to tory identification of a grass believed to be come very serious agricultural and envi- South American. Nassella is essentially a member of the Stipeae, or if other ronmental weeds, as they possess abun- from South America while Piptochaetium is grasses, unknown to local agriculture of- dant cleistogenes that promote dispersal from both North and (mainly) South ficers, are proving cause for concern, a and survival under cultivation. A. American. Piptatherum is (mainly) Eura- flowering or seeding specimen should be brachychaetum remains poorly known sian but is also represented in North forwarded to an appropriate agency for due to its similarity and confusion with America and is represented by only one expert identification (usually the State A. caudatum. N. charruana poses a sig- species in Australia, P. miliaceum (L.) Coss. Herbarium, situated in each of the nificant weed threat due to its invasive- As this species appears to be confined to Australian capital cities). The specimen ness and unpalatibilty. N. megapotamia urban settlements (Walsh and Entwisle may represent the first wave of the inva- and Piptochaetium montevidense are 1994) it will not be considered. Species of sion of a potentially troublesome or dev- poorly known species with little to no in- the other genera are cause for serious astating weed and its early detection and formation available on their ecology and alarm from both an environmental and eradication could save untold expense weed status in Australia. Attempts to agricultural perspective. and hours of labour. eradicate Jarava plumosa in South Aus- In Australia 11 species of exotic stip- tralia have proved difficult. Ten recom- oid species are naturalized. They are: References mendations are made. Achnatherum brachychaetum (Godron) Jacobs, S.W.L. and Everett, J. (1996). Barkworth, A. caudatum (Trin.) S.W.L. Austrostipa, a new genus, and new Introduction Jacobs & J. Everett, Jarava plumosa names for Australasian species for- Many potential weeds are regarded as (Sprengel) S.W.L. Jacobs & J. Everett, merly included in Stipa (Gramineae). ‘sleepers’ whose populations may slowly Nassella charruana (Arech.) Barkworth, N. Telopea 6, 579-95. increase (lag phase) but not be noticed for hyalina (Nees) Barkworth, N. leucotricha Jacobs, S.W.L. and Everett, J. (1997). Jarava many years, before they increase dramati- (Trin. & Rupr.) Pohl., N. megapotamia plumosa (Gramineae), a new combina- cally making eradication almost impossi- (Spreng. ex Trin.) Barkworth, N. neesiana tion for the species formerly known as ble. Groves (1986) divided this weed inva- (Trin. & Rupr.) Barkworth, N. trichotoma Stipa papposa. Telopea 7, 301-2. sion process into three phases. An intro- (Nees) Hack. ex Arechav., Piptatherum Ross, J.H. (1996). ‘Census of vascular duction phase (the process of invading a miliaceum and Piptochaetium montevidense plants in Victoria’, Fifth edition. (Royal previously unoccupied region), a colo- (Spreng.) Parodi. Due to the resemblance Botanic Gardens, Melbourne). nization phase (the process of being able of these South/North American stipoid Vickery, J.W., Jacobs, S.W.L. and Everett, to survive and reproduce, producing species with indigenous Austrostipa spe- J. (1986). Taxonomic studies in Stipa a self-perpetuating population) and a cies, they can be easily overlooked as (Poaceae) in Australia. Telopea 3, 1-132. naturalization phase (the weed dis- weeds, increasing their likelihood of suc- Walsh, N.G. (1994). Poaceae. In ‘Flora of perses widely and creates further self- cessful naturalization. Victoria’, eds. N.G. Walsh and T.J. perpetuating populations which become The ability of a weed to invade, repro- Entwisle, Volume 2, pp. 356-627. incorporated into the resident flora). The duce and increase is largely dependent (Inkata Press, Melbourne). introduction of several South and North upon habitat and its adaptive characteris- American stipoid species into Australia tics (i.e. dispersal adaptations, seed pro- has raised concerns about the impacts duction etc.). Habitat has been defined as Plant Protection Quarterly Vol.13(2) 1998 63 ‘the sum of the factors at a point in space A climate analysis was used to deter- In 1988, N. trichotoma was estimated to that may affect a plant’s ability to survive mine the potential distributions of each cost the Australian Wool Industry ap- and to contribute to the next generation’ species. Latitude, longitude and altitude proximately $12.9 million annually (Cousens and Mortimer 1995). These may data were obtained from a representative (Sloane et al. 1988). A recent report pro- include abiotic factors such as climate sample of sites for each species in Aus- duced (Aberdeen 1995) stated that Victo- (temperature, rainfall, humidity), soil tralia. They were analysed by the ria could save approximately $35 million type, day length, and biotic factors such as BIOCLIM program (Nix 1986) using the per year if it restricted the distribution of competition from neighbouring plants, CLIMATE system to predict areas in Aus- N. trichotoma to 200 000 ha. A conservative predators and diseases. tralia that possess similar climatic profiles. figure for the cost of N. trichotoma in Victo- Since the factors defining the suitability ria is $5 million per year (Nicholson et al. of a habitat to a particular weed may be Results and discussion 1997) and for New South Wales $40 mil- unknown, computer models which create lion per year (Jones and Vere 1998). an empirical set of parameters based on Serrated tussock, Nassella trichotoma In contrast to the vast literature on the current distribution can be used to de- Nassella trichotoma is a perennial, drought impacts of N. trichotoma on agricultural scribe areas for weed survival. These pa- resistant species that is native to the pam- productivity, there is little on its environ- rameters can then be used to predict the pas grasslands of Argentina, Uruguay, mental impacts. Carr et al. (1992) classified potential spread of weed species by ana- Chile and Peru (Parodi 1930, Rosengurtt et N. trichotoma as a very serious environ- lysing the climatic variables where the al. 1970) and has been reported from Bo- mental weed that invades dry coastal veg- species is naturalized (Pheloung and Scott livia (Walsh and Entwisle 1994). etation, lowland grassland, grassy wood- 1996, Cousens and Pheloung 1996). A cli- Nassella trichotoma is a proclaimed nox- land, sclerophyll forest and woodland and mate matching system called CLIMATE ious weed in the Australian Capital Terri- rocky outcrop vegetation ( Table 1). has been developed by Agriculture West- tory, New South Wales, Victoria, South ern Australia from the concepts contained Australia and Tasmania and has been de- Chilean needle grass, Nassella in the BIOCLIM (Busby 1991) and scribed as potentially causing greater re- neesiana (Syn. Stipa neesiana Trin. & CLIMEX (Sutherist and Maywald 1985) ductions in carrying capacity than any Rupr.) prediction systems. The CLIMATE system other plant in Australia (Parsons and Nassella neesiana is a tufted perennial that generates a prediction of a species’ distri- Cuthbertson 1992). It has also naturalized is becoming a serious pasture and envi- bution based on the climate of its known in New Zealand and South Africa while ronmental weed in south eastern Aus- distributions and is used particularly small infestations also occur in England, tralia. It is indigenous to Argentina, Bo- where detailed biological data on a species France, Italy, Scotland (Campbell 1982, livia, Chile, Ecuador, Southern Brazil and are lacking. It does not take into consid- Stace 1997) and in the United States Uruguay (Rosengurrt et al. 1970). This spe- eration soil type, day length or biotic fac- (Westbrooks 1991, Westbrooks and Cross cies is a serious weed in New Zealand tors and as such may represent an overes- 1993). (Bourdôt and Hurrell 1989). It has also timate of the plant’s potential distribu- Nassella trichotoma was probably intro- been recorded in south east England tion. duced into Australia in the early 1900s but (Stace 1997) and has been found on ballast Predictions of a species’ distribution was not recorded in Australia until 1935 dumps such as in Mobile, Alabama (US based on its climatic potential are useful when a collection was made at Yass (55 Department of Agriculture 1953) in the when making management decisions as km N.E. of Canberra) (Campbell and Vere United States but there have been no re- they allow land managers to identify land 1995, Figure 1). However, the earliest cent records according to Barkworth at risk of infestation. This may provide a lodged collection is based on a specimen (1993). focus on a species, which may have other- collected at Yass on 7 February 1936 (NSW The earliest known collection of N. wise escaped attention. It can act as a use- Herbarium, specimen No 115759) and a neesiana in Australia was made in October ful aid for making decisions on: further two collections were made later 1934 in Northcote, an inner northern sub- i. Declaration of a species as a noxious that year, also at Yass. In 1977 it occupied urb of Melbourne (MELU specimen) but weed. 680 000 ha (Campbell 1977) and now oc- was ‘originally identified as Stipa elatior (S. ii. Assessing possible environmental and cupies more than 870 000 ha in New South scabra var. elatior)’ i.e. Austrostipa flavescens agricultural impacts. Wales with an estimated 2 000 000 ha at (Figure 3). In New South Wales, the earli- iii. Assessing and developing guidelines risk of infestation (McGowan personal est known collection was made in 1944 at for importation of plants into Australia. communication, Figure 1). In Victoria N. Glen Innes on the New England Table- iv. The future direction of weed research trichotoma was first collected on 19 Decem- lands (284 km S.W. of Brisbane) (Figure 3). and weed control resources. ber 1954 at Broadmeadows (15 km N. neesiana is also naturalized in South N.N.W. of Melbourne). By 1979 it had Australia where it was first recorded from Materials and methods spread to occupy approximately 30 000 ha Lucindale (265 km S.E. of Adelaide) on 18 Thirty-five herbaria across Australia were (Lane et al. 1980) and by 1998 it occupied November 1988 and ‘it does not seem at contacted for collection records for all spe- in excess of 130 000 ha (Pest Management this stage that it is causing any trouble’ cies of Achnatherum, Jarava, Nassella and Information System, Keith Turnbull Re- (J.P. Jessop, AD Herbarium, personal com- Piptochaetium recorded in Australia. De- search Institute, Figure 1). N. trichotoma is munication). In New South Wales the spe- partments of Agriculture and Natural Re- also found in Tasmania where it was is cies is declared as a category W3 noxious sources and Environment were also con- was first recorded in 1956 (Parsons and weed in the New England tablelands, Sev- tacted for species’ distribution data. Fur- Cuthbertson 1992) and is currently spread ern Shire County and the Glen Innes mu- ther data were obtained from the observa- in scattered populations over an area of nicipality, while it has yet to be declared tions, fieldwork and collections by Stajsic approximately 1000 ha (C. Goninon per- in Victoria and South Australia (J. Fisher and Gardener. These data were then sonal communication). personal communication). mapped in ARCVIEW (ESRI 1996). By using CLIMATE, the potential dis- Currently there are no published esti- The maps for N. trichotoma, were com- tribution of N. trichotoma in Australia has mates of the area infested with N. neesiana pared with past surveys from New South been estimated at 32 million ha (best pre- from any of the three states where it oc- Wales (Campbell 1977) and Victoria (Lane diction only, Figure 2) with substantial ar- curs. By using CLIMATE, the potential et al. 1980) to determine the increase in eas of New South Wales, Victoria and Tas- distribution of N. neesiana has been esti- spread over the last 20 years. mania at risk of invasion. mated at 41 million ha (best prediction 64 Plant Protection Quarterly Vol.13(2) 1998 Table 1. Vegetation impacts of exotic stipoid species. Species/Vegetation Locations Species associated/Invaded/Reference formations invaded Serrated tussock, Nassella trichotoma Dry coastal • Torquay (81 km S.W. of Melbourne) Leptospermum laevigatum, Melaleuca lanceolata, Leucopogun parviflorus, vegetation Poa poiformis, Poa labillardieri (P. Wlodarczyk personal observation) Lowland grassland • Bacchus Marsh, Melton, Exford, Parwan, Grey box, Eucalyptus microcarpa – understorey species being seriously and grassy Melbourne Airport (20–50 km W. of Melb.) threatened. (V. Stajsic, D. McLaren personal observation) woodland • St. Albans, Rockbank, Mt. Cotterell, Austrostipa/Austrodanthonia dominated grasslands, Themeda triandra Melton, Bailliang E. (20–50 km W. of Melb.) (V. Stajsic, D. McLaren, G. Carr, C. Hocking personal observation) Roadside reserves • Geelong area (70 km W. of Melbourne) Themeda triandra (M. Trengrove personal observation) Dry sclerophyll • Plenty Gorge Park (20 km N.W. of Melb.) Eucalyptus melliodora, E. leucoxylon ssp. connata, E. goniocalyx forest (V. Stajsic personal observation) • Studley Park (8 km N.W. of Melbourne) Eucalyptus leucoxylon ssp. connata (G. Carr personal observation) • St. Andrews (35 km N.E. of Melbourne) Eucalyptus goniocalyx, E. macrorhycha (P. Wlodarczyk personal comm.) Rocky outcrop • Werribee River (33 km W. of Melbourne), Themeda triandra, Austrostipa sp., Austrodanthonia sp., Poa sieberiana, vegetation Deep Creek (35 km N.W. of Melbourne) Echinopogon ovatuss, Bothriochloa macra (V. Stajsic, D. McLaren personal observation) Chilean needle grass, Nassella neesiana Lowland grassland • Derrimut and Laverton North grassland Themeda triandra (M. Bartley personal communication) reserves (18 km W. of Melbourne) Grassy woodland • Tarnagulla and Tooleen(123 km N. of Grey box, Eucalyptus microcarpa (Liebert, 1996) Melbourne) flora reserves • Melbourne Airport (20 km N.W. of Melb.) Eucalyptus microcarpa (V. Stajsic personal observation) • Long Forest Flora Reserve area at Eucalyptus microcarpa (P. Wlodarczyk personal communication) Coimadai (49 km N.W. of Melbourne) Riparian vegetation • Lollypop Creek, Little River (You Yangs), (V. Stajsic personal observation) Coimadai Creek (Long Forest Reserve 49 km N.W. Melbourne), Tullaroop Creek (N.E. of Clunes) • Tarnagulla (160 km NW Melb). (Liebert 1996) Cane needle grass, Nassella hyalina Grasslands • Ravenhall, Tarneit, Rockbank, Organ Themeda triandra, Austrostipa and Austrodanthonia species Pipes National Park (20–30 km W.N.W. of Melb.), Turpin’s Falls (85 km N.W. of Melb.), Sutherland Creek (70 km S.W. of Melbourne) • Epping (20 km N. of Melbourne) N. charruana, Rosa rubiginosa, Plantago lanceolata, Bromus hordeaceus, Avena barbata, Cynosurus echinatus, Erodium botrys (V. Stajsic personal observation) Riparian vegetation • Ravenhall, Barfold Gorge (90 km N.N.W. Eucalyptus camaldulensis, Callistemon sieberi, Hymenanthera dentata of Melbourne) var. angustifolia and Poa labillardieri (V. Stajsic personal observation) Texas needle grass, Nassella leucotricha Native grasslands • Taradale (90 km N.W. of Melbourne), Austrostipa/Austrodanthonia, Themeda triandra Tullaroop Creek (40 km N. of Ballarat), Mt. Ridley (30 km N. of Melbourne) Lobed needle grass, Nassella charruana Native grasslands • Thomastown (15 km N.N.E. of Melbourne) N. neesiana, N. hyalina, N. trichotoma, N. leucotricha, Phalaris aquatica (V. Stajsic personal observation) • Janefield Reserve in Plenty Gorge Kunzea phylicoides, Acacia pycnantha, A. mearnsii and scattered Metropolitan Park (18 km N.E. of Melbourne) Eucalyptus melliodora, Poa labillardieri, Themeda triandra, Austrostipa rudis and Astroloma humifusum (V. Stajsic personal observation) • Epping (20 km N.E. of Melbourne) N. hyalina (abundant), Rosa rubiginosa, Plantago lanceolata, Bromus hordeaceus, Avena barbata, Cynosurus echinatus, Erodium botrys (V. Stajsic personal observation) Uruguayan ricegrass, Piptochaetium montevidense Grassland • Cherry Lake Altona (15 km S.W. of Melbourne) Themeda triandra (G. Carr personal communication) Short-spined needle grass, Nassella megapotamia Grassy woodland • Black Mountain Canberra Dry sclerophyll forest Broad kernal espartillo, Achnatherum caudatum Riparian vegetation • Dunnolly (150 N.W. of Melbourne) Threatening the vulnerable hairy anchor plant (Discaria pubescens) Tullaroop, Birch and Creswick creeks at Creswick Creek (McPhee and May 1992, V. Stajsic and E. Bruzzese (120–130 km N.W. of Melbourne) personal observation) • Edgars Creek (8 km N. of Melbourne) Melbourne (R. Hore, D. McLaren, V. Stajsic personal observation) Narrow kernal espartillo, Achnatherum brachychaetum Grassland • Merriwa (225 km N.W. of Sydney) No data Plumerillo, Jarava plumosa Grassland • Waite Agricultural Inst. (South Australia) Austrodanthonia spp. (dominant), Convulvulus erubescens, Einadia nutans, Enchylaena tomentosa, Maireana enchylaenoides (J.P. Gardner personal communication). Plant Protection Quarterly Vol.13(2) 1998 65 only, Figure 4) with substantial areas of Victoria and New South Wales at risk. Likewise there have been no estimates or reports of the economic losses incurred by N. neesiana. The competitive ability and efficient re- productive mechanisms of N. neesiana have enabled it to dominate large areas of highly productive pastures on the North- ern Tablelands of New South Wales and on the Volcanic Plain of Victoria (Gar- Figure 1. Nassella trichotoma 1935. Figure 2. Nassella trichotoma. dener and Sindel 1998). During warmer months it produces large numbers of un- palatable flower stalks and very little leaf material, resulting in a severe reduction in summer stock carrying capacity. Con- versely, a reasonable quantity of good feed is produced during the winter months on the New England Tablelands (Gardener and Sindel 1998). Nassella neesiana has been described as being potentially the worst environmental weed of indigenous grasslands in Victoria (C. Hocking personal communication). Carr et al. (1992) classified N. neesiana as a Figure 3. Nassella neesiana 1934. Figure 4. Nassella neesiana. very serious environmental weed that invades lowland grassland, grassy woodland and rocky outcrop vegetation (Table 1). It tolerates drought and heavy grazing and, at least in Victoria, it also tolerates soils or sites that are subject to seasonal water-logging such as at Derrimut and the Laverton North grassland reserves (V. Stajsic personal observation) and the Tarnagulla (160 km N.W. of Melbourne) flora reserve (Liebert, 1996). It has also Figure 5. Nassella hyalina 1951. Figure 6. Nassella hyalina. been found on the alluvial flats that are subject to seasonal waterlogging at the Wattle Park (12 km E. of Melbourne) (G. Carr personal communication). Liebert (1996) comments that N. neesiana often es- tablishes in damp depressions such as drainage lines and roadsides and then radiates out into the drier grassland. Its apparent drought tolerance and ability to tolerate seasonal waterlogging gives this species a wide ecological amplitude and potential to spread and overrun existing Figure 7. Nassella leucotricha 1934. Figure 8. Nassella leucotricha. indigenous vegetation. The presence of cleistogenes hidden at the base of the tillers (Gardener and Sindel 1998) allows this species to reproduce after most of the plant has been destroyed in a fire. The cleistogenes represent approximately 50% of the total annual seed production (R. Parsons personal communication) and in New Zealand it has been observed that frequent burning of sites pro- motes N. neesiana and assists it in forming a monoculture (Bourdôt personal commu- Figure 9. Nassella charruana 1995. Figure 10. Nassella charruana. nication). Nassella neesiana is much more invasive Figures 1, 3, 5, 7 and 9: Figures 2, 4, 6, 8 and 10: in Themeda triandra dominated grasslands The first recorded actual than is N. trichotoma (M. Trengove per- distributions in Australia. Best prediction (10% of mean) sonal communication). In trial plots, N. (20% of mean) neesiana has not only invaded areas of (30% of mean) T. triandra but has also choked out Worst prediction (40% of mean) N. trichotoma (Hunt 1996). 66 Plant Protection Quarterly Vol.13(2) 1998 Nassella neesiana is frequently associ- The term cleistogamous can be used to re- panicles are grazed (Barkworth et al. 1989). ated with watercourses, growing along fer to the presence of cleistogenes. A Seeds are similar to N. neesiana and be- the banks of streams or even on islands cleistogamous flower is one that remains comes readily attached to the hair and that are subject to temporary flooding. closed, is self-pollinating and sets fertile wool of grazing animals and can cause in- Floodwaters play a significant role in the seed. A cleistogene is a hard awnless nut- jury to stock (Leithead et al. 1971). dispersal of seeds (Liebert 1996). like structure hidden at the base of the tiller within the leaf sheaths. They are dif- Lobed needle grass, Nassella Cane needle grass, Nassella hyalina ferent in appearance and structure from charruana (Syn. Stipa charruana (Syn. Stipa hyalina Nees) the inflorescence seeds. A cleistagomous Arech.) Nassella hyalina is a tufted, perennial grass floret does not necessarily produce a Nassella charruana is indigenous to Uru- indigenous to Argentina, southern Brazil cleistogene, it either produces a ‘seed’ like guay, Argentina and south east Brazil and Uruguay (Caro 1966, Rosengurrt et al. that produced by the inflorescence or it (Rosengurrt et al. 1970). It is a perennial 1970). In Argentina it is a common species can produce a cleistogene which is usually that has a very distinctive seed with large but is quite sparse and is of only interme- awnless, hard and nut-like. apical lemma lobes (Rosengurrt et al. diate feed value. It occurs predominantly By using CLIMATE, the potential dis- 1970). It forms dense competitive infesta- on fertile soils in variable situations and is tribution of N. hyalina in Australia has tions in Australia (D. McLaren, V. Stajsic also found in woodlands (Rosengurrt et al. been estimated at 0.9 million ha (best pre- personal observation) and Argentina (M. 1970, M. Gardener personal observation). diction only, Figure 6) with substantial ar- Gardener personal observation). It pro- It is reportedly palatable to stock eas of Victoria and New South Wales at vides productive winter fodder but its (Rosengurrt et al. 1970) and is regarded as risk. seeds can penetrate the fur and skin of producing reasonable fodder. Currently it stock (Rosengurrt et al. 1970). In Argentina is reported as being naturalized in both Texas needle grass, Nassella N. charruana was regarded as very poor Victoria (Walsh and Entwisle 1994) and leucotricha (Syn. Stipa leucotricha Trin. fodder. Unlike N. trichotoma and N. New South Wales (Harden 1993). It was & Rupr.) neesiana it was considered an extremely first recorded between Glen Innes and Nassella leucotricha is a tufted perennial damaging noxious weed due to its inva- Inverell in central New South Wales in grass indigenous to Oklahoma, Texas and siveness, competitiveness, unpalatability 1951. central Mexico (Leithead et al. 1971, Reyna and very sharp and clinging seeds (M. In Victoria it was first recorded from a and Barkworth 1994). Thus far, it has only Gardener personal observation). collection made at Woodstock on 24 Janu- naturalized in Victoria where it was first It is naturalized only in Victoria and it ary 1964. Major infestations are presently collected in October 1934 in Northcote, an was first collected and determined in 1995 centred around the outer western suburbs inner northern suburb of Melbourne. By at Thomastown (G. Carr personal commu- of Melbourne and central Victoria (Figure 1948, it was found approximately 14 km nication). It has also been recorded at 5, Table 1). away in the suburb of North Brighton. It Janefield Reserve (C. Beardsal personal At Ravenhall, in the outer western sub- has since been collected from various communication, V. Stajsic personal obser- urbs of Melbourne, it has been observed northern and western suburbs of Mel- vation) and near Cooper St. Epping where that when the existing pasture is of low bourne, as well as from Taradale in cen- it has been reportedly growing for more quality, N. hyalina is grazed. It is preferen- tral Victoria and near Mt. Beckworth (Fig- than 40 years (P. Haberfield personal com- tially avoided when more palatable pas- ure 7). By using CLIMATE, the potential munication) (Figure 9, Table 1). It was ture species such as Themeda triandra and distribution of N. leucotricha in Australia growing primarily in direct sunlight or various Austrostipa and Austrodanthonia has been estimated at 4.8 million ha (best light shade and appears to prefer wet de- species are present (V. Stajsic personal ob- prediction only, Figure 8) with substantial pressions, but also grows on stoney rises. servation). areas of Victoria at risk. It was discovered on clay (grey/black Recently, an unusual mechanism of In Texas the species is known as either cracking) which Rosengurrt et al. (1970) seed dispersal was observed. After seed Texas needle grass or Texas wintergrass, comments is the preferred soil type in drop, the penultimate stem node becomes it is readily grazed by livestock and is ap- South America. fragile and can be broken by passing ani- parently of significant value for early The Department of Natural Resources mals, wind or water. The apical section of spring or winter grazing (Leithead et al. and Environment has recently begun a the stem which contain the hidden stem 1971, Gould 1978). In its indigenous habi- program to eradicate this weed. At the seeds are thus dispersed (i.e. typical tat, N. leucotricha thrives under conditions Thomastown site, the infestation occurs in awned seed, not cleistogenes) (V. Stajsic of moderate disturbance and is frequently line with road works for the Western ring and E. Bruzzese personal observation). abundant on roadsides, in open grassland road. The infestation was sprayed prior to Carr et al. (1992) considered N. hyalina a sites and heavily grazed pastures commencement of road works and con- serious risk as an environmental weed. It (Leithead et al. 1971). To date no informa- taminated soil was stockpiled at a known is primarily a weed of indigenous tion is available about its fodder value in location to enable control of re-growth. grasslands (Table 1) but has also been ob- Australia. The road works contractor was instructed served growing in areas subject to sea- In Victoria, N. leucotricha invades native to implement a vehicle hygiene program sonal waterlogging and riparian vegeta- pasture and native grasslands (Table 1). to reduce spread of the weed. At Janefield tion Cleistogenes are produced in its native Reserve, a population of 105 N. charruana Walsh and Entwistle (1994) comments habitat but have not been observed in plants ranging from seedlings to adult that N. hyalina commonly produces Australia (Walsh and Entwisle 1994). Un- plants were sprayed with glyphosate on cleistogenes in its native countries, but the like N. hyalina, the literature appears to be 24 December 1997 (V. Stajsic personal ob- Australian material examined lacks these clearer concerning their presence servation). A large infestation (10–15 ha) structures. However, it is unclear from the (Dysterhuis 1945, Leithead et al. 1971, at Cooper Street is currently being as- South American literature whether N. Barkworth et al. 1989). Their potential im- sessed for an extermination program over hyalina actually produces cleistogenes. portance is indicated by studies of N. the next few months. A detailed survey This states that N. hyalina is predomi- leucotricha that increased its density in re- and community awareness campaign will nantly cleistogamous (Rosergurrt et al. sponse to grazing. This is partially attrib- be implemented next spring when it is in 1970). The terms cleistogamous and utable to the cleistogenes which provide a flower and is easily identified. Young cat- cleistogenous/cleistogene are confused. source of new plants even if the exposed tle will not eat it. Plant Protection Quarterly Vol.13(2) 1998 67 By using CLIMATE, the potential distribution of N. charruana in Australia has been estimated at 0.6 million ha (best prediction only) with a substantial area of Victoria at risk (Figure 10).

Short-spined needle grass, Nassella megapotamia (Syn. Stipa megapotamia Spr. ex Trin.) Nassella megapotamia is indigenous to Ar- Figure 11. Nassella megapotamia Figure 12. Nassella megapotamia. gentina and Southern Brazil (Rosengurtt 1961. et al. 1970) where it inhabits undisturbed areas and is rarely found on grazed land. It is considered rare, palatable and of low to medium productivity potential. The seeds of N. megapotamia are considered in- nocuous (Rosengurrt et al. 1970). The first collection was made in 1961 at the CSIRO site at Black Mountain, Canberra (Figure 11) and it appears to be confined to this area. No collections have been lodged at the New South Wales and Canberra her- Figure 13. Piptochaetium Figure 14. Piptochaetium baria since the 1960s but it was still montevidense 1988. montevidense. thought to be surviving at Black Mountain during the 1980s (S. Jacobs personal communication). It is apparently an escapee from the CSIRO plant introduction plots (R. Pullen personal communication). The environmental weed status of this species is unknown in Australia and an urgent survey of Black Mountain is required to determine the status of this species. How- ever, N. megapotamia could be considered a potential environmental weed (M. Lazarides personal communication) with a potential distribution as indicated in Fig- Figure 15. Achnatherum caudatum Figure 16. Achnatherum caudatum. ure 12. 1959. Uruguayan ricegrass, Piptochaetium montevidense This grass is uncommon in Argentina and is a small perennial that produces many seeds. Its stock food value is unknown, its seeds cause no problems to stock and have low weed potential (M. Gardener personal communication). It is indigenous to Argentina, Bolivia, southern Brazil, Figure 17. Achnatherum Figure 18. Achnatherum Paraguay, Uruguay and Chile (Roig brachychaetum 1955. brachychaetum. 1978). It was first recorded in 1988 from Cherry Lake, Altona (G. Carr personal communication, Figure 13) and it is uncer- tain whether it is still extant. Its impact as an agricultural or environmental weed is unknown. By using CLIMATE, the potential distribution of P. montevidense in Australia has been estimated at 0.6 million ha (20% prediction only) with only a relatively small area of Victoria at risk (Figure 14). Figure 19. Jarava plumosa 1968. Figure 20. Jarava plumosa. Broad-kernel espartillo, Achnatherum caudatum (Syn. Stipa caudata Trin.) Figures 11, 13, 15, 17 and 19: Figures 12, 14, 16, 18 and 20: Achnatherum caudatum is a perennial The first recorded actual densely tufted grass indigenous to Chile distributions in Australia. Best prediction (10% of mean) and Argentina (Rosengurtt et al. 1970, (20% of mean) Caro and Sanchez 1971). A. caudatum, like (30% of mean) the very closely related species A. Worst prediction (40% of mean) brachychaetum, has been identified as a 68 Plant Protection Quarterly Vol.13(2) 1998 problem weeds in lucerne crops in both prediction only) with a substantial area of By using CLIMATE, the potential dis- Argentina and California (Parsons and Victoria, New South Wales and Tasmania tribution of J. plumosa has been estimated Cuthbertson 1992). In Chile and Argen- at risk (Figure 16). at 1.8 million ha (best prediction only, Fig- tina A. caudatum is regarded of being of lit- ure 20) with a substantial area of South tle to no fodder value, inhabits fertile ar- Narrow-kernel espartillo, Australia and Western Australia at risk. eas but its seeds are not harmful to stock. Achnatherum brachychaetum (Syn. It is considered an aggressive plant on fal- Stipa brachychaeta Godron) Conclusions and recommendations low lands of calcareous soils (Rosengurrt Native to Uruguay, Chile and Central Ar- The introduction and proliferation of ex- et al. 1970). gentina (Rosengurrt et al. 1970). In Chile otic stipoid grasses over the past 100 years The earliest known collection in Aus- and Argentina A. brachychaetum is re- is seriously threatening agricultural pro- tralia was made in the Cootamundra dis- garded of being of little to no fodder value, ductivity and the integrity of Australia’s trict of New South Wales on 5 November inhabits fertile areas but its seeds are not indigenous flora and fauna, particularly 1959 and has since spread to the harmful to stock. It is considered an ag- its grasslands. How these weeds have en- Deniliquin area (Parsons and Cuthbertson gressive plant on fallow lands with calcar- tered Australia is unclear. However, 1992) (Figure 15). In Victoria it was first eous soils (Rosengurrt et al. 1970). N. trichotoma was introduced into the observed near Dunnolly on 30 November The earliest Australian record comes United States in 1988 as a contaminant of 1984. It has also been collected from from Merriwa, New South Wales on 15 eight shipments of tall fescue (Festuca Cambells Creek near Castlemaine. Ac- November 1955 (Figure 17). It has been arundinacea Schreb.) seed from Argentina. cording to McPhee and May (1992), A. difficult to obtain reliable data on this spe- A recall of contaminated material was caudatum was first introduced to Clunes in cies in New South Wales due its close re- made in early 1989 but by then over 24 000 gravel, possibly during the 1970s. It has semblance to A. caudatum. Like A. kg of contaminated seed had already been recently been found invading riparian caudatum, A. brachychaetum produces sold to retail customers in over 49 counties vegetation along Edgars Creek, Coburg cleistogenes in the lower leaf sheaths. in Illinois, Kentucky, Missouri, North (Table 1). Achnatherum brachychaetum is listed by Carolina and South Carolina (Westbrooks This species also occurs in Tasmania. It the Federal Government of the United and Cross 1993). It would be interesting to was recorded on Flinders Island in 1979 States as a noxious weed and was col- establish whether Australia has also re- (Parsons and Cuthbertson 1992) and on lected from ballast near Portland Oregon ceived shipments of tall fescue or other mainland Tasmania at Bridgewater and is and occurs in California (USA Depart- seed from Argentina. Several exotic declared as a noxious prohibited species. ment of Agriculture 1953, Barkworth stipoid species appear to have originated It has yet to be declared in New South 1993). from the northern suburbs of Melbourne. Wales and Victoria. By using CLIMATE, the potential dis- A former trotting stud located on Darebin In New South Wales, A. caudatum is be- tribution of A. brachychaetum has been es- Creek Epping, owned by a Mr. Tatlo, is coming a serious weed, invading pasture timated at 0.6 million ha (best prediction rumoured to have been a source of ‘needle particularly after cultivation. It invades re- only) with a large area of New South grass’ in the area. These were often re- sown pasture and becomes prominent by Wales at risk (Figure 18). ferred to as ‘Tatlo needle grass’ (P. the third year. In native pasture it is lim- Haberfield personal communication). ited to areas of disturbance and along Plumerillo, Jarava plumosa (Syn. Stipa Other potential sources of introduction fence lines. Near Clunes in Victoria, A. papposa Nees) could be via cropping (oats and barley caudatum poses a serious threat to grazing Jarava plumosa is indigenous to southern were planted in the locality during the production and an unknown threat to Brazil, Uruguay, Argentina and Chile 1930s) or from contaminated stock/fod- cropping and horticulture. It is a poor fod- (Roig 1978). Its seed has an apical pappus der (dairying, sheep and pigs were com- der plant but starving animals will feed on and is the only exotic stipoid species in mon in this area) (P. Haberfield personal young plants that were still vigorous un- Australia that has seed adapted for wind communication). der heavy grazing pressure (McPhee and dispersal (Jacobs and Everett 1997). This is Nassella trichotoma is regarded as one of May 1992). At Maryborough, cattle were not to be confused with wind dispersed the worst agricultural weeds in Australia observed to feed on it where little or no inflorescences of N. trichotoma. It is report- (Campbell and Vere 1995) and is also rec- other pasture species remained (V. Stajsic, edly of little fodder value and its seed is ognized as a serious environmental weed E. Bruzzese personal observation). irritable to stock (Rosengurrt et al. 1970). (Carr et al. 1992). It sets a precedent against Achnatherum caudatum is reportedly This species has been recorded in Catalo- which the impacts of other exotic stipoid spread by water, particularly after flood- nia in Spain (Fornell and De Blas 1985) species can be measured. The lesson we ing and by stock along stock routes (J. and also at Berkley, California in 1983 but should learn is that prompt control action Cherry personal communication, McPhee has not persisted (Barkworth 1993). should be undertaken to eradicate these and May 1992). It is also spread by slash- Jarava plumosa was first introduced as a weed species before their populations get ing, mowing and soil disturbance by ma- potential pasture plant by the Waite Agri- beyond extirpation. chinery along roadsides in the Mary- cultural Research Institute, probably in the borough, Talbot and Clunes areas (V. early 1940s and the first herbarium record Recommendations Stajsic personal observation, McPhee and came from a cultivated glasshouse speci- 1. A ban is placed on introduction of ex- May 1992). In Victoria, A. caudatum was men on 10 January 1941 (Gardner et al. otic stipoid grass species into Australia. observed invading riparian vegetation in 1996, Figure 19). The species has estab- The increased interest in grasses in central Victoria and Melbourne (Table 1). lished itself periodically between 1968 landscaping will make it very tempting The species produces abundant hard and 1995 but it was not recorded as natu- for the horticulture industry to import awnless ‘nut-like’ cleistogenes at the base ralized as it was confined to the Arbore- attractive exotic stipoid grasses. of the leaf sheaths. The tussocks are spiny tum where infestations were grubbed 2. That a weed alert system be put in place at the crown which may serve to protect out. However, in 1994 a population was that links herbariums, weed experts, the basal sheaths containing the discovered at South Parklands, bordering the horticultural industry and the com- cleistogenes (McPhee and May 1992). Adelaide which has also been grubbed out munity so that new weeds can be By using CLIMATE, the potential dis- (Gardner et al. 1996). At the Waite Arbore- quickly identified and eradicated. tribution of A. caudatum in Australia has tum it grows on Urrbrae fine sandy loam 3. That a weed extermination contingency been estimated at 12.9 million ha (best (Gardner 1990). plan is formulated that will lay down a Plant Protection Quarterly Vol.13(2) 1998 69 framework to ensure that new, poten- Campbell, M.H. (1977). Assessing the area ‘Resilience in Mediterranean-type Eco- tially disastrous weeds are destroyed and distribution of serrated tussock systems’, eds. B. Dell, A.J.M. Hopkins before populations get out of control. (Nassella trichotoma), St. John’s wort and B.B. Lamont, pp. 129-45. (Dor- 4. That research is conducted on the biol- (Hypericum perforatum var. angusti- drecht, Junk). ogy, ecology, digestibility, competitive- folium) and sifton bush (Cassinia Harden, G.J. (1993). ‘Flora of New South ness and control techniques for these arcuata) in New South Wales. Depart- Wales’, Volume 4. (NSW Press, Ken- stipoid species. ment of Agriculture, NSW, Technical sington). 5. That N. charruana, N. megapotamia, A. Bulletin 18, 1-23. Hunt, P. (1996). Action urged on Chilean brachychaetum, P. montevidense and J. Campbell, M.H. (1982). The biology of needle grass. The Weekly Times, 18 De- plumosa be exterminated. Australian weeds 9. Nassella trichotoma cember 1996. 6. That a biological control program is ini- (Nees) Arech. Journal of the Australian Jacobs, S.W.L. and Everett, J. (1996). tiated against N. trichotoma and N. Institute of Agricultural Science 48, 76-84. Austrostipa, a new genus and new neesiana that could be extended to in- Campbell, M.H. and Vere, D.T. (1995). names for Australasian species for- clude N. leucotricha, N. hyalina and A. Nassella trichotoma (Nees) Arech. In ‘The merly included in Stipa (Gramineae). caudatum. Biology of Australian Weeds Volume Telopea 6, 579-95. 7. That an Australia wide ‘exotic stipoid’ 1’, eds. R.H. Groves, R.C.H. Shepherd Jacobs, S.W.L. and Everett, J. (1997). Jarava awareness campaign is initiated that and R.G. Richardson, pp. 189-202. (R.G. plumosa (Gramineae), a new combina- provides clear information on how to and F.J. Richardson, Melbourne). tion for the species formally known as identify these weed species. Caro, J.A. (1966). Las especies de Stipa Stipa papposa. Telopea 7, 301-2. 8. That where environmental impact (Gramineae) de la region central Ar- Jones, R.E. and Vere, D.T. (1998). The eco- studies are conducted with regard to gentina. Kurtziana 3, 7-119. nomics of serrated tussock in New physical works (i.e. roadworks), weeds Caro, J.A. and Sanchez, E. (1971). La South Wales. Plant Protection Quarterly as well as endangered species are con- identidad de Stipa brachychaeta Godron, 13, 70-6. sidered so that vehicle/equipment hy- S. caudata Trinius y S. bertrandii Lane, D., Riches, K. and Combellack, giene procedures can be put in place to Philippi. Darwiniana 16, 637-53. H. (1980). A survey of distribution reduce weed spread. Carr, G.W., Yugovic, J.V. and Robinson, of the noxious weeds in Victoria. 9. That a program is initiated to investi- K.E. (1992). ‘Environmental weed inva- Unpublished report. Department of gate the impact of these weeds on flora sions in Victoria’. (Department of Con- Conservation and Natural Resources, and fauna biodiversity. servation and Environment and Eco- Keith Turnbull Research Institute, Vic- 10. That research is undertaken into reha- logical Horticulture Pty. Ltd.). toria. bilitation of infested lands, particularly Cousens, R.D. and Mortimer, M. (1995). Leithead, H.L., Yarlett, L.L. and Shiflet, with native species. ‘Dynamics of weed populations’. T.N. (1971). 100 native forage grasses in (Cambridge University Press). 11 southern states. Agriculture hand- Acknowledgments Cousens, R.D. and Pheloung, P. (1996). book No. 389. (Soil Conservation Serv- The authors wish to thank the following What limits geographic distributions ice, US Department of Agriculture, people. Paul Pheloung (climate analysis), of cruciferous weeds in Australia? Washington DC, USA). Jim Backholer (preparation of maps in Proceedings of the Second Interna- Liebert, A. (1996). Chilean needle grass: ARCVIEW), Ian McGowan (New South tional Weed Control Congress, Copen- Stipa neesiana. Unpublished report. De- Wales), Christion Goninon (Tasmania) hagen. partment of Conservation and Natural and Phillip Wierzbowski (Victoria) for Dysterhuis, E.J. (1945). Axillary cleisto- Resources, North Central CALP Re- supply of infestation data and to the staff genes in Stipa leucotricha and their role gion. from herbariums around Australia who in nature. Ecology 26, 195-9. McPhee, D. and May, A. (1992). Stipa kindly provided their time in supplying ESRI (1996). ArcView GIS. The geographic caudata in the Clunes district. Survey re- us data. We would also like to express our information system for everyone. Envi- port. Unpublished Report, Department gratitude to the many people who pro- ronmental Systems Institute Inc. of Conservation and Environment, vided their valuable knowledge and ob- Fornell, T.C.I. and De Blas, A.F.I. (1985). Ballarat Region. servations. Stipa papposa Nees, Eragrostis curvula Nicholson, C., Patterson, A. and Miller, L. (Schrad.) Nees I Chenopodium pumilio (1997). The cost of serrated tussock con- References R.Br.: tres especies exotiques noves per trol in central western Victoria. Unpub- Aberdeen, I. (1995). Report on serrated a Catalunya. Collect. Bot. Barc. Bot. Inst. lished report prepared for the Victorian tussock. Inland Agriculture. Ed. 16, 161-4. Serrated Tussock Working Group. Barkworth, M.E. (1993). North American Gardener, M.R. and Sindel, B.M. (1998). Nix, N.H. (1986). A biographic analysis of Stipeae (Gramineae): Taxonomic The biology of Nassella and Australian elapid snakes. In ‘Atlas of changes and other comments. Achnatherum species naturalized in Australian Elapid Snakes’, ed. R. Phytologia 74, 1-25. Australia and the implications for man- Longmore, pp. 4-15. (Bureau of Flora Barkworth, M.E., Valdes-Reyna, J. and agement on conservation lands. Plant and Fauna, Canberra). Landers, R.Q. (1989). Stipa clandestina: Protection Quarterly 13, 76-9. Parodi, L.R. (1930). Ensayo fitogeo- New weed threat on southwestern Gardner, J.P. (1990). ‘The Waite Arbore- graphico sobre el partido de rangelands. Weed Technology 3, 699-702. tum – A guide and catalogue of trees’. Pergamino. Revisita de la Facultad de Bourdôt, G.W. and Hurrell, G.A. (1992). (University of Adelaide). Agronomia y Veterinaria. Entrega 1 VII, Aspects of the ecology of Stipa neesiana Gardner, J.P., Jessop, J.P. and Symon, D.E. 65-289. Trin. & Rupr. Seeds. New Zealand Jour- (1996). The escape of Stipa papposa. Jour- Parsons, W.T. and Cuthbertson, E.G. nal of Agricultural Research 35, 101-8. nal of the Adelaide Botanic Gardens 17, (1992). ‘Noxious weeds of Australia’. Busby, J.R. (1991). BIOCLIM – A 173-6. (Inkata Press, Melbourne). bioclimatic analysis and prediction sys- Gould, F.W. (1978). ‘The grasses of Texas’, Pheloung, P.C. and Scott, J.K. (1996). Cli- tem. In ‘Nature conservation: cost effec- First edition. (Texas University Press, mate based prediction of Asparagus tive biological surveys and data analy- College Station, USA). asparagoides and A. declinatus distribu- sis’, eds. C.R. Margules and M.P. Aus- Groves, R.H. (1986). Invasion of Mediter- tion in Western Australia. Plant Protec- tin, pp. 64-8. (CSIRO, Canberra). ranean ecosystems by weeds. In tion Quarterly 11, 51-3. 70 Plant Protection Quarterly Vol.13(2) 1998 Reyna, J.V. and Barkworth, M.E. (1994). El genero Nassella (Poaceae: Stipeae) en The economics of serrated tussock in New South Mexico. Acta Botanica Mexicana 26, 63-75. Wales Roig, F.A. (1978). Stipa. In ‘Flora Patagonica Parte III. Gramineae’, ed. R.E. Jones and D.T. Vere, Co-operative Research Centre for Weed E.G. Nicora. (Coleccion Cientifica del Management Systems and NSW Agriculture, Orange Agricultural Institute, Instituto Nacional de Technologia Forest Road, Orange, New South Wales 2800, Australia. Agropecuaria (I.N.T.A.) Tomo VIII. Buenos Aires). Rosengurtt, B., Arrillaga De Maffei, B.R. Summary Serrated tussock has no grazing value and Izaguirre De Artucio, P. (1970). Serrated tussock (Nassella trichotoma) is because of its high fibre (86%) and low Gramineas Uruguayas. Universidad de a grass native to South America which protein content (4%). Consequently infes- la Republica. Departmento de has become a serious weed in Australia, tations of this weed result in a significant publicaciones, coleccion ciencias 5. Monte- New Zealand and South Africa because loss in livestock production. Heavy infes- video. firstly, it results in significant losses in tations of serrated tussock can reduce the Sloane Cook and King Pty. Ltd. (1988). livestock production due to heavy reduc- carrying capacity of both improved and ‘The economic impact of pasture tions in carrying capacity in infested pas- natural pastures by as much as 90% while weeds, pests, and diseases on the Aus- tures. Secondly, control by pasture im- moderate infestations can reduce stock tralian wool industry’. (Australian provement requires a large capital in- numbers by 40%. Wool Corporation, Melbourne). vestment which hinders the adoption of The first survey of the area and distri- Stace, C. (1997). ‘New flora of the British control recommendations for many bution of serrated tussock was by Isles’, second edition. (Cambridge Uni- landholders. Thirdly, significant exter- Campbell (1977) who determined that the versity Press, UK). nal costs can be attributed to this weed. total area of infestations in New South Sutherist, R.W. and Maywald, G.F. (1985). Spread is generally by wind with seeds Wales was 680 000 ha (Table 1). Campbell A computerized system for matching from uncontrolled areas travelling up to classified infestations into three densities: climates in ecology. Agriculture, 20 km a day. i. dense infestations in which animal pro- Ecosytems and Environment 13, 281-99. The distribution and density of ser- duction was seriously diminished United States Department of Agriculture rated tussock has been surveyed for 19 (Class 1), (1953). Grasses introduced into the local government areas in central and ii. scattered patches with isolated plants United States. US Department of Agri- southern New South Wales. These data interspersed which would soon in- culture, Forest Service, Agriculture have been incorporated into a GIS which crease to (i) in the absence of control Handbook No. 58, pp. 55. has been combined with data on soil fer- (Class 2), and Walsh, N.G. and Entwisle, T.J. (1994). tility and rainfall to provide the neces- iii. scattered plants with no heavy concen- ‘Flora of Victoria. Volume 2: Ferns and sary constraints for a regional linear pro- trations (Class 3). allied plants, conifers and mono- gramming model to estimate the produc- Subsequent serrated tussock surveys by cotyledons’. (Inkata Press, Melbourne). tion losses due to this weed. Econometric Campbell (1987) and Gorham (unpub- Westbrooks, R.G. (1991). Plant Protection models of the wool and livestock indus- lished) in 1994 (Table 1) indicated that the Issues 1. A Commentary on new weeds tries were used to estimate the economic area of serrated tussock had declined by in the United States. Weed Technology 5, impact of serrated tussock on the New about 30% between 1977 and 1987, but by 232-7. South Wales central and southern table- 1994 the infested area of 740 716 ha had Westbrooks, R.G. and Cross, G. (1993). lands. increased above the 1977 level of 680 000 Serrated tusssock (Nassella trichotoma) ha. Campbell (1987) attributed the release in the United States. Weed Technology 7, Introduction of the chemical tetrapion as one of the sig- 525-9. Serrated tussock (Nassella trichotoma) is a nificant reasons for the decline in serrated grass native to South America and is a se- tussock by 1987. Gorham gave no reasons rious weed in Australia, New Zealand and for the subsequent increase by 1994. South Africa. The threat posed by this Serrated tussock has been the principal weed was first recognized in 1935 in noxious weed in New South Wales for the southern New South Wales after its intro- past 15 years despite the development and duction in fodder shipments imported extension of proven control technologies during droughts. By the 1950s serrated and the demonstration of the economic tussock had occupied large areas of south- benefits of these methods in areas favour- eastern Australia with most infestations able to pasture improvement, as well as occurring within areas bounded by a 21°C continued enforcement of control legisla- isotherm for mean January temperature tion by local government. The information and an average rainfall between 500 and derived from both the Campbell and 990 mm. This area covers most of the cen- Gorham surveys was collected using tral and southern tablelands of New South mail questionnaires to all New South Wales. Wales local government area (LGA) weed Table 1. Estimated areas (ha) infested with serrated tussock in New South Wales by various surveys. Campbell (1977) Campbell (1987) Gorham (1994) Class 1 71 200 47 000 55 268 Class 2 147 100 61 800 86 253 Class 3 461 700 382 600 599 195 Total 680 000 491 400 740 716