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The Distribution, Impacts and Identification of Exotic Stipoid Grasses in Australia

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Plant Protection Quarterly Vol.19(2) 2004 59 • Texas needlegrass (N. leucotricha Trin. & Rupr.) The distribution, impacts and identifi cation of exotic • Lobed needlegrass (N. charruana Are- stipoid grasses in Australia chav.) • Short-spined needlegrass (N. megapota- A,D B C mia Spreng. ex Trin.) David A. McLaren , Val Stajsic and Linda Iaconis • Uruguayan ricegrass (Piptochaetium A Primary Industries Research Victoria (PIRVic), Department of Primary montevidense (Spreng.) Parodi) Industries, Frankston Centre, PO Box 48, Frankston, Victoria 3199, Australia. • Broad-kernel espartillo (Achnatherum B National Herbarium of Victoria, Royal Botanic Gardens, Birdwood Avenue, caudatum Trin.) South Yarra, Victoria 3141, Australia. • Narrow-kernel espartillo (A. brachycha- C Catchment and Agriculture Services, Department of Primary Industries, etum (Godr.) Barkworth) and Frankston Centre, PO Box 48, Frankston, Victoria 3199, Australia. • Plumerillo (Jarava plumosa (Spreng.) D CRC for Australian Weed Management. S.W.L.Jacobs & J.Everett). All of these species are proclaimed plants in South Australia, under the Animal and Plant Control (Agricultural Protection and Other Purposes) Act, 1986. Abstract For each species, a summary has been Exotic stipoid grasses are one of the structures at the base of a spikelet) which produced of its: most signifi cant issues affecting grazing are often purplish in colour, and one fl oret • Distribution – known overseas distri- industries and threatening nationally im- (in which the seed is formed). The fl oret butions, current Australian distribu- portant remnant grasslands in Australia. consists of the lemma and palea. The lem- tion and potential distribution in Aus- This paper documents their distribution, ma is usually terete (i.e. circular in cross tralia (based on its current distribution impacts and identifi cation. It also dis- section) or gibbous (i.e. asymmetric) and in Australia). cusses how these grasses are coming into fi rmly membranous. The palea is enfolded • Impacts – agricultural and environ- Australia and makes recommendations and concealed by the lemma. Seed may be mental. on how this could be addressed. tipped by a callus of hairs (see Figure 1), • Identifi cation – vegetative and fl oral and has an awn (a curved, bristle-like tail) characteristics that help differentiate Introduction at the opposite end. the species. South-eastern Australian indigenous The exotic stipoid grasses are one of grasslands are now regarded as one of the most signifi cant threats facing graz- Serrated tussock, Nassella Australia’s most threatened ecosystems. ing industries and indigenous grasslands trichotoma Only half of one percent (10 000 hectares) in south-eastern Australia (McLaren et al. Distribution of the original two million hectares of low- 1998). Eleven exotic stipoid grass species Nassella trichotoma (syn. Stipa trichotoma) land grasslands now remain in near natu- have naturalized in Australia (McLaren is a perennial, drought resistant species ral condition, and they contain the greatest et al. 1998), whilst white tussock (Nassella that is native to the pampas grasslands number of species facing extinction (Mar- tenuissima (Trin.) Barkworth) has been sold of Argentina, Uruguay, Chile and Peru riott and Marriott 1998). Since European in Australia through the nursery trade (Parodi 1930, Rosengurtt et al. 1970) and settlement, native grasslands have been (McLaren et al. 1999). The stipoid grasses it has been reported from Bolivia (Walsh rapidly transformed due to land clear- come from the Poaceae Family that com- and Entwisle 1994). It has also natural- ance, urbanization, grazing by introduced prises approximately 9500 species and 650 ized in Australia, New Zealand and South ungulates (e.g., sheep, cattle, horses) genera worldwide (Walsh and Entwisle Africa, whilst small infestations also occur and large scale agricultural production 1994). The Stipeae is a cosmopolitan tribe in England, France, Italy, Scotland (Camp- (cropping and grazing using introduced of approximately 450 species in 14 genera bell 1982, Stace 1997) and the United States grasses and wide-scale addition of su- (Barkworth 1993, Reyna and Barkworth (Westbrooks 1991, Westbrooks and Cross perphosphate). Introduced pests such as 1994, Jacobs and Everett 1996). There are 1993). rabbits and weeds have added additional six stipoid genera in Australia, of which Nassella trichotoma was probably intro- pressures to these remnant grasslands. At fi ve are of exotic origin. Austrostipa is the duced into Australia in the early 1900s but the same time, sheep and beef production only indigenous Australian genus. The was not recorded in Australia until 1935 have become some of Australia’s most im- exotic genera include Achnatherum, Jarava, when a collection was made at Yass, 55 portant rural industries. For many years Nassella, Piptochaetium and Piptatherum. km north-east of Canberra (Campbell and Australia’s economy was said to ‘live off As rice millet (Piptatherum miliaceum (L.) Vere 1995). In 1977 it occupied 680 000 the sheep’s back’. This paper examines the Coss.) appears to be confi ned to urban hectares (Campbell 1977) and now occu- impacts caused by exotic stipoid grasses to settlements, in Victoria at least (Walsh and pies more than 870 000 hectares in New agriculture and the environment and how Entwisle 1994), it will not be considered in South Wales with an estimated 2 000 000 we can recognize these serious weeds. this paper. Species of the other genera are a hectares at risk of infestation (McGowan The Stipeae are strongly tussock cause for serious alarm from both an envi- personal communication). In Victoria N. forming, mostly perennial grasses that ronmental and agricultural perspective. trichotoma was fi rst collected in 1954 at generally have narrow, inrolled leaves. Eleven exotic stipoid grass species are Broadmeadows where infestations were The ligule (a small fl ap at the junction described in this paper, in the following then estimated at four hectares (Lane of the leaf blade and leaf sheath) is often order: personal communication). By 1979 it had short, membranous and fringed. Au- • Serrated tussock (Nassella trichotoma spread to occupy approximately 30 000 ricles (paired projections either side of (Nees) Hack. ex Arechav.) hectares (Lane et al. 1980) and by 1995 the ligule) are glabrous or fringed. The • White tussock (N. tenuissima (Trin.) it occupied in excess of 130 000 hectares infl orescence (fl owering stem) is a panicle Barkworth) (Pest Management Information System, which is rarely branched at the base or • Chilean needlegrass (N. neesiana Trin. & Department of Primary Industries (DPI) occasionally reduced to a few spikelets. Rupr.) Frankston). The Victorian Government Each spikelet has two glumes (leaf-like • Cane needlegrass (N. hyalina Nees) has recently increased N. trichotoma 60 Plant Protection Quarterly Vol.19(2) 2004 control operations that have been fa- Identifi cation White tussock, Nassella tenuissima cilitated by the Victorian Serrated Tussock Vegetative characters Nassella trichotoma Distribution Working Party. It has been estimated that forms a very dense tussock, to 50 cm high Nassella tenuissima (syn. Stipa tenuissima) in excess of 70 000 hectares of serrated tus- and 60 cm across, composed of numerous is native to Argentina, Chile, New Mexico sock infestations have now been treated in fi ne leaves. Leaves are tightly rolled and and Texas (Jacobs et al. 1998). In 1996, Victoria (Boyle personal communication). appear cylindrical when cut in cross sec- N. tenuissima was found being sold at a N. trichotoma now occupies 82 000 hectares tion. Unlike Australian native grasses, N. nursery in Melbourne. Its potential dis- in Victoria, which is a 37% reduction from trichotoma leaves, when rolled between tribution in Australia, predicted from its the 1995 infestation (Boyle 2003). N. tri- the index fi nger and thumb, roll smoothly countries of origin, has been estimated at chotoma is also found in Tasmania where – like a needle. N. trichotoma leaves are 14.2 million hectares (McLaren et al. 1999). it was fi rst recorded in 1956 (Parsons and rough to touch due to small serrations N. tenuissima can potentially occupy six Cuthbertson 1992) and is currently spread on their surfaces and these are easily felt times the area predicted for N. trichotoma in scattered populations over an area of when drawn between the fi ngers. Mature in Australia. The availability of N. ten- approximately 1000 hectares (Goninon plants have drooping leaves. Flower- uissima via the internet and other plant personal communication). Its potential ing stems emerge in spring and grow to purchasing situations makes its entry and distribution in Australia, predicted from a length of 95 cm, twice as long as the naturalization in Australia almost inevita- its current distribution in Australia, has leaves. They are initially erect but droop ble (McLaren et al. 1999). been estimated at 32 million hectares at maturity. They are much branched and (McLaren et al. 1998). usually break off at the base after seed set. Impacts The ligule is about 1 mm long, rounded, In Argentina N. tenuissima is regarded as Impacts membranous and glabrous. an unpalatable grass (Moretto and Distel Nassella trichotoma probably accounts for 1998). It has been classifi ed as a non-pre- a greater reduction in pasture carrying Floral characters The general floral ferred species that can become dominant capacity than any other weed in Australia characteristics of the Genus Nassella under continual
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