Download Sporobolus jacquemontii

Weeds of Australia - Biosecurity Queensland Edition Fact Sheet
Sporobolus jacquemontii
Scientific Name
Sporobolus jacquemontii Kunth
Synonyms
Sporobolus pyramidalis P. Beauv. var. jacquemontii (Kunth) Jovet & Guédès
Vilfa jacquemontii (Kunth) Trin.
habit (Photo: John Thompson)
Family
Gramineae (South Australia)
Poaceae (Queensland, New South Wales, the ACT, Victoria, Tasmania, Western
Australia and the Northern Territory)
Common Names
American rat's tail grass, American ratstail grass, giant smutgrass, large smutgrass,
smutgrass, West Indian dropseed, West Indian rush-grass, West Indies smutgrass
Origin
Native to Mexico, Central America, the Caribbean and tropical South America
(i.e. French Guiana, Guyana, Surinam, Venezuela, Brazil, Bolivia, Colombia, Ecuador and
Peru).
habit (Photo: John Thompson)
Naturalised Distribution
This species is widely distributed in the north-eastern parts of Australia, and is most
commonly found in the coastal regions of northern and central Queensland. It is also
scattered in south-eastern Queensland and present in the northern parts of Western
Australia.
Habitat
A weed of pastures, roadsides, creek banks, disturbed sites, open woodlands and
grasslands in tropical and sub-tropical regions.
stems and leaves (Photo: John Thompson)
Habit
An upright (i.e. erect), densely tufted, and long-lived (i.e. perennial) grass usually
growing 50-75 cm tall.
Distinguishing Features
an upright and tufted long-lived grass usually growing 50-75 cm tall.
its long and narrow leaf blades (up to 40 cm long and 2.5-3.5 mm wide) may
be flat or somewhat rolled.
roots and lower leaves (Photo: John Thompson)
its seed-heads are relatively thin and elongated in appearance (8-25 cm long
and 5-30 mm wide).
they are spike-like with numerous slightly spreading, relatively long,
branches (5-10 cm long).
each of these branches bears numerous tiny flower spikelets (1.5-2 mm
long).
Stems and Leaves
The flowering stems (i.e culms) are relatively slender (1-5 mm thick), but somewhat
wiry, and may be branched.
The leaves are very thin (i.e. linear or filiform) with a leaf sheath, which partially
encloses the stem, and a spreading leaf blade. The leaf sheaths are hairless (i.e.
glabrous) and the leaf blades (up to 40 cm long and 2.5-3.5 mm wide) may be flat or
somewhat rolled (i.e. convolute). These leaf blades are also hairless (i.e. glabrous) and
close-up of leaves (Photo: John Thompson)
have pointed tips (i.e. acuminate apices). Where the leaf sheath meets the leaf blade
there is a fringe of tiny hairs (i.e. ciliated ligule) or a tiny membrane topped with hairs
(i.e. ciliated membrane) 0.2-0.3 mm long.
Flowers and Fruit
The seed-heads are borne at the top of the stems and are thin and elongated (i.e.
lanceolate) in appearance (8-25 cm long and 5-30 mm wide). They are slightly open
panicles, with relatively long branches (5-10 cm long) that diverge slightly away from
the central stalk of the seed-head (i.e. rachis). Each of these branches bears numerous,
tiny, elongated (i.e. lanceolate) or oval (i.e. elliptic) flower spikelets almost to their
bases. The dark green or greyish-green flower spikelets (1.5-2 mm long) contain a
single tiny flower (i.e. floret) inside two bracts (i.e. glumes). The lower bract (i.e. glume)
is 0.3-0.4 mm long and the upper bract (i.e. glume) is 0.5-0.8 mm long (i.e. less than half
the length of the flower spikelet). Flowering occurs throughout the year.
seed-heads (Photo: John Thompson)
The tiny seeds (i.e. grains or caryopses) turn reddish-brown in colour as they mature
and are oblong or egg-shaped (i.e. obovoid). These seeds (0.8-1 mm long and up to 0.5
mm wide) separate from the remainder of the flower spikelet at maturity (i.e. the pale
coloured old glumes remain on the seed-head).
Reproduction and Dispersal
This species produces large quantities of tiny seeds that are somewhat sticky when wet.
These seeds may be spread after becoming attached to animals, clothing and vehicles.
They may also be dispersed by water, in mud, and in contaminated agricultural produce
(e.g. in fodder and pasture seed lots).
seed-heads of various ages (Photo: John Thompson)
Environmental Impact
American rat's tail grass ( Sporobolus jacquemontii ) is regarded as an environmental
weed in Queensland.
Legislation
This species is declared under legislation in the following states and territories:
Queensland: Class 2 - landowners must take all reasonable steps to keep
land free of this species (throughout the entire state). It is also illegal to sell a
declared plant or its seed in this state.
close-up of mature flower spikelets and seeds (Photo:
Sangita Shrestha)
Western Australia: Unassessed - this species is declared in other states or territories and is prohibited until assessed via a weed risk
assessment (throughout the entire state).
Management
For information on the management of this species see the following resources:
the Biosecurity Queensland Fact Sheet on giant rats tail grass and other weedy Sporobolus species, which is available online at
http://www.dpi.qld.gov.au.
Similar Species
American rats-tail grass ( Sporobolus jacquemontii ) is very similar to other introduced rats-tail grasses ( Sporobolus spp.), including giant
Parramatta grass ( Sporobolus fertilis), Parramatta grass ( Sporobolus africanus ), and the giant rats-tail grasses ( Sporobolus pyramidalis and
Sporobolus natalensis ). It is also similar to some native species such as the slender rats-tail grasses (Sporobolus creber and Sporobolus
elongatus). Distinguishing between these species is often very difficult and a specialist may need to be consulted, however the following is a guide
to the differences that may be apparent:
American rats-tail grass ( Sporobolus jacquemontii) is a moderately-sized plant (usually 50-75 cm tall) with relatively small elongated
seed-heads (8-25 cm long). These seed-heads have numerous relatively long branches (50-100 mm long) that usually spread away from
the main stem. These branches are normally densely arranged and the seed-head is un-interrupted. Its flower spikelets are relatively
small (1.5-2 mm long).
giant Parramatta grass ( Sporobolus fertilis) is a relatively large plant (usually 80-160 cm tall) with relatively large spike-like (i.e.
spiciform) seed-heads (15-50 cm long). These seed-heads have numerous moderately long branches (20-80 mm long) that are held
closely (i.e. appressed) to the main stem or slightly spreading. These branches are normally densely arranged and the seed-head is
mostly un-interrupted (except occasionally at the base). Its flower spikelets are relatively small (1.5-2 mm long).
Parramatta grass ( Sporobolus africanus) is a relatively small plant (usually less than 50 cm tall) with relatively small spike-like (i.e.
spiciform) seed-heads (6-35 cm long). These seed-heads have numerous short branches (10-20 mm long) that are usually held closely
(i.e. appressed) to the main stem. These branches are normally densely arranged and the seed-head is mostly un-interrupted (except
occasionally at the base). Its flower spikelets are relatively large (2-2.8 mm long).
giant rats-tail grass ( Sporobolus pyramidalis) is a relatively large plant (usually 90-200 cm tall) with relatively large pyramid-shaped (i.e.
pyramidal) seed-heads (20-45 cm long). These seed-heads have numerous relatively long branches (50-100 mm long) that stiffly spread
away from the main stem. Its flower spikelets are moderately-sized (1.7-2.2 mm long).
giant rats-tail grass ( Sporobolus natalensis) is a relatively large plant (60-150 cm tall) with relatively large spike-like (i.e. spiciform) seedheads (20-30 cm long). These seed-heads have numerous relatively long branches (30-70 mm long) that usually spread away from the
main stem. These branches are normally densely arranged and the seed-head is un-interrupted. Its flower spikelets are moderatelysized (1.6-2.3 mm long).
slender rats-tail grass ( Sporobolus creber) is a moderately-sized plant (usually less than 100 cm tall) with relatively long and very narrow
spike-like (i.e. spiciform) seed-heads (18-60 cm long). These seed-heads have numerous short stiff branches (5-10 mm long) that are
always held closely (i.e. appressed) to the main stem. These branches are normally widely spaced and the seed-head is interrupted
(except near the top). Its flower spikelets are relatively small (1.2-1.7 mm long).
slender rats-tail grass ( Sporobolus elongatus) is a moderately-sized plant (usually 50-100 cm tall) with relatively long and narrow spikelike (i.e. spiciform) seed-heads (10-30 cm long). These seed-heads have numerous relatively long branches (40-80 mm long) that are
usually held closely (i.e. appressed) to the main stem (sometimes slightly spreading). These branches are normally densely arranged
and the seed-head is mostly un-interrupted (except occasionally at the base). Its flower spikelets are moderately-sized (1.5-2.3 mm long).
Fact sheets are available from Department of Employment, Economic Development and Innovation (DEEDI) service centres and our Customer Service Centre (telephone 13
25 23). Check our website at www.biosecurity.qld.gov.au to ensure you have the latest version of this fact sheet. The control methods referred to in this fact sheet
should be used in accordance with the restrictions (federal and state legislation, and local government laws) directly or indirectly related to each control method. These
restrictions may prevent the use of one or more of the methods referred to, depending on individual circumstances. While every care is taken to ensure the accuracy of
this information, DEEDI does not invite reliance upon it, nor accept responsibility for any loss or damage caused by actions based on it.
Copyright © 2016. All rights reserved. Identic Pty Ltd. Special edition of Environmental Weeds of Australia for Biosecurity Queensland.
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