Leersia hexandra (southern cut grass)
- Taxonomic Tree
- Notes on Taxonomy and Nomenclature
- Distribution Table
- Habitat List
- Hosts/Species Affected
- Host Plants and Other Plants Affected
- Biology and Ecology
- Uses List
- Similarities to Other Species/Conditions
- Prevention and Control
- Links to Websites
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Leersia hexandra Swartz
Preferred Common Name
- southern cut grass
International Common Names
- English: swamp rice grass
- Spanish: arrocillo rosado; hieba de arroz; lambedora (Dominican Republic); lamedora (Nicaragua); pasto de agua
Local Common Names
- Brazil: andrequice; arroz-bravo; arroz-de-Guiana; capim-marreca; grama-boiadeira; grama-de-brejo
- Japan: taiwanashikaki
- Thailand: yaa sai
- LERHE (Leersia hexandra)
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Monocotyledonae
- Order: Cyperales
- Family: Poaceae
- Genus: Leersia
- Species: Leersia hexandra
Notes on Taxonomy and NomenclatureTop of page L. hexandra belongs to the tribe Oryzeae (Gramineae [Poaceae]: Bambusoideae)
The most conspicuously variable characters of L. hexandra are scabrousness and general size of the leaves and stem. Pyrah (1969) used these variables to divide the species into four groups: dwarf, scabrous plants; dwarf, smooth plants; robust, scabrous plants; robust, smooth plants. However, there is a continuum of phenotypes between these groups.
Large populations of L. hexandra probably represent single clones since propagation is mainly vegetative and sexual reproduction is rare (Pyrah, 1969). Occasional cross pollination results in heterogeneous genotypes which may give phenotypically different clones. Because of the immense variation in the genus, Launert (1965) has commented that with the presence of such variation it would be a vain attempt to try and subdivide this taxon. Furthermore, the wide range of distribution would also make subdividing difficult without worldwide field observation. Launert also comments on an extreme form of Leersia from Africa, with spikelets 5.1-5.9 mm long; most species have spikelets 3.1-4.4 mm long and have some lateral pubescence. However, many specimens of L. hexandra from the USA have spikelets 4.4-5.0 mm long and are glabrous laterally and somewhat acuminate apex, these specimens are scabrous and depauperate (Pyrah, 1969).
DescriptionTop of page L. hexandra is very like plants from the genus Oryza and can be distinguished in many cases because the auricle at the junction of sheath and blade and the lower and upper glume are lacking. In addition, the leaves of Leersia are very rough to the touch, Leersia having retrorse hairs on the underside of the midrib; however, some samples of Leersia have been described as having glabrous leaves (Pyrah, 1969) and would therefore be less rough to the touch.
Description: after Pyrah (1969)
Perennial grass plant similar in appearance to rice (Oryza sativa); rhizomes elongate; culms 25-150 cm long, decumbent, rooting at the nodes, terminal portion erect, often floating, glabrous to coarsely scabrous near the nodes; nodes exposed, densely retrorse-pubescent to nearly glabrous, often somewhat shrunken, especially upon drying; sheaths coarsely scabrous-hispid to glabrous, margins often conspicuously ciliate; ligule truncate, 1-6 mm long, auriculate; blades 5-25 cm long, 3-5 mm wide, scabrous to nearly glabrous above and beneath; panicles terminal, 5-15 cm long, exserted, branches 3-13 cm long, filiform, ascending to somewhat spreading in more robust forms, usually one per node but sometimes two; spikelet 3.0-4.4 (5.0) mm long, imbricate, generally turning purple; lemma acute to acuminate, ciliate (to 0.6 mm long) on keel and margins; short hispid to glabrous laterally; palea sub equal with lemma, ciliate on keel; stamens 6, anthers 2-3 mm long; pistil about 2.5 mm; caryopsis usually not developed. Chromosome number 2n=48.
DistributionTop of page L. hexandra is abundant in wet areas of tropical and subtropical regions of the world, in the southern USA, Central America, northern and central South America, Africa (south of the Sahara), India, tropical regions of China, South-East Asia and Australia. In Japan and neighbouring areas it is replaced by L. japonica (Pyrah, 1969).
It is reported as a serious weed of rice in Guyana and Brazil and a principal weed in Madagascar, the Philippines, Sumatra and Sarawak. It is also a weed of rice in Cambodia, India, Indonesia, Malaysia, Nigeria, the Philippines, Suriname and Thailand. It is a weed of maize in Indonesia, rubber in Malaysia and sugarcane in Australia and Tanzania. The plants are also a problem in drainage and irrigation ditches where the dense mat of vegetation that forms can impede water flow and cause erosion of banks (Holm et al., 1977).
L. hexandra is recorded in the floras of China, Ghana, Hong Kong, Israel, Jamaica, Myanmar, Puerto Rico and South Africa, but it is not clear if it is a weed in these areas (Holm et al., 1979).
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|Bangladesh||Present||Holm et al., 1979|
|Brunei Darussalam||Present||Waterhouse, 1993|
|Cambodia||Present||Holm et al., 1979|
|China||Present||Present based on regional distribution.|
|-Fujian||Present||Wang et al., 1990|
|-Guangdong||Present||Wang et al., 1990|
|-Hong Kong||Present||Pyrah, 1969|
|India||Present||Present based on regional distribution.|
|-Indian Punjab||Present||Pyrah, 1969|
|-West Bengal||Present||Pyrah, 1969|
|Indonesia||Present||Present based on regional distribution.|
|Israel||Present||Holm et al., 1979|
|-Sarawak||Present||Holm et al., 1979|
|Sri Lanka||Present||Pyrah, 1969|
|Angola||Present||Gibbs-Russel et al., 1990|
|Botswana||Present||Gibbs-Russel et al., 1990|
|Ghana||Present||Holm et al., 1979|
|Lesotho||Present||Gibbs-Russel et al., 1990|
|Madagascar||Present||Holm et al., 1979|
|Namibia||Present||Gibbs-Russel et al., 1990|
|Nigeria||Present||Holm et al., 1979|
|South Africa||Present||Gibbs-Russel et al., 1990|
|Swaziland||Present||Gibbs-Russel et al., 1990|
|USA||Present||Present based on regional distribution.|
|-North Carolina||Present||Pyrah, 1969|
|-South Carolina||Present||Pyrah, 1969|
Central America and Caribbean
|Costa Rica||Present||Pyrah, 1969|
|Dominican Republic||Present||Pyrah, 1969|
|El Salvador||Present||Pyrah, 1969|
|Puerto Rico||Present||Pyrah, 1969|
|Trinidad and Tobago||Present||Pyrah, 1969|
|Brazil||Present||Holm et al., 1979|
|-Mato Grosso||Present||Pyrah, 1969|
|-Rio de Janeiro||Present||Pyrah, 1969|
|-Rio Grande do Norte||Present||Pyrah, 1969|
|-Rio Grande do Sul||Present||Pyrah, 1969|
|-Santa Catarina||Present||Pyrah, 1969|
|French Guiana||Present||Pyrah, 1969|
|Australia||Present||Present based on regional distribution.|
|-Australian Northern Territory||Present||Watson and Dallwitz, 1985|
|-New South Wales||Present||Watson and Dallwitz, 1985|
|-Queensland||Present||Watson and Dallwitz, 1985|
|-Victoria||Present||Watson and Dallwitz, 1985|
|Papua New Guinea||Present||Pyrah, 1969|
HabitatTop of page L. hexandra is a tall perennial, tufted, aquatic or swamp grass that reproduces predominantly vegetatively, by creeping rhizomes, and by seeds (rare).
It is found in a variety of moist, usually freshwater, habitats, along irrigation ditches, streams and other waterways, in humid thickets, in ponds, in flooded ricefields and on moist arable lands.
Habitat ListTop of page
Hosts/Species AffectedTop of page L. hexandra is reported as a serious weed of rice in Guyana and Brazil and a principal weed in Madagascar, the Philippines, Sumatra and Sarawak. It is also a weed of rice in Cambodia, India, Indonesia, Malaysia, Nigeria, the Philippines, Suriname and Thailand. It is a weed of maize in Indonesia, rubber in Malaysia and sugarcane in Australia and Tanzania. It is a serious weed of tea in Indonesia. The plants are also a problem in drainage and irrigation ditches where the dense mat of vegetation that forms can impede water flow and cause erosion of banks (Holm et al., 1977).
Host Plants and Other Plants AffectedTop of page
Biology and EcologyTop of page L. hexandra is an aquatic perennial grass which grows from 30 cm to 1 m high, forming matted carpets. It propagates vegetatively by rhizomes and by seed, which is rare; Pyrah (1969) noted that of the several hundred specimens he studied, only one had developed seeds. L. hexandra is sometimes infected by the fungus Testicularia leersiae which attacks the ovary, causing swelling which resembles seed. L. hexandra is sometimes known as 'rice grass' and resembles rice in appearance. Flowering will depend upon the climate and is probably year-round in the tropics.It has a high crude-protein content (12.4%) and low fibre content (30.9%) and is regarded as a fodder crop in the Philippines, Sri Lanka, India and Indonesia.
L. hexandra is host to a number of pests of economic importance, including rice viruses, virus vectors and insects. Among the insects are: brown planthopper Nilaparvata lugens (Claridge, 1990); green planthopper Nilaparvata bakeri (Claridge and Morgan, 1993); green rice leafhopper Nephotettix malayanus, in Queensland, Australia (Kay and Brown, 1992); gall midge Orseolia oryzae, in south China, where it overwinters on the weed (Chiu, 1980); and leaf folder Brachmia arotraea [Helcystogramma arotraea], in India (Natarajam et al., 1978).
The populations of N. lugens from rice and from L. hexandra represent two distinct, but very closely allied, sympatric species (Claridge et al., 1985). Heinrichs and Medrano (1984) noted that the brown planthopper population that occurs on L. hexandra is distinct from that on rice because it does not survive on rice and the rice population does not survive on L. hexandra. However, the L. hexandra population is important in the management of brown planthopper on rice because it is attacked by the same predators, parasites and pathogens.
L. hexandra is susceptible to leaf yellowing, a virus disease of rice in India (Raychandhuri et al., 1967); to the fungus Piricularia sp. [Pyricularia] in Thailand (Chandrasrikul, 1962); to Xanthomonas campestris pv. oryzae (bacterial leaf blight of rice) in Texas (Gonzales et al, 1991); to brown spot (Cochliobolus miyabeanus); to rice grassy stunt tenuivirus, transmitted by N. lugens; to Tungro virus (rice tungro bacciliform virus) (Bottenberg et al, 1990); and to rice yellow dwarf MLO. L. hexandra plants were a source of the nematode, Ditylenchus angustus, which causes Ufra disease, and were found to transmit the nematode to uninfected plants downstream in the water flow; methods to control spread of the nematode include control of L. hexandra in the water currents, (Sein and Zan, 1977).
L. hexandra has also been used as a living mulch in sugarcane, with a view to suppressing the growth of weed Echinochloa spp., which are more difficult to control; treatments to control L. hexandra are applied later (Bushundial, 1991).
ImpactTop of page L. hexandra constitutes one of the aquatic weed flora of flooded rice of South-East Asia and has been described as a serious weed of rice in Guyana and Brazil and a principal weed of rice in Madagascar, the Philippines and Sarawak (Holm et al., 1977). It occurs as a weed of wetland, flooded or irrigated rice in Cambodia, India, Indonesia, Malaysia, Nigeria, Suriname and Thailand. It is a serious weed of tea in Indonesia. It has also been reported as a weed of maize in Indonesia and of sugarcane in Australia, the Philippines and Tanzania (Holm et al 1977). In north-west Nigeria, L. hexandra is reported as increasing in importance as a pest in lowland rice (Imeokparia, 1989)
Usually, L. hexandra will be one of several weeds that cause problems in rice; therefore, yield losses cannot usually be attributed to L. hexandra alone. Ampong-Nyarko and De Datta (1991) reported estimates of 44-96% yield losses caused by uncontrolled weed growth, depending on the method of rice culture.
L. hexandra plants indirectly limit crop production by serving as hosts for organisms that adversely affect rice; this weed provides food, shelter and reproductive sites for insects, nematodes, pathogens and rodents (see Biology and Ecology). Yield losses attributed to these factors are difficult to determine.
In addition to competition with rice for resources, L. hexandra is also a problem associated with blockage of irrigation ditches.
Uses ListTop of page
Animal feed, fodder, forage
- Fodder/animal feed
Similarities to Other Species/ConditionsTop of page The genus Leersia is very closely allied to the genus Oryza; they can be distinguished because Leersia has bisexual spikelets and there are no sterile lemmas (Pyrah, 1969; Clayton and Renvoize, 1992).
Prevention and ControlTop of page Introduction
The choice of control method depends upon the size of weed infestation, the cost of labour, the value of the crop, and the cost and availability of herbicide.
Methods that are commonly used to control perennial grasses and that can be used for L. hexandra include: preparation of a clean seedbed; rotation of rice with lowland, non-irrigated crops; tillage methods, i.e. ploughing, to destroy rhizomes; and applications of systemic herbicides, such as glyphosate, with attention to the selectivity of the herbicide: for example, if the crop is susceptible to glyphosate then apply it pre-planting (Ampong-Nyarko and De Datta, 1991).
Other methods that have proved useful in the control of weeds in wetland rice are: closer row spacing to increase crop competition; thorough hand weeding; and burning stubble during the dry season (Moody, 1982).
Glyphosate (pre-planting and post-emergence), fenoxaprop-ethyl (post-emergence), fluazifop-butyl and fluazifop-P-butyl (post-emergence) and imazapyr (pre- and post-emergence) may be used for control. Rates of application will vary depending upon the crop and the timing of application: for a full description of weed control in rice, see Ampong-Nyarko and De Datta (1991). See also Soerjani et al. (1987) for further information on chemical control in Malaysia.
Integrated Pest Management
A range of control methods is used in the management of weeds in rice. The following descriptions illustrate the factors that are important for weed control in wetland rice systems. The list is not comprehensive: for further details, see Ampong-Nyarko and De Datta (1991).
Land preparation is important in all rice cultivation and contributes to good weed management. Methods used will vary according to the crop system, especially concerning the management of perennial weeds. In transplanted rice, ploughing and puddling to destroy weeds and incorporate them into the earth provide a major source of weed control. In dry-seeded wetland rice and direct-seeded rice, land is prepared by ploughing and is kept weed-free before use, either by hand weeding or by herbicide application. Use of herbicides will be determined by the water management of the cropping system: for instance, in dry-seeded rice, after land preparation, weeds are allowed to emerge and are then destroyed either by shallow cultivation or with a non-residual contact herbicide, such as paraquat; in transplanted rice, puddling is followed by a pre-planting treatment with glyphosate on emergent weeds. In dry-seeded wetland rice, a pre-planting herbicide, such as glyphosate, or a pre-crop-emergence herbicide, such as imazapyr or fenoxaprop, could be used.
Taller rice cultivars with more tillers shade out weeds and reduce weed competition. Rotation of rice with other crops, such as jute (Corchorus sp.), can be important in reducing the build-up of large populations of perennial grass weeds.
Rice planted with close spacing (e.g. 15 x 15 cm) will shade weeds and reduce competition, while still allowing some mechanized weed control if required (Moody, 1982).
Additional hand weeding is usually done early in the season, during the critical period and, if weed populations are high, then later hand weeding is a common practice. If labour is scarce, herbicides such as glyphosate, applied locally to weeds only, or bensulfuron or fenoxaprop are used. Hand weeding alone can give as good weed protection as herbicide use: for example, in rice that is direct seeded onto wet soil, seeds are sown onto a weed-free field and two or three timely hand weedings are sufficient to ensure optimum yields (Moody, 1982; Ampong-Nyarko and De Datta, 1991).
Cultivation followed by hand weeding has been shown to give sufficient control of L. hexandra in sugarcane (Keya, 1980).
ReferencesTop of page
Bottenberg H; Litsinger JA; Barrion AT; Kenmore PE, 1990. Presence of tungro vectors and their natural enemies in different rice habitats in Malaysia. Agriculture, Ecosystems & Environment, 31(1):1-15
Bushundial DP, 1991. Recent work on the control of Echinochloa pyrimidalis (Lam.) Hitch. and Chase and Echinochloa polystachya (Kunth) Hitchc. Proceedings of the 24th West Indies Sugar Techologists' Conference, Kingston, Jamaica, 8-12 April 1991., 279-285.
Chandrasrikul A, 1962. A preliminary host list of plant diseases in Thailand. Technical Bulletin 6. Bangkok, Thailand: Department of Agriculture.
Claridge MF, 1990. Variation in pest and natural enemy populations - relevance to brown planthopper control strategies. Pest management in rice (conference held by the Society of Chemical Industry, London, UK, 4-7 June 1990) [edited by Grayson, B.T.; Green, M.B.; Copping, L.G.] Barking, UK; Elsevier Applied Science Publishers Ltd., 143-154
Claridge MF; Hollander J den; Morgan JC, 1985. The status of weed-associated populations of the brown planthopper, Nilaparvata lugens (Stal)
Claridge MF; Morgan JC, 1993. Geographical variation in acoustic signals of the planthopper, Nilaparvata bakeri (Muir), in Asia: species recognition and sexual selection. Biological Journal of the Linnean Society, 48(3):267-281
Clayton WD, 1970. Gramineae (Part 1). In: Milne-Redhead E, Polhill RM, eds. Flora of Tropical East Africa. London, UK: Crown Agents for Oversea Governments and Administrations.
Clayton WD; Renvoize SA, 1992. Genera Graminum, Grasses of the World. Kew Bulletin Additional Series. London, UK: HMSO.
Gibbs-Russel GE; Watson L; Koekmoer M; Smook L; Barker NP; Anderson HM; Dallwitz MJ, 1990. Grasses of Southern Africa. South Africa: National Botanic Gardens.
Launert, 1965. Senck. Biol, 46:144.
Pyrah GL, 1969. Taxonmomic and distributional studies on Leersia (Gramineae). Iowa State Journal of Science, 44(2):215-270.
Raychandhuri S; Mishra W; Ghosh; A, 1967. The virus diseases of the rice plant. International Rice Research Institute. Baltimore, USA: John Hopkins Press.
Wang Z; Mingyuan X; Dehui M, 1990. Farmland weeds in China: a collection of coloured illustrative plates. Agricultural House: China.
Waterhouse DF, 1993. The Major Arthropod Pests and Weeds of Agriculture in Southeast Asia. ACIAR Monograph No. 21. Canberra, Australia: Australian Centre for International Agricultural Research, 141 pp.
Watson L; Dallwitz MJ, 1985. Australian grass genera, anatomy, morphology, keys, classification. Canberra, Australia: The Australian National University.
Distribution MapsTop of page
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