Imperata cylindrica (cogon grass)

Pictures

Picture	Title	Caption	Copyright
Title Leaves and inflorescence - colour illustration Caption A perennial grass of variable height. Inflorescence a white, spike-like panicle. Copyright NOVARTIS	Leaves and inflorescence - colour illustration	A perennial grass of variable height. Inflorescence a white, spike-like panicle.	NOVARTIS
Title Inflorescence - line drawing Caption Inflorescence terminal, fluffy, 5-20 cm long and up to 2.5 cm in diameter. Copyright NOVARTIS	Inflorescence - line drawing	Inflorescence terminal, fluffy, 5-20 cm long and up to 2.5 cm in diameter.	NOVARTIS
Title Spikelet - line drawing Caption Spikelets numerous, 3.5-5.0 mm long, each surrounded by a basal ring of silky hairs 10 mm long. Copyright NOVARTIS	Spikelet - line drawing	Spikelets numerous, 3.5-5.0 mm long, each surrounded by a basal ring of silky hairs 10 mm long.	NOVARTIS
Title Leaf and ligule - line drawing Caption Leaves stiff, linear-lanceolate, up to 120 cm long and 4-18 mm wide, with a prominent white midrib. Ligule an inconspicuous membrane. Copyright NOVARTIS	Leaf and ligule - line drawing	Leaves stiff, linear-lanceolate, up to 120 cm long and 4-18 mm wide, with a prominent white midrib. Ligule an inconspicuous membrane.	NOVARTIS
Title Roots - colour illustration Caption Roots fibrous, emerging from the base of the culm and the nodes on the rhizome. Copyright NOVARTIS	Roots - colour illustration	Roots fibrous, emerging from the base of the culm and the nodes on the rhizome.	NOVARTIS
Title Exposed shoots Caption I. cylindrica shoots held at soil level to show variable depth of origin. Copyright ©Chris Parker/Bristol, UK	Exposed shoots	I. cylindrica shoots held at soil level to show variable depth of origin.	©Chris Parker/Bristol, UK
Title Exposed rhizomes Caption I. cylindrica rhizomes exposed at 20 cm depth, Nigeria. Copyright ©Chris Parker/Bristol, UK	Exposed rhizomes	I. cylindrica rhizomes exposed at 20 cm depth, Nigeria.	©Chris Parker/Bristol, UK
Title Whole plant - line drawing Caption a, Ligule, ventral view; b, spikelet; c, caryopsis, two views. Copyright SEAMEO-BIOTROP	Whole plant - line drawing	a, Ligule, ventral view; b, spikelet; c, caryopsis, two views.	SEAMEO-BIOTROP

Identity

Preferred Scientific Name

• Imperata cylindrica (Linnaeus) Raeuschel (1797)

Preferred Common Name

• cogon grass

Other Scientific Names

• Calamagrostis lagurus Koel. (1802)
• Imperata allang Jungh. (1840)
• Imperata angolensis Fritsch (1901)
• Imperata arundinacea Cyr. (1792)
• Imperata arundinacea var. africana Andersson (1855)
• Imperata arundinacea var. europea Andersson (1855)
• Imperata arundinacea var. genuine Hack (1889)
• Imperata arundinacea var. glabrescens Büse (1854)
• Imperata arundinacea var. indica Andersson (1855)
• Imperata arundinacea var. koenigii (Retz.) Benth. (1861)
• Imperata arundinacea var. latifolia Hook. F (1896)
• Imperata arundinacea var. pedicellata (Steud.) Debeaux (1878)
• Imperata arundinacea var. thunbergi (Retz.) Stapf (1898)
• Imperata cylindrica forma pallida Honda (1930)
• Imperata dinteri Pilg. (1912)
• Imperata koenigii (Retz.) P. Beauv. (1812)
• Imperata koenigii var. major (Retz.) P. Beauv. (1841)
• Imperata pedicellata Steud. (1846)
• Imperata sieberi Opiz (1825)
• Imperata thunbergii (Retz.) Roem & Schult. (1817)
• Lagurus cylindricus L. (1759)
• Saccarum europaeum Pers. (1805)
• Saccarum sisca Cav. (1795)
• Saccharum cylindricum (L.) Lam. (1785)
• Saccharum koenigii Retz.
• Saccharum laguroides Pourr.
• Saccharum thunbergii Retz. (1789)

International Common Names

• English: bedding grass; blady grass; imperata; Japanese blood grass; satintail; silver spike; spear grass; sword grass; thatch grass
• Spanish: carrizo; cisca; cogón; marciega
• French: impérate; paille de dys; paillotte
• Arabic: halfa
• Chinese: manu-kan tso; mao-kan tso; mao-tsao

Local Common Names

• Australia: bladygrass
• Cambodia: sbauv
• Cameroon: baya; ndongo limba; sosongo
• Congo: binkba; moto-moto; nianga
• Congo Democratic Republic: nianga
• Côte d'Ivoire: nse
• Cyprus: xiphara
• Egypt: beni el sham; deil el qott; halfa; hishka; sill
• Fiji: gi; ngi
• Germany: Silberhaargras
• India: chero; dabh; dharba; dhub; modewa gaddi; ooloo; siru; tharpai pullu
• Indonesia: alang-alang; eurih
• Iran: santintail
• Iraq: cylindrical ha
• Italy: falasco bianco
• Japan: chi; chigaya; tsubana
• Kenya: nyeki
• Laos: yakha
• Madagascar: manevika; tena
• Malaysia: alang-alang; lalang
• Mauritius: lalang
• Myanmar: kyet-mei; thetke
• New Zealand: imperata
• Nigeria: ata; ekan; gasa kigere; ias; soyo; tibin; tofa; zarenshi
• Palau: kasoring
• Papua New Guinea: auturra; kawva; kunai grass; kuru-kuru
• Philippines: buchid; bulum; gaon; ilib; kogon; parang
• South Africa: mohlorumo; um tente
• Sri Lanka: darbai-pul; iluk; inanka-pilu
• Sudan: doiya; mayani
• Syria: halfa; meshian; sill; sulel
• Taiwan: bái-máu
• Tanzania: chiambi; moto-moto; sanu
• Thailand: yah-ka
• Tunisia: dis
• Vietnam: cb tranh; cò tranh; cogranh
• West Africa: dole; gombi; hada; nounour; soyo
• Zimbabwe: ibamba; luwamba; silenge; silverspike

EPPO code

• IMPCY (Imperata cylindrica)

Summary of Invasiveness

I. cylindrica is a serious weed not only in crops but also in natural areas, causing serious economic and environmental damage. The ability of I. cylindrica to effectively compete for water and nutrients, spread and persist through the production of seeds and rhizomes that can survive a wide range of environmental conditions, and its allelopathic effects and pyrogenic nature, allow it to exclude native plant species and other desirable plants and dominate large areas of land.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Monocotyledonae
•                     Order: Cyperales
•                         Family: Poaceae
•                             Genus: Imperata
•                                 Species: Imperata cylindrica

Notes on Taxonomy and Nomenclature

The genus Imperata Cyr. contains eight species which are found throughout the tropics, extending to warm temperate regions. Hackel (1889) divides the genus into two sections on the basis of the number of stamens in the flower: Imperatella has two stamens and contains a single species, I. cylindrica; Eriopogon has one stamen and contains the other seven species, namely I. converta, I. brasiliensis, I. brevifolia, I. minutiflora, I. tenuis, I. cheesemani and I. contracta (Eussen, 1980). Whilst I. cylindrica is an Old World species, with the exception of occurrences in Chile, Colombia and USA, I. brasiliensis Trin. and I. contracta (Kunth) Hitchc. are weeds of the New World, particularly Latin America.

Hubbard et al. (1944) recognize five varieties of I. cylindrica: var. major (Nees) C.E. Hubbard is found in tropical Asia; var. africana (Anderss.) C.E. Hubbard is from Africa; var. europaea (Anderss.) Aschers & Graebn. occurs mainly in the Mediterranean region; var. condensata (Steud.) Hack. ex Stuckert is a native of the coastal region of Chile and possibly Argentina; and var. latifolia (Hook. f.) C.E. Hubbard is found in India. Clayton and Renvoize (1982) claim that only three varieties are commonly recognized, var. africana, var. major and var. cylindrica, and the others are recorded as synonyms.

Description

I. cylindrica is a perennial grass which varies in height (30-150 cm). The culms (above-ground stems) are short, erect and arise from rhizomes (underground stems). The rhizomes are tough, white, commonly 1 m long but can be considerably more, are extensively branched and covered with papery scale leaves at the nodes. Roots are fibrous, emerging from the base of the culm and the nodes on the rhizome. Leaves are stiff, linear-lanceolate, up to 120 cm long and 4-18 mm wide, with a prominent, off-centre, whitish midrib, scabrid margin and pointed tip. The ligule is an inconspicuous membrane. The inflorescence is a white, spike-like panicle, terminal, fluffy, 5-20 cm long and up to 2.5 cm in diameter. Spikelets are numerous, 3.5-5.0 mm long, each surrounded by a basal ring of silky hairs 10 mm long. The grain is oblong, pointed, brown and 1-1.5 mm long.

Plant Type

Distribution

I. cylindrica is ubiquitous in the humid tropics of west Africa and Asia. Weber (2003) suggests it is native only in southern Europe and Africa, but other sources indicate both East Africa and South-East Asia as sources, the latter assumed to be more correct. It is virtually certain that the weed can be found in all countries within these regions. It is widespread in southern China, but Wu et al. (2006) note that attempts to cultivate the weed deliberately as an ornamental in Beijing failed because of its susceptibility to the cold winter conditions.

Distribution Table

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.

History of Introduction and Spread

The accidental introduction of I. cylindrica into the south-eastern USA occurred in Mobile County, Alabama, in 1911 through a shipment of oranges from Japan (Tabor, 1952). I. cylindrica was then intentionally introduced from the Philippines into Florida and Mississippi between 1921 and the 1940s for forage and erosion control purposes (Tabor, 1949; Dickens and Buchanan, 1971; Dickens, 1974). I. cylindrica was reportedly introduced into Oregon through ballast in 1971 but there are no recent accounts of its establishment in the north-west USA. According to Dickens and Buchanan (1971), the eradication of I. cylindrica in the south-eastern USA was recommended as early as 1948. Collins et al. (2007) concluded that I. cylindrica was able to invade habitats in Southern USA regardless of the diversity of the flora, hence not obeying Elton’s Hypothesis which proposes that diversity reduces invasibility.

I. cylindrica was introduced into New Zealand in 1911 and is listed as one of the potential problem weeds in New Zealand as of 1996 (PIER, 2008). According to PIER (2008), I. cylindrica is also an invasive species in Micronesia and has been recommended for eradication.

Introductions

Risk of Introduction

I. cylindrica is on the Federal Noxious Weed List of the US Department of Agriculture-Animal and Plant Health Inspection Service-Plant Protection and Quarantine (USDA-APHIS-PPQ). It is included in the 1993 Florida Exotic Pest Plant Council (EPPC) List of Most Invasive Plant Species and is considered as a noxious weed designated for eradication or control in Hawaii and a noxious weed in North Carolina. It scored very highly in a pest risk analysis for the Pacific, and I. cylindrica is an invasive species in Micronesia where it has been recommended for eradication (PIER, 2008).

It remains a consistent seed contaminant. For example, over a one year period (2005-06) in the Port of Puget Sound, Washington, USA, 44 (5.5%) of 799 botanical interceptions processed were Federal noxious weeds of which  the most frequently intercepted seeds were I. cylindrica (Smither-Kopperl, 2007).

Habitat

The habitats of I. cylindrica vary from dry sand dunes of shores and deserts to swamps and river margins. This weed is found at altitudes from sea level to 2700 m and rainfalls of 500-5000 mm/year (Holm et al., 1977). It occupies a wide range of habitats including grassland, cultivated annual crops, plantations, abandoned farm land, road and railway embankments, reclaimed mined areas, pine and hardwood forests, recreational areas and deforested areas. It is commonly associated with slash-and-burn agriculture in West Africa and South-East Asia. I. cylindrica grasslands are widely believed to indicate poor soil fertility but Imperata occurs on a broad range of soil types and is not confined to the poorest soils (Santoso et al., 1996).

In Benin, Cameroon, Ghana and Nigeria, I. cylindrica is most frequently found in transition forest, mountain forest and wet savannah, and is least common in the rain forest and dry savannah (Chikoye et al., 1999). In Taiwan, I. cylindrica occurs in various habitats including estuary mangrove forests (highly saline), coastal saline areas (beaches), inland areas with a drought season in the winter or with drought conditions during most seasons, and sites with mild weather (Cheng and Chou, 1997). I. cylindrica is widely distributed in the warmer regions of the USA (south-eastern states) and is found in pastures, golf courses, roads, railways, mine reclamation areas, forests, pine plantations and natural areas (Bryson and Carter, 1993; Dozier et al., 1998; Willard et al., 1990). In Australia, I. cylindrica is commonly found in riparian zones (Wetland Care Australia, 2003). I. cylindrica also occurs on bars in the Monobe River in Shikoku, Japan (Ishikawa and Nishiyama, 1998). It has also been found in the seasonal floodplains located in the Nxaraga Lagoon area of Okavango Delta in Botswana (Bonyongo et al., 2000).

 

Habitat List

Hosts/Species Affected

I. cylindrica is a weed of 35 crops worldwide (Holm et al., 1977) and 21 crops in West Africa (Chikoye et al., 2000). Some examples are cited in the list of hosts but most crops of the high rainfall tropics are likely to be affected by this weed.

Host Plants/Plants Affected

Biology and Ecology

Genetics

Chromosome numbers vary according to the variety of I. cylindrica: 2n = 20 for var. major, 2n = 40 for var. europa and 2n = 60 for var. africana (Santiago, 1980). Genetic variation has also been observed to occur within I. cylindrica. In a study by Cheng and Chou (1997) based on six populations of I. cylindrica collected from various habitats around Taiwan, a high level of genetic heterogeneity was found among populations of I. cylindrica. Genetic differences among the populations were correlated with morphological features. Among the populations studied, only those collected from mangrove areas possessed a hollow structure in the midrib of the leaf and villous trichomes on the abaxial leaf surface, features that are considered to be adaptive mechanisms to saline environments. Chou and Tsai (1999) also found that there is variation in IGS (intergenic spacer) length and sequence of rDNA among intra- and inter-specific populations of I. cylindrica based on PCR-amplified RFLP.

I. cylindrica is also known to hybridize with other species, with Gabel (1982) providing evidence of hybridization between I. cylindrica and I. brasiliensis. Intergeneric hybrids have been obtained with Saccharum (Watson and Dallwitz, 1992).

Reproductive Biology

I. cylindrica is a prolific producer of seeds which are dispersed by wind over long distances to colonize cleared or previously un-infested land. It can produce as many as 3000 seeds per plant (Holm et al., 1977), and 95% of I. cylindrica seeds can germinate within one week of being harvested but can also retain viability for at least one year (Santiago, 1965). I. cylindrica is not capable of self-pollination (Gabel, 1982) and produces viable seeds only through cross-pollination (McDonald et al., 1996). Flowering is variable between individual plants and can occur in response to stress from slashing, grazing, burning, mowing, or the addition of nitrogen (Holm et al., 1977; Willard, 1988).

Physiology and Phenology

Suspected allelopathic properties (Eussen et al., 1976) and a vigorous growth habit have made I. cylindrica one of the most competitive weeds. The aggressive and invasive nature of I. cylindrica is largely attributed to its extensive rhizome system which is concentrated in the upper 20 cm of soil. The lateral buds can remain dormant for long periods and give I. cylindrica its perennating habit. The bud from a single rhizome node can give rise to 350 shoots in 6 weeks, which can cover up to 4 m² in 11 weeks (Eussen, 1980). Other reports of I. cylindrica's productivity are that 2.73 m of rhizome can be produced in 109 days (Wilcutt et al., 1983) and that a 15 cm length of rhizome can produce 181 shoots per m² in 6.5 months (Lee, 1977).

The regenerative capacity of I. cylindrica rhizomes is affected by their age (Ayeni and Duke, 1985); older rhizomes regenerate better than those that are young and contain relatively few nutrients. There is a greater chance of sprouting in larger or longer rhizomes because of their higher nutrient status (Soerjani and Soemarwoto, 1969; Ivens, 1975). Mature buds closest to the apex are the first to sprout when the rhizome is fragmented from the parent plant. Rhizomes which develop during the rainy season do not regenerate as well as those formed in the dry season. Bud germination of rhizomes is favoured by exposure to light (Soerjani, 1970). Rhizome regeneration increases when oxygen is introduced into the rhizosphere (Wilcutt et al., 1983) but decreases with increased depth of burial (Ivens, 1980).

There is marked seasonal variation in the growth of I. cylindrica. During the dry season, the number of living shoots and the emergence of new shoots are relatively low compared with in the wet season. Any production of new shoots is balanced by the death of older shoots. Low shoot emergence is associated with low rainfall and soil moisture. During the dry season, the mass of dead shoots can exceed that of live shoots. It appears that I. cylindrica sacrifices its shoots in order to maintain healthy, nutrient-rich rhizomes.

I. cylindrica assimilates carbon dioxide by the C4 photosynthetic pathway (Paul and Elmore, 1984) giving it a competitive advantage over C3 plants (such as rice) in tropical conditions. However, in common with many C4 plants, I. cylindrica is relatively intolerant of shade. Light is inevitably important in the growth of I. cylindrica although contradictory results exist on the production of shoots versus rhizomes under a range of light intensities. In one investigation (Eussen, 1981) it was shown that after 6 months’ growth, I. cylindrica had more rhizomes than shoots at all light intensities (20-100% intensity) but, in another (Soerjani, 1970), I. cylindrica tended to have more shoots (11.5 t/ha) than rhizomes (7.0 t/ha). However, there is evidence that I. cylindrica produces more shoots than rhizomes under low light conditions.

I. cylindrica is capable of capturing material flowing from higher areas in the landscape through erosion, hence, it is possible that it can cause the build-up of vesicular arbuscular (VA) mycorrhizal inoculum. The spore density and species richness of VA fungi is found to be high in Imperata grasslands, except at the most degraded sites (Hairiah et al., 2003).

Associations

There is extensive occurrence of endomycorrhizas on I. cylindrica collected from around Indonesia (Tjitrosemito et al., 1994). The existence of a mycorrhizal relationship is usually associated with the host plant being able to utilize available phosphorus. This gives I. cylindrica an advantage over plants without mycorrhizas in situations where phosphate is limiting.

In Nepal, grasslands dominated by I. cylindrica support a number of vulnerable, endangered or critically endangered species such as swamp deer (Cervus duvauceli) (Ghimire, 1996), hispid hare (Caprolagus hispidus), pygmy hog (Sus salvanis) (Oliver, 1985) and Bengal florican (Eupodotis bengalensis) (Inskipp and Inskipp, 1983). I. cylindrica grasslands also support a dense population of chital (Axis axis) in Nepal. I. cylindrica constitutes the major portion of the diet of hog deer (Axis porcinus) which live in protected areas of sub-Himalayan West Bengal (Bhowmik et al., 1999).

Environmental Requirements

This weed is found at altitudes from sea level to 2700 m and rainfalls of 500-5000 mm/year (Holm et al., 1977).

Fire-based cultivation methods (slash and burn) have been known to transform forest areas to grasslands dominated by I. cylindrica. Aside from this practice, soil degradation resulting from cropping systems that do not supply enough organic inputs in the soil or provide a permanent cover on the soil (i.e. pastures that are routinely mowed, etc.) also allow for colonization by I. cylindrica (Hairiah et al., 2003). I. cylindrica can dominate vast tracts of degraded land because of its ability to survive under conditions of low soil fertility. It is also able to thrive in different types of soil and can tolerate a wide range of soil pH conditions. Once established, it will continue to persist even when there is environmental stress such as drought, flooding or fire. Seedhead formation is induced by slashing, mowing, grazing, burning and the application of fertilizers (Colvin et al., 1993). Burning also stimulates vegetative growth. Under conditions of high light intensity, high temperatures and limited moisture, the C4 pathway of I. cylindrica allows it to photosynthesize more efficiently and gives it a competitive edge over C3 species.

Due to its requirement for sunlight, I. cylindrica survives poorly in closed-canopy forest or plantations where shading occurs. According to Moosavi-nia and Dore (1979), increasing shade levels of >50% reduces shoot dry weight and both rhizome length and dry weight, causing an increase in the shoot/rhizome ratio. The ability of rhizomes to resprout after the above ground biomass has been removed reportedly declined when the mowed stand was subjected to 88% shade for more than 2 months (Hairiah et al., 2003). The light compensation point of I. cylindrica is 32 µmol/m²/s or 2% of ambient sunlight, and biomass reduction was observed when ambient light was 1% or 15 µmol/m²/s (Gaffney, 1996).

I. cylindrica grows poorly in heavily cultivated lands where it is kept in check mechanically (Van Loan et al., 2002). It is also sensitive to excessive soil moisture during early seedling development, hence, excessive moisture could restrict invasion of I. cylindrica by seed. However, once established, the tolerance of I. cylindrica to flooding increases (King and Grace, 2000). The spread of I. cylindrica in the USA has been limited to south-eastern parts and this is attributed to temperature. I. cylindrica survived the 1984 winter season in Alabama, USA, where the coldest air temperature recorded was -14°C; however, it did not survive the -28.9°C winter temperature in Texas in 1984 (Wilcut et al., 1988). Cold temperatures may be a limiting factor to the spread of I. cylindrica beyond the south-eastern regions of the USA. However, a red-tipped ornamental cultivar of I. cylindrica, also known as Rubra, Japanese Bloodgrass or Red Baron, is very cold tolerant and has persisted for several years in an ornamental garden in Michigan, USA. Shilling et al. (1997) expressed concern that its introduction and possible hybridization with I. cylindrica will result in hybrids that may exhibit both invasiveness and cold tolerance allowing range extension to northern and western regions of the USA. I. cylindrica thrives at altitudes from sea level to 2000 m in the Himalayas (Holm et al., 1977).
 

Climate

Latitude/Altitude

Air Temperature

Rainfall

Soil Tolerances

Soil drainage

• free
• impeded
• seasonally waterlogged

Soil reaction

• acid
• alkaline
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• infertile
• saline
• shallow
• sodic

Natural Enemies

Notes on Natural Enemies

Numerous pathogens have been found in association with I. cylindrica. Fungi occurring on this grass include Bipolaris sacchari, B. setariae, Cochliobolus heterostrophus, Colletotrichum caudatum, Glomerella graminicola [Colletotrichum graminicola], Gibberella imperatae, Myriellina imperatae, Puccinia fragosoana, P. imperatae, P. rufipes, Sphacelotheca schweinfurthiana and Tilletiopsis flava. The bacterium Xanthomonas albineans has also been reported on I. cylindrica.

Nematodes found in association with this grass include Heterodera sinensis, Rotylenchulus reniformis, Discocriconenella spermata, Actus baqrus and Meloidogyne fujianensis. Other plant parasitic nematodes recorded on I. cylindrica include Aglenchus sp., Aphelenchoides sp., Criconemella obtusicaudata, Criconemoides sp., C. citri, C. curvatus, C. xenoplax, Helicotylenchus dihystera, H. pseudorobustus, Hemicriconemoides wessoni, Longidorus sp., Meloidodera floridensis, Meloidogyne sp., Paratrichodorus christei, Trophotylenchulus sp., T. floridensis, Xiphinema americanum, X. denoudeni and X. radicicola (DOACS, 2003)

Insects reported to feed on I. cylindrica include Atalopedes campestris, Hylephila phyleus, Pelopidas mathias, Orseolia javanica, Dicranoctetes brachyelytrifoliella, Dicladispa armigera, Melanitis leda ismene and Mythimna separata.
 

Means of Movement and Dispersal

Natural Dispersal (Non-Biotic)

I. cylindrica is a prolific producer of seeds, which are dispersed by wind over long distances to colonize cleared or previously uninfested land.

Accidental Introduction

Fragmentation of the rhizomes of I. cylindrica by agricultural equipment (e.g. ploughs, harrows and hoes) breaks dormancy, promoting the growth of new shoots. Rhizome fragments are dispersed when they become temporarily attached to tillage equipment and other farm machinery, and can also be transported in soil attached to the roots of transplanted material such as tree nursery stock, or in fill dirt during road construction (Willard, 1988; Patterson and McWhorter, 1993).

Intentional Introduction

I. cylindrica variety 'Rubra', also known as Japanese Bloodgrass or Red Baron, is sold as an ornamental plant and can be procured through the mail from suppliers (MSUCARES, 2002).

Pathway Causes

Pathway Vectors

Impact Summary

Economic Impact

I. cylindrica is reported as a weed in 73 countries, and in 35 crops (Holm et al., 1977). It is considered to be the worst perennial grass weed of southern and eastern Asia and is a serious problem in all crops grown in the lowland moist savannahs of West and Central Africa, and also at forest fringes where human population pressure on land has prevented the re-establishment of forest vegetation. Brook (1989), citing other authors, reports up to 64.5 million hectares of grassland in Indonesia, 5 million hectares in Papua New Guinea, and 0.3 million hectares in Fiji as being dominated by I. cylindrica. Over 40% of rubber plantations in Java and 1.5-2.0 million hectares of rubber plantations in Malaysia are affected. In a wide-ranging review, MacDonald (2004) notes that ‘Cogongrass is a major impediment to reforestation efforts in southeast Asia, the number one weed in agronomic and vegetable production in many parts of Africa, and is responsible for thousands of hectares of lost native habitat in the southeastern US’.

The combined area infested by I. cylindrica in Alabama, Florida and Mississippi, USA is estimated to be at least 100,000 hectares (Dickens, 1974; Schmitz and Brown, 1994), and according to Kaczor (2003), citing other authors, it is estimated that between 200,000 and 400,000 hectares in Florida alone are infested by I. cylindrica. The Florida Department of Environmental Protection has spent $350,000 within a 6-year period, battling cogongrass as part of a programme to control invasive species on public conservation lands. It is estimated that the removal of I. cylindrica from forest land through the application of herbicides can cost as much as $400 per hectare (Van Loan at al., 2002).

Where infestations occur, farmers allocate most of their time and labour to weeding speargrass (Vissoh et al., 2008). I. cylindrica is a strong competitor with plantation and food crops not only because it effectively competes for water and nutrients but also because it has allelopathic effects on crops such as maize and cucumber (Eussen, 1978). Crop yield losses due to I. cylindrica vary according to crop type, cultural practices and environmental conditions (Chikoye et al., 2001). Plantation crops such as coconut and oil palm are particularly susceptible to I. cylindrica at the early stages of development because they do not develop sufficient canopy to adequately shade the weed. The negative effects of I. cylindrica on coconuts also include delayed flowering and reduction in the number of nuts (Hairiah et al., 2003).

Trees are vulnerable to competition from I. cylindrica during the establishment of plantations (Otsama et al., 1997), e.g. tapping of rubber trees can be delayed for up to 3 years if I. cylindrica is present, and I. cylindrica has been shown to retard the growth of rubber by 96% within a period of 5 years (Soedarsan, 1980). Coconut is also affected as indicated by a 54% yield increase following the use of glyphosate for I. cylindrica control (Samarajeewa et al., 2004). Field crops such as upland rice, maize, grain legumes and vegetable crops are very susceptible to competition from this weed. In root and tuber crops, such as cassava and yams, loss is not only from yield reduction (direct competition), but also from secondary fungal infections which occur when rhizomes of I. cylindrica pierce the roots and tubers. In West Africa, I. cylindrica reportedly caused 62-80% yield reduction in maize and cassava (Koch et al., 1990; Udensi et al., 1999).

I. cylindrica is an inferior forage crop for domesticated animals. The silica bodies and the sharp edges of the leaves render it undesirable and unpalatable to grazing animals (Coile and Shilling, 1993). Herbage yields of I. cylindrica are relatively low even under heavy fertilization. I. cylindrica crude protein, which is estimated to be about 4%, is far below the required 7% crude protein to initiate voluntary intake by cattle. The liveweight gain of cattle that feed on I. cylindrica ranges only from 21.6 to 77.5 kg/ha (Lanting, 2004, personal communication).

I. cylindrica is an alternative host of the following insect pests of rice: Pelopidas mathias (Mazusawa et al., 1983), Melanitis leda ismene and Mythimna separata (IRRI, 2003). It is also as an alternative host for Rotylenchulus reniformis and Rice tungro virus and associated viruses (IRRI, 1988). It is reported as a host for the breeding of several species of Papuana (Sar et al., 1997). 

Environmental Impact

I. cylindrica occupies natural areas that are habitats of federally listed endangered species and threatened native plant species (Langeland and Burks, 1998). It has been reported as a poor habitat of wildlife in the USA, particularly in Florida. According to anecdotal information, gopher tortoises (Gopherus polyphemus) in Florida abandon areas infested with I. cylindrica, which then results in the disappearance of numerous species that depend on their burrows, including gopher frogs (Rana capito aesopus), eastern indigo snakes (Drymarchon corais) and scarab beetles. I. cylindrica may also affect the nesting and foraging of the endangered red-cockaded woodpeceker (Picoides borealis) because the trees in which woodpeckers nest, such as long-leaf pine, are vulnerable to intense fires that can result from the presence of I. cylindrica (Myers, 1990).

I. cylindrica can hinder the establishment of desirable perennial species because it can extract soil moisture from the shallow layers of the soil and exude allelopathic substances that inhibit the growth of other plant species. It is highly pyrogenic and its vegetative growth is stimulated by fire. According to Lippincott (1997), the presence of I. cylindrica in a sandhill ecosystem can predispose it to intense, widespread and frequent fires that can seriously damage or kill most fire-intolerant species. As it can alter the fire regime, I. cylindrica has the potential to form grasslands that are devoid of trees and prone to fires. I. cylindrica has been blamed for two major forest fires in Ocala, Florida, USA, in 1996 and 2000 (Kaczor, 2003).

The spread of I. cylindrica is often linked to loss of soil fertility which leads to reduced crop vigour and greater chances for the grass to dominate because it competes more effectively at lower fertility levels. I. cylindrica is capable of capturing material flowing from higher areas in the landscape through erosion, hence, it is possible that it can cause the build-up of vesicular arbuscular (VA) mycorrhizal inoculum. It has been found that spore density and species richness of VA fungi are high in Imperata grasslands, except at the most degraded sites (Hairiah et al., 2003).
 

Social Impact

Millions of hectares of good farmland are being abandoned to I. cylindrica each year in West and Central Africa and this is an increasing source of concern in affected regions. Farmers abandon infested fields, not only because of the competitiveness of the weed, but also because the sharp points of emerging plants can pierce the feet of humans and livestock (Terry et al., 1997). Severe infestations of I. cylindrica can cause total crop loss in cereals such as upland rice and maize. The burning of Imperata grasslands is a major threat to adjacent forests and tree crops (Wibowo et al., 1996). Poor smallholder farmers, large estates and forest plantations are all afflicted by I. cylindrica which causes incalculable losses in productivity and profits.

Risk and Impact Factors

Impact mechanisms

• Allelopathic
• Competition - monopolizing resources
• Competition - shading
• Pest and disease transmission
• Produces spines, thorns or burrs
• Rapid growth
• Rooting

Impact outcomes

• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Host damage
• Modification of fire regime
• Modification of nutrient regime
• Modification of successional patterns
• Monoculture formation
• Negatively impacts agriculture
• Negatively impacts animal health
• Negatively impacts cultural/traditional practices
• Negatively impacts forestry
• Negatively impacts livelihoods
• Negatively impacts tourism
• Reduced amenity values
• Reduced native biodiversity
• Soil accretion
• Threat to/ loss of native species

Invasiveness

• Abundant in its native range
• Fast growing
• Has a broad native range
• Has high genetic variability
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Highly adaptable to different environments
• Highly mobile locally
• Invasive in its native range
• Is a habitat generalist
• Long lived
• Pioneering in disturbed areas
• Proved invasive outside its native range
• Reproduces asexually
• Tolerant of shade
• Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc

Likelihood of entry/control

• Difficult to identify/detect as a commodity contaminant
• Difficult/costly to control
• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately

Uses

Townson (1991) reviewed methods of utilizing I. cylindrica which include grazing, paper-making, soil and moisture conservation, packing materials, brush-making, rope-making, fuel, sugar and alcohol production and a range of medicinal purposes. Few uses are of economic importance, with the exception of thatching for which I. cylindrica is highly valued in parts of Asia. The flowers and roots of I. cylindrica have antibacterial, diuretic, emollient, febrifuge, sialagogue, styptic and tonic properties. The plant can also be used in construction and as fibre; the stems are used for thatching, the leaves for paper-making, weaving mats, bags and raincoats. It is also planted and sold as an ornamental; I. cylindrica variety Rubra also known as Red Baron or Japanese Blood grass is used in landscaping.

Uses List

Animal feed, fodder, forage

• Fodder/animal feed
• Forage

Environmental

• Erosion control or dune stabilization
• Revegetation
• Soil conservation

General

• Ornamental

Medicinal, pharmaceutical

• Traditional/folklore

Ornamental

• Cut flower

Similarities to Other Species/Conditions

The combination of erect habit, fluffy white inflorescence and extensive rhizome system makes I. cylindrica quite distinct from most other weeds.

I. cylindrica may be confused with I. brasiliensis (Brazilian satintail) because of their very similar morphology, but I. brasiliensis differs from I. cylindrica in having one stamen whereas I. cylindrica has two.

Prevention and Control

Brook (1989) and Townson (1991) summarized control methods in their reviews of I. cylindrica. IRRI/NRI (1996) produced a practical guide to the management of I. cylindrica by smallholder farmers in South-East Asia and a companion volume on grassland rehabilitation using agroforestry and assisted natural regeneration has been produced by ICRAF (1999). Mechanical and/or chemical control are the principal components of any strategy to manage I. cylindrica. At present, there is no scope for biological control with pathogens or predators.

Physical/Mechanical Control

Successful mechanical control of I. cylindrica necessitates destruction of the capacity to regrow after treatment, usually by physical damage, burial or complete removal, or to inhibit growth of the weed so severely that it ceases to be a problem. In bad infestations, this requires the management of a large biomass. The rhizomes alone can have fresh weights of 40 t/ha reaching depths of 1 metre or more in the soil, and have millions of viable buds with the potential to re-infest land if control is less than complete. In practice, such complete control is virtually impossible but mechanical control has been, and remains, one of the most widely used methods of managing I. cylindrica, either as a stand-alone treatment or as an integrated technique with other methods.

The main method of control practised by smallholder farmers is to slash or hand weed. Bush burning is a common feature of fields in the moist savannah of West and Central Africa but it enhances seed production. Clearing land of I. cylindrica with a hand hoe can require 85 man-days/ha. In West Africa, farmers generally weed maize fields infested with I. cylindrica five times to minimize yield reduction by this weed. For larger areas of land, soil cultivation by tractors is more appropriate, best done during the dry season when most of the plant’s biomass is in the rhizomes and when desiccation is most effective. Timing of cultivation is critical, as if done in the wet season, not only is it difficult but there is insufficient sunshine to kill the exposed rhizomes, and regrowth soon occurs. A typical sequence of operations is to burn off the Imperata, disc plough the field to a depth of 30-40 cm, leave for at least 2 weeks, then plough again at right angles to the previous direction. The field is then harrowed twice at an interval of about 2 weeks. ‘The integration of deep ridging, deep hoe weeding and shading suppressed speargrass more effectively than farmers' practices’ (Vissoh et al., 2008).

Grass pressing (i.e. lodging, rolling) is a simple, low-cost technique that is used to control the growth of I. cylindrica. It can be used to clear areas for planting and as part of an integrated approach to enable the establishment of legume ground covers (IRRI/NRI, 1996; ICRAF, 1999). When pressing, it is important that grass shoots are only pressed down, i.e. bent or crimped, like folding a plastic water hose. If shoots are broken, as in cutting or burning, then rapid shoot development results. With pressing, dense stands of I. cylindrica can have regrowth decreased by 40-80%. As much as 90% of pressed I. cylindrica decomposes or dries up within 1 month and it can take more than 6 months for the regrowth to reach its previous population density (Anon, 1989). The best growth stage to press I. cylindrica is when it is about 1 metre high, because stems usually remain permanently bent after being pressed. Appropriate equipment to use includes logs which are rolled over the Imperata and planks held by rope or wooden handles which the operator stands on, lifts, moves and repeats the process over the area to be pressed.

Biological Control

Ivens (1980) was sceptical about the potential for biological control of I. cylindrica due to its worldwide distribution and its regenerative capacity. However, there has been a search for organisms which can be used for classical or augmented control. A selection of these is given in the list of natural enemies, but no fully effective means of biological control are yet available. Yandoc et al. (2005) tested the fungi Bipolaris sacchari and Drechslera gigantean in greenhouse and field and concluded ‘the level of injury caused by these fungi is sufficient to support their use as components for integrated management of cogongrass.’

Chemical Control

Many herbicides have been evaluated and used for the control of I. cylindrica (Brook, 1989; Townson, 1991). Of the four main products (dalapon, glyphosate, glufosinate and imazapyr) used in recent years, glyphosate has become the market leader. A typical high-volume application involves spraying glyphosate in 250-800 l/ha of water using knapsack or tractor-mounted equipment. There is scope for using low volume applications of <50 l/ha with very-low-volume and spinning-disc sprayers and also for the use of weed wipers. Nielsen et al. (2005) found little difference between knapsack and spinning-disc sprayers in effectiveness, but the knapsack was more economical on areas over 2 ha. Rope-wick applications was slightly less effective, but was the least expensive and most suitable for farmers without access to protective clothing.

Much effort has been given to improving the activity of glyphosate with formulation adjuvants (Townson, 1991). Proprietary additives, such as those based on tallow amines, are available for making tank mixtures with the herbicide, though reliable improvement in the performance of glyphosate in all situations cannot be guaranteed. The optimum time for applying glyphosate is when I. cylindrica is actively growing, with a large, green, leaf surface area. Cutting or burning the weed to encourage vigorous regrowth produces a good sward for spraying. A study by Lum et al. (2005) concluded that 150-200 g/ha of nicosulfuron applied at 1 or 2 weeks after planting maize gave effective control of I. cylindrica while significantly increasing crop yield.

IPM

After eradication of I. cylindrica, it is necessary to establish useful species which suppress regrowth of weeds and conserve soil fertility (Anwar and Bacon, 1986). Legume cover crops are widely advocated because of their smothering effect on weeds, stabilization of soil, fixing of nitrogen and ease of removal when the land is to be cropped. Calopogonium caeruleum, C. mucunoides, Desmodium intortum, Centrosema pubescens, Mucuna spp., Pueraria phaseoloides, P. triloba and Stylosanthes guianensis are examples of legumes that are used to rehabilitate I. cylindrica grassland or provide ground cover in plantation crops. For the small-scale farmer who is less inclined to use legume ground covers, intensive agricultural land use will prevent re-establishment of I. cylindrica.

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Contributors

10/04/2008 Updated by:

Chris Parker, Consultant, UK

Distribution Maps

• = Present, no further details
• = Evidence of pathogen
• = Widespread
• = Last reported
• = Localised
• = Presence unconfirmed
• = Confined and subject to quarantine
• = See regional map for distribution within the country
• = Occasional or few reports

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