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16 November 2021

Digitaria abyssinica (East African couchgrass)

Datasheet Types: Pest, Invasive species, Host plant

Abstract

This datasheet on Digitaria abyssinica covers Identity, Overview, Distribution, Hosts/Species Affected, Diagnosis, Biology & Ecology, Natural Enemies, Impacts, Uses, Prevention/Control, Further Information.

Identity

Preferred Scientific Name
Digitaria abyssinica (A. Rich.) Stapf (1907)
Preferred Common Name
East African couchgrass
Other Scientific Names
Digitaria abyssinica var. scalarum (Schweinf.) Stapf (1907)
Digitaria eichingeri Mez (1921)
Digitaria hackelii (Pilg.) Stapf (1919)
Digitaria merkeri Mez (1921)
Digitaria mutica Rendle (1911)
Digitaria scalarum (Schweinf.) Chiov. (1916)
Digitaria somaliensis Chiov. (1917)
Digitaria tangaensis Henr. (1934)
Digitaria vestita Fig. & De Not. (1854)
Panicum abyssinicum A. Rich. (1851)
Panicum hackelii Pilg. (1901)
Panicum kafuroense K. Schum. (1807)
Panicum muticum A. Rich. (1851)
Panicum scalarum Schweinf. (1894)
Local Common Names
East Africa
lumbugu
sangari
Ethiopia
bora
sargida
sari-zaba
ura
waria
wariote
Kenya
blue couch
chemorut
ekenyambi
lumbugu sogule
ombugo
siratet
thangari
South Africa
Abyssinian fingergrass
African couchgrass
couch finger grass
Dunn's finger grass
Dunns-vingergras
kweekvingergras
Tanzania
sanguri
Zambia
nsangani
EPPO code
DIGSC (Digitaria scalarum)

Pictures

D. abyssinica inflorescence (1-9 cm long, 2-25 racemes) and leaf (15 x 0.2-0.8 cm).
Inflorescence and leaf
D. abyssinica inflorescence (1-9 cm long, 2-25 racemes) and leaf (15 x 0.2-0.8 cm).
©Chris Parker/Bristol, UK

Taxonomic Tree

Domain
Eukaryota
Kingdom
Plantae
Phylum
Spermatophyta
Subphylum
Angiospermae
Class
Monocotyledonae
Order
Cyperales
Family
Poaceae
Genus
Digitaria
Species
Digitaria abyssinica

Notes on Taxonomy and Nomenclature

Until a revision of the genus in East Africa by Clayton and Renvoize (1982), D. abyssinica was known as D. scalarum. Digitaria is derived from the Latin digitus, finger, a reference to the racemes in the inflorescence; abyssinicus means 'of Africa'.

Description

D. abyssinica is a creeping, perennial grass with long, slender, branching rhizomes which form a dense mat beneath the soil surface. Culms decumbent near base, becoming erect, about 50 cm, occasionally up to 1 m high. Basal sheath usually glabrous. Leaf blade flat, up to 15 cm long and 2-8 mm wide, often a bluish-green colour. Ligule membranous, 1-2 mm long. Inflorescence consisting of 2-25 racemes arranged in a more or less whorled arrangement on a 1-9 cm long axis. Racemes upwardly pointing, 2-11 cm long. Spikelets paired, on a triquetrous rachis, about 2 mm long, glabrous, lower glume less than 1 mm, upper glume two thirds as long as the spikelet . Fruit ellipsoid in various shades of light brown, grey and purple.

List of Pests

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Distribution

The distribution of D. abyssinica is from Nigeria to Arabia, and southwards to South Africa. It has also been recorded in Madagascar, India and Sri Lanka. It is particularly common as a weed in East Africa.

Distribution Table

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Hosts/Species Affected

D. abyssinica is a weed of many crops, including large- and small-grain cereals, fibres (cotton, flax and sisal), tree crops (coffee, forestry nurseries, tea and wattle) and plantation crops including pineapple, pyrethrum and sugarcane.

Host Plants and Other Plants Affected

Similarities to Other Species/Conditions

In East Africa, where D. abyssinica is most important as a weed, 50 species of Digitaria are recognized (Clayton and Renvoize, 1982). The perennial habit of D. abyssinica distinguishes it from annual weeds such as D. ciliaris, D. leptorrachis, D. nuda, D. sanguinalis and D. velutina. There are three perennial species of Digitaria in the East African region which have been described as weeds: D. gazensis is tufted and has hairy spikelets; D. milanjiana has 2-18 digitate, or almost digitate, racemes; D. pearsonii, a straggling perennial with wiry rhizomes, is intermediate between D. velutina and D. abyssinica and is often confused with these two species.The spikelets of D. personii are slightly pubescent and the fruits are characteristically golden or mahogany brown.In the vegetative stage, D. abyssinica might be confused with Cynodon dactylon, but in the latter the ligule is a fringe of hairs and the leaves are 2-3 per node instead of just one.

Habitat

D. abyssinica is widely distributed in East Africa from sea level to 2900 m, particularly in moister districts. It occurs as a weed in a wide range of crops and soils, including those where minimum tillage is practised. It is a common component of natural grasslands at higher altitudes in East Africa.

Environments

HabitatPresenceStatus
Terrestrial  

Biology and Ecology

D. abyssinica grows best under high light intensity and is more troublesome in unshaded than shaded plantations (Popay and Ivens, 1982). Mature stands of this weed can have a leaf area index of 3, approximately the same as a fully grown maize crop (Duthie, 1957, reporting paper by AN Prentice). D. abyssinica forms a dense mat of rhizomes penetrating the soil to considerable depths, reputedly 60 cm or more, with densities of 220 m of rhizome/m² (Duthie, 1957). It produces a whole plant fresh weight biomass of 36-44 tonnes/ha (Richardson, 1967). Lateral buds on the rhizome lose their dormancy when cultivation or natural processes break the rhizome, causing loss of apical dominance. Rhizome fragments have been reported not to emerge when buried to 16 cm (Mshiu, 1978). This may have some practical significance for control.D. abyssinica seeds profusely; Harker (1957) found seed production of 78 kg/ha in Uganda; equivalent to 26,000 seeds/m². Germination potential varies considerably; up to 7% germination has been found in seed samples 3-5 weeks old, but this increased to 78% in 18-month-old seed (Harker, 1957). Seeds are, therefore, presumed to be important in the propagation and spread of D. abyssinica, however, this is a poorly researched topic. Bogdan (1965) found that 6% of wheat samples in Kenya contained seeds of D. abyssinica.

Notes on Natural Enemies

Sileshi (1997) conducted a search for potential biological control agents of D. abyssinica. The Atherigona spp. were most damaging, causing up to 77% damage to growing points within the heart of young shoots of D. abyssinica.

Natural enemies

Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Atherigona conigeraHerbivore
Growing point
Stems
    
Atherigona dentifoliaHerbivore
Growing point
Stems
    
HispaHerbivore
Leaves
    
OulemaHerbivore
Leaves
    
Puccinia aohuensisPathogen
Leaves
    

Impact

D. abyssinica is the most troublesome weed in the crops of Ethiopia, Kenya, Uganda and Tanzania (Ivens, 1989). It is reported as the most important weed of coffee in Kenya and of cotton in Uganda (Holm et al., 1977). The growth and yield of crops is greatly reduced in the presence of D. abyssinica. Heavy infestations can kill coffee bushes (Ivens, 1989), reduce sisal yields by 2 t/ha (Richardson, 1965) and cotton yields by 50% (Prentice, 1957). This may be caused, in part, by toxins released from the roots of D. abyssinica which have an allelopathic effect on the crop (Wallis, 1959). Serious mechanical damage can occur when trying to remove rhizomes entwined in crop roots.

Uses

D. abyssinica is palatable to cattle and has been grown as a pasture grass in South Africa (Rethman et al., 1988) but it is not sufficiently productive to make a good pasture species in East Africa (Popay and Ivens, 1982). Its rhizomatous habit binds soil and can reduce erosion on sloping land.

Uses List

Environmental > Erosion control or dune stabilization
Animal feed, fodder, forage > Forage

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
Mechanical ControlA forked hoe will remove many rhizomes, however, this method is very labour intensive and total eradication of all viable fragments left in the soil is virtually impossible (Terry, 1974). Where high densities of D. abyssinica are present, ploughing with draught animals is impeded. The increased traction can cause injury to the shoulders of draught animals. Mechanical tillage with tractors can expose rhizomes to desiccation on the soil surface, but can also spread the fragmented rhizomes. In laboratory conditions, desiccation of rhizomes for four days at temperatures of 7°C to 27°C led to complete kill (Mshiu, 1978). Field trials with cover crops have shown that noug (Guizotia abyssinica) and linseed (Linum usitatissimum) considerably suppress D. abyssinica in coffee with no significant effect on the crop (Dubale, 1987). Rotation with noug (Guizota abyssinica) is also regarded as a useful control measure in Ethiopia.Chemical ControlHerbicides that have been tested and used against D. abyssinica include alloxydim, amitrole, asulam, butylate, dalapon, glufosinate-ammonium, glyphosate, haloxyfop, hexazinone, metribuzin, MSMA, sethoxydim, sulfosate (glyphosate-trimesium) and TCA - sodium. Dalapon was a standard treatment to young foliage (Ivens, 1989) but this has largely been superseded by glyphosate (Terry, 1974; Baguma et al., 1995).

Links to Websites

NameURLComment
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.

Distribution Map

This content is currently unavailable.

References

Baguma SD, Webb M, Osiru DSO, 1995. Control of Digitaria abyssinica (A. Rich.) Stapf. with glyphosate. Africa Crop Science Journal, 3:433-442.
Bogdan AV, 1965. Weeds in Kenya wheat. Weed Research, 5:351-352.
Clayton WD, Renvoize SA, 1982. Flora of Tropical East Africa. Graminea (Part 3). Rotterdam, The Netherlands: A.A. Balkema, 448 pp.
Drummond RB, 1984. Arable Weeds of Zimbabwe. Harare, Zimbabwe: Agricultural Research Trust of Zimbabwe.
Dubale P, 1987. The effect of cover crops on the control of couch grass (Digitaria abyssinica) in arabica coffee. Ethiopian Journal of Agricultural Sciences, 9(2):67-82.
Duthie DW, 1957. The First East African Herbicide Conference. II - Summary of Papers and Discussion. The East African Agricultural Journal, 23:6-21.
EPPO, 2014. PQR database. Paris, France: European and Mediterranean Plant Protection Organization. http://www.eppo.int/DATABASES/pqr/pqr.htm
Harker KW, 1957. A note on Digitaria scalarum seed. The East African Agricultural Journal, 23:11.
Holm LG, Pancho JV, Herberger JP, Plucknett DL, 1979. A geographical atlas of world weeds. New York, USA: John Wiley and Sons, 391 pp.
Holm LG, Plucknett DL, Pancho JV, Herberger JP, 1977. The World's Worst Weeds. Distribution and Biology. Honolulu, Hawaii, USA: University Press of Hawaii.
Hutchinson J, Dalziel JM, Hepper FN, 1972. Flora of West Tropical Africa, Vol. III. London, UK: Crown Agents for Oversea Governments and Administrations.
Ivens GW, 1989. East African Weeds and their Control, 2nd edition. Nairobi, Kenya: Oxford University Press.
Mshiu EP, 1978. Studies on Digitaria scalarum (Chiou) Schweinf. Studies on Digitaria scalarum (Chiou) Schweinf. M.Sc. Tech. Crop Protection Thesis, University of Reading., 36 pp.
Popay AI, Ivens GW, 1982. East Africa. In: Holzner W, Numata M, eds. Biology and Ecology of Weeds. The Hague, Netherlands: Dr. W. Junk Publishers, 345-372.
Rethman NFG, Witt CCde, 1988. The yield potential and crude protein content of five rhizomatous and stoloniferous grass pastures in the escarpment areas of the eastern Transvaal. South African Journal of Plant and Soil, 5(4):222-224
Richardson FE, 1965. Bromacil, a herbicide suitable for sisal nurseries. Kenya Sisal Board Bulletin, 54:41-42.
Richardson FE, 1967. Chemical control of couch grass (Digitaria scalarum) by heavy applications of sodium trichloroacetate (Na-TCA). Kenya Sisal Board Bulletin, 59:29-33.
Seychelles Department of Agriculture, 1974. Herbicides. In: Seychelles Department of Agriculture Annual Report.
Sileshi G, 1997. Potential biocontrol agents for the blue couch grass, Digitaria abyssinica (A. Rich.) Stapf., in East Africa. International Journal of Pest Management, 43(2):173-176; 27 ref.
Stroud A, Parker C, 1989. A Weed Identification Guide for Ethiopia. Rome, Italy: Food and Agriculture Organization.
Terry PJ, 1974. Field evaluation of glyphosate, asulam and dalapon on African couch grass (Digitaria scalarum). East African Agricultural and Forestry Journal, 39(4):386-390.
Terry PJ, Michieka RW, 1987. Common Weeds of East Africa. Rome, Italy: Food and Agriculture Organization of the United Nations.
Vernon R, unda. Field guide to important arable weeds of Zambia. Field guide to important arable weeds of Zambia. Department of Agriculture Chilanga Zambia, 151pp.
Wallis JAN, 1959. Herbicides in Kenya coffee IV. PANS(C), 5:40-58.
Wells MJ, Balsinhas AA, Joffe H, Engelbrecht VM, Harding G, Stirton CH, 1986. A catalogue of problem plants in South Africa. Memoirs of the botanical survey of South Africa No 53. Pretoria, South Africa: Botanical Research Institute.
Macharia, I., Backhouse, D., Wu, S. B., Ateka, E. M., 2016. Weed species in tomato production and their role as alternate hosts of Tomato spotted wilt virus and its vector Frankliniella occidentalis.Annals of Applied Biology, 169(2) 224-235.

Distribution References

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Information & Authors

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Published online: 16 November 2021

Language

English

Authors

Affiliations

CABI
CABI Head Office, Wallingford, UK

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