Urochloa decumbens (Stapf) R.D. Webster, Poaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Reject, score: 10 (Go to the risk assessment)

Other Latin names:  Brachiaria decumbens Stapf

Common name(s): [more details]

English: Basilisk signal grass, Surinam grass, basalisk signal grass, common signalgrass, signal grass

Spanish: braquiaria, pasto alambre, zacate Surinam

Habit:  grass

Description:  "Perennial to 1-1.5-(2) m tall; sometimes with short rhizomes; culms geniculate and rooting at the lower nodes, those internodes relatively short and bearing short blades, branching from the lower and middle nodes, the internodes flattened, solid or the lower becoming hollow, glabrous, often pilose just below the nodes, the nodes glabrous. Sheaths compressed, shorter than the internodes on flowering culms, papillose-hirsute, ciliate, the collar glabrous or sparsely pubescent; ligule 0.8-2.0 mm long, the membrane 0.3-0.7 mm long, the cilia 0.5-1.3 mm long; blades 5-19 cm long, 1.0-1.89 cm wide, linear to linear-lanceolate, papillose-hirsute, acuminate, the base asymmetrical, rounded, the margin wrinkled, strongly serrate with uneven teeth, cartilaginous. Panicle 6-14 cm long; common rhachis 2-9 cm long, hirsute, ending in a rudimentary branch; racemes 2-4, 3-8 cm long, somewhat curved, the rhachis winged, c. 1.5 mm wide, often curved, prominently nerved, glabrous on the back or pubescent at the pedicels inconspicuous to 0.5 mm long. Spikelets 4.6-5.2 mm long, imbricate, strongly secund, solitary, 2-rowed, sparsely pilose, green or purplish, acute and short-apiculate; lower glume 1.8-2.4 mm long, the lower portion adnate to the pedicel for up to 0.2 mm, ovate, broadly acute, glabrous, 9-11-nerved, the nerves anastomosing, rhachilla between the glumes elongated; upper glume as long as the floret, broadly elliptic-ovate, 7-9-nerved, sparsely pilose toward the tip; lower floret staminate, the lemma as long as the upper floret, broadly elliptic-ovate, 5-nerved, the nerves connected with cross-veinlets at the tip, very sparsely pilose at the tip, the palea as long as the upper floret; upper floret 4.1-4.3 mm long, 1.9-2.0 mm wide, elliptic, acute, minutely pitted; anthers 2.5-3.0 mm long; stigmas purple" (Dassanayake, 1994; p. 86).

"Closely related to [U.] brizantha and often confused with that species outside its native range. [Urochloa] decumbens differs from [U.] brizantha primarily in its more broadly winged raceme rhachises and in its decumbent habitat with generally shorter leaf blades. Some of the selections that have been widely introduced as forage grasses could be of hybrid origin and identification is not always easy" (Dassanayake, 1994; p. 86).

Description from GrassBase.

Habitat/ecology:  (no habitat/ecology info known by PIER)

Propagation:  Seed

Native range:  Tropical Africa.

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Ecuador (Galápagos Islands) Isabela Group	Isabela Island	introduced invasive cultivated	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Isabela Group	Volcán Sierra Negra, Isabela Island	introduced invasive cultivated	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) San Cristóbal Group	San Cristóbal Island	introduced invasive cultivated	Charles Darwin Foundation (2008)
Ecuador (Galápagos Islands) Santa Cruz Group	Santa Cruz Island	introduced invasive cultivated	Charles Darwin Foundation (2008)
Fiji Fiji Islands	Vanua Levu Island	introduced cultivated	Smith, Albert C. (1979) (p. 328) See comment below. Voucher cited: DA L.13387
Fiji Fiji Islands	Viti Levu Island	introduced cultivated	Smith, Albert C. (1979) (p. 328) See comment below.
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Snow, Neil/Lau, Alex (2010) (p. 49) Voucher cited: L.W. Pratt 3341 (BISH)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive	Starr, Forest/Starr, Kim/Loope, Lloyd L. (2006) (p. 39) Misidentified as Brachiaria brizantha per Snow & Lau, 2010; p. 49. Voucher cited: Starr & Starr 040607-4 (BISH)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive	Snow, Neil/Lau, Alex (2010) (p. 49) Voucher cited: F. Starr & K. Starr 040607-4 (BISH)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Snow, Neil/Lau, Alex (2010) (p. 49) Vouchers cited: C. Trauernicht 208 & M. Clark (BISH), T. Flynn 7371 (BISH)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced cultivated	Starr, Forest/Starr, Kim/Loope, Lloyd L. (2006) (p. 39) Misidentified as Brachiaria brizantha per Snow & Lau, 2010; p. 49. Voucher cited: Joy HA-5222 (BISH)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced cultivated	Snow, Neil/Lau, Alex (2010) (p. 49) Voucher cited: R. Joy s.n. (BISH 634161)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Lau, Alex/Frohlich, Danielle (2013) (p. 10) Voucher cited: J. Beachy, J. Hawkins, M. Adiona, D. Frohlich & A. Lau US Army 272 (BISH)
Solomon Islands Solomon Islands	Solomon Islands	introduced cultivated	Hancock, I. R./Henderson, C. P. (1988) (p. 52)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Queensland	introduced invasive	Queensland Herbarium (2002) (p. 2) As Brachiaria decumbens

Comments:  Pasture trials in Fiji (Smith, 1979, p. 328). Present status not known.

Control:  If you know of control methods for Urochloa decumbens, please let us know.