Contributed by: Dr. Robert D. Webster; Research School of Biological
Sciences; The Australian National University; Canberra City, A.C.T. 2601;
Australia. U.S. Department of Agriculture APHIS-PPQ. Noxious weeds of the Federal Noxious Weed Act, No. 37
Family Name: Poaceae [Gramineae]
Genus Name: Rottboellia L.f., Nov. Gram. Gen. 23. 1779., nom. cons. Type species:
Rottboellia exaltata auct., non (L.) L.f. 1779. (= Rottboellia
cochinchinensis (Lour.) Clayton, Kew Bull. 35:817. 1981.)
Plants annual herbs; culms erect; internodes solid. Leaf sheaths with
spreading, rigid hairs; auricles absent; ligule a hairy membrane; blades long
and flat, the blades nearest the inflorescence reduced. Inflorescence a
spike-like raceme, cylindrical, disarticulating into floral units which consist
of a fertile sessile spikelet, pedicellate spikelet, and internode; internode
swollen, hollow, enlarged at the apex, glabrous, the lower spikelet embedded in
the internode; callus truncate and peg-like; pedicel shorter but otherwise
similar to and fused to the internode. Spikelets paired, heteromorphic,
awnless, abaxial, dorsa-ventrally compressed. First glume of sessile
spikelet many-nerved, smooth to muricate, indurate, with inrolled margins;
second glume many-nerved, boat-shaped, closely following the outline of the
internode; lower floret staminate, the lower lemma mambranous to chartaceous,
the lower palea well-developed; upper floret perfect, with lemma hyaline and
awnless, the stigmas purple, the caryopsis ovate. Pedicellate spikelet
sterile and green; the first glume many-nerved, with scabrous and inrolled
margins and usually cleft apex.
Rottboellia is a small genus of about four species native to the tropics
of the Old World. It is a typical member of the grass tribe Andropogoneae,
which is characterized by the inflorescence disarticulating into floral units
consisting of a sessile spikelets, pedicellate spikelet, and internode.
Some closely related genera include Manisuris, Coelorachis, and
Hemarthria. Diagnostic features of Rottboellia include the
racemose inflorescence, a pedicel fused to the swollen floral internode, and
heterotropic and awnless spikelets. One species of the genus
Rottboellia cochinchinensis, is presently included on the list of weeds for
the Federal Noxious Weed Act.
Species Name: Rottboellia cochinchinensis (Lour.) Clayton, Kew Bull. 35: 817. 1981.
Rottboellia exaltata auct., non. (L.) L.f. 1779.
Stegosia cochinchensis Lour., Fl. Cochinch. 51. 1790.
Manisuris exaltata Kuntze, Rev. Gen. Pl. 2:779. 1891.
Stegosia exaltata Nash, N. Am. Fl. 17:84. 1909.
A list of common names of Rottboellia cochinchinensis (as R. exaltata)
has been compiled by Holm et al. (1977). This list has been incorporated
into the following list: Kokoma grass (Australia); sancarana (Cuba); guinea-fowl
grass (Eastern Africa); barsali, bura swooate, dholu, konda panookoo (India?);
bandjangan, djoekoet kikisian (Indonesia); rice grass (Jamaica); aguingay,
annarai, bukal, gaho, girum, nagei, sagisi (Philippines); guineafowl grass,
kokomo grass, shamva grass (Rhodesia); corn grass (Trinidad); itchgrass, Raoul
grass (United States); paja peluda (Venezuela); jointed grass, mulungwe, shamwa
Annual grasses; inflorescence a jointed, cylindrical raceme 3-15 cm long; floral
units consisting of a sessile spikelet, pedicellata spikelet, and internode;
pedicel fused to the swollen floral internode; spikelets awnless, 3.5-6 mm long,
2.5-3 mm wide.
Plants tall annuals, frequently with prop-roots; flowering culms 5-30 dm
tall, branched, mostly 5- to 10-noded; nodes glabrous; internodes glabrous,
grooved, ribbed, solid to spongy. Leaf sheaths keeled to rounded,
distinctly ribbed, smooth, usually covered with stiff, irritating, papillose-based,
setaceous hairs, the upper sheaths hairy or glabrous, without auricles; ligule a
hair-fringed membrane 1-2 mm long, truncate; blades not distinctly distichous,
flat, keeled, mostly 25-40 cm long, 5-25 mm broad, linear, acuminate, base
cordate, hairy or glabrous, scabrous, margins scabrous; prophyllum with
pronounced scabrous wings. Inflorescence a jointed raceme, 3-15 cm long,
cylindrical, the upper spikelets becoming reduced, disarticulating into floral
united which consist of a sessile spikelet, pedicellate spikelet, and internode;
internode minutely muricate, 5-8 mm long, deeply grooved on the lower part, apex
hollow; callus soft, smooth, truncate and peg-like; pedicel similar in
appearance and fused to the internode, but shorter 3-5 mm long. Sessile
spikelet embedded in the internode, 3.5-6 mm long, 2.5-3 mm wide; first glume as
long as the spikelet, oblong to lanceolate, 9- to 11-nerved, rounded to cleft,
indurate, convex, muricate, glabrous, slightly winged at the apex, margins
inrolled; second glume many-nerved, keeled on the upper part, boat-shaped,
smooth on the lower part and muricate upwards, indurate to cartilaginous,
following the outline of the internode; lower lemma oblong to lanceolate,
faintly 3-nerved, as long as the second glume, membranous to chartaceous; lower
palea well-developed and similar to the lemma; upper floret perfect, hyaline.
Caryopsis oblong, 3-4 mm long.
A native of the Old World tropics, widespread in tropical Asia and the Pacific
Islands. The species has been introduced into tropical America and now
occurs in Central and northern South America, throughout the Caribbean, and in
Florida and Louisiana in the United States. It has also spread into
Australia and much of Africa.
Rottboellia cochinchinensis. A. Lower portion of culm,
showing annual nature (with inset showing solid stem) (0.75x); B.
Upper portion of culm, showing pubsecence and spikelike raceme (0.75x); C.
Sheath/blade joint, showing ligule (4.5x); D. Young flowering branch
(0.75x); E. Top portion of inflorescence (1.5x); F. Floral unit
(sessile spikelet, pedicellate spikelet, and internode (9x).
Source: Williams 2623, Philippines (NY).
Rottboellia cochinchinensis is an aggressive weed under various
ecological conditions. In some areas, it seems to prefer wet,
coarse-textured soils at the lower altitudes, sometimes even growing in shallow
water. In other areas it is prominant in open, well-drained places at
higher altitudes, and is one of the important species in old field succession.
In the Americas it is an aggressive weed of sugarcane fields. In Africa
and Malayasia it causes severe crop damage to corn, cotton, peanut, soybean, and
sugarcane. Thomas (1970) reported the species in Rhodesia only in heavier
soils--clay to sandy clay loams--the type of soil in Louisiana sugarcane growing
areas, where the weed is becoming more of a problem each year.
The species is presently most destructive in eastern Afrcia, the Philippines,
and along the shores and islands of the Gulf of Mexico and the Caribbean area.
See Holm et al. (1977) for a detailed list of countries where Rottboellia
cochinchinensis is a serious problem, and the crops involved.
The common name "itchgrass" is derived from the presence of rigid penetrating
hairs on the leaf sheaths. Although attempts have been made to use the
plant for pasture in many areas, these hairs will break off in flesh and cause
severe irritation, making the species a poor fodder.
Rottboellia cochinchinensis is an alternate host of the virsuses
causing corn leaf gall and rice leaf gall (Agati and Calica 1949).
The name Rottboellia exaltata has been misapplied and this nomemclatural
problem was reviewed by Clayton (1980, 1981). The correct name for this
widespread species is Rottboellia cochinchinensis (Lour.) Clayton.
However, Simon (1982--Taxon 564-573) has formally proposed to conserve the name
Rottboellia exaltata L.f.
Diagnostic features useful in distinguishing this species from other members
of the genus include sharp irritating hairs on the leaf sheaths, the length of
the spike-like raceme (3-15 cm long), and spikelet length (3.5-6 mm long).
Agati, J. and C. Calica. 1949. The leaf-gall disease of rice and
corn in the Philippines. Phil. J. Agr. 14:31-38.
Clayton, W.D. 1980. Proposal to conserve Rottboellia L.f. 1781
against Rottboellia L.f. 1779. Taxon 29:692.
1981. Notes on the tribe Andropogoneae (Gramineae). Kew Bull.
Holm, L.G., D.L. Plucknett, J.V. Pancho, and J.P. Herberger. 1977.
The world's worst weeds: Distribution and biology. University Press of
Hawaii, Honolulu. 609 pp.
Thomas, P. 1970. A survey of the weeds of arable lands in Rhodesia.
Rhod. Agr. J. 67(2):34-37.