I. rugosum is a vigorous annual (in strongly desiccating soil) or short-lived perennial, tufted, sometimes with stilt roots, rooting at the nodes, with erect, slanting or ascending, often much-branched culms, up to 1.5 m tall. The species can be identified by the distinctive, prominent transverse ribs or ridges on the lower glume of the spikelet. The spinal awns are prominent and the nodes of the culm are tufted and hairy.
The leaf sheaths are usually loose, up to 16 cm long, glabrous or hairy like the blades, with some long, slender, bulbous-based hairs on the margin and at the base at the node (Gilliland et al., 1971). The leaf blades are acuminate, the lower ones narrowed gradually to the base;30 cm long x 1.5 cm wide;the margin is cartilaginous and scabrid, the base densely hairy. The ligule is variable, a brownish membrane, 6 mm deep.
The inflorescence is terminal, apparently simple when young, but separating with age into its two constituent racemes, usually 7-10 cm long;each raceme with the spikelets arranged in pairs, one sessile, one pedicelled, on one side of the triangular, hairy rachis. Sessile spikelet, callus thick, lower glume keeled and membraneous, 5 mm long with distinct transverse ridges (hence 'rugosum;upper glume ovate-acute, keeled 5.2 mm long;lower floret usually male, 4.6 mm long;epper lemma with a twisted awn up to 20 mm long;anthers 3, 2 mm long;grain ovoid, brown, 2 mm long. Pedicelled spikelet on a stout pedicel, 1 mm long;lower glume ovate-acute, 4.4 mm long;upper glume boat-shaped, keeled, acute, 4.1 mm long;lower lemma hyaline, 3-nerved, the margins folded;palea similar, 2-nerved, upper lemma male, 3 mm, hyaline without an awn or with a very small, thin one (Gilliland et al., 1971).
Related invasive species
- Ischaemum rugosum
Related Farm Practice
- Soil
- Rooting
- Hosts
I. rugosum is a C 4 grass species widely cultivated and naturalized in moist, tropical habitats around the world (Clayton et al., 2015;USDA-ARS, 2015). It is an opportunistic and effective colonizer of open and disturbed areas, swamps, and along roadsides. It is a serious weed in many crops, especially in paddy fields and sugarcane plantations (Holm et al., 1977;Baki and Manidool, 1992). I. rugosum is a highly invasive grass which can produce up to 4,000 seeds per plant and has the potential to grow even in shaded areas (Holm et al., 1977;PROTA, 2015). I. rugosum is listed as invasive in Costa Rica, Cuba, the Dominican Republic and Fiji (Kairo et al., 2003;Chacon and Saborio, 2012;Oviedo Prieto et al., 2012;PIER, 2015). In the USA, the Department of Agriculture considers it a noxious weed;plants found growing within the continental USA should be promptly reported to that agency (Barkworth et al., 2003).
I. rugosum is found mainly in rice, but also amongst other crops which are grown under wetland conditions. It is also sometimes found in sugarcane (Holm et al., 1977). It is named by Holm et al. (1977) as a weed of six or more crops in Cuba, Colombia, Malaysia and China, and of between two and five crops in Peru and Guyana.