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Plantwise Technical Factsheet

greater club rush (Scirpus grossus)

Host plants / species affected
Oryza sativa (rice)
Description
S. grossus is a stout, erect, coarse plant with a tufted, robust and strongly 3-angled stem reaching about 1.5-2.5 m tall. It is strongly tillering with long stolons ending in small tubers; stems are sharply 3-angular with concave sides, septate, smooth or slightly scabrid apically, 70-200 cm x 6-12 mm.

Leaves are long and acuminate, 1.5 cm wide; bracts are long and acuminate, about 6 cm long. Leaves all originate from the base of the stem, in a rosette, linear, 60-100 cm x 0.5-3.5 cm, gradually tapered to the tip, margins scabrid and bristly.

The inflorescence is a terminal, irregular, compound umbel of corymbs; axils scabrid, minutely bristled, 5-20 cm long, base with several leaf-like unequal flat bracts; spikelets branched on slender stalks, many, solitary sessile or reduncled, ovoid to oblong ovoid, acutish, densely many flowered, 5-10 x 4-5 mm; rachilla persistent, not winged; glumes helically arranged, membranous, appressed, concave, broadly oval, reddish-brown with green midrib, glabrous to more or less hairy, minutely ciliate, shortly mucroannulated, 2-3 mm x 1.5-2.0 mm; the lower 1-3 glumes empty. The flowers are bisexual with stamens 3; the style is slender, short, glabrous with 3 stigmas, nut 3-angled, and about half as long as the glume, brown and smooth.

For a more detailed description of the morphology of S. grossus, see Soerjani et al. (1987).
Prevention and control
Integrated Weed Management

The management of S. grossus in ricefields and waterways has traditionally been herbicide based (Baki, 1981; Baki and Azmi, 1992). The integration of chemical control with other control options is minimal, with the exception of cultural control methods. A minor limitation in the use of herbicides to control S. grossus in ricefields or waterways has been the need to deal with a complex array of weed species, often in sympatric existence within a habitat. The need to suppress the population of S. grossus to below an acceptable threshold is often hampered by the need to suppress the population of other, more noxious species, namely Echinochloa species.

In the development of integrated weed management strategies for Scirpus, different control protocols may be harnessed to suppress the population below a threshold. Biological control of S. grossus has not been widely explored. In order to be effective, these control tactics require a thorough understanding of the ecology of both the crop and the weed (Waterhouse, 1993).


Cultural Control and Phytosanitary Methods

Proper tillage regimes and water management are effective in suppressing the population of S. grossus in rice. Invariably, 2-3 rounds of dry or wet rotovation followed by raking and the removal of stolon debris in direct-seeded or transplanted rice culture reduces S. grossus populations to below the economic threshold of 4-5 plants/m². The population of shoot nodules of S. grossus was depleted by slowly increasing the depth of inundation to 20 cm.

Increasing the seeding rate to 120 kg/ha in direct-seeded rice reduced the population of S. grossus and effectively maintained the weed population below an acceptable level.


Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

Impact
S. grossus can cause severe losses to ricefields in Malaysia. Four to five plants/m² can inflict a yield loss of about 10-15% in the direct-seeded rice variety MR84. Keeping ricefields free of S. grossus within the first 30-40 days of the crop can alleviate such yield loss. In Indonesia and elsewhere in South-East Asia, southern China, tropical Australia and India, the weed is considered a species of minor importance (Holm et al., 1991).

S. grossus has some economic value. It serves as a good herbage when ploughed in as green manure. S. grossus var. kysoor, occurring in India and Malesia, produces tubers which are a good source of starch, containing about 62-79% digestible carbohydrates and 7.5-11.8% protein (Burkhill, 1966). S. grossus is also used in traditional medicine in the Indian subcontinent. In the Philippines and Perak state of Peninsular Malaysia, S. grossus is harvested for mat-making and string.
Related treatment support
 
External factsheets
IRRI Factsheets, International Rice Research Institute (IRRI), English language
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