Family: Poaceae

Synonyms: Imperata arundinacea Cyr.

Common names: alang-alang, lalang-alang, bladygrass, cogon grass, carrizo, paillotte

A perennial grass which produces loose to compact tufts with erect culms (10-280 cm long) arising from tough, branched, whitish, creeping rhizomes. Most rhizomes are found in the upper 40 cm of the soil profile but they can grow to depths of more than one metre. The inflorescence is a cylindrical, spike-like panicle, 3-60 cm long and 0.5-2.5 cm wide, consisting of many spikelets surrounded by hairs which give the inflorescence a silky, white appearance.

There are several varieties of I. cylindrica: major, africana, latifolia and europa.

A common weed (C4 plant) in hot climatic conditions in several countries of Africa south of Sahara, South and South East Asia I. cylindrica may reproduce by seed and rhizomes. Flowering of I. cylindrica is usually initiated by stress, such as burning, cutting or drought. Numerous seeds produced (as many as 3,000 per plant) which can be wind-dispersed over long distances. 95 percent of seeds can germinate within a week of harvest and seeds can remain viable for at least one year. I. cylindrica also reproduces vegetatively. A single rhizome node could lead to the production of 350 shoots in six weeks and ground cover of 4 m2 in 11 weeks.

I. cylindrica is tolerant of burning and rapid regrowth occurs from the {{rhizomes}g} which are protected by the soil. 

Flattening foliage with rollers or boards can help to suppress I. cylindrica, if used in combination with a legume cover crop. Legumes, such as Mucuna pruriens, have been effective in suppressing Imperata. So one method of control would be intercropping of tree crops, such as rubber and oil palm, with Mucuna pruriens as an alternative to control Imperata whilst using land productively.

Glyphosate is applied typically at a dose rate of 1.8 kg a.e./ha to actively growing foliage of I. cylindrica from where it is absorbed and translocated to the rhizomes, causing death of most of the plant within 2-4 weeks. A little regrowth is almost inevitable and this should be treated with spot applications. Glyphosate can be applied in volume rates ranging from 20 l/ha (using spinning disc sprayers) to 600 l/ha (using hand-held hydraulic sprayers). Glyphosate should be applied 6-8 hours before rain falls and washes it off the weed.

I. cylindrica is a common weed of rubber, oil palm, coconut, pineapple, tea and forestry, in addition to a wide range of annual crops including upland rice, maize, groundnut, cotton and many others It is a major weed in South & South East Asia, and Africa south of Sahara. Introduced in Alabama, USA, from Japan, in 1912.

Countries: Algeria, Benin, Cameroon, Indonesia, Iran, Nigeria, Uganda

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