Amaranthus viridis L. - AMARANTHACEAE - Dicotyledon

Synonymes : Amaranthus gracilis Desf. ex Poir., Chenopodium caudatum Jacq., Euxolus caudatus Moq., Euxolus viridis L. Moq.

Common name : Pig weed
Common name in Bengali : Marissag, shak natey
Common name in Hindi : Jangali chaulai

Habit - © Juliana PROSPERI - Cirad Inflorescence - © Juliana PROSPERI - Cirad Leaf - © Juliana PROSPERI - Cirad Leaves tip with a mucro - © Juliana PROSPERI - Cirad Flowers reduced and grouped in small balls - © Juliana PROSPERI - Cirad Tap root - © Juliana PROSPERI - Cirad Botanical line drawing - © -

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Diagnostic characters Biology Ecology and distribution Nuisance Weed control Botany Uses/Remark References

Diagnostic characters :

Amaranthus viridis is an erect, perennial broadleaf herb, growing up to 75 to 100cm high. The stems are green, often reddish and angled in cross section. The tap root goes deep in the soil. The leaves are alternate and long-petiolated. The flowers are green, reduced and grouped in small dense balls. The subglobose fruit contains only one shiny brown or black seed.

Biology :

This annual herb reproduces only from seeds. The plant can produce 7000 seeds dispersed by the water or wind.

Ecology and distribution :

From East Asian origin, A. viridis widespread in tropical and subtropical regions of the world and in the upland rice. It is found in well drained soils, in open waste places and cultivated land, especially in volcanic soils. The plant grows best in soils with no standing water and has good development in soils rich in organic matter and nitrogen.
In Pakistan this species is found all over Punjab province, but more frequent in the irrigated areas.

Nuisance :

The slender amaranth is considered as one of the most harmful weeds which may lead to heavy losses in crop yield. Its weedy status is more important than its culinary value. In Bangladesh can cause yield reduction up to 80%.

Weed control :

- Cultural
Cultivation favours A. viridis emergence, and is a useful means of killing seedlings before sowing rice.
- Biological
A weevil, Hypolixus trunculatus whose larve tunnel in the stems and form galls, is known from Pakistan, India and Thailand and feeds on A. viridis. But its suitability as a biological control agent is hampered by its relatively long life cycle and low reproductive capacity. The caterpillars of Hymenia recurvalis in large number defoliate the weed and, where infestation is severe, practically every plant is infested. But H. recurvalis has a wide host range, is a pest of several vegetable crops, and is unsuitable for biological control of A. viridis.
- Chemical
Butachlor applied pre-emergence at 2.0 to 2.5 kg ha-1 gives excellent control. Post-emergence application of 2_4-D at 500 g/ha.

Botany :

Erected and much branched herb.
One or several ramified tap roots.
Slender, cylindrical, smooth and striate.
Alternate leaves, long-petiolated, 4 to 10cm long with a broad base, 1.5 to 5.5cm wide, and a narrow, rounded tip with a sharp point (emarginated) with a mucro. Entire margin, 7 to 8 lateral nerves well visible and lightly arched. Upper and lower sides glabrous, with numerous small translucid dots.
Simple or branched at the top of the stem, and in the leaf axils, 2.5 to 12cm long and 2 to 5mm wide. Flowers sessile, small, dense, green in color, forming a glomerule or grouped in a spike; sepals 3, 1mm long, linear or lanceolated, stamens 3. The pistillate flowers are at the base of the spike and are more numerous than staminate ones. The male flowers at the upper part of the spike have 5 stamens.
The fruit is an ovoid capsule, indehiscent, 1.2mm long and 1mm large, with one seed. The upper side of the fruit has a short stigma divided into three-pieces.
1 to 1.25mm in diameter, brown or black, shiny, slightly compressed, reticulate and with shallow outgrowths on the reticulum.
Cotyledons linear to lanceolate and petiolated. Lamina 18mm long and 3mm large, smooth, without apparent nerves. The lower side could be purple. First leaves simple, alternate, long-petiolated. The lamina is first elliptic and later ovate. The top of the lamina is deeply emarginated. The extremity of the central nerve forms a mucron. The lower side is generally purple.

Uses/Remark :

A. viridis is used as vegetable.

References :

- Le Bourgeois T., Jeuffrault E., Grard P., Carrara A. 2001. AdvenRun V.1.0. Les principales mauvaises herbes de La Réunion. CD-ROM. Cirad, SPV. France.
- Galinato M., Moody K., Piggin C. M. 1999. Upland rice weeds of South and Southeast Asia. IRRI. Philippines.
- Nayyar M. M., Ashiq M., Ahmad J. 2001. Manual on Punjab weeds (Part I). Directorate of Agronomy. Ayub Agricultural Research Institute, Faisalabad Pakistan.
- Waterhouse D. F. 1994. Biological control of weeds: Southeast Asian prospects. ACIAR Monograph No. 26, 302 pp.
- Bari, M. N. 1997. Major rice weeds in Bangladesh. Department of Agronomy. BSMR Agricultural University, Gazipur, Bangladesh.

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