Family: Cyperaceae

Synonyms: Cyperus purpuro-variegatus Boeckeler, Cyperus stoloniferum pallidus Boeckeler, Cyperus tetrastachyos Desf., Cyperus tuberosus Roxb.

Common names: Purple Nutsedge, nutgrass, coquito, cebollín, cebolleta, chufa, cipero, coyolillo, juncia, titiriça, capim-dada, herbe-a-oignon, souchet, kruglaya sit tiririça vermelha.

A perennial sedge with a triangular stem up to 50 cm tall, without nodes and longer than the leaves.Leaves linear (grass-like), 15-20 cm long. The inflorescence is a simple or compound umbel, reddish-brown and supported by a bract of leaves. The fruit is an achene.

Roots fibrous, extensively branched. The plant produces long rhizomes and chains of numerous basal bulbs and tubers that extend to considerable depth in soil. Matured tubers are black and fibrous. C. rotundus is a C4 plant. It is a common weed in nearly all tropical and sub-tropical areas. It prevails in hot and moist areas. However, it does not like heavy wet conditions as in lowland rice. It is also susceptible to shade. Crops producing wide and extensive canopy easily suppress C. rotundus growth.

C. rotundus is not a common plant in salty soils.

The plant reproduces via seed and rhizomes/tubers. The level of reproduction is quite fast under hot and moist conditions.

The weed effectively competes with other plants through the release of several toxic susbtances contained either in basal bulbs or in tubers.

Normally C. rotundus prevail in areas repeatedly treated with several soil-acting herbicides. Therefore the best way to reduce its stand is through crop rotation using fastgrowing crops to avoid the use of herbicides. These crops suppress the growth of the weed through their canopies and shade over C. rotundus seedlings.

In citrus plantations and pineapple, some herbicides are effective against C.rotundus, such as early post-emergence treatment of bromacil and glyphosate. The later is effective provided that no rains occur six hours after its appplication.

It is considered the most troublesome weed. It is found in several annual and perennial crops of many tropical and sub-tropical countries.

Countries: Bahamas, Belize, Cameroon,Chile, Colombia,  Congo (Democratic), Costa Rica, Egypt, Eritrea, Jordan, India, Iran, Mexico, Morocco Nepal, Nicaragua, Pakistan, Philippines, Togo, Thailand, Venezuela, Vietnam

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