AGP - Weeds R - U
 

RHYNCHELYTRUM REPENS (Willd.) C.E. Hubbard 


Family:
Poaceae

Synonyms: Tricholaena repens var. rosea Alb., Rhynchelytrum roseum (Nees) Stapf & C.E. Hubb, Panicum roseum Steud., Melinis rosea Hack

Annual; culms slender, about 1 m tall or often shorter with sparsely hairy sheaths; the blades 5-20 cm long, 2-8 mm wide, hairy or glabrous; panicles 10-20 cm long, reddish, purple or white; spikelets about 5 mm long, with hairs extending 4-5 mm beyond. It reproduces by seeds and flowers all the year. R. repens


Countries:
Thailand


SCIRPUS JUNCOIDES Roxb.

Family: Cyperaceae

Synonym: Scirpus erectus Poir

An erect annual weed, 20-70 cm high. Seeds germinate at 13-14 °C but it cannot germinate under dryland conditions. It flowers at 40-50 days after germination and ripens 1 month after flowering. S. juncoides produces seed, 2.0-2.3 mm long, 1.6-1.7 mm wide and 0.8-0.9 mm thick. This weed is very difficult to distinguish from Eleocharis kuroguwai at the vegetative stage. Leaves have very short blades. The stem is flattened at the base, strongly angled at the top.

This weed reproduces by seeds. Seeds normally germinate at 25-35 °C with a germination of 10-25%. Seeds readily germinates at 1 cm water depth on 1-1.5 cm soil depth but there is no appreciable germination 3-5 cm soil depth. Seed dormancy is broken by low temperature under moist conditions, it also require light for germination.

A common plant in lowland rice in North America, Asia, Southern Africa and some Mediterranean countries.

Stale seedbed is on of the best ways to control this annual weed. Seeds should not be buried deeply in soil because of seed dormancy. Once the weed seeds come back close to the soil surface they will readily germinate.

Countries: Korea (South), Thailand


SIDA ACUTA Burn. f.

Family: Malvaceae

Erect, branched, suffrutescent herb, 0.5-1 m high. Leaves lanceolate, acute, 3-5 cm long, pale green. Flowers axillary, solitary or in pairs, the pedicels jointed near the middle; corolla yellow, about 1.9 cm in diameter.

It reproduces by seeds. A pantropical plant, common in hot and semi-dry environment, frequent in orchards, grassland and waste places.

Hormone weed killers are effective when applied in early growth of the weed.

Countries: Bahamas,


SONCHUS OLERACEUS L.

Family: Asteraceae

A glabrous, erect, annual herb with milky juice and up to a meter, sometimes more, tall. Stem soft and hollow. Leaves alternate, sessile; leaf-bases with large irregular auricles. Heads about 2 cm long and in diameter, in terminal cymose panicles. Florets ligulate, yellow. Achenes brown and compressed. It reproduces by seeds.

It is a weed widely distributed all over the tropical and sub-tropical world, very common in vegetables, legumes and other annual crops.

Countries: Eritrea, Iran, Morocco, United Arab Emirates


SPHENOCLEA ZEYLANICA Gaertn.

Family: Sphenocleaceae

An erect, aquatic annual broadleaf that grows to 30-150 cm. The stem is smooth, stout, fleshy, hollow and much-branched. Leaves are simple, spirally arranged, oblong to lanceloate up to 10 cm long, 3 cm wide, narrowed to a point at the tip with a short stalk and entire margins. The inflorescence has green, cylindrical, dense terminal spikes, up to 7.5 cm long, 12 mm wide on a stalk up to 8 cm in length. Flowers are sessile, densely crowded, white to greenish and it is about 2.5 mm long and wide. Fruits are flattened, globular capsules, 4-5 mm across, splitting transversely. Seeds are numerous, yellowish-brown, 0-5 mm long.

It is propagated by seeds. S. zeylanica grows well in wet soils, but it prefers stagnant water in lowland areas in many countries of Asia.

Countries: Guyana, Nepal, Philippines, Thailand, Vietnam

 


SYNEDRELLA NODIFLORA (L.)Gaertn.

Family: Asteraceae

Annual, branched with erect stems, up to 1 m height; leaves opposite and ovate. Inflorescence, clustered yellow flower heads (1-7), with leaf-like bracts. It reproduces by seeds.

It is a common plant of hot environment, either in humid or semi-dry areas.

Countries: Cameroon, Gambia, Vietnam


UROCHLOA MUTICA (Forsk.) Stapf.

Family: Poaceae

Synonyms: Panicum purpurascens Raddi, Panicum muticum,. Forsk., Brachiaria purpurascens Henr, Urochloa mutica (Forsk.)Nguyen

Common names: Paragrass Watergrass Paraná Yerba del Paral, Herbe de Para, Capim do Pará, Capim do Angola.

Perennial stoloniferous grassweed, culms erect, rooting at nodes, up to 150 cm tall, leaves linear-lanceolate 10-30 cm long, ligule membranous, inflorescence panicles of up to 30 cm long, with nearly opposite racemes, spikelet elliptic

It reproduces well through its stolons. Seed reproduction is quite low in general.

A common plant in wet areas, very common in the borders of ditches and canals, and paddy fields. It also grows well in soils poor of Ca. It is a weed in rice and also in irrigated sugar cane areas.

It is found in tropical and subtropical areas of America, Africa, Asia, Australia, Southern Europe and Middle East.
Land preparation exposing stolons to the soil surface for some time helps to dessicate them and to reduce B. mutica infestations. In rice areas water removal for a while reduces the stand of the weed. It is also well controlled by fop and dim post-emergence graminicides.

Countries: Burkina Faso, Congo (Democratic), Cuba, Thailand

 

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