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Datasheet

Amaranthus hybridus (smooth pigweed)

Summary

  • Last modified
  • 22 June 2017
  • Datasheet Type(s)
  • Pest
  • Invasive Species
  • Host Plant
  • Preferred Scientific Name
  • Amaranthus hybridus
  • Preferred Common Name
  • smooth pigweed
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae

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Pictures

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PictureTitleCaptionCopyright
Amaranthus hybridus (smooth pigweed); flowering habit.
TitleFlowering habit
CaptionAmaranthus hybridus (smooth pigweed); flowering habit.
Copyright©Markus Hagenlocher - CC BY-SA 3.0
Amaranthus hybridus (smooth pigweed); flowering habit.
Flowering habitAmaranthus hybridus (smooth pigweed); flowering habit.©Markus Hagenlocher - CC BY-SA 3.0

Identity

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Preferred Scientific Name

  • Amaranthus hybridus L. (1753)

Preferred Common Name

  • smooth pigweed

Other Scientific Names

  • Amaranthus chlorostachys Willd.
  • Amaranthus frumentaceus Buch.-Ham. ex Roxb.
  • Amaranthus incurvatus Timeroy ex Gren. & Godr.
  • Amaranthus patulus Bertol. (1837)

International Common Names

  • English: green amaranth; slim amaranth
  • Spanish: bledo; quelite
  • French: amarante hybride
  • Portuguese: caruru-de-folha-larga

Local Common Names

  • Brazil: caruru-branco; caruru-roxo
  • Germany: Bastard - Amarant; Gruenaehriger Amarant; Gruenaehriger Fuchsschwanz
  • Japan: honagaaogeito
  • Netherlands: basterdamarant

EPPO code

  • AMACH (Amaranthus hybridus)

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Caryophyllales
  •                         Family: Amaranthaceae
  •                             Genus: Amaranthus
  •                                 Species: Amaranthus hybridus

Notes on Taxonomy and Nomenclature

Top of page A. hybridus has a chromosome number of 2n = 32 (Murray, 1940; Grant, 1959). It readily hybridizes with closely related species, but the F1 generation is highly sterile (Tucker and Sauer, 1958). Hybrids often have oddly shaped inflorescences. Brenan (1961) distinguished three subspecies of A. hybridus on the basis of the relative length of the bracts compared with the length of the sepals.

A. hybridus is sometimes confused with the cultivated species A. hypochondriacus and A. caudatus (love-lies-bleeding), both of which have long, thin often reddish inflorescences. However, Sauer (1967) contends that A. hypochondriacus was derived mainly from A. powellii, and A. caudatus mainly from A. quitensis. A. hybridus is thought to be the progenitor of A. cruentus, a cultivated grain and ornamental plant. Introgression has undoubtedly occurred among the weedy and domesticated amaranths. While this represents the current status of A. hybrudus in the strictest sense, it must be noted that the 'cultivated' A. cruentus often occurs as a weed and is sometimes referred to as 'A. hybridus' in weed literature. Hence it is likely that a number of the recorrds in this data-sheet might refer more strictly to A. cruentus (or to other closely related species).

Description

Top of page A. hybridus is an annual herbaceous plant which reproduces only by seeds. It produces a tap root and erect, often branched stems from 0.1 to 2.0 m in height. The stems are thick and often ribbed or tinged with red. Its leaves are alternate, long-stalked, and ovate to rhombic-ovate. Leaf and stem surfaces have small fine hairs. Flowers are numerous, green, and crowded into finger-like spikes forming a long, dense terminal panicle, with axillary spikes below. The terminal spike is often lax. Perianth segments 5, lanceolate, acute, 2-3 mm long, subtended by bracteoles somewhat longer, about 4 mm, with a long, sharp tip, causing the inflorescence to feel distinctly prickly. Stamens 5. At maturity, the entire plant may be reddish in colour. Seeds are round, dark brown, shiny, somewhat flattened, and 1.0 to 1.5 mm in diameter.

Distribution

Top of page A. hybridus is a native riverbank pioneer of eastern North America and parts of Mexico, Central America and northern South America (Sauer, 1967). It is much more common in the eastern than the western half of the USA. Its range has expanded to Africa, south-central Asia and Australia, possibly because of its use as a green vegetable.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

BhutanPresentParker, 1992
IndiaPresentHolm et al., 1991
-Andaman and Nicobar IslandsPresentDagar et al., 1991
IndonesiaPresentHolm et al., 1991
JapanPresentHolm et al., 1991
JordanPresentAbu-Irmaileh, 1982
LebanonPresentHolm et al., 1991
PakistanPresentHolm et al., 1991
ThailandWidespreadHolm et al., 1991

Africa

BotswanaPresentWells et al., 1986
Côte d'IvoirePresent,
EgyptPresentTackholm, 1974
EthiopiaWidespreadHolm et al., 1991
GhanaPresent,
GuineaPresent,
KenyaWidespreadTownsend, 1985; Holm et al., 1991
LesothoPresentWells et al., 1986
MalawiPresentTownsend, 1988
MaliPresent,
MoroccoPresentHolm et al., 1991
MozambiquePresentTownsend, 1988
NamibiaPresentWells et al., 1986
NigeriaPresent, ; Holm et al., 1991
Sierra LeonePresent,
South AfricaWidespreadWells et al., 1986; Holm et al., 1991
SwazilandPresentWells et al., 1986
TanzaniaWidespreadTownsend, 1985; Holm et al., 1991
UgandaPresentTownsend, 1985
ZambiaWidespreadTownsend, 1988; Holm et al., 1991
ZimbabwePresentTownsend, 1988; Rambakudzibga, 1991

North America

CanadaPresentWeaver and McWilliams, 1980
-OntarioPresentWeaver and McWilliams, 1980
MexicoWidespreadHolm et al., 1991
USAWidespreadLorenzi and Jeffery, 1987; Holm et al., 1991
-ArkansasPresentde Lugo et al., 1995
-CaliforniaPresentHauptli and Jain, 1978
-ColoradoPresentAnderson, 1994
-GeorgiaPresentVencill and Banks, 1994
-HawaiiPresentHolm et al., 1991
-IllinoisPresentSimpson and Stoller, 1995
-KansasPresentChaisattapagon and Zhang, 1992
-KentuckyPresentScott et al., 1995
-MarylandPresentJordan, 1996
-MississippiPresentMcLean and Roy, 1991
-New JerseyPresentMajek et al., 1993
-New YorkPresentSenesac, 1985
-North CarolinaPresentYenish et al., 1996
-PennsylvaniaPresentHartzler and Roth, 1993
-South CarolinaPresentTedford and Fortnum, 1988
-TexasPresentGraham et al., 1988
-VirginiaPresentJordan, 1996
-WisconsinPresentBirschbach et al., 1993

Central America and Caribbean

Costa RicaPresentSalas, 1985
HondurasPresentPortillo et al., 1996

South America

ArgentinaWidespreadHolm et al., 1991
BrazilWidespreadHolm et al., 1991
-Espirito SantoPresentLorenzi, 1982
-GoiasPresentLorenzi, 1982
-Mato Grosso do SulPresentLorenzi, 1982
-Minas GeraisPresentLorenzi, 1982
-ParanaPresentLorenzi, 1982
-Rio Grande do SulPresentLorenzi, 1982; Ferreira et al., 1991
-Santa CatarinaPresentLorenzi, 1982
-Sao PauloPresentLorenzi, 1982
ChilePresentHolm et al., 1991
ColombiaWidespreadHolm et al., 1991
PeruWidespreadHolm et al., 1991
VenezuelaPresentMorros et al., 1990

Europe

AlbaniaPresentAellen and Akeroyd, 1993
AustriaPresentAellen and Akeroyd, 1993
BulgariaPresentAellen and Akeroyd, 1993
Czech RepublicPresentAellen and Akeroyd, 1993
FrancePresentAellen and Akeroyd, 1993
GermanyPresentAellen and Akeroyd, 1993
GreecePresentAellen and Akeroyd, 1993
HungaryPresentAellen and Akeroyd, 1993
ItalyPresentAellen and Akeroyd, 1993
PortugalPresentQueiros, 1989; Aellen and Akeroyd, 1993
-AzoresPresentAellen and Akeroyd, 1993
RomaniaPresentChirila and Pintilie, 1985; Aellen and Akeroyd, 1993
Russian FederationPresentAellen and Akeroyd, 1993
SpainPresentAellen and Akeroyd, 1993; Cavero et al., 1996
-Balearic IslandsPresentAellen and Akeroyd, 1993
SwitzerlandPresentAellen and Akeroyd, 1993
UKPresentAellen and Akeroyd, 1993
Yugoslavia (former)PresentAellen and Akeroyd, 1993

Oceania

AustraliaPresentHolm et al., 1991
-Australian Northern TerritoryPresentLazarides et al., 1997
-New South WalesPresentLazarides et al., 1997
-QueenslandPresentLazarides et al., 1997
-South AustraliaPresentLazarides et al., 1997
-TasmaniaPresentLazarides et al., 1997
-VictoriaPresentLazarides et al., 1997
-Western AustraliaPresentLazarides et al., 1997
New ZealandWidespreadHolm et al., 1991

Habitat

Top of page A. hybridus is found on a wide variety of soil types and textures. It is a common weed of cultivated fields, gardens, waste places, roadsides, riverbanks, and other open, disturbed habitats where annual weeds predominate. It is seldom found in closed or shaded communities (Weaver and McWilliams, 1980).

Hosts/Species Affected

Top of page A. hybridus is a common weed of many field and horticultural row crops throughout the temperate areas of the world.

Host Plants and Other Plants Affected

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Plant nameFamilyContext
Beta vulgaris (beetroot)ChenopodiaceaeMain
Capsicum (peppers)SolanaceaeOther
Glycine max (soyabean)FabaceaeMain
Gossypium (cotton)MalvaceaeMain
Nicotiana tabacum (tobacco)SolanaceaeOther
Phaseolus vulgaris (common bean)FabaceaeMain
Pisum sativum (pea)FabaceaeOther
Solanum tuberosum (potato)SolanaceaeOther
Sorghum bicolor (sorghum)PoaceaeMain
Triticum aestivum (wheat)PoaceaeOther
Zea mays (maize)PoaceaeMain

Biology and Ecology

Top of page A. hybridus is a summer annual herbaceous weed that reproduces solely by seed with maximum emergence in late spring or early summer (Weaver and McWilliams, 1980; Anderson, 1994). Plants which emerge in late May generally begin to flower in late July or early August, and produce ripe seed by the beginning of September (Weaver, 1984). Its small seeds are easily dispersed by wind, and germinate primarily from the top 2 cm of soil in disturbed habitats. Germination is stimulated by light and/or high temperatures, with greatest germination occurring at alternating temperatures of 20/35°C in the light (Weaver and McWilliams, 1980; Weaver, 1984).

A. hybridus possesses the C4 pathway of photosynthesis, a low carbon dioxide compensation point, little photorespiration, and its optimum temperature for net photosynthesis lies between 30 and 40°C (Patterson, 1976). Separate male and female flowers occur on the inflorescence, and pollination is generally by wind. A single vigorous plant may produce as many as 100,000 seeds. Seed longevity has not been reported, but seeds of the closely related species A. retroflexus and A. powellii, can remain viable for many years when buried in soil.

Natural enemies

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Natural enemyTypeLife stagesSpecificityReferencesBiological control inBiological control on
Albugo bliti Pathogen Leaves/Stems
Coleophora lineapuluella Herbivore Seeds
Coleophora versurella Herbivore Leaves
Contrachelus seniculus Herbivore Leaves
Erwinia rhapontici Pathogen Leaves
Herpetogramma bipunctalis Herbivore Leaves

Notes on Natural Enemies

Top of page A. hybridus is a host plant for a variety of insect pests and diseases which attack crops, however damage is rarely severe enough to serve as biological control.

Impact

Top of page A. hybridus is a principal weed in a variety of field and vegetable row crops, and has been reported to substantially reduce yields of maize, soyabeans, cotton, sugarbeet, sorghum and peas (Holm et al., 1977; Weaver and McWilliams, 1980). It can also reduce harvesting efficiency because of increased lodging of weed infested crops (Nave and Wax, 1971).

A. hybridus accumulates nitrates in its tissues and has caused poisoning of cattle (Ferreira et al., 1991).

A. hybridus is an alternative host for members of the parasitic nematode genus Meloidogyne and for tobacco mosaic tomabovirus (Holm et al., 1977; Tedford and Fortnum, 1988). It also serves as a host for Colletotrichum capsici, which causes anthracnose on tomato fruit and cotton seedlings (McLean and Roy, 1991).

Amaranthus species have been reported to cause allergic reactions in humans, primarily due to wind-borne pollen (Weber et al., 1978; Mitchell and Rook, 1979).

Uses

Top of page A. hybridus has been reported to be a highly nutritious herbage and a potentially valuable forage crop (Mugerwa and Bwabye, 1974). It is used as a green vegetable in parts of South Africa, India, Mexico and the southern USA (Holm et al., 1977; Sealy et al., 1990). Hauptli and Jain (1978) suggested that it could be used as breeding material for recombining desirable yield characteristics in the cultivated grain amaranths.

Uses List

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Animal feed, fodder, forage

  • Fodder/animal feed

Genetic importance

  • Related to

Human food and beverage

  • Vegetable

Medicinal, pharmaceutical

  • Traditional/folklore

Similarities to Other Species/Conditions

Top of page A. hybridus is similar in appearance to A. retroflexus and A. powellii, particularly in the vegetative state. Flowering plants of A. retroflexus differ in having shorter, thicker branches on the terminal inflorescence, sepals rounded or blunt and often reflexed, bracteoles less distinctly spiny. A. powelli also has a somewhat thicker inflorescence, the bracteoles are longer (up to 6 mm), and stamens usually 3, not 5.

A. caudatus and A. hypochondriacus are ornamental, domesticated plants, with larger terminal inflorescences, often bright red in colour, with a utricle equalling or exceeding the bract and sepals in length. The utricle of A. hybridus, A. retroflexus, and A. powellii is shorter than the bracts and sepals. The seeds of the weedy amaranths are usually dark brown, whereas many forms of the cultivated grain amaranths have ivory seeds.

Many other Amaranthus species are superficially similar. Of those included as data-sheets in this compendium, A. spinosus has spines, A. viridis has much smaller flowers, A. bitum has indented leaf tips, and A graecizans and A. blitoides have axillary inflorescences. Further species can occur as weeds on a local basis and reference to local floras is therefore recommended.

Prevention and Control

Top of page Cultural Control

Seedlings of A. hybridus can be controlled by cultivation, but older plants often recover from mechanical damage by producing axillary branches and inflorescences.

Chemical Control

A. hybridus is readily controlled by almost all the standard soil-applied and foliar-applied herbicides used for controling broadleaved weeds, including atrazine, simazine, metribuzin, linuron, bromoxynil, 2,4-D, dicamba, imazethapyr, thifensulfuron-methyl, rimsulfuron, nicosulfuron, acifluorfen, fomesafen and pendimethalin (Weaver and McWilliams, 1980; Manley et al., 1996; Robinson et al., 1996). Its pattern of intermittent germination throughout the growing season, however, make the application of residual soil-applied herbicides, or sequential post-emergence treatments, necessary in heavily infested fields. Lorenzi (1984) indicates that A. hybridus is only moderately susceptible to oxyfluorfen, butylate or vernolate.

Populations of A. hybridus resistant to triazine herbicides have been reported in the USA, France, Switzerland, Italy, Spain, Israel and South Africa (Heap, 1997). Populations resistant to the imidazolinone herbicides have been found in the USA (Heap, 1997).

Biological Control

Reputed biological control agents for A. hybridus are the pathogenic bacterium, Erwinia carotovora var. rhapontici [Erwinia rhapontici], (Gonzalez-Mendoza and Rodriguez, 1990), and insects Herpetogramma bipunctalis and Conotrachelus seniculus (Perez Panduro et al., 1990), all in Mexico.

References

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Abu-Irmaileh BE, 1982. Weeds of Jordan. Amman, Jordan: University of Jordan.

Aellen P; Akeroyd JR, 1993. Amaranthus L. In: Tutin TG, Burges NA, Chater AO, Edmondson JR, Heywood VH, Moore DM, Valentine DH, Walters SM, Webb DA, eds. Flora Europaea. Volume 1. Psilotaceae to Platanaceae. 2nd edition. Cambridge, UK: Cambridge University Press, 130-132.

Anderson RL, 1994. Characterizing weed community seedling emergence for a semiarid site in Colorado. Weed Technology, 8(2):245-249; 32 ref.

Birschbach ED; Myers MG; Harvey RG, 1993. Triazine-resistant smooth pigweed (Amaranthus hybridus) control in field corn (Zea mays L.). Weed Technology, 7(2):431-436

Brenan JPM, 1961. Amaranthus in Britain. Watsonia, 4:261-280.

Cavero J; Zaragoza C; Gil Ortega R, 1996. Tolerance of direct-seeded pepper (Capsicum annuum) under plastic mulch to herbicides. Weed Technology, 10(4):900-906; 26 ref.

Chaisattapagon C; Zhang NQ, 1992. Identifying effective criteria for weed detection using machine vision. Paper - American Society of Agricultural Engineers, No. 92-3576.

Chirila C; Pintilie C, 1985. The principal weeds and their control (XVIII). Wild pigweed (Amaranthus retroflexus L.), field pigweed (Amaranthus hybridus L.) and creeping pigweed (Amaranthus blitoides S. Wats.). Productia Vegetala, Cereale si Plante Tehnice, 37(7):28-31

Dagar JC; Gangwar B; Sharma AK, 1991. Distribution and integrated management of weeds in Bay Islands. Journal of the Andaman Science Association, 7(1-2):31-52.

Ferreira JLM; Riet-Correa F; Schild AL; Méndez MDC, 1991. Poisoning of cattle by Amaranthus spp. (Amaranthaceae) in Rio Grande de Sul, southern Brazil. Pesquisa Veterinária Brasileira, 11(3/4):49-54; 22 ref.

Gonzalez Mendoza L; Rodriguez MM de L, 1990. Isolation, identification and pathogenicity of bacteria of Amaranthus hybridus L. and possibilities of their biological control. Revista Chapingo, 15:67-68.

Graham PL; Steiner JL; Wiese AF, 1988. Light absorption and competition in mixed sorghum-pigweed communities. Agronomy Journal, 80(3):415-418

Grant WF, 1959. Cytogenetic studies in Amaranthus. III. Chromosome numbers and phylogenetic aspects. Canadian Journal of Genetics and Cytology, 1:313-328.

Hartzler RG; Roth GW, 1993. Effect of prior year's weed control on herbicide effectiveness in corn (Zea mays). Weed Technology, 7(3):611-614; 7 ref.

Hauptli H; Jain SK, 1978. Biosystematics and agronomic potential of some weedy and cultivated amaranths. Theoretical and Applied Genetics, 52(4):177-185

Heap IM, 1997. International Survey of Herbicide-Resistant Weeds. Annual Report, Weed Science Society of America.

Holm LG; Pancho JV; Herberger JP; Plucknett DL, 1991. A Geographic Atlas of World Weeds. Malabar, Florida, USA: Krieger Publishing Company.

Holm LG; Plucknett DL; Pancho JV; Herberger JP, 1977. The World's Worst Weeds. Distribution and Biology. Honolulu, Hawaii, USA: University Press of Hawaii.

Hutchinson J; Dalziel JM, 1954. Flora of West Tropical Africa, Volume 1, Part 1 (revised by Keay RWJ). London, UK: Crown Agents.

Jordan N, 1996. Effects of the triazine-resistance mutation on fitness in Amaranthus hybridus (smooth pigweed). Journal of Applied Ecology, 33(1):141-150; 32 ref.

Lazarides M; Cowley K; Hohnen P, 1997. CSIRO handbook of Australian weeds. CSIRO handbook of Australian weeds., vii + 264 pp.

Lorenzi H, 1982. Weeds of Brazil, terrestrial and aquatic, parasitic, poisonous and medicinal. (Plantas daninhas de Brasil, terrestres, aquaticas, parasitas, toxicas e medicinais.) Nova Odessa, Brazil: H. Lorenzi, 425 pp.

Lorenzi H, 1984. Manual de Identificacao e Controle de Plantas Danhinas. Odessa, Brazil: H. Lorenzi.

Lorenzi HJ; Jeffery LS(Editors), 1987. Weeds of the United States and their control. New York, USA; Van Nostrand Reinhold Co. Ltd., 355 pp.

Lugo Mde L; Gonzßlez A; Talbert RE, 1995. Smooth pigweed (Amaranthus hybrid[u]s L.) interference with snap bean (Phaseolus vulgaris L.) quality. Journal of Agriculture of the University of Puerto Rico, 79(3-4):173-179; 6 ref.

Majek BA; Neary PE; Polk DF, 1993. Smooth pigweed interference in newly planted peach trees. Journal of Production Agriculture, 6(2):244-246

Mamarot J; Rodriguez A, 1997. Sensibilité des Mauvaises Herbes aux Herbicides. 4th edition. Paris, France: Association de Coordination Technique Agricole.

Manley BS; Wilson HP; Hines TE, 1996. Smooth pigweed (Amaranthus hybridus) and livid amaranth (A. lividus) response to several imidazolinone and sulfonylurea herbicides. Weed Technology, 10(4):835-841; 22 ref.

McLean KS; Roy KW, 1991. Weeds as a source of Colletotrichum capsici causing anthracnose on tomato fruit and cotton seedlings. Canadian Journal of Plant Pathology, 13(2):131-134

Mitchell J; Rook A, 1979. Botanical Dermatology: plants and plant products injurious to the skin. Vancouver, Canada: Greengrass.

Morros ME; Trujillo B; Ponce M, 1990. Description of the genus Amaranthus L. with 3 new records for Venezuela and a key for the species. Ernstia, 58-59-60:45-51

Mugerwa JS; Bwabye R, 1974. Yield, composition and in vitro digestibility of Amaranthus hybridus subspecies incurvatus. Tropical Grasslands, 8:49-53.

Murray MJ, 1940. The genetics of sex determination in the family Amaranthaceae. Genetics, 25:409-431.

Nave WR; Wax LM, 1971. Effect of weeds on soybean yield and harvesting efficiency. Weed Science, 19:533-535.

Parker C, 1992. Weeds of Bhutan. Weeds of Bhutan., vi + 236 pp.

Patterson DT, 1976. C4 photosynthesis in smooth pigweed [Amaranthus hybridus]. Weed Science, 24(1):127-130

Perez Panduro A; Solis Aguilar JF; Trujillo Arriaga J; Romero Rosales F, 1990. Biological agents for population regulation of Tithonia tubaeformis (Jacq) Cass (Asteraceae), Amaranthus hybridus L. and A. spinosus L. (Amaranthaceae) in Chapingo, State of Mexico and Tecalitlan, Jalisco. Revista Chapingo, 15(67-68):126-129

Portillo HE; Pitre HN; Meckenstock DH; Andrews KL, 1996. Oviposition preference of Spodoptera latifascia (Lepidoptera: Noctuidae) for sorghum, maize and non-crop vegetation. Florida Entomologist, 79(4):552-562; 25 ref.

Queir=s M, 1989. Cytotaxonomic studies of Amaranthus in Portugal. Lazaroa, 11:9-17; 63 ref.

Rambakudzibga AM, 1991. Allelopathic effects of aqueous wheat (Triticum aestivum L.) straw extracts on the germination of eight arable weeds commonly found in Zimbabwe. Zimbabwe Journal of Agricultural Research, 29(1):77-79.

Robinson DK; Monks DW; Monaco TJ, 1996. Potato (Solanum tuberosum) tolerance and susceptibility of eight weeds to rimsulfuron with and without metribuzin. Weed Technology, 10(1):29-34; 11 ref.

Salas CA, 1985. Wheat in Costa Rica. Wheats for more tropical environments. A proceedings of the international symposium Mexico City, Mexico: CIMMYT, 46-50.

Sauer JD, 1967. The grain amaranths and their relatives: A revised taxonomic and geographic survey. Annals of the Missouri Botanic Garden, 54:103-137.

Scott JE; Weston LA; Jones RT, 1995. Clomazone for weed control in transplanted cole crops (Brassica oleracea). Weed Science, 43(1):121-127

Sealy RL; McWilliams EL; Novak J; Fong F; Kenerley CM; Simon JE, 1990. Vegetable amaranths: cultivar selection for summer production in the south. In: Janick J, ed. Advances in new crops. Proceedings of the First National Symposium 'New Crops: Research, Development, Economics', Indianapolis, USA. Oregon, USA: Timber Press, 396-398.

Senesac AF, 1985. Aspects of the biology and control of pigweed (Amaranthus spp.) in New York. Dissertation Abstracts International, B (Sciences and Engineering), 46(4):1007B

Simpson DM; Stoller EW, 1995. Response of sulfonylurea-tolerant soybean (Glycine max) and selected weed species to imazethapyr and thifensulfuron combinations. Weed Technology, 9(3):582-586

Tackholm V, 1974. Students' Flora of Egypt. 2nd edition. Cairo, Egypt: University of Cairo.

Tedford EC; Fortnum BA, 1988. Weed hosts of Meloidogyne arenaria and M. incognita common in tobacco fields in South Carolina. Annals of Applied Nematology, 2:102-105.

Townsend CC, 1985. Amaranthaceae. In: Polhill RM, ed. Flora of Tropical East Africa. Rotterdam, Netherlands: A.A. Balkema, 1-2, 20-24, 35-36.

Townsend CC, 1988. Amaranthaceae. In: Launert E, ed. Flora Zambesiaca. Volume 9, Part 1. London, UK: Flora Zambesiaca Management Committee, 28-133.

Tucker JM; Sauer JD, 1958. Aberrant Amaranthus populations of the Sacramento-San Joaquin Delta, California. Madrono, 14:252-261.

Vencill WK; Banks PA, 1994. Effects of tillage systems and weed management on weed populations in grain sorghum (Sorghum bicolor). Weed Science, 42(4):541-547

Weaver SE, 1984. Differential growth and competitive ability of Amaranthus retroflexus, A. powellii and A. hybridus. Canadian Journal of Plant Science, 64(3):715-724

Weaver SE; McWilliams EL, 1980. The biology of Canadian weeds. 44. Amaranthus retroflexus L., A. powellii S. Wats. and A. hybridus L. Canadian Journal of Plant Science, 60(4):1215-1234

Weber RW; Mansfield LE; Nelson HS, 1978. Cross-reactivity among weeds of the amaranth and chenopod families. Journal of Allergy and Clinical Immunology, 61:172.

Wells MJ; Balsinhas AA; Joffe H; Engelbrecht VM; Harding G; Stirton CH, 1986. A catalogue of problem plants in South Africa. Memoirs of the botanical survey of South Africa No 53. Pretoria, South Africa: Botanical Research Institute.

Yenish JP; Worsham AD; York AC, 1996. Cover crops for herbicide replacement in no-tillage corn (Zea mays). Weed Technology, 10(4):815-821; 19 ref.

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