Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Ageratum conyzoides
(billy goat weed)

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Datasheet

Ageratum conyzoides (billy goat weed)

Summary

  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Ageratum conyzoides
  • Preferred Common Name
  • billy goat weed
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • A. conyzoides is an annual erect herb reported as an invasive, noxious weed in agricultural lands and as a coloniser of open fields and degraded areas, causing crop yield reductions and affecting biodiversity (...

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Pictures

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PictureTitleCaptionCopyright
A. conyzoides seedlings.
TitleSeedlings
CaptionA. conyzoides seedlings.
Copyright©Chris Parker/Bristol, UK
A. conyzoides seedlings.
SeedlingsA. conyzoides seedlings.©Chris Parker/Bristol, UK
A. conyzoides is an erect, branching, annual herb with shallow, fibrous roots. The branched, terminal or axillary inflorescence bears 4-18 flower heads arranged in showy, flat-topped clusters.
TitleFlowering shoot
CaptionA. conyzoides is an erect, branching, annual herb with shallow, fibrous roots. The branched, terminal or axillary inflorescence bears 4-18 flower heads arranged in showy, flat-topped clusters.
Copyright©Chris Parker/Bristol, UK
A. conyzoides is an erect, branching, annual herb with shallow, fibrous roots. The branched, terminal or axillary inflorescence bears 4-18 flower heads arranged in showy, flat-topped clusters.
Flowering shootA. conyzoides is an erect, branching, annual herb with shallow, fibrous roots. The branched, terminal or axillary inflorescence bears 4-18 flower heads arranged in showy, flat-topped clusters. ©Chris Parker/Bristol, UK
A. conyzoides inflorescences.
TitleInflorescences
CaptionA. conyzoides inflorescences.
Copyright©Colin Wilson
A. conyzoides inflorescences.
InflorescencesA. conyzoides inflorescences.©Colin Wilson
Leaves of Ageratum conyzoides (a) and A. houstonianum (b).|Leaves of Ageratum conyzoides (a) and A. houstonianum (b). The leaves of A. conyzoides are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins.
TitleLeaves
CaptionLeaves of Ageratum conyzoides (a) and A. houstonianum (b).|Leaves of Ageratum conyzoides (a) and A. houstonianum (b). The leaves of A. conyzoides are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins.
Copyright©Chris Parker/Bristol, UK
Leaves of Ageratum conyzoides (a) and A. houstonianum (b).|Leaves of Ageratum conyzoides (a) and A. houstonianum (b). The leaves of A. conyzoides are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins.
LeavesLeaves of Ageratum conyzoides (a) and A. houstonianum (b).|Leaves of Ageratum conyzoides (a) and A. houstonianum (b). The leaves of A. conyzoides are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins.©Chris Parker/Bristol, UK
Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b).|Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b). Individual flower heads of A. conyzoides are light blue, white or violet, carried on 50-150 mm long peduncles, and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops.
TitleInflorescences
CaptionInflorescences of Ageratum conyzoides (a) and A. houstonianum (b).|Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b). Individual flower heads of A. conyzoides are light blue, white or violet, carried on 50-150 mm long peduncles, and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops.
Copyright©Chris Parker/Bristol, UK
Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b).|Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b). Individual flower heads of A. conyzoides are light blue, white or violet, carried on 50-150 mm long peduncles, and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops.
InflorescencesInflorescences of Ageratum conyzoides (a) and A. houstonianum (b).|Inflorescences of Ageratum conyzoides (a) and A. houstonianum (b). Individual flower heads of A. conyzoides are light blue, white or violet, carried on 50-150 mm long peduncles, and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops. ©Chris Parker/Bristol, UK

Identity

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Preferred Scientific Name

  • Ageratum conyzoides L.

Preferred Common Name

  • billy goat weed

Other Scientific Names

  • Ageratum album Willd. Ex Steud.
  • Ageratum arsenei B.L.Rob.
  • Ageratum ciliare L.
  • Ageratum conyzoides var hirtum (Lam.) DC.
  • Ageratum cordifolium Roxb.
  • Ageratum hirsutum Lam.
  • Ageratum hirtum Lam.
  • Ageratum humile Salisb.
  • Ageratum iltisii R.M.King & H.Rob
  • Ageratum latifolium Cav.
  • Ageratum microcarpum (Benth.) Hemsl.
  • Ageratum muticum Griseb.
  • Ageratum nanum Hort. Ex Sch. Bip.
  • Ageratum obtusifolium Lam.
  • Ageratum odoratum Vilm.
  • Ageratum suffruiticosum Regal
  • Alomia microcarpa (Benth.) B.L.Rob.
  • Cacalia mentrasto Vell.
  • Caelestina microcarpa Benth. ex Oerst.
  • Caelestina suffruticosa Sweet
  • Carelia brachystephana (Regel) Kuntze
  • Carelia conyzoides (L.) Kuntze
  • Carelia mutica (Griseb.) Kuntze
  • Eupatorium conyzoides (L.) E.H.Krause
  • Eupatorium paleaceum Sessé & Moc.
  • Sparganophorus obtusifolius Lag.

International Common Names

  • English: blue flowered groundsel; blue top; goat weed; mother brinkley; tropical ageratum; white weed; winter weed
  • Spanish: barba de chivo; catinga de bode; chuva; hierba del perro; hierba del zorro; hierbe de chivo
  • French: azier francois; baume blanc; baume mauve; bouton; bouton blan; bouton ble; eupatoire bleue; herbe a femme; herbe a pisser; herbe a sorcier; herbe de bouc; pain doux; petit pain doux; zerisson blanc
  • Chinese: hou xiang ji

Local Common Names

  • Brazil: agerato; camará apeba; camará iapó; camará japê; camara opela; catinga de barao; catingo do bode; erva de Santa Lucia; erva de Santa Maria; erva de Sao Joao; erva de Sao Jose; macela francesa; maria preta; mentrasto; pica roxo
  • Colombia: manrubio
  • Cuba: celestina azul; celestina blanca; lora; moratoria
  • Dominican Republic: rompezaragüey; yerba de chivo
  • East Africa: adwolo; gathenge (Kikuyu); kimavi cha kuku (Kiswahili)
  • El Salvador: hierba de perro; mejorana
  • Fiji: botekoro; mata mothemothe; mbotembotekoro; sogovanua; sogovanua; songovanua
  • French Guiana: azier francois; ponclit; radie francois; raguet-francois
  • French Polynesia: maire vaihi; miri
  • Gambia: gobu; jambo-serila
  • Germany: Leberbalsam, Dürrwurzähnlicher
  • Ghana: efoe momoe
  • Guam: mumutung
  • Guatemala: flor noble; mejoran chaparro; mejorana
  • Honduras: cola de alacrán; flor azul; garrapata; hierba de pollo; mozotillo; verbena
  • India: gundhaubon; mahakaua; neela phulnu
  • Indonesia: babadota; bandotan; berokan; dus-bedusan; wedusan
  • Italy: agerato; celestina
  • Japan: kakkoazami
  • Malaysia: herbe de bouc; rumput pereh jarang; rumput sekedok; ruput tahi-ayam; tahi anjing
  • Mauritius: herbe de bouc
  • Micronesia, Federated states of: amshiip; olloowaisiip; ololopon; omusiip; opolopon; oponupon; pokaniko; pwisehnkou; uárong nga lípesedj
  • Nauru: bwiyat tsige; bwiyat ziege
  • Netherlands: ageratum
  • Nigeria: imiesu; tamasondji bata
  • Niue: sekose sea; tekote tea
  • Palau: agmak; ngmak
  • Peru: huarmi
  • Philippines: asipukpuk; bahu-bahu; bahug-bahug; budbuda; bulak-manok; kakalding; kamabuag; kolokong-kabanyo; kulong-kogong-babae; singilan
  • Puerto Rico: mentastro; yerba de cabrío
  • Samoa: tae’oti
  • South Africa: bokkruid; indringer-ageratum; invading ageratum
  • Suriname: bokkeruid; bokki boontje; boko-boko-wiwiri; weti hedem; wetie ete; wit ede
  • Taiwan: hwo-hsiang-ji
  • Thailand: saapkaa; thiam mae haang; ya-sap-raeng; ya-tabsua
  • Tonga: te’ehosi
  • Uganda: nnamirembe
  • USA: kamabuag; tropic ageratum,
  • USA/Hawaii: maile hohono; maile honohono; maile kula
  • Vietnam: co cut-heo
  • Zambia: kabalakila; kafwaya; nthongola; ntongola
  • Zimbabwe: jerimani; nyani

EPPO code

  • AGECO (Ageratum conyzoides)

Summary of Invasiveness

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A. conyzoides is an annual erect herb reported as an invasive, noxious weed in agricultural lands and as a coloniser of open fields and degraded areas, causing crop yield reductions and affecting biodiversity (Kohli et al., 2006; GISD, 2016; PIER, 2016). It is also a host of pathogens and nematodes that affect crop species (BioNET-EAFRINET, 2016). It is listed as invasive throughout Asia; in Kenya, Mayotte, Morocco, Reunion, Tanzania, South Africa and Uganda in Africa; California (USA) in North America; Cuba in the Caribbean; Easter Island in South America; and in much of Oceania (Oviedo-Prieto et al., 2012; BioNET-EAFRINET, 2016; Encylopedia of Life, 2016; GISD, 2016; PIER, 2016).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Asterales
  •                         Family: Asteraceae
  •                             Genus: Ageratum
  •                                 Species: Ageratum conyzoides

Notes on Taxonomy and Nomenclature

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Ageratum comes from the Greek “a”, not, and “geras”, old age, in reference to the flowers lasting for a long time (Johnson, 1971). Ageratum ranges from Southeastern North America to Central America, but the centre of origin is in Central America and the Caribbean. A. conyzoides is the species designated by Linnaeus as the type for the genus (Johnson, 1971). The epithet conyzoides refers to the species' resemblance to the genus Conyza (Encyclopedia of Life, 2016).

Johnson (1971) recognized two subspecies of A. conyzoides between which there is a genetic barrier to cross fertilization. Although both are natives of South and Central America, the tetraploid (2 n = 40) A. conyzoides (L.) subsp. conyzoides, has been introduced as a weed pantropically. The diploid A. conyzoides (L.) subsp. latifolium (Cav.) M.F. Johnson is restricted to the Americas and some Caribbean Islands. 

The plant has a rank smell, likened in Australia to that of a male goat, hence the common name billy goat weed.

Description

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A. conyzoides is an erect, branching, annual herb with shallow, fibrous roots. It may, depending upon environmental conditions, reach 50-1500 mm tall at flowering. The stems, which may root where the bases touch the ground, are cylindrical, and become strong and woody with age; nodes and young parts of the stem are covered with short, white hairs. Leaves are opposite, 20-100 mm long, 5-50 mm wide, on hairy petioles 5-75 mm long, broadly ovate, with a rounded or narrowed acute base and an acute or obtuse or sometimes acuminate tip and toothed margins. Both leaf surfaces are sparsely hairy, rough with prominent veins and when crushed the leaves have a characteristic odour which is reminiscent of the male goat. The branched, terminal or axillary inflorescence bears 4-18 flower heads arranged in showy, flat-topped clusters. Individual flower heads are light blue, white or violet, are carried on 50-150 mm long peduncles and are 5 mm across, 4-6 mm long with 60-75 tubular flowers. The flower head is surrounded by two or three rows of oblong bracts which are green with pale or reddish-violet tops. The bracts are 3-5 mm high, outer ones 0.5-1.75 mm wide, sparsely hairy, evenly toothed in the upper part, with an abruptly acuminate, acute tip. Flowers are 1.5-3 mm long and scarcely protrude above the bracts. The fruit is a ribbed or angled, black achene, 1.25-2 mm long, roughly hairy, with a pappus of 5, rarely 6, rough bristles, white to cream coloured, 1.5-3 mm long with upward turning spines.

Plant Type

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Broadleaved
Herbaceous
Seed propagated

Distribution

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Native to South and Central America, A. conyzoides is a common pantropical weed that can extend into subtropical and temperate zones where it grows during the summer or as an ornamental (Encyclopedia of Life, 2016; Greuter, 2016). Its native range is not clear, but includes parts of South and Central America and probably the West Indies (Johnson, 1971; Acevedo-Rodríguez and Strong, 2012; PROTA; 2016). It has been recognized as an ornamental and in cultivated crops in Europe since before 1697 (Johnson, 1971). The species is now found in Asia, Africa, North America, Central America, the Caribbean, South America, Europe and Oceania (See Distribution Table for details; Acevedo-Rodríguez and Strong, 2012; PROTA, 2016; PIER, 2016; Missouri Botanical Garden, 2016). Its distribution is perhaps more extensive than currently published because the species is also used as an ornamental. Some records of A. conyzoides, for example in the USA, are probably escapes from cultivation.

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

BangladeshPresentIntroduced Invasive GISD, 2016
BhutanWidespreadIntroduced Not invasive Parker, 1992
Brunei DarussalamPresentIntroduced Not invasive Waterhouse, 1993; GISD, 2016
CambodiaPresentIntroduced Not invasive Holm et al., 1979; Waterhouse, 1993; PIER, 2016
Chagos ArchipelagoPresentIntroduced Invasive PIER, 2016Diego Garcia Island
ChinaPresentIntroduced Not invasive Holm et al., 1979; Wang, 1990
-AnhuiPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-FujianPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-GuangdongPresentIntroduced Not invasive Liang et al., 1994; Flora of China Editorial Committee, 2016
-GuangxiPresentIntroduced Not invasive Pu et al., 1990; Flora of China Editorial Committee, 2016
-GuizhouPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-HainanPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-HebeiPresent only in captivity/cultivationIntroducedFlora of China Editorial Committee, 2016
-HenanPresentIntroducedFlora of China Editorial Committee, 2016; Flora of China Editorial Committee, 2016Naturalized
-Hong KongPresentIntroduced Not invasive Holm et al., 1979
-HunanPresentIntroduced Not invasive Zhou et al., 1994
-JiangsuPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-JiangxiPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-ShaanxiPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-SichuanPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-YunnanPresentIntroducedFlora of China Editorial Committee, 2016Naturalized
-ZhejiangPresent only in captivity/cultivationNativeFlora of China Editorial Committee, 2016
Christmas Island (Indian Ocean)PresentIntroduced Invasive PIER, 2016
Georgia (Republic of)Present, few occurrencesIntroducedGreuter, 2016adventitious (casual)
IndiaPresentIntroduced Not invasive Holm et al., 1979; IRRI, 1989
-Andaman and Nicobar IslandsPresentIntroduced Not invasive Salam, 1991
-Andhra PradeshPresentIntroduced Not invasive Mahmood, 1990
-AssamPresentIntroduced Not invasive Saikia and Sarma, 1996
-BiharPresentIntroduced Not invasive Rafey and Prasad, 1995
-GujaratPresentIntroducedPROTA, 2016
-Himachal PradeshPresentIntroduced Not invasive Angiras and Rana, 1995
-Indian PunjabPresentIntroduced Not invasive Cheema, 1991
-KarnatakaPresentIntroduced Not invasive Sridhara et al., 1995
-KeralaPresentIntroduced Not invasive Kamalam and Bridgit, 1993
-Madhya PradeshPresentIntroduced Not invasive Singh and Bajpai, 1994; Agrawal et al., 1995
-MaharashtraPresentIntroduced Not invasive Ghate, 1991
-ManipurPresentIntroducedPROTA, 2016
-MeghalayaPresentIntroduced Not invasive Raj and Singh Patel, 1992
-NagalandPresentIntroduced Not invasive Sharma et al., 1994
-OdishaPresentIntroduced Not invasive Mishra and Bhol, 1996
-SikkimPresentIntroduced Not invasive Singh, 1992
-Tamil NaduPresentIntroduced Not invasive Rajamani et al., 1992
-Uttar PradeshPresentIntroduced Not invasive Singh and Ram, 1990
-West BengalPresentIntroduced Not invasive Kabir et al., 1991
IndonesiaPresentIntroduced Not invasive Holm et al., 1979; IRRI, 1989; Waterhouse, 1993; PIER, 2016
-JavaPresentIntroduced Not invasive Everaarts, 1981
-MoluccasPresentIntroducedPROTA, 2016
-Nusa TenggaraPresentIntroducedPROTA, 2016
-SulawesiPresentIntroducedPROTA, 2016
-SumatraPresentIntroduced Not invasive Nasution, 1984
JapanPresentIntroduced Not invasive Holm et al., 1979
-Bonin IslandPresentIntroduced Invasive PIER, 2016
-Ryukyu ArchipelagoPresentIntroduced Not invasive Reed, 1977
JordanPresentIntroducedGreuter, 2016
Korea, DPRPresentIntroduced Invasive GISD, 2016Established
Korea, Republic ofPresentIntroduced Not invasive Kang et al., 1996
LaosPresentIntroduced Not invasive IRRI, 1989; Waterhouse, 1993; Roder et al., 1997
LebanonPresentIntroducedPROTA, 2016
MalaysiaWidespreadIntroduced Not invasive Barnes and Chandapillai, 1972; IRRI, 1989; Waterhouse, 1993
-Peninsular MalaysiaPresentIntroducedPROTA, 2016
-SabahPresentIntroduced Not invasive Holm et al., 1979
-SarawakPresentIntroducedPROTA, 2016
MaldivesPresentIntroducedPIER, 2016
MyanmarPresentIntroduced Not invasive Waterhouse, 1993
NepalPresentIntroduced Not invasive Holm et al., 1979; Ranjit and Bhattarai, 1988; IRRI, 1989; Poudyal and Adhikari, 2013
PakistanPresentIntroduced Not invasive Holm et al., 1979
PhilippinesWidespreadIntroduced Not invasive Pancho et al., 1969; Moody et al., 1984; IRRI, 1989; Waterhouse, 1993
Saudi ArabiaPresentIntroducedPROTA, 2016
SingaporePresentIntroduced Invasive Waterhouse, 1993; Chong et al., 2009
Sri LankaPresentIntroduced Not invasive Holm et al., 1979; IRRI, 1989; Scheldeman et al., 1995
TaiwanPresentIntroducedHolm et al., 1979; Flora of China Editorial Committee, 2016Cultivated and naturalized
ThailandPresentIntroduced Not invasive Holm et al., 1979; IRRI, 1989; Waterhouse, 1993; PIER, 2016
VietnamPresentIntroduced Not invasive Holm et al., 1979; IRRI, 1989; Waterhouse, 1993; PIER, 2016

Africa

AngolaPresentIntroduced Not invasive Holm et al., 1979
BeninPresentIntroduced Not invasive Ahanchede and Gasquez, 1997
BotswanaPresentIntroduced Not invasive Wells et al., 1986
Burkina FasoPresentIntroducedRoyal Museum for Central Africa, 2016
BurundiPresentIntroducedMissouri Botanical Garden, 2016
CameroonPresentIntroduced Not invasive Ngouajio & Daelemans, 1993; Adams, 1963; Holm et al., 1979
Cape VerdePresentIntroducedPROTA, 2016
Central African RepublicPresentIntroducedMissouri Botanical Garden, 2016
ComorosPresentIntroducedRoyal Museum for Central Africa, 2016
Congo Democratic RepublicPresentIntroduced Not invasive Holm et al., 1979; Missouri Botanical Garden, 2016
Côte d'IvoirePresentIntroduced Not invasive Adams, 1963; Holm et al., 1979
EgyptPresentIntroduced Not invasive Holm et al., 1979; Boulos and El Hadidi, 1984
Equatorial GuineaPresentIntroduced Not invasive Adams, 1963
EthiopiaPresentIntroduced Not invasive Holm et al., 1979
GabonPresentIntroducedMissouri Botanical Garden, 2016
GambiaPresentIntroduced Not invasive Adams, 1963; Jones, 1994
GhanaPresentIntroduced Not invasive Adams, 1963
GuineaPresentIntroduced Not invasive Adams, 1963; Holm et al., 1979
KenyaPresentIntroduced Invasive Holm et al., 1979; BioNET-EAFRINET, 2016
LiberiaPresentIntroduced Not invasive Adams, 1963; Holm et al., 1979
MadagascarPresentIntroducedMissouri Botanical Garden, 2016
MalawiWidespreadIntroduced Not invasive Holm et al., 1979; Banda and Morris, 1985
MaliPresentIntroduced Not invasive Adams, 1963; Holm et al., 1979
MauritiusPresentIntroduced Not invasive Holm et al., 1979; McIntyre, 1991; PIER, 2016
MayottePresentIntroduced Invasive PIER, 2016
MoroccoPresentIntroduced Invasive Royal Museum for Central Africa, 2016
MozambiquePresentIntroduced Not invasive Johnson, 1971; Grabandt, 1985
NigeriaPresentIntroduced Not invasive Adams, 1963; Holm et al., 1979; Enyinnia, 1992
RéunionPresentIntroduced Invasive PIER, 2016
Rodriguez IslandPresentIntroducedPROTA, 2016
RwandaPresentIntroduced Not invasive Johnson, 1971
Saint HelenaPresentIntroduced Not invasive Reed, 1977
Sao Tome and PrincipePresentIntroducedPROTA, 2016
SenegalPresentIntroduced Not invasive Adams, 1963; Berhaut, 1967; Holm et al., 1979
SeychellesPresentIntroduced Not invasive Robertson, 1989
Sierra LeonePresentIntroduced Not invasive Adams, 1963
South AfricaPresentIntroduced Not invasive Holm et al., 1979; Grabandt, 1985; Invasive Species South Africa, 2016
SudanPresentIntroduced Not invasive Bebawi and Neugebohrn, 1991
SwazilandPresentIntroduced Not invasive Grabandt, 1985
TanzaniaPresentIntroduced Invasive Holm et al., 1979; BioNET-EAFRINET, 2016; Missouri Botanical Garden, 2016
TogoPresentIntroducedPROTA, 2016
UgandaPresentIntroduced Not invasive Lind and Tallantire, 1962; Holm et al., 1979; BioNET-EAFRINET, 2016
ZambiaPresentIntroduced Not invasive Vernon, undated
ZimbabwePresentIntroduced Not invasive Holm et al., 1979; Drummond, 1984

North America

MexicoWidespreadNativeJohnson, 1971; Missouri Botanical Garden, 2016Chiapas, Chihuahua, Hidalgo, Jalisco, Michoacán, Morelos, Nayarit, Nuevo León, Oaxaca, Puebla, Quintana Roo, Tabasco, Veracruz, Yucatán
USAPresentIntroduced Not invasive Holm et al., 1979
-AlabamaPresentIntroduced Not invasive USDA-NRCS, 2004; Diamond, 2015
-CaliforniaPresentIntroduced Not invasive USDA-NRCS, 2004; PIER, 2016
-ConnecticutPresentIntroduced Not invasive USDA-NRCS, 2004
-FloridaPresentIntroduced Not invasive Reed, 1977
-GeorgiaPresentIntroduced Not invasive USDA-NRCS, 2004
-HawaiiPresentIntroduced Invasive Holm et al., 1979; PIER, 2016Invasive in Hawai’i, Kaho’olawe, Kaua’i, Lana’i, Maui, Moloka’I, Ni’ihau and O’ahu Islands
-KentuckyPresentIntroducedUSDA-NRCS, 2016
-LouisianaPresentIntroduced Not invasive USDA-NRCS, 2016
-MarylandPresentIntroduced Not invasive USDA-NRCS, 2004
-MississippiPresentIntroduced Not invasive USDA-NRCS, 2004
-MissouriPresentIntroduced Not invasive USDA-NRCS, 2004
-North CarolinaPresentIntroduced Not invasive Reed, 1977

Central America and Caribbean

AnguillaPresentIntroduced Not invasive Fournet and Hammerton, 1991
Antigua and BarbudaPresentIntroduced Not invasive Fournet and Hammerton, 1991
BahamasPresentIntroduced Not invasive Johnson, 1971
BarbadosPresentIntroduced Not invasive Fournet and Hammerton, 1991
BelizePresentNativeMissouri Botanical Garden, 2016
British Virgin IslandsPresentNativeAcevedo-Rodriguez and Strong, 2012
Cayman IslandsPresentNativeAcevedo-Rodriguez and Strong, 2012
Costa RicaPresentIntroduced Not invasive Holm et al., 1979; Missouri Botanical Garden, 2016
CubaPresentIntroduced Invasive Holm et al., 1979; Acevedo-Rodriguez and Strong, 2012; Oviedo Prieto et al., 2012
DominicaPresentIntroduced Not invasive Fournet and Hammerton, 1991
Dominican RepublicPresentNativeHolm et al., 1979; Acevedo-Rodriguez and Strong, 2012
El SalvadorPresentNativeHolm et al., 1979; Missouri Botanical Garden, 2016Ahuachapán, La Libertad, Santa Ana
GrenadaPresentIntroduced Not invasive Fournet and Hammerton, 1991
GuadeloupePresentIntroduced Not invasive Fournet and Hammerton, 1991
GuatemalaPresentNativeJohnson, 1971; Missouri Botanical Garden, 2016Alta Verapaz, Chiqumula, Escuintla, Huehuetenango, Izabal, Jalapa, Jutiapa, Petén, Quetzaltenango, Retalhuleu, Sacatepéquez, San Marcos, Santa Rosa, Sololá, Sichitequepéz, Zacapa.
HaitiPresentNativeJohnson, 1971; Acevedo-Rodriguez and Strong, 2012
HondurasPresentNativeJohnson, 1971; Missouri Botanical Garden, 2016Comayagua, Francisco Morazán, Gracias a Dios, La Paz, Ocotepeque
JamaicaPresentIntroducedAcevedo-Rodriguez and Strong, 2012; Missouri Botanical Garden, 2016
MartiniquePresentIntroduced Not invasive Fournet and Hammerton, 1991
MontserratPresentIntroduced Not invasive Fournet and Hammerton, 1991
Netherlands AntillesPresentIntroduced Not invasive Fournet and Hammerton, 1991
NicaraguaWidespreadNativeHolm et al., 1979; Missouri Botanical Garden, 2016Atlántico Norte, Atlántio Sur, Boaco, Carazo, Chinandega, Chontales, Estelí, Jinotega, León, Madriz, Managua, Masaya, Matagalpa, Nueva Segovia, Río San Juan
PanamaPresentNativeJohnson, 1971; Missouri Botanical Garden, 2016Bocas del Toro, Canal Area, Chiriquí, Coclé, Darién, Panamá
Puerto RicoPresentNativeJohnson, 1971; Acevedo-Rodriguez and Strong, 2012Vieques
Saint Kitts and NevisPresentIntroduced Not invasive Fournet and Hammerton, 1991
Saint LuciaPresentNativePROTA, 2016
Saint Vincent and the GrenadinesPresentIntroduced Not invasive Fournet and Hammerton, 1991
Trinidad and TobagoPresentIntroduced Not invasive Kasasian, 1964; Holm et al., 1979; Fournet and Hammerton, 1991
United States Virgin IslandsPresentNativePIER, 2004; Acevedo-Rodriguez and Strong, 2012St. Croix, St. John, St. Thomas

South America

ArgentinaPresentNativeJohnson, 1971; Missouri Botanical Garden, 2016Corrientes, Jujuy, Misiones, Salta, Tucumán
BoliviaPresentNative Not invasive Gonzales and Webb, 1989; Missouri Botanical Garden, 2016
BrazilPresentNative Not invasive Holm et al., 1979
-AcrePresentNativeFlora do Brasil, 2016
-AlagoasPresentNative Not invasive Lorenzi, 1982
-AmapaPresentNativeFlora do Brasil, 2016
-AmazonasPresentNative Not invasive Lorenzi, 1982
-BahiaPresentNative Not invasive Lorenzi, 1982
-CearaPresentNative Not invasive Lorenzi, 1982
-Espirito SantoPresentNative Not invasive Lorenzi, 1982
-Fernando de NoronhaPresentNative Not invasive Lorenzi, 1982
-GoiasPresentNative Not invasive Lorenzi, 1982
-MaranhaoPresentNative Not invasive Lorenzi, 1982
-Mato GrossoPresentNative Not invasive Lorenzi, 1982
-Mato Grosso do SulPresentNative Not invasive Lorenzi, 1982
-Minas GeraisPresentNative Not invasive Lorenzi, 1982
-ParaPresentNative Not invasive Lorenzi, 1982
-ParaibaPresentNative Not invasive Lorenzi, 1982
-ParanaPresentNative Not invasive Lorenzi, 1982
-PernambucoPresentNative Not invasive Lorenzi, 1982
-PiauiPresentNative Not invasive Lorenzi, 1982
-Rio de JaneiroPresentNative Not invasive Lorenzi, 1982
-Rio Grande do NortePresentNative Not invasive Lorenzi, 1982
-Rio Grande do SulPresentNative Not invasive Lorenzi, 1982
-RondoniaPresentNative Not invasive Lorenzi, 1982
-RoraimaPresentNativeFlora do Brasil, 2016
-Santa CatarinaPresentNative Not invasive Lorenzi, 1982
-Sao PauloWidespreadNative Not invasive Lorenzi, 1982
-SergipePresentNative Not invasive Lorenzi, 1982
ChilePresentNative Not invasive Johnson, 1971
-Easter IslandPresentIntroduced Invasive PIER, 2016
ColombiaPresentNativeHolm et al., 1979; Missouri Botanical Garden, 2016Antioquia, Chocó, Huila, Meta, Nariño, Putumayo, Santander, Valle del Cauca
EcuadorPresentNative Not invasive Holm et al., 1979
French GuianaPresentNative Not invasive Johnson, 1971
GuyanaPresentNative Not invasive Johnson, 1971
ParaguayWidespreadNativeMissouri Botanical Garden, 2016Amambay, Caazapá, Canindeyú, Central, Cordillera, Guairá, Itapúa, Paraguarí, San Pedro
PeruPresentNative Not invasive Alva, 1973; Holm et al., 1979; Missouri Botanical Garden, 2016
SurinamePresentNative Not invasive Holm et al., 1979
VenezuelaPresentNativeHolm et al., 1979; Missouri Botanical Garden, 2016Apure, Aragua, Barinas, Bolívar, Distrito Federal, Falcón, Lara, Mérida, Miranda, Sucre, Táchira, Trujillo, Zulia.

Europe

Bosnia-HercegovinaPresent only in captivity/cultivationIntroducedGreuter, 2016
BulgariaPresent only in captivity/cultivationIntroducedGreuter, 2016
FrancePresentIntroduced Not invasive Reed, 1977
GermanyUnconfirmed recordIntroducedGreuter, 2016Presence questionable
ItalyPresent, few occurrencesIntroducedGreuter, 2016adventitious (casual)
PortugalPresentPresent based on regional distribution.
-MadeiraPresentIntroducedPROTA, 2016An occasional garden escape
SpainPresentIntroducedGISD, 2016
SwedenPresentIntroducedGISD, 2016
UKPresent only in captivity/cultivationIntroducedPROTA, 2016

Oceania

American SamoaPresentIntroduced Not invasive Waterhouse, 1997
AustraliaPresentIntroduced Not invasive Holm et al., 1979
-Australian Northern TerritoryPresentIntroduced Not invasive Auld and Medd, 1992
-New South WalesPresentIntroduced Not invasive Auld and Medd, 1992
-QueenslandPresentIntroduced Not invasive Auld and Medd, 1992; PIER, 2016
Cook IslandsPresentIntroduced Not invasive Waterhouse, 1997
FijiWidespreadIntroduced Not invasive Parham, 1958; Holm et al., 1979; Waterhouse, 1997; PIER, 2016
French PolynesiaPresentIntroduced Not invasive Waterhouse, 1997; PIER, 2016
GuamPresentIntroduced Not invasive Waterhouse, 1997; PIER, 2016
KiribatiPresentIntroducedGISD, 2016
Marshall IslandsPresentIntroduced Invasive PIER, 2016Also cultivated
Micronesia, Federated states ofPresentIntroduced Invasive PIER, 2016Invasive in Puluwat Atoll, Kosrae and Pohnpei Islands
NauruPresentIntroduced Invasive PIER, 2016
New CaledoniaWidespreadIntroduced Not invasive Waterhouse, 1997; PIER, 2016
NiuePresentIntroduced Not invasive Waterhouse, 1997; PIER, 2016
Norfolk IslandPresentIntroduced Invasive PIER, 2016
Northern Mariana IslandsPresentIntroduced Invasive PIER, 2016Agrigan, Alamagan, Anatahan, Guguan, Pagan and Sarigan Islands
PalauPresentIntroduced Invasive PIER, 2016Angaur, Babeldaob,Koror, Malakal, Ngerkebesang and Ngchus Islands.
Papua New GuineaPresentIntroduced Not invasive Waterhouse, 1997
SamoaPresentIntroduced Not invasive Whistler, 1983; Sauerborn and Sauerborn, 1984; Waterhouse, 1997; PIER, 2016
Solomon IslandsPresentIntroduced Not invasive Waterhouse, 1997; GISD, 2016
TongaPresentIntroduced Not invasive Whistler, 1983; Waterhouse, 1997; PIER, 2016
VanuatuPresentIntroduced Not invasive Waterhouse, 1997
Wallis and Futuna IslandsPresentIntroduced Invasive PIER, 2016

History of Introduction and Spread

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A. conyzoides is regarded as the first Ageratum cultivated in Europe, found in Belgium before 1697 (Johnson, 1971). Other early cultivation records are in England (UK) prior to 1714 and in Sweden by 1748 (Johnson, 1971). In was introduced to the Philippines after being carried on galleons sailing from Mexico to Manila (Johnson, 1971).

Although the species had been recorded before the 1940s in East Africa, it appears to have become more common between 1960 and 1980 (Stadler et al., 1998). This regional spread is correlated with intensification in arable agriculture. Early records were restricted to higher altitudes but with the increasing human population and the associated increase of agricultural activities (e.g. irrigation in arid areas) the weed was able to spread to lower altitudes. The weed has also become dominant on upland maize fields in Vietnam as the length of fallows has declined in recent years with increasing population pressure (Wezel, 2000). The spread had been facilitated by the seeds being readily dispersed on clothing or other items of the traveler and garden escapes having established and formed weedy populations in open cultivated areas.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Belgium Before 1697 Horticulture (pathway cause) No No Johnson (1971)
Sweden 1748 Horticulture (pathway cause) No No Johnson (1971)
UK 1714 Horticulture (pathway cause) No No Johnson (1971)

Risk of Introduction

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A. conyzoides is a pantropical herb with a high risk of introduction.  It is a common, undesirable weed of agricultural lands along most of its introduced range, and also extensively used as an ornamental (GISD, 2016). It is easily transported as a contaminant in grains, soil, clothes and machinery; all facilitating its unintentional introduction and spread (BioNET-EAFRINET, 2016). Its use as an ornamental also contributes to the species expanding its range.   

Habitat

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A. conyzoides grows in grasslands, forests, wastelands, clearings, roadsides, riparian zones, wetlands, coastal dunes, degraded pastures and rapidly colonizes cultivated areas on both light and heavy soils (BioNET-EAFRINET, 2016; PIER, 2016; PROTA, 2016). It occurs as a major to intermediate weed of frequently disturbed areas, such as vegetables and other cultivated crops, pastures (especially when overgrazed), plantations, orchards and roadsides. It can be found in wide-spaced annual row crops and permanent tree crops. It has a facultative wetland and facultative upland wetland indicator status in the USA (USDA-NRCS, 2016); indicating that the species can occur in wetland and non-wetland areas.

Habitat List

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CategoryHabitatPresenceStatus
Littoral
Coastal areas Present, no further details Harmful (pest or invasive)
Terrestrial-managed
Cultivated / agricultural land Present, no further details Harmful (pest or invasive)
Disturbed areas Present, no further details Harmful (pest or invasive)
Managed forests, plantations and orchards Present, no further details Harmful (pest or invasive)
Rail / roadsides Present, no further details Natural
Urban / peri-urban areas Present, no further details Natural
Terrestrial-natural/semi-natural
Natural forests Present, no further details Harmful (pest or invasive)
Natural grasslands Present, no further details Harmful (pest or invasive)
Riverbanks Present, no further details Harmful (pest or invasive)
Riverbanks Present, no further details Natural
Wetlands Present, no further details Harmful (pest or invasive)
Wetlands Present, no further details Natural

Hosts/Species Affected

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A. conyzoides is a common weed of plantation crops and overgrazed pastures but can also be found in the important tropical and subtropical annual crops of rainfed or irrigated dryland systems. It has been reported from 36 different crops in 46 countries (Holm et al., 1977).

Biology and Ecology

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Genetics

The chromosome number reported for A. conyzoides is 2n=40 (PROTA, 2016). DNA barcode information for the species is available at the Barcode of Life Data Systems (BOLDS, 2016).  

Reproductive Biology

A. conyzoides has no photoperiodic requirement. It is self-incompatible and pollinated by insects, producing up to 40,000 seeds per plant (GISD, 2016; PROTA, 2016). Seeds are dispersed by wind and water (Baker, 1965). A. conyzoides does not possess any marked dormancy (Sauerborn, 1985) but requires light for germination (Sauerborn et al., 1988) and is therefore unable to germinate when buried below the soil surface. Optimum germination has been noted at 20°C but will occur in the range of 15 to 30°C. The lower limit allows it to thrive at higher altitudes. Seed viability is often lost within 12 months (Marks and Nwachuku, 1986).

Physiology and Phenology

A. conyzoides can complete its life cycle in less than 2 months. Although it can flower when less than two true leaves have expanded, it is more commonly seen in favourable conditions as a well-branched plant up to 90 cm tall with hundreds of flower heads (Holm et al., 1977).

Ecology

A. conyzoides  thrives best in rich, moist, mineral soils, and will not grow in the shade (PROTA, 2016). It grows particularly well where soil fertility is high, with dense populations developing when fertilizer is used (Marnotte, 1984). Although preferring a moist habitat, it also grows in dry areas. The drier and less fertile conditions typical of Pacific atolls do not suit the plant so well (PIER, 2004). It is reported at altitudes from sea level to about 2500 m (PROSEA, 2016). 

Climate

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ClimateStatusDescriptionRemark
Af - Tropical rainforest climate Preferred > 60mm precipitation per month
Am - Tropical monsoon climate Preferred Tropical monsoon climate ( < 60mm precipitation driest month but > (100 - [total annual precipitation(mm}/25]))
As - Tropical savanna climate with dry summer Preferred < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Preferred < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
BS - Steppe climate Tolerated > 430mm and < 860mm annual precipitation
BW - Desert climate Tolerated < 430mm annual precipitation
Cf - Warm temperate climate, wet all year Tolerated Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Tolerated Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Tolerated Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
55 43

Air Temperature

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Parameter Lower limit Upper limit
Mean annual temperature (ºC) 20 26
Mean maximum temperature of hottest month (ºC) 28 30
Mean minimum temperature of coldest month (ºC) 2 23

Rainfall

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ParameterLower limitUpper limitDescription
Dry season duration46number of consecutive months with <40 mm rainfall
Mean annual rainfall5603590mm; lower/upper limits

Rainfall Regime

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Summer

Soil Tolerances

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Soil drainage

  • free
  • seasonally waterlogged

Soil reaction

  • acid
  • alkaline
  • neutral

Soil texture

  • heavy
  • light
  • medium

Notes on Natural Enemies

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Following a review of natural enemies for A. conyzoides, Waterhouse (1994) provided a long list of insects and pathogens. However, almost all were polyphagous and many were pests of useful plants. Holm et al. (1977) list a number of pathogens and nematodes that have been isolated from A. conyzoides. There is no evidence that these cause significant damage, unlike virus infections, particularly Bidens Mottle Virus (Logan and Zettler, 1984), which can be a problem where A. conyzoides is used for garden bedding. Microcephalothrips abdominalis, which is a vector of the Tobacco Streak Virus, has also been seen affecting A. conyzoides (Sánchez-Monge et al., 2011).

Means of Movement and Dispersal

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Natural Dispersal (Non-Biotic)

Seeds are dispersed by wind and water (Baker, 1965).

Vector Transmission (Biotic)

A.  conyzoides seeds are dispersed on the hairs of animals, and attached to clothes and agricultural machinery (BioNET-EAFRINET, 2016).

Accidental Introduction

The species has been reported as a contaminant of garden waste and crops (BioNET-EAFRINET, 2016; PROTA, 2016). It is also accidentally dispersed on clothes and agricultural machinery (BioNET-EAFRINET, 2016). In Yunnan, China, density in correlated with distance from roads, suggesting that primary colonization in this area occurs along road margins (GISD, 2016).

Intentional Introduction

A. conyzoides has been reported as introduced as an ornamental plant in some of its range (Johnson, 1971; BioNET-EAFRINET, 2016

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Crop productionWeed in agricultural lands Yes PROTA, 2016
DisturbanceWeed of disturbed sites Yes PROTA, 2016
Garden waste disposal Yes Yes BioNET-EAFRINET, 2016
HorticultureIntroduced as an ornamental Yes Yes PROTA, 2016
Internet sales Yes Yes
Medicinal useUsed in ethnobotany over its range Yes Yes PROTA, 2016
Ornamental purposesUsed as an ornamental over its range. Yes Yes PROTA, 2016

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Clothing, footwear and possessionsDispersed by attaching to clothes. Yes BioNET-EAFRINET, 2016
Machinery and equipmentDispersion by attaching to agricultural machinery. Yes BioNET-EAFRINET, 2016
Water Yes Baker, 1965
Wind Yes Baker, 1965

Plant Trade

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Plant parts liable to carry the pest in trade/transportPest stagesBorne internallyBorne externallyVisibility of pest or symptoms
True seeds (inc. grain) Pest or symptoms not visible to the naked eye but usually visible under light microscope
Plant parts not known to carry the pest in trade/transport
Bark
Bulbs/Tubers/Corms/Rhizomes
Flowers/Inflorescences/Cones/Calyx
Fruits (inc. pods)
Growing medium accompanying plants
Leaves
Roots
Seedlings/Micropropagated plants
Stems (above ground)/Shoots/Trunks/Branches
Wood

Wood Packaging

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Wood Packaging not known to carry the pest in trade/transport
Loose wood packing material
Non-wood
Processed or treated wood
Solid wood packing material with bark
Solid wood packing material without bark

Impact Summary

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CategoryImpact
Animal/plant collections None
Animal/plant products None
Biodiversity (generally) Negative
Crop production Negative
Environment (generally) None
Fisheries / aquaculture None
Forestry production Negative
Human health None
Livestock production None
Native fauna None
Native flora Negative
Rare/protected species None
Tourism None
Trade/international relations None
Transport/travel None

Economic Impact

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Holm et al. (1977) consider A. conyzoides and A. houstonianum to be among the commonest weeds in warmer regions of the world. A. conyzoides can be expected to be found as an important weed in all crops in the tropics and subtropics, except in deep shade. It is also a weed of turf in Guangxi Province, China (Ma YueFeng et al., 2002). Year-round flowering (providing soil moisture is adequate) and the production of large quantities of seed allows A. conyzoides to heavily infest crops, often carpeting the soil where conditions are favourable.

In East Africa, Holm et al. (1977) report that A. conyzoides is widespread in arable crops from the coast up to 3125 m. They further list it as an important weed of maize in Ghana, Nigeria, the Philippines and Sri Lanka; groundnut in Ghana, Indonesia and Sri Lanka; chillies and upland rice in Indonesia, the Philippines and Sri Lanka; cotton in Uganda; tea in Taiwan, India, Indonesia, Mauritius and Sri Lanka; cocoa in Brazil; potatoes in Colombia; oil palm in Nigeria; and over-grazed pasture in Australia, Hawaii and India. A. conyzoides competes with crops as one component of a mixed weed flora.

Roder et al. (1998) demonstrated that upland rice yield is negatively correlated with A. conyzoides density. In agricultural fields of India where A. conyzoides is found as a weed, there is evidence of yield reduction (Kohli et al., 2006). Wesel (2000) also report a reduced crop yield and a high labour input needed for weed management due to A. conyzoides and other weeds in maize fields in Vietnam. Most of the crop yield reduction is reported as due to germination or growth inhibition by allelopathic compouds produced by A. conyzoides and/or by light competition (GISD, 2016). The species is also a seed contaminant in harvested crops (PROTA, 2016).

A. conyzoides is also important as an alternate host of a number of economically important crop pathogens and nematodes, and where fallowing is practised, can provide a source of infection. It is a symptomless carrier of Burkholderia solanacearum [Ralsonia solanacearum], important in potato in India (Sunaina et al., 1989) and is a host of the banana nematodes Radopholus similis and Helicotylenchus multicinctus in Brazil (Zem and Lordello, 1983) and of the root knot nematode, Meloidogyne javanica, in many parts of the world (e.g. Mamaril and Alberto, 1989). It is also the host of the Tomato Yellow Leaf Curl Tanzania Virus (TYLCTZV) and the Ageratum Yellow Vein Virus (GISD, 2016).

Environmental Impact

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Impact on Habitats

A. conyzoides can form monocultures in grasslands, forest, and plantations and fields (Dogra et al., 2009). It is an aggressive short-term colonizer of gaps in vegetation. It can become dominant following overgrazing, a situation reported from Mudumalai Wildlife Sanctuary, Jaldapara Wildlife Sanctuary and Gorumara National Parks in India (Bhowmik et al., 1999; Silori and Mishra, 2001). A. conyzoides can initially dominate as a pioneer where fields are abandoned at shifting cultivation sites in tropical regions.  However, it is rapidly succeeded by pioneer shrub or tree species within a few years (Ohtsuka, 1998). The species is also reported by Dogra et al. (2009) as altering the soil properties by releasing allelochemicals that could inhibit the growth of other species. They also compared the soil composition of areas with native vegetation vs. ones invaded with A. conyzoides, finding a significant increase in organic carbon and other nutrients. They concluded that the increase in soil nutrients and the allelopathic effect promotes the growth of the invasive species.

Impact on Biodiversity

A. conyzoides is one of a number of competitive introduced species which threaten the survival of indigenous species in Hawaii, including Brighamia insignis (Centre for Plant Conservation, 2004). As an alien invader, A. conyzoides is noted to be of special interest in the Kruger National Park in South Africa (National Park Service, 2004). In India, it outcompetes the native grasses in rangelands, causing a shortage of fodder species (Kohli et al., 2006). In the northwestern Himalayas of India, species diversity of areas invaded by A. conyzoides has been drastically affected, with reductions in the number of plant species by 32%, the Margalef’s index of species by 37%, α diversity by 41%, and the evenness index by 15% (Dogra et al., 2009).

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Cyanea recta (Kealia cyanea)National list(s) National list(s); USA ESA listing as threatened species USA ESA listing as threatened speciesHawaiiCompetition - monopolizing resourcesUS Fish and Wildlife Service, 1995
Cyrtandra limahuliensis (Limahuli cyrtandra)NatureServe NatureServe; USA ESA listing as threatened species USA ESA listing as threatened speciesHawaiiCompetition - monopolizing resourcesUS Fish and Wildlife Service, 1995
Isodendrion longifolium (longleaf isodendrion)EN (IUCN red list: Endangered) EN (IUCN red list: Endangered); USA ESA listing as threatened species USA ESA listing as threatened speciesHawaiiCompetition - monopolizing resourcesUS Fish and Wildlife Service, 2011b
Platydesma rostrataCR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered); USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition - monopolizing resources; Ecosystem change / habitat alterationUS Fish and Wildlife Service, 2010b
Poa mannii (Mann's bluegrass)CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered); USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition - monopolizing resourcesUS Fish and Wildlife Service, 2010a
Schiedea apokremnos (Kauai schiedea)CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered); USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition (unspecified)US Fish and Wildlife Service, 2010c
Spermolepis hawaiiensis (Hawaii scaleseed)USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition - monopolizing resources; Ecosystem change / habitat alterationUS Fish and Wildlife Service, 2010d
Vigna o-wahuensis (Oahu cowpea)EN (IUCN red list: Endangered) EN (IUCN red list: Endangered); USA ESA listing as endangered species USA ESA listing as endangered speciesHawaiiCompetition - monopolizing resources; Ecosystem change / habitat alterationUS Fish and Wildlife Service, 2011a
Wikstroemia villosa.CR (IUCN red list: Critically endangered) CR (IUCN red list: Critically endangered)HawaiiCompetition (unspecified)US Fish and Wildlife Service, 2012

Social Impact

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Although A. conyzoides is used as a medicinal plant, it is also reported as toxic, capable of producing liver lesions and tumors (GISD, 2016). PROTA (2016) list it as poisonous to vertebrates but without further details. A. conyzoides has been reported as the main reason of a mass poisoning incident in Ethiopia due to grain being contaminated with the species (Encyclopedia of Life, 2016). It can also cause allergic reactions (GISD, 2016).

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Abundant in its native range
  • Highly adaptable to different environments
  • Is a habitat generalist
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Highly mobile locally
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
Impact outcomes
  • Increases vulnerability to invasions
  • Loss of medicinal resources
  • Modification of nutrient regime
  • Modification of successional patterns
  • Monoculture formation
  • Negatively impacts agriculture
  • Negatively impacts human health
  • Negatively impacts animal health
  • Negatively impacts livelihoods
  • Reduced native biodiversity
  • Threat to/ loss of native species
  • Negatively impacts trade/international relations
Impact mechanisms
  • Allelopathic
  • Causes allergic responses
  • Competition - monopolizing resources
  • Competition - shading
  • Pest and disease transmission
  • Poisoning
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Highly likely to be transported internationally deliberately
  • Difficult to identify/detect as a commodity contaminant

Uses

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Social Benefit

Apart from use as a garden ornamental, A. conyzoides plays a role in folk medicine over much of its range, being used to treat a diversity of ailments including skin complaints, cuts, wounds, burns pneumonia, sleeping sickness, stomach ache, malaria, coughs, colds, diarrhoea, as a purgative enema, a painkiller during childbirth and to treat snakebites (Johnson, 1971; PROTA, 2016). It has been reported as having anti-inflammatory and anti-allergic properties, as well as being attributed magical and superstitious properties by some cultures (PROTA, 2016). Its essential oils are used for treating dandruff and as a hair wash (PROTA, 2016). Although cited as poisonous, it is also used as a fodder for cattle, guinea-pigs, horses and goats (PROTA, 2016).

Environmental Services

Maintaining a ground cover of A. conyzoides in citrus orchards is a valuable component of Integrated Pest Management (IPM) of citrus mite as the weed provides refuge for predators of the mites (Zhou et al., 1994). It is also planted as a ground cover in rubber plantations (PROTA, 2016). There is considerable interest in the insecticidal and fungicidal properties of extracts from A. conyzoides, which have shown potential for controlling Dysdercus flavidus, which transmits diseases in cotton in Mauritius, the potato tuber moth (Phthorimaea operculella) and the rice disease (Cochliobolus miyabeanus) (Fagoonee and Umrit, 1980; Asthana et al., 1982; Pandey et al., 1982). Bouda et al. (2001) found that essential oils of A. conyzoides were effective as an insecticide for the control of Sitophilus zeamais, the maize grain weevil. It is attacked easily by the nematode Heterodera radicola [Meloidogyne arenaria], and because of that A. conyzoides is suggested to be planted near other susceptible plants (PROTA, 2016).

Uses List

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General

  • Ornamental
  • Ritual uses

Human food and beverage

  • Vegetable

Materials

  • Essential oils
  • Pesticide
  • Poisonous to mammals

Medicinal, pharmaceutical

  • Traditional/folklore

Similarities to Other Species/Conditions

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The closely related species Ageratum houstonianum is often confused in the herbarium or field with A. conyzoides. The habits, fruit and the strong smell of freshly crushed foliage of both species are similar. However, the combination of ovate leaves with cordate bases and narrowly lanceolate, conspicuously pilose involucre bracts with glandular hairs on the gradually acuminate apex distinguishes A. houstonianum. This species also has larger flower heads of 75-100 flowers compared with 60-75 in A. conyzoides. In the former species the styles are clearly visible extending above the line of the involucral bracts, whereas the flowers of A. conyzoides scarcely extend above the involucre. 

Prevention and Control

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Prevention

The species is included in the list of noxious weeds for South Africa, acknowledging it as a prohibited plant that needs to be controlled (BioNet-EAFRINET, 2016).

Control

Cultural control

Short periods of flooding provide effective control in Eucalyptus plantations in India (Paradkar et al., 1998). In field crops in the dry tropics, the density of the weed is reduced by minimum tillage systems (Zelaya et al., 1997).

Mechanical control

A. conyzoides is shallow-rooted and relatively easy to control using mechanical means. As it is a prolific seeder, it is important to destroy plants before they flower. 

Chemical control

A wide range of herbicides have been used to control the weed selectively in major crops. Bentazone, butachlor, 2,4-D, MCPA and oxidiazon are effective treatments in rice (Ampong-Nyarko and de Datta, 1991); nicosulphuron is used in maize (Ferreira et al., 1996); cyanazine, metolachlor, metribuzin and cinmethylin are used in soyabean (de Souza, 1988), acetochlor gives good control in maize (Silva et al., 1986); and atrazine and simazine are used in peaches (Gautam and Chauhan, 1984). Metribuzin provides residual control in tea (Satyanarayana et al., 1981) and terbutryne with ametryne are selective in sugarcane (Reddi et al., 1977). Imazethapyr provides effective control in soybean (Angiras and Rana, 1995).

Gaps in Knowledge/Research Needs

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Research on the quantitative measurements of the impact of the species on biodiversity is recommended (GISD, 2016).

References

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Acevedo-Rodríguez P, Strong MT, 2012. Catalogue of the Seed Plants of the West Indies. Smithsonian Contributions to Botany, 98:1192 pp. Washington DC, USA: Smithsonian Institution. http://botany.si.edu/Antilles/WestIndies/catalog.htm

Adams CD, 1963. Compositae. In: Hutchinson J, Dalziel JM, Hepper FN, eds. Flora of West Tropical Africa, Volume 2, Second edition. London, UK: Crown Agents

Adams CD, Kasasian L, Seeyave J, 1970. Common Weeds of the West Indies. St Augustine, Trinidad: University of the West Indies

Agrawal SK, Agrawal KK, Jain KK, 1995. Effect of herbicides and spacings on weed dynamics in soybean-weed association. World Weeds, 2(2):83-92; 2 ref

Ahanchede A, Gasquez J, 1997. Weeds of rainfed crop fields in northeastern Benin. Agriculture et De^acute~veloppement, May (special issue):17-23; 14 ref

Alva AS, 1973. Manual de las Malezas de al Costa Norperuana. Truijillo, Peru: Universidad Nacional de Truijillo

Ampong-Nyarko K, Datta SK de, 1991. Handbook for weed control in rice. Manila, Philippines: International Rice Research Institute

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15/09/2016 Updated by:

Jeanine Vélez-Gavilán, University of Puerto Rico at Mayagüez

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