Ageratum conyzoides
(billy goat weed)

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)

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

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.

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.

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.

Soil drainage

• free
• seasonally waterlogged

Soil reaction

• acid
• alkaline
• neutral

Soil texture

• heavy
• light
• medium

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) 

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).

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).

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).

• 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

• 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

• Allelopathic
• Causes allergic responses
• Competition - monopolizing resources
• Competition - shading
• Pest and disease transmission
• Poisoning
• Rapid growth

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately
• Difficult to identify/detect as a commodity contaminant

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).