Parthenium hysterophorus L., Asteraceae

Click on an image for links to BIGGER PICTURES

Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  Reject, score: 18 (Go to the risk assessment)

Common name(s): [more details]

Chinese: yin jiao ju

English: Santa Maria, bitterweed, carrot grass, false ragweed, feverfew, parthenium weed, ragweed parthenium, whitetop

French: fausse camomille

Spanish: escoba amarga

Habit:  herb

Description:  "Taprooted annual herbs 3-10 dm tall; stems unbranched in lower part, branched in upper part, longitudinally striate, hirsute.  Lower leaves in a basal rosette, these deciduous at maturity and stem leaves remaining, 3-20 cm long, 2-10 cm wide, bipinnatifid or pinnatifid.  Heads small, numerous in open panicles; rays white, 0.6 mm long; disk corollas cream-colored, ca. 1 mm long; pappus of 2 petaloid scales inserted close to the corolla on either side, entire or notched.  Achenes black, obovate, 2-2.5 mm long"  (Wagner et al., 1999; p. 347).

Description from the Flora of China online.
Description from the Flora of North America online.
Description from the Digital Flora of Taiwan.

Habitat/ecology:  "A pioneer species it invades grazing land, disturbed areas, roadsides and cultivated areas" (Smith, 2002; p. 64). "A weed of croplands, pastures, and natural and recreation areas.  Can cause 90% reduction in carrying capacity of pastures.  Contains sesquiterpines and phonolics, which makes parthenium weed allelopathic (suppressive) and causes dermatitis and other allergic reactions in humans and livestock, especially horses.  High water requirement.  Does best in neutral to high pH soils, less prolific on other soils"  (Motooka et al., 2003). "In Hawai‘i, "naturalized in low elevation, dry pastures or along roadsides." (Wagner et al., 1999; p. 347). In New Caledonia, "espèce largement répandue et parfois envahissante" (MacKee, 1994; p. 37).  In Taiwan, "widely naturalized on open seashores and in lowland waste places throughout the island"  (Digital Flora of Taiwan).

Propagation:  "Seed is dispersed by wind, water, as a contaminant of harvested material and by vehicles, machinery or animals. Seeds are light and produced in large quantities, often within three weeks of germination" (Smith, 2002; p. 64).

Native range:  Tropical America, but widely naturalized.

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
French Polynesia French Polynesia Islands	French Polynesia Islands		Waterhouse, D. F. (1997) (p. 63)
French Polynesia Marquesas Islands	Hiva Oa Island	introduced invasive	Lorence, David H./Wagner, Warren L. (2013)
French Polynesia Marquesas Islands	Hiva Oa Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Naturalisée
French Polynesia Society Islands	Raiatea (Havai) Island	introduced invasive cultivated	Welsh, S. L. (1998) (p. 78) Voucher cited: Moore 682
French Polynesia Society Islands	Tahiti Island	introduced invasive cultivated	Welsh, S. L. (1998) (p. 78) Voucher cited: Grant 4514
French Polynesia Society Islands	Tahiti Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Naturalisée
French Polynesia Austral (Tubuai) Islands	Rurutu Island	introduced invasive	Florence, J./Chevillotte, H./Ollier, C./Meyer, J.-Y. (2013) Voucher cited: J. Florence 6132 (PAP) Naturalisée
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 347) Kona. Voucher cited: Kawasaki s. n.
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 347)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 347)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 347)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R. (1995) (p. 16) Voucher cited: E. Funk s.n. (BISH)
New Caledonia Îles Loyauté (Loyalte Islands)	Îles Loyauté (Loyalty Islands)	introduced invasive	Tassin, Jacques (2005)
New Caledonia Îles Loyauté (Loyalte Islands)	Île Maré	introduced invasive	MacKee, H. S. (1994) (p. 37) Voucher cited: Sarasin 482 (Z)
New Caledonia Îles Loyauté (Loyalte Islands)	Îles Ouvéa (Ouvea Atoll)	introduced invasive	MacKee, H. S. (1994) (p. 37) Voucher cited: Däniker 2200
New Caledonia Îles Loyauté (Loyalte Islands)	Île Tiga	introduced invasive	MacKee, H. S. (1994) (p. 37) Voucher cited: MacKee 45864
New Caledonia Îles Loyauté (Loyalte Islands)	Île Walpole	introduced invasive	MacKee, H. S. (1994) (p. 37) Voucher cited: Cherrier in MacKee 43813
New Caledonia Îles Loyauté (Loyalte Islands)	Île Walpole	introduced	Renevier, Alain/Cherrier, Jean-Francois (1991) (p. 16) Voucher cited: Cherrier in MacKee 44070
New Caledonia New Caledonia	New Caledonia Islands	introduced invasive	Meyer, Jean-Yves (2000) (p. 100)
New Caledonia New Caledonia	New Caledonia Islands	introduced invasive	Gargominy, Oliver/Bouchet, Philipe/Pascal, Michel/Jaffre, Tanguy/Tourneu, Jean-Christophe (1996) (p. 379) Largement répandue et parfois envahissante.
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced invasive	Tassin, Jacques (2005)
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced invasive	MacKee, H. S. (1994) (p. 37) Vouchers cited: Brousmiche 739, Blanchon 799 (NOU), MacKee 16068, MacKee 29584, MacKee 30768
New Caledonia New Caledonia Archipelago	Île des Pins (Isle of Pines)	introduced invasive	Tassin, Jacques (2005)
New Caledonia New Caledonia Archipelago	Île des Pins (Isle of Pines)	introduced invasive	MacKee, H. S. (1994) (p. 37) Voucher cited: MacKee 23464
Vanuatu New Hebrides Islands	Vanuatu (Republic of)	introduced invasive	Shine, C./Reaser, J. K./Gutierrez, A. T., eds. (2003) (p. 179)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Northern Territory	introduced invasive	Smith, Nicholas M. (2002) (p. 64) Found at Limmen Bight and the Borroloola region.
Australia Australia (continental)	Queensland	introduced invasive	Smith, Nicholas M. (2002) (p. 64)
Central America Central America (Pacific rim)	Guatemala (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
China China	China (People's Republic of)	introduced invasive	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) Fields, roadsides; below 1500 m. Guangdong, Guangxi, Guizhou, Yunnan.
China China	Hong Kong	introduced invasive	Wu, Te-lin (2001) (p. 285) In wasteland.
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 190)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Taiwan Taiwan Island	Taiwan Island	introduced invasive	Ching-I Peng, ed. (2013)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Mauritius Mautitius Islands (Mauritius and Rodrigues)	Mauritius Island		Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. (1979) (p. 266)
French Territory of Mayotte Mayotte Islands	Mayotte Island	introduced invasive	Comité français de l'Union Internationale pour la Conservation de la Nature en France (2013) Envahissant principalement dans les milieux perturbés.
Seychelles Seychelles Islands	Seychelles Islands	introduced	Invasive Species Specialist Group (2017)

Comments:  Moderately invasive in New Caledonia (Meyer, 2000; p. 100). A "weed of national significance" in Australia. "A declared noxious weed in Queensland, Northern Territory and Western Australia" (Smith, 2002; p. 64).

Control: 

Physical:  "Australian authorities have imposed strict quarantines on contaminated equipment and stock to avoid spread into new areas.  Since the weed only invades bare soil, good pasture management is effective for prevention"  (Motooka et al., 2003).

Chemical: "Effective herbicides include 2,4-D, atrazine, hexazinone, and metsulfuron. Triclopyr is effective on most Asteraceae"  (Motooka et al., 2003).

Biological:  "Australian scientists report the moth Epiblema strenuana promising.  They are also looking at the rust Puccina abrupta var. parthenenicicola and fungi that affect the weed in Mexico"  (Motooka et al., 2003).