Parthenium hysterophorus L., Asteraceae

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Present on Pacific Islands?  yes

Threat only at high elevations?  no

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

Common name(s): [more details]

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

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).

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 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
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	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)		Swarbrick, John T. (1997) (p. 95)

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)
Guatemala Guatemala	Guatemala (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Honduras Honduras	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2007)

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)

Comments:  Moderately invasive in New Caledonia (Meyer, 2000; p. 100). "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).

Additional information:  Information from the book "Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide" (Motooka et al., 2003). (PDF format).
Pest Alert No.30 - Incursion of Parthenium weed (Parthenium hysterophorus) in Papua New Guinea

Web site of the International Parthenium Research News Group (IPRNG).

References:

Gargominy, Oliver/Bouchet, Philipe/Pascal, Michel/Jaffre, Tanguy/Tourneu, Jean-Christophe. 1996. Conséquences des introductions d'espèces animales et végétales sur la biodiversité en Nouvelle-Calédonie. Rev. Ecol. (Terre Vie) 51:375-401.

Holm, Leroy/Pancho, Juan V./Herberger, James P./Plucknett, Donald L. 1979. A geographical atlas of world weeds. John Wiley & Sons, New York. 391 pp.

MacKee, H. S. 1994. Catalogue des plantes introduites et cultivées en Nouvelle-Calédonie. Muséum National d'Histoire Naturelle, Paris, 164 p.

Meyer, Jean-Yves. 2000. Preliminary review of the invasive plants in the Pacific islands (SPREP Member Countries). In: Sherley, G. (tech. ed.). Invasive species in the Pacific: A technical review and draft regional strategy. South Pacific Regional Environment Programme, Samoa. 190 pp.

Motooka, Philip/Castro, Luisa/Nelson, Duane/ Nagai, Guy/Ching, Lincoln. 2003. Weeds of Hawaii‘s Pastures and Natural Areas; An Identification and Management Guide. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa. 184 pp.

Renevier, Alain/Cherrier, Jean-Francois. 1991. Flore et vegetation de l'Ile de Walpole. Smithsonian Institution, Atoll Research Bulletin No. 352. 21 pp.

Smith, Nicholas M. 2002. Weeds of the wet/dry tropics of Australia - a field guide. Environment Centre NT, Inc. 112 pp.

Swarbrick, John T. 1997. Weeds of the Pacific Islands. Technical paper no. 209. South Pacific Commission, Noumea, New Caledonia. 124 pp.

Tassin, Jacques. 2005. Jacques Tassin (IAC-CIRAD), personal communication.

U.S. Dept. Agr., Agr. Res. Serv. 2007. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Wagner, Warren L./Herbst, Derral R. 1995. Contributions to the Flora of Hawai‘i. IV. New Records and name changes. In: Evenhuis, Neal L. and Miller, Scott, E., eds. Records of the Hawaii Biological Survey for 1994. Part 2: Notes. Bishop Museum Occasional Papers. 42:13-27.

Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. 1919 pp. (two volumes).

Waterhouse, D. F. 1997. The major invertebrate pests and weeds of agriculture and plantation forestry in the Southern and Western Pacific. The Australian Centre for International Agricultural Research, Canberra. 93 pp.

Welsh, S. L. 1998. Flora Societensis: A summary revision of the flowering plants of the Society Islands. E.P.S. Inc., Orem, Utah. 420 pp.