Acacia confusa Merr., Fabaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  High risk, score: 10 (Go to the risk assessment)

Common name(s): [more details]

Carolinian: serepa, soschghi

Chamorro: boiffuring, shoshigi, sosigi, sosugi

Chinese: tai wan xiang si

English: Formosa acacia, Formosan koa

Japanese: sosijyu

Palauan: ianángi, yanangi

Pohnpeian: pilampwoia

Habit:  tree

Description:  "Small tree; adult foliage of falcate phyllodes, juvenile and sucker-shoot foliage of bipinnate leaves; trunk up to 1 m thick in very old trees; phyllodes alternate, coriaceous, parallel-curving-veined, 8-10 cm long, narrowed at both ends; flowers yellow, in small globose heads 6-8 mm in diameter; heads 1 or 2 in axil of phyllode; pods few together, linear or somewhat curved, flat or slightly twisted, brown, 5-10 cm long, 1 cm broad or a little more or less, with about 8 seeds; seeds compressed, brown" (Stone, 1970; p. 295).

Description from Flora of China online.

Habitat/ecology:  "Mesic to humid areas in both pastures and forests.  Forms monotypic stands in pastures and disturbed sites in forests; eliminates ground cover"  (Motooka et al., 2003).  Grows well in both dry and mesic habitats. Will often resprout after fire. In Hawai‘i, it was planted for windbreaks on Maui and has since formed monotypic stands at lower elevations and continues to spread up to 1000 m (Randy Bartlett, communication on Aliens list server).

Propagation:  Seeds present in the ground can germinate profusely after fire. Spread through forestry and ornamental plantings. Can be reproduced from cuttings.

Native range:  A native of the Northern Philippines, naturalized extensively in Taiwan, Okinawa, and Saipan. In Hawai'i, "widely cultivated and now naturalized in dry to mesic, disturbed areas, 3-915 m" (Wagner et al., 1999; p. 641).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Aguijan (Agiguan, Aguihan) Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Aguijan (Agiguan, Aguihan) Island		Bishop Museum (Honolulu) (1952) (voucher ID: BISH 152469) Taxon name on voucher: Acacia confusa Merr.
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Aguijan (Agiguan, Aguihan) Island		Bishop Museum (Honolulu) (1952) (voucher ID: BISH 152470) Taxon name on voucher: Acacia confusa Merr.
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Rota Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Rota Island	introduced invasive cultivated	Space, James C./Waterhouse, Barbara/Denslow, Julie S./Nelson, Duane (2000) (p. 6) Some naturalization noted.
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Sarigan Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Sarigan Island	introduced cultivated	Fosberg, F. R./Falanruw, M. V. C./Sachet, M.-H. (1975) (p. 26) Voucher cited: Fosberg 31427 (US)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Sarigan Island		Bishop Museum (Honolulu) (1967) (voucher ID: BISH 401441) Taxon name on voucher: Acacia confusa Merr.
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Tinian Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Commonwealth of the Northern Mariana Islands (US) Northern Mariana Islands	Tinian Island	introduced invasive	Meyer, Jean-Yves (2000) (p. 101)
Commonwealth of the Northern Mariana Islands (US) Saipan	Saipan Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Commonwealth of the Northern Mariana Islands (US) Saipan	Saipan Island	introduced invasive	Meyer, Jean-Yves (2000) (p. 101)
Commonwealth of the Northern Mariana Islands (US) Saipan	Saipan Island	introduced cultivated	Space, James C./Falanruw, Marjorie (1999) (p. Field notes.)
Commonwealth of the Northern Mariana Islands (US) Saipan	Saipan Island		Bishop Museum (Honolulu) (1946) (voucher ID: BISH 152468) Taxon name on voucher: Acacia confusa Merr.
Commonwealth of the Northern Mariana Islands (US) Saipan	Saipan Island		Bishop Museum (Honolulu) (1946) (voucher ID: BISH 567924) Taxon name on voucher: Acacia confusa Merr.
Commonwealth of the Northern Mariana Islands (US) Saipan	Saipan Island		Bishop Museum (Honolulu) (1966) (voucher ID: BISH 659659) Taxon name on voucher: Acacia confusa Merr.
Federated States of Micronesia Chuuk Islands	Tol Island		Wagner, W. L./ Herbst, D. R./Weitzman, A./Lorence, D.H. (2013)
Federated States of Micronesia Chuuk Islands	Weno (Moen) Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Federated States of Micronesia Chuuk Islands	Weno (Moen) Island		Bishop Museum (Honolulu) (1935) (voucher ID: BISH 152473) Taxon name on voucher: Acacia confusa Merr.
Federated States of Micronesia Chuuk Islands	Weno (Moen) Island		Bishop Museum (Honolulu) (1980) (voucher ID: BISH 659660) Taxon name on voucher: Acacia confusa Merr.
Federated States of Micronesia Chuuk Islands	Weno (Moen) Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1965) (voucher ID: PTBG 23985) Taxon name on voucher: Acacia confusa
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	introduced	Meyer, Jean-Yves (2000) (p. 90) "Potential invader"
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	introduced	Glassman, S. F. (1952) (p. 74)
Federated States of Micronesia Pohnpei Islands	Pohnpei Island	introduced cultivated	Herrera, Katherine/Lorence, David H./Flynn, Timothy/Balick, Michael J. (2010) (p. 88)
Federated States of Micronesia Yap Islands	Yap (Waqab) Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Federated States of Micronesia Yap Islands	Yap (Waqab) Island	introduced	Meyer, Jean-Yves (2000) (p. 90) "Potential invader"
Guam Guam Island	Guam Island	introduced cultivated	Stone, Benjamin C. (1970) (p. 295)
Guam Guam Island	Guam Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Guam Guam Island	Guam Island		Bishop Museum (Honolulu) (1965) (voucher ID: BISH 659661) Taxon name on voucher: Acacia confusa Merr.
Guam Guam Island	Guam Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1988) (voucher ID: PTBG 22715) Taxon name on voucher: Acacia confusa
Guam Guam Island	Guam Island		National Tropical Botanical Garden (U.S.A. Hawaii. Kalaheo.) (1965) (voucher ID: PTBG 23144) Taxon name on voucher: Acacia confusa
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive cultivated	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
Japan (offshore islands) Ogasawara (Bonin) Islands	Bonin (Ogasawara) Islands	introduced invasive	Toyoda, Takeshi (2003) (p. 281) Naturalized
Japan (offshore islands) Ogasawara (Bonin) Islands	Bonin (Ogasawara) Islands	introduced	Kato, Hidetoshi (2007)
Palau Palau (Belau ) (main island group)	Babeldaob Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Palau Palau (Belau ) (main island group)	Babeldaob Island	introduced cultivated	Space, James C./Waterhouse, Barbara/Miles, Joel E./Tiobech, Joseph/Rengulbai, Kashgar (2003) (p. 84)
Palau Palau (Belau ) (main island group)	Koror (Oreor) Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 90)
Palau Palau (Belau ) (main island group)	Koror (Oreor) Island	introduced cultivated	Space, James C./Waterhouse, Barbara/Miles, Joel E./Tiobech, Joseph/Rengulbai, Kashgar (2003) (p. 79)
Palau Palau (Belau ) (main island group)	Koror (Oreor) Island		Bishop Museum (Honolulu) (1950) (voucher ID: BISH 152465) Taxon name on voucher: Acacia confusa Merr.
Palau Palau (Belau ) (main island group)	Koror (Oreor) Island		Beleu National Museum (Republic of Palau. Koror.) (1966) (voucher ID: BNM 414) Taxon name on voucher: Acacia confusa Merr.
Palau Palau (Belau ) (main island group)	Koror (Oreor) Island		Beleu National Museum (Republic of Palau. Koror.) (1967) (voucher ID: BNM 413) Taxon name on voucher: Acacia confusa Merr.
Palau Palau (Belau ) (main island group)	Malakal (Ngemelachel) Island	introduced cultivated	Space, James C./Waterhouse, Barbara/Miles, Joel E./Tiobech, Joseph/Rengulbai, Kashgar (2003) (p. 79)
Palau Palau (Belau ) (main island group)	Ngerkebesang Island	introduced cultivated	Space, James C./Waterhouse, Barbara/Miles, Joel E./Tiobech, Joseph/Rengulbai, Kashgar (2003) (p. 79)
Philippines Philippine Islands	Philippine Islands	native	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
Philippines Philippine Islands	Philippine Islands	native	ILDIS Co-ordinating Centre (2013)
Philippines Philippine Islands	Philippine Islands	invasive	Merrill, Elmer D. (1923) (pp. 248-249) On slopes and in open dry forests at low altitudes, very local.

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
China China	China (People's Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
China China	China (People's Republic of)	introduced cultivated	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) "Widely cultivated".
China China	Hong Kong	introduced cultivated	Wu, Te-lin (2001) (p. 129)
Indonesia Indonesia	Indonesia (Republic of)	introduced	ILDIS Co-ordinating Centre (2013)
Japan Japan	Japan	introduced	Mito, Toshikazu/Uesugi, Tetsuro (2004) (p. 184)
Japan Ryukyu Islands	Ryukyu Islands	introduced	ILDIS Co-ordinating Centre (2013)
Malaysia Malaysia	Malaysia (country of)	introduced	ILDIS Co-ordinating Centre (2013)
Singapore Singapore	Singapore (Republic of)	introduced cultivated	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 9) Cultivated only
Taiwan Taiwan Island	Taiwan Island	native	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 641)
Taiwan Taiwan Island	Taiwan Island	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Taiwan Taiwan Island	Taiwan Island	introduced cultivated	Zhengyi, Wu/Raven, Peter H./Deyuan, Hong (2013) "Widely cultivated".

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	introduced	ILDIS Co-ordinating Centre (2013)
Seychelles Seychelles Islands	Frégate Island		Robertson, S. A./Todd, D. M. (1983) (p. 51) Voucher cited: Procter 4172
Seychelles Seychelles Islands	Seychelles Islands	introduced	ILDIS Co-ordinating Centre (2013)
Seychelles Seychelles Islands	Seychelles Islands	introduced	Invasive Species Specialist Group (2017)

Comments:  This species is being planted in Micronesia. It is a major pest elsewhere. While little reproduction was noted in planted stands, the species should be monitored for invasive behavior. It would probably be wise not to introduce the species to islands where it is not already present (Space & Falanruw, 1999).

An older (probably pre-war) tree was observed in limestone forest on Saipan with no reproduction and a native forest understory, which would indicate limited invasiveness (Space & Falanruw, 1999). Some naturalizing was noted on Rota (Space et al., 2000).

The species is planted in Palau, but no naturalization was noted (Space et al., 2003).

Control: 

Chemical:  "Saplings sensitive to foliar application of 2,4-D at 1 lb/acre and of triclopyr at 1 lb/acre in a trial at Wailua, Kauai.  Triclopyr at 2 lb/acre provided 80% control but 2,4-D at 2 lb/acre caused moderate injury and metsulfuron at 0.4 oz active/acre was ineffective at Kala'e, Molokai. Somewhat tolerant of dicamba. Sensitive to cut-surface applications of 2,4-D, dicamba, glyphosate, picloram (45) and triclopyr in trials at Wailua, Kauai. However, in trials at Kala'e, Molokai, results were less impressive with picloram and dicamba providing serious but not lethal injury and glyphosate and 2,4-D providing moderate injury to Formosan koa. Sensitive to very-low volume basal bark application of 20% triclopyr in oil. Staff at the Hawaii Volcanoes National Park (HAVO) used triclopyr ester at 5% of product in diesel oil applied to the basal bark (Chris Zimmer, HAVO). Tolerant of tebuthiuron pellets."  (Motooka et al., 2003)