Prosopis pallida (Humb. & Bonpl. ex Willd.) Kunth, Fabaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results: 

Australia:  Reject, score: 20 (Prosopis sp.) (Go to the risk assessment)
Risk assessment for Prosopis pallida from the Government of Queensland, Australia (PDF format)

Common name(s): [more details]

English: algaroba, mesquite

Hawaiian: kiawe

Spanish: algarrobo, algarrobo americano, huarango

Habit:  tree

Description:  "Trees 8-20 m tall, ± with slender stipular spines 0.3-1 (-1.7) cm long.  Leaves with (1-) 3-4 pairs of pinnae, each with 6-15 pairs of leaflets, these oblong to elliptic-oblong, 2.5-10 mm long, 1.4-4 mm wide, veins prominent on lower surface, pubescent, sometimes only along margins and on rachis, apex mucronate or weakly acuminate, base rounded, usually oblique.  Flowers numerous, in cylindrical spikes 7-12 cm long;  corolla yellowish green, ca. 6 mm long, inner surface of petals pilose; stamens 5-6 mm long.  Pods yellowish brown, subcylindrical, often irregularly curved, 6-25 cm long, 1-1.5 cm wide, stipe 1.3-1.8 cm long.  Seeds brown, narrowly obovoid, ca. 6.5 mm long"  (Wagner et al., 1999; pp. 692-693).

Habitat/ecology:  Well adapted to dry habitats. It overshadows other vegetation and the deep tap roots use all available water. Sea level to 700 m in Hawai‘i.  "Broad canopy shades out forages in pasturesand native plants in coastal natural areas.  Because of thorns and drooping branches, kiawe can also physically block passage of people and animals.  Its deep roots deprive shallow rooted plants of water"  (Motooka et al., 2003).

In Hawai‘i, P. palida is "a dominant component of the vegetation in low elevation, dry, disturbed sites, from the vegetation line behind beaches, on raised limestone reefs, dry slopes and gulches, and in degraded dry forest, 0-610 m" (Wagner et al., 1999; pp. 692-693).

Propagation:  Seed. Prolific producer of seed. Seed pods and seeds can be transported by floodwater or eaten by animals and spread in their manure. "Seed is also dispersed by water and in mud adhering to animals, boots, machinery and vehicles.  Reproduces by suckering and layering which thicken up existing stands.  Widely planted as a shade and shelter tree."  (Waterhouse, 2003).

Native range:  Peru, Colombia and Ecuador.

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
French Polynesia Marquesas Islands	Ua Huka (Huahuna, Uahuka) Island	introduced cultivated	Lorence, David H./Wagner, Warren L. (2013)
Guam Guam Island	Guam Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 94) Cultivated?
State of Hawaii Hawaiian Islands	Hawai‘i (Big) Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 692-693)
State of Hawaii Hawaiian Islands	Kaho‘olawe Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 692-693)
State of Hawaii Hawaiian Islands	Kaua‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 692-693)
State of Hawaii Hawaiian Islands	Lāna‘i Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 692-693)
State of Hawaii Hawaiian Islands	Ni‘ihau, Lehua Islet	introduced invasive	Wood, K. R./LeGrande, Maya (2006) (pp. 23-24) Vouchers cited: K.R. Wood et al. 9218 (BISH, PTBG), K.R. Wood 11616 (PTBG) Single tree, no reproduction noted.
State of Hawaii Hawaiian Islands	Maui Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 692-693)
State of Hawaii Hawaiian Islands	Moloka‘i Island	introduced invasive	Hughes, Guy D'Oyly (1995) (p. 6) Voucher cited: Hughes s.n. (BISH) Dominates dry, lowland and coastal areas.
State of Hawaii Hawaiian Islands	O‘ahu Island	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 692-693)
Kiribati Kiribati	Kiribati (Republic of)	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1979) (p. 94) Cultivated?
Kiribati Tungaru (Gilbert) Islands	Tarawa Atoll		Wagner, W. L./ Herbst, D. R./Weitzman, A./Lorence, D.H. (2013)
New Caledonia New Caledonia Archipelago	Île Grande Terre	introduced cultivated	MacKee, H. S. (1994) (p. 79) Vouchers cited: Toutain 3842 (NOU), MacKee 42809, Cherrier in MacKee 43035
United States (other Pacific offshore islands) Johnston Atoll	Johnston Island	introduced cultivated	Amerson, A. Binion, Jr./Shelton, Philip C. (1976) (p. 56)
United States (other Pacific offshore islands) Midway Atoll	Midway Atoll	introduced invasive	Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (pp. 692-693)

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	Csurhes, S./Edwards, R. (1998) (p. 191)
Australia Australia (continental)	Northern Territory	introduced invasive	Australian Biological Resources Study (2013)
Australia Australia (continental)	Queensland	introduced invasive	Csurhes, S./Edwards, R. (1998) (p. 191)
Australia Australia (continental)	Queensland	introduced invasive	Australian Biological Resources Study (2013) "This species grows in fine, red, alluvial soil of the coastal plain".
South America (Pacific rim) South America (Pacific rim)	Colombia	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Ecuador (Republic of) (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
South America (Pacific rim) South America (Pacific rim)	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)

Comments:  P. pallida is on the U.S. exclusion list.

Control: 

Physical:  "Mechanical control techniques, ranging from blade ploughing to grubbing and chaining, are aimed at removing as much of the root system as possible to prevent the tree reshooting. Mechanical control has varying levels of effectiveness depending on the size and species of the plant, but will kill mesquite if the roots can be removed to a depth of 300 mm.  Blade ploughing is considered to be the most cost-effective form of mechanical control and has been shown to be effective on P. velutina and its hybrid, and on P. pallida. Mechanical control can assist the germination and growth of pasture grasses, especially if the area is reseeded following blade ploughing.  Mesquite seedling germination will also increase, requiring follow-up control. Ploughs can be pulled or pushed, with maximum costs at approximately &$36;120 per hectare in dense infestations. In southwestern Queensland P. velutina has been mechanically controlled using ‘grubber’ attachments on bulldozers and tractors, with best results gained in late autumn and winter in a normal wet season year. However, grubbing is only cost-effective for treating light infestations or small areas of dense infestations - costs exceeded $200 per hectare in grubbing one dense infestation of P. pallida. Chain pulling is the cheapest but least effective mechanical control because of low kill rates. Permits may be required to conduct mechanical control if native species will be affected"  (CRC for Australian Weed Management).

Chemical: "Saplings sensitive to basal bark applications of 2,4-D and triclopyr at 2% of product in diesel or crop oil. HAVO staff reported control with triclopyr ester at 5% product in diesel oil applied to basal bark (Zimmer, HAVO)" (Motooka et al., 2003).

"The basal bark and cut-stump techniques used with an appropriate registered herbicide are effective on mature trees. Basal bark treatment (spraying around the entire stem up to 750 mm from the ground) should be used during the growing season (approximately October to April, depending on species and location). The cut-stump technique, where herbicide is immediately applied to a stump that has been cut horizontally very close to the ground, is effective year round. Seedlings can be controlled by spraying foliar herbicide over the entire plant. This is particularly effective for dealing with actively growing, dense stands of mesquite up to 1.5 m tall"  (CRC for Australian Weed Management).

Biological:  Two insect species from Argentina have been released [in Australia] since a biological control program was initiated by CSIRO Entomology in 1994. A leaf tying moth (Evippe sp. #1) that causes defoliation and a leaf sucking bug (Prosopidopsylla flava) that causes dieback were released in 1998. The first species has established itself at most release sites and is having an impact on mesquite, particularly in the Pilbara region where seed production and growth rates are reduced. It is doubtful that the second species will establish itself in populations large enough to damage mesquite despite numerous introduction efforts. Two seed-feeding beetles that were released by the Queensland Department of Natural Resources and Mines are widely established but not affecting mesquite"  (CRC for Australian Weed Management).