Pacific Island Ecosystems at Risk (PIER)

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Digitaria insularis
(L.) Mez ex Ekman, Poaceae
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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Risk assessment results:  High risk, score: 20 (Go to the risk assessment)

Other Latin names:  Trichachne insularis (L.) Nees.

Common name(s): [more details]

English: sourgrass

Habit:  grass

Description:  "Large perennial grass with more or less erect culms, branching up to 1.5 m tall; cataphylls densely-soft-hairy; sheaths apically carinate, longer than internodes, hirsute; ligule 3-4 mm long; blades 10-30 cm long, 2-12 mm wide; margins finely scabrid; panicles 15-30 cm long, slender, congested, tawny to whitish, the branches steeply ascending; spikelets 3.5-4 mm long; first glume 0.5 mm long, glabrous; second glume and sterile lemma both densely silky-hairy with hairs longer than spikelet; fertile lemma dark, 3-3.5 mm long; caryopsis beaked, pale, 1.5 mm long" (Stone, 1970; p. 226).

Description from GrassBase.

Habitat/ecology:  Infests disturbed areas in mesic and dry natural areas, roadsides and waste areas up to 300 m elevation. In Hawai‘i, "naturalized in abandoned fields, disturbed sites, and along roadsides, 0-340 m"  (Wagner et al., 1999; p. 1531). "Forms dense stands in mesic pastures and disturbed forests.  Infests disturbed areas in mesic and dry natural areas, roadsides, and waste areas"  (Motooka et al., 2003). In New Guinea, "a weed of grazing land, headlands and roadsides; not a serious problem in cultivation" (Henty & Pritchard, 1975; p. 38).

Propagation:  "Large volumes of wind-dispersed seed.  Vegetative propagation from runner fragments."  (Waterhouse & Mitchell, 1998; pp. 67-68).

Native range:  Tropical and subtropical Americas; widely naturalized elsewhere (GRIN).

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
Saipan Island introduced
Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 38)
Managaha Island.
Commonwealth of the Northern Mariana Islands (US)
Northern Mariana Islands
Tinian Island introduced
Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 38)
Commonwealth of the Northern Mariana Islands (US)
Northern Mariana Islands
Tinian Island   Bishop Museum (Honolulu) (1946) (voucher ID: BISH 124245)
Taxon name on voucher: Digitaria insularis (L.) Mez ex Ekman
Commonwealth of the Northern Mariana Islands (US)
Northern Mariana Islands
Tinian Island   Bishop Museum (Honolulu) (1985) (voucher ID: BISH 540172)
Taxon name on voucher: Digitaria insularis (L.) Mez ex Ekman
Commonwealth of the Northern Mariana Islands (US)
Northern Mariana Islands
Tinian Island   Bishop Museum (Honolulu) (1980) (voucher ID: BISH 588179)
Taxon name on voucher: Digitaria insularis (L.) Mez ex Ekman
Commonwealth of the Northern Mariana Islands (US)
Northern Mariana Islands
Tinian Island   Bishop Museum (Honolulu) (1980) (voucher ID: BISH 588180)
Taxon name on voucher: Digitaria insularis (L.) Mez ex Ekman
Fiji
Fiji Islands
Fiji Islands   Waterhouse, D. F. (1997) (p. 61)
Guam
Guam Island
Guam Island introduced
invasive
Stone, Benjamin C. (1970) (p. 226)
Guam
Guam Island
Guam Island introduced
Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 38)
State of Hawaii
Hawaiian Islands
Hawai‘i (Big) Island introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1531)
State of Hawaii
Hawaiian Islands
Kaho‘olawe Island introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1531)
State of Hawaii
Hawaiian Islands
Kaua‘i Island introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1531)
State of Hawaii
Hawaiian Islands
Lāna‘i Island introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1531)
State of Hawaii
Hawaiian Islands
Ni‘ihau, Lehua Islet introduced
invasive
Wood, K. R./LeGrande, Maya (2006) (p. 26)
Voucher cited: K.R. Wood & VanderWerf 9875 (BISH, PTBG, US)
State of Hawaii
Hawaiian Islands
Maui Island introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1531)
State of Hawaii
Hawaiian Islands
Moloka‘i Island introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1531)
State of Hawaii
Hawaiian Islands
O‘ahu Island introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1531)
Japan (offshore islands)
Ogasawara (Bonin) Islands
Bonin (Ogasawara) Islands introduced
Kato, Hidetoshi (2007)
Marshall Islands
Ralik Chain
Bikini (Pikinni) Atoll introduced
Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 38)
Marshall Islands
Ralik Chain
Bikini (Pikinni) Atoll   Bishop Museum (Honolulu) (1946) (voucher ID: BISH 127176)
Taxon name on voucher: Digitaria insularis (L.) Mez ex Ekman
Marshall Islands
Ralik Chain
Enewetak (Ãnewetak, Eniwetok) Atoll introduced
Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 38)
Marshall Islands
Ralik Chain
Enewetak (Ãnewetak, Eniwetok) Atoll introduced
invasive
St. John, Harold (1960) (p. 323)
Voucher cited: Fosberg 24328, Lane 57-138
Marshall Islands
Ralik Chain
Enewetak (Ãnewetak, Eniwetok) Atoll introduced
invasive
Fosberg, F. R. (1955) (p. 5)
Voucher cited: Fosberg 24328 (US)
Marshall Islands
Ralik Chain
Enewetak (Ãnewetak, Eniwetok) Atoll   Bishop Museum (Honolulu) (1957) (voucher ID: BISH 576848)
Taxon name on voucher: Digitaria insularis (L.) Mez ex Ekman
Marshall Islands
Ralik Chain
Enewetak (Ãnewetak, Eniwetok) Atoll   Bishop Museum (Honolulu) (1946) (voucher ID: BISH 697533)
Taxon name on voucher: Digitaria insularis (L.) Mez ex Ekman
Marshall Islands
Ralik Chain
Kwajalein (Kuwajleen) Atoll introduced
invasive
Fosberg, F. R. (1955) (p. 5)
Voucher cited: Fosberg 26502 (US)
Marshall Islands
Ralik Chain
Kwajalein (Kuwajleen) Atoll   Bishop Museum (Honolulu) (1946) (voucher ID: BISH 124244)
Taxon name on voucher: Digitaria insularis (L.) Mez ex Ekman
Papua New Guinea
Papua New Guinea (eastern New Guinea Island)
Papua New Guinea (eastern New Guinea Island) introduced
invasive
Waterhouse, B. M./Mitchell, A. A. (1998) (pp. 67-68)
Papua New Guinea
Papua New Guinea (eastern New Guinea Island)
Papua New Guinea (eastern New Guinea Island) introduced
invasive
Henty, E. E. (1969) (p. 76)
Becoming common in the lower Markham Valley, where it was first noticed in 1952.
Philippines
Philippine Islands
Philippine Islands introduced
invasive
Waterhouse, B. M./Mitchell, A. A. (1998) (pp. 67-68)
Solomon Islands
Solomon Islands
Solomon Islands   Swarbrick, John T. (1997) (p. 91)
Solomon Islands
Solomon Islands
Solomon Islands native
Hancock, I. R./Henderson, C. P. (1988) (p. 66)
United States (other Pacific offshore islands)
Midway Atoll
Midway Atoll introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1531)
United States (other Pacific offshore islands)
Midway Atoll
Sand Island introduced
invasive
Starr, Forest/Starr, Kim/Loope, Lloyd (2008) (pp. B-8)
United States (other Pacific offshore islands)
Wake Islands
Wake Island introduced
invasive
Fosberg, F. R. (1959) (p. 9)
Voucher cited: Fosberg 34476
United States (other Pacific offshore islands)
Wake Islands
Wake Island introduced
invasive
Fosberg, F. R./Sachet, M.-H. (1969) (p. 5)
Voucher cited: Sachet 894
United States (other Pacific offshore islands)
Wake Islands
Wake Island introduced
invasive
Fosberg, F. R. (1955) (p. 5)
Voucher cited: Fosberg 34476 (US)
Vanuatu
New Hebrides Islands
Vanuatu (Republic of)   Waterhouse, D. F. (1997) (p. 61)
Pacific Rim
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
Colombia
Colombia
Colombia (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Costa Rica
Costa Rica
Costa Rica (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Ecuador (Mainland)
Ecuador
Ecuador (Republic of) (continental) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
El Salvador
El Salvador
El Salvador (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Guatemala
Guatemala
Guatemala (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Honduras
Honduras
Honduras (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Mexico
Mexico
Mexico (United Mexican States) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Nicaragua
Nicaragua
Nicaragua (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Panama
Panama
Panama (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Perú
Perú
Perú (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Also reported from
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
United States (continental except west coast)
United States (other states)
United States (other states) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Arizona, Texas
United States (continental except west coast)
United States (other states)
USA (Florida) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)

Control: 

Physical:  Grazing management in pastures (Motooka et al., 2003).

Chemical: Sensitive to glyphosate (Motooka et al., 2003).


Need more info? Have questions? Comments? Information to contribute? Contact PIER! (pier@hear.org)

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This page was created on 1 JAN 1999 and was last updated on 16 APR 2013.