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	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
Commonwealth of the Northern Mariana Islands (US) Saipan	Saipan Island	introduced	Fosberg, F. R./Sachet, Marie-Hélène/Oliver, Royce (1987) (p. 38) Managaha Island.
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
Central America Central America (Pacific rim)	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	El Salvador (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
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)
Central America Central America (Pacific rim)	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2013)
Central America Central America (Pacific rim)	Panama (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)
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)

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).