Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Habit:  grass

Description:  Digitaria is a genus of plants in the grass family native to tropical and warm temperate regions. Common names include crabgrass, finger-grass, and fonio. Digitaria species are typically slender monocotyledonous annual and perennial lawn, pasture, and forage plants; some are often considered lawn pests. Digitus is the Latin word for "finger", and Digitaria species are distinguished by the long, finger-like inflorescences they produce. (adapted from Digitaria Wikipedia entry, cited 12 May 2017)
(see also Kew Garden's Grass Database entry for the genus Digitaria)

Habitat/ecology:  "These species often become problem weeds in lawns and gardens, growing especially well in thin lawns that are watered lightly, underfertilized, and poorly drained." "In the autumn when the plants die, they leave large voids in the lawn. The voids then become prime areas for the crabgrass seeds to germinate the following season." (Digitaria Wikipedia entry, cited 12 May 2017)
(see also Kew Garden's Grass Database entry for the genus Digitaria)

Propagation:  "They are annual plants, and one plant is capable of producing 150,000 seeds per season. The seeds germinate in the late spring and early summer and outcompete the domesticated lawn grasses, expanding outward in a circle up to 30 cm (12 in) in diameter." (Digitaria Wikipedia entry, cited 12 May 2017)
(see also Kew Garden's Grass Database entry for the genus Digitaria)

Native range:  (see Kew Garden's Grass Database entry for the genus Digitaria)

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Palau Kayangel Atoll	Kayangel Islet	introduced invasive	Miles, Joel (2015) (p. 2) ref cites other taxa as "Cultivated," but not this one, so implication is that this taxon was found in a non-cultivated situation (PT@PhilipT.com/20170602)
Palau Kayangel Atoll	Ngeriungs Islet	introduced invasive	Miles, Joel (2015) (needs to be identified to species on Ngeriungs Islet per http://www.hear.org/pier/reports/kayangel_2015_survey_report.htm">Miles, Joel. 2015. Report to Kayangel State: 2015 Survey of Invasive Plant Species. Palau Bureau of Agriculture. April 2015.)

Comments:  (see Kew Garden's Grass Database entry for the genus Digitaria)

Control:  "Biological control is preferable over herbicide use on lawns, as crabgrass emergence is not the cause of poor lawn health but a symptom, and it will return annually if the lawn is not restored with fertilization and proper watering. Crabgrass is quickly outcompeted by healthy lawn grass because, as an annual plant, crabgrass dies off in autumn and needs open conditions for its germination the following spring." (Digitaria Wikipedia entry, cited 12 May 2017)