Research directed by C. Daehler (UH Botany) with funding from the Kaulunani Urban Forestry Program and US Forest Service

Information on Risk Assessments
Original risk assessment

Pennisetum purpureum (elephant grass, napier grass, merker grass)

Answer

1.01

Is the species highly domesticated?

y=-3, n=0

n

1.02

Has the species become naturalized where grown?

y=-1, n=-1

y

1.03

Does the species have weedy races?

y=-1, n=-1

n

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

See Append 2

2

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

2

2.03

Broad climate suitability (environmental versatility)

y=1, n=0

y

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

y

2.05

Does the species have a history of repeated introductions outside its natural range? y=-2

?=-1, n=0

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n=0

n

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n=0

y

3.04

Environmental weed y = 2*multiplier (see Append 2)

n=0

y

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n=0

y

4.01

Produces spines, thorns or burrs

y=1, n=0

n

4.02

Allelopathic

y=1, n=0

n

4.03

Parasitic

y=1, n=0

n

4.04

Unpalatable to grazing animals

y=1, n=-1

n

4.05

Toxic to animals

y=1, n=0

n

4.06

Host for recognized pests and pathogens

y=1, n=0

n

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

n

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

4.09

Is a shade tolerant plant at some stage of its life cycle

y=1, n=0

n

4.1

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y=1, n=0

y

4.11

Climbing or smothering growth habit

y=1, n=0

n

4.12

Forms dense thickets

y=1, n=0

y

5.01

Aquatic

y=5, n=0

n

5.02

Grass

y=1, n=0

y

5.03

Nitrogen fixing woody plant

y=1, n=0

n

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

y=1, n=0

n

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

n

6.02

Produces viable seed.

y=1, n=-1

y

6.03

Hybridizes naturally

y=1, n=-1

6.04

Self-compatible or apomictic

y=1, n=-1

y

6.05

Requires specialist pollinators

y=-1, n=0

n

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

y

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

See left

1

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

y=1, n=-1

n

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

y

7.04

Propagules adapted to wind dispersal

y=1, n=-1

y

7.05

Propagules water dispersed

y=1, n=-1

n

7.06

Propagules bird dispersed

y=1, n=-1

n

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

n

7.08

Propagules survive passage through the gut

y=1, n=-1

n

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

n

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

y=1, n=-1

n

8.03

Well controlled by herbicides

y=-1, n=1

y

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y=1, n=-1

y

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

y=-1, n=1

Total score:

16

Source

Notes

1.01

No evidence.

1.02

(1)Naturalized in Florida. (2)Naturalized in Hawai‘i in fields, along roadsides and in pastures. (3)established in American Samoa and one of the most aggressive grasses there.

(1)http://aquat1.ifas.ufl.edu/mcplnt1p.html (2)Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. Honolulu.(3)http://www.hear.org/pier3/asreport.htm#m-elsewhere

1.03

No evidence.

2.01

Native to tropical Africa. Introduced to South America, Puerto Rico, Philippine Islands, Hawaii and southern United States.

http://www.hort.purdue.edu/newcrop/duke_energy/Pennisetum_purpureum.html

2.02

2.03

(1)'...common worldwide between latitudes 23 N and 23 S.' (2) altitude range 10 to 1220 m on the Hawaiian islands. (3)Widely grown from sea level to 2000 m alt.

(1)http://aquat1.ifas.ufl.edu/mcplnt1p.html (2)Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. Honolulu. (3)Bogdan, A.V. 1977. Tropical pasture and fodder plants. Longman, London

2.04

(1)Naturalized in Florida. (2)Naturalized in Hawai‘i in fields, along roadsides and in pastures.. (3)established in American Samoa and one of the most aggressive grasses there.

(1)http://aquat1.ifas.ufl.edu/mcplnt1p.html (2)Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. Honolulu.(3)http://www.hear.org/pier3/asreport.htm#m-elsewhere

2.05

Native to tropical Africa. Introduced to South America, Puerto Rico, Philippine Islands, Hawaii and southern United States.

http://www.hort.purdue.edu/newcrop/duke_energy/Pennisetum_purpureum.html#Toxicity

3.01

(1)Naturalized in Florida. (2)Naturalized in Hawai‘i in fields, along roadsides and in pastures.. (3)established in American Samoa and one of the most aggressive grasses there.

(1)http://aquat1.ifas.ufl.edu/mcplnt1p.html (2)Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. Honolulu.(3)http://www.hear.org/pier3/asreport.htm#m-elsewhere

3.02

No evidence.

3.03

Listed as a serious weed in Columbia, Ghana, Mozambique and Trinidad.

Holm, L, Pancho, J.V.,Herberger,J.P. and Plucknett, D.L. 1979. A geogrpahical atlas of world weeds. John Wiley and sons. New York.

3.04

FLEPC Category I wildland invader., Now commonly naturalized in and south Florida, infrequently in north and west Florida, most often in dis-turbed areas such as roadsides, canal banks, and fields, but also in scrub, pine rockland, hammock, sink, lake shore, swamp, and prairie habitats

3.05

P. clandestinum is listed as a serious weed in several countries. Also P. pedicellatum is a serious weed in Thailand.

Holm, L, Pancho, J.V.,Herberger,J.P. and Plucknett, D.L. 1979. A geogrpahical atlas of world weeds. John Wiley and sons. New York.

4.01

No evidence of spines, thorns or burrs.

Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. Honolulu.

4.02

Not allelopathic.

http://plants.usda.gov/cgi_bin/topics.cgi

4.03

No evidence.

4.04

(1)Medium palatability. (2)The grass is valued for its … palatability…'

(1)http://plants.usda.gov/cgi_bin/topics.cgi (2)Bogdan, A.V. 1977. Tropical pasture and fodder plants. Longman, London

4.05

(1)Not toxic. (2)Seiler et al. (1979) report fatal nitrate poisonings in cattle whose diet consisted solely of Napier grass. Levels of nitrate averaged 28.3 mg/g with some samples as high as 44 mg which levels in the same species from non-toxic areas was 3.9 mg/g. (due to grown in soil with excessive N) 3)It is one of the most valuable forage, soilage and silage crops in the wet tropics

(1)http://plants.usda.gov/cgi_bin/topics.cgi (2)http://www.hort.purdue.edu/newcrop/duke_energy/Pennisetum_purpureum.html#Toxicity 3)http://www.ecoport.org/default.htm

4.06

This website lists 88 species of fungi that are found on P. purpureum (only a few generalists are economically important.)

http://nt.ars-grin.gov/fungaldatabases/all/FindRecOneFungusFrame.cfm

4.07

No evidence.

4.08

Not fire resistant and high fire tolerance.

http://plants.usda.gov/cgi_bin/topics.cgi

4.09

Shade intolerant.

http://plants.usda.gov/cgi_bin/topics.cgi

4.1

1) It is a rapid colonizer of disturbed areas and prospers in a broad range of conditions. 2)Requires a rich soil 3)However, it will also grow on poorly drained soils to dry sandy soils of low fertility.

1) http://aquat1.ifas.ufl.edu/mcplnt1p.html 2)http://www.hort.purdue.edu/newcrop/duke_energy/Pennisetum_purpureum.html 3)http://www.ecoport.org/default.htm

4.11

No evidence. Not a vine.

4.12

'Forms dense perennial stands, difficult to penetrate, which inhibits establishment of other vegetation.'

http://www.hear.org/pier/pepur.htm

5.01

Semi-aquatic grass

http://aquat1.ifas.ufl.edu/mcplnt1p.html

5.02

Perennial grass.

http://plants.usda.gov/cgi_bin/topics.cgi

5.03

5.04

6.01

No evidence.

6.02

if grown from seed, it is started in a nursery and transplanted

http://www.hort.purdue.edu/newcrop/duke_energy/Pennisetum_purpureum.html

6.03

(1)P. purpureum hybridizes with P. americanum readily under artificial conditions. No evidence of natural hybridization. (2) 'Many cultivars and hybrids occur, a well known example is Banagrass, a cross with P. glaucum.' - again no evidence that this occurs naturally.

Bogdan, A.V. 1977. Tropical pasture and fodder plants. Longman, London

6.04

A selfed progeny of the 'Merkeron' cultivar was produced (also, likely to be apomictic)

http://www.hort.purdue.edu/newcrop/proceedings1993/V2-294.html#Napiergrass

6.05

Probably not. Most grasses are wind pollinated - the flower morphology does not reveal adaptation to a specialist pollinator.

6.06

is sometimes stoloniferous with a creeping rhizome. (sreads slowly this way)

http://www.ecoport.org/default.htm

6.07

R. Criley, UH department of Horticulture (but assessment was given with low confidence, could required 2 years)

7.01

Propagules do not have any means of attachment.

7.02

Pasture grass, sometimes grown as an ornamental.

7.03

Weed: potential seed contaminant (fide Weed CIBA) (Stalks are cut and transported for feeding livestock. Some seeds are likely transported (accidentally) in the process)

http://www.ars-grin.gov/cgi-bin/npgs/html/taxon.pl?27208

7.04

plumose spikelets

7.05

7.06

7.07

Propagules do not have any means of attachment.

7.08

No evidence.

8.01

'Pennisetum purpureum produces, with occasional exception little or no seed, …'

Bogdan, A.V. 1977. Tropical pasture and fodder plants. Longman, London

8.02

(1)Caryposis 2 mm long. (2)'Pennisetum purpureum produces, with occasional exception little or no seed, …'3)Does not readily produce viable seed in many countries,

(1)Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. (2)Bogdan, A.V. 1977. Tropical pasture and fodder plants. Longman, London 3)http://www.fleppc.org/pdf/Pennisetum%20purpureum.pdf

8.03

(1)Foliar application of 1%-3% Roundup Pro. If non-target damage is a concern, cut stems to ground level and allow sprouts to reach 8-12 inches and treat the same as Neyraudia above. Broadcast 3-5 quart/acre Roundup Pro, 2 quart/acre Arsenal, or 1 quart Arsenal and 2 quart Roundup Pro.
(2)The herbicide glyphosate provides acceptable control in aquatic sites

(1)http://edis.ifas.ufl.edu/BODY_WG209#TABLE_1 (2)http://aquat1.ifas.ufl.edu/mcplnt1p.html

8.04

1) No resprout ability. 2)Resprouts easily from small rhizomes left after mechanical control 3) regrows following frequent clipping (harvesting for animal fodder)

1) http://plants.usda.gov/cgi_bin/topics.cgi 2)http://www.fleppc.org/pdf/Pennisetum%20purpureum.pdf 3)http://www.hort.purdue.edu/newcrop/duke_energy/Pennisetum_purpureum.html

8.05

Biological controls for napier grass are unknown in Florida.

http://aquat1.ifas.ufl.edu/mcplnt1p.html