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

Stylosanthes guianensis (stylo)

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

n

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

n

3.04

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

n=0

n

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

y

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

n

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

n

5.01

Aquatic

y=5, n=0

n

5.02

Grass

y=1, n=0

n

5.03

Nitrogen fixing woody plant

y=1, n=0

y

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

n

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

y

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

n

7.04

Propagules adapted to wind dispersal

y=1, n=-1

n

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

y

7.08

Propagules survive passage through the gut

y=1, n=-1

y

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

y

8.03

Well controlled by herbicides

y=-1, n=1

n

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:

11

Notes

Source

1.01

'In a recent revision of this species 't Mannetje (1977) was able to distinguish 6 varieties of S. guianensis. Some varieties at least are variable and contain forms which come from and are adapted to quite different climatic and geographic conditions... .To ease communication ... the various forms have been defined in terms of their morphological (M) and agronomic (A) characteristics ... and will be subsequently referred to as MA groups.'

Burt, R. L., Rotar, P. P. , Walker, J. L. and Silvey, M. W. The Role of Centrosperma, Desmodium and Stylosanthes in improving tropical pastures. 1983. Westview Press. Boulder, Colorado.

1.02

Naturalized in Australia and elsewhere

Stanley and Ross.Flora of southeastern Queensland

1.03

No evidence.

2.01

(1) A genus of tropical and subtropical areas except Australia. (2) Stylosanthes, a diverse tropical and subtropical forage legume naturally distributed in Central and South America.

(1) Wagner,W. L., D. R. Herbst & S. H. Sohmer. 1990. Manual of flowering plants of Hawaii.University of Hawaii at Press. Honolulu.(2)Kelemu-S {a}; Badel-J-L; Moreno-C-X; Miles-J-W. 1996. Virulence spectrum of South American isolates of Colletotrichum gloeosporioides on selected Stylosanthes guianensis genotypes. Plant-Disease. 1996; 80 (12) 1355-1358.

2.02

2.03

(1) 'S. guianensis is relatively limited climatically - it is rarely found outside the wetter areas - but has a wide geographical range.' (2) Latitudinal limits: About 23°N and S

(1) Burt, R. L., Rotar, P. P. , Walker, J. L. and Silvey, M. W. The Role of Centrosperma, Desmodium and Stylosanthes in improving tropical pastures. 1983. Westview Press. Boulder, Colorado. (2) http://www.fao.org/ag/AGP/AGPC/doc/Gbase/DATA/Pf000070.htm

2.04

It is native to South and Central America.

Sharp, D. Braithwaite, K. S. Irwin, J.A. G., and Manners, J. M. 1990. Biochemical and cytochemical responses of Stylosanthes guianensis to infection by Colletrotricum gloeosporioides: association of callose deposition with resistance. Canadian Journal of Botany. 68(3): 505

2.05

It is native to South and Central America but has been introduced as pasture legume in subtropical and tropical regions worldwide.

Sharp, D. Braithwaite, K. S. Irwin, J.A. G., and Manners, J. M. 1990. Biochemical and cytochemical responses of Stylosanthes guianensis to infection by Colletrotricum gloeosporioides: association of callose deposition with resistance. Canadian Journal of Botany. 68(3): 505

3.01

Naturalized in Australia and elsewhere

Stanley and Ross.Flora of southeastern Queensland

3.02

No evidence

3.03

Holm listed as a 'weed of unknown importance' only in Peru. This species is always described as beneficial to agriculture (as a cover crop and to reclaim weed-infested pastures)

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

(1) Listed as common OR "weedy" in Micronesia and (2) in Niue but no details are given and no evidence that it is a causing a specific environmental problem is available. It has been deliberately sown there in fields and can re-seed. This is normally desirable to the field owners.

(1) http://www.hear.org/pier/mappendix2.htm#Table 2 (2) http://www.hear.org/pier/nappendix2.htm

3.05

S. hamata, S. sundaica and S. viscosa are listed as weeds of unknown importance in Jamaica, Australia and Jamaica respectively. These are certainly not serious weeds and each one could be questioned, which would change the answer to "no".

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

Does not have thorns, spines or burrs.

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

4.02

'None has been reported, but it has a toxic effect on succeeding cotton crops at Serere, Uganda (Horrell and Newhouse, 1965). Leaf and stem exudate depressed seed germination of Pennisetum typhoides in Petri dishes. At Ngeta, Zambia, van Rensburg (1968) found that it reduced subsequent cotton yields by 30 percent and also cottonseed germination. The toxic effect was confirmed by pot tests in which stylo leaves were incorporated in the soil. Rijkebusch (1967) also observed an adverse effect on subsequent crops of sisal in Tanzania.' 

http://www.fao.org/ag/AGP/AGPC/doc/Gbase/DATA/Pf000070.htm

4.03

Did not find any evidence that the species is parasitic.

4.04

(1) Common stylo is not very palatable, and is generally not eaten until autumn. (2)It is relatively unpalatable in the early stages of growth. ...Nwosu (1960) also observed this lack of early palatability and suggested that it was due to the harsh hairs on the plant. 3) Forage quality (crude protein and digestibility) of Savanna was equal to or better than either alyceclover or hairy indigo from August until November

1) http://www.dpi.qld.gov.au/pastures/4484.html (2) http://www.fao.org/ag/AGP/AGPC/doc/Gbase/DATA/Pf000070.htm 3)http://edis.ifas.ufl.edu/BODY_AA194

4.05

No evidence

4.06

'Anthracnose has been reported in Brazil under wet conditions (Otero, 1952). Corticium and Rhizoctonia solani attack it under wet conditions in Zaire (Blouard and Thuriaux, 1962), and Diplodia in Malaysia (Vivian, 1959). Hutton and Grylls (1956) listed it as susceptible to little-leaf. Generally, however, stylo is one of the most disease-free of the tropical legumes. Grazing management can limit damage by pathogens.'
A variety of insects attack the plant and reduce seed yields under wet conditions in Panama and Bolivia. The caterpillar of the moth Lamprosema diemenalis Gueen. did some slight damage. Colbran (1963) recorded the nematode Meloidogyne hapla on the roots of stylo. In east Nigeria it is recommended in an arable crop rotation because it is not susceptible to the particular nematode affecting these crops (Tuley, 1968).
[The above fungi are listed as widely prevalent on the aphis webpage and the moth and nematode are not listed in the aphis database.]

http://www.fao.org/ag/AGP/AGPC/doc/Gbase/DATA/Pf000070.htm

4.07

No evidence that the species causes allergies or that it toxic to humans.

4.08

(1) On a scale from 1 to 5 this table lists the resistance to fire as 1. (1=lowest, 5=highest) (2) It is advisable to exclude fire from common stylo, as dense stands may be weakened. Light fires or fires passing when the ground is wet are less severe and may even stimulate it. Hot fires when the soil is dry will kill it, and two successive fires will virtually eliminate it. Seeds survive, however and fire stimulates new seedling growth by breaking seed dormancy. 

(1) Humphreys, L. R. Environmental adaptation of tropical pasture plants. 1981. Macmillan publishers Ltd. London. (2) http://www.fao.org/ag/AGP/AGPC/doc/Gbase/DATA/Pf000070.htm

4.09

On a scale from 1 to 5 this table lists the resistance to shade by S. guianensis as 2. (1=lowest, 5= highest) 2)not shade tolerant

Humphreys, L. R. Environmental adaptation of tropical pasture plants. 1981. Macmillan publishers Ltd. London. 2)http://www2.ctahr.hawaii.edu/sustainag/Stylo.htm

4.1

'Does well on the coarser textured soils, but not so well on heavy clays. It grows on tropical latosols, gleys, loams and sandy podzolic soils. Does not do well on fine-textured montmorillonitic clays; prefers well-drained open-textured soils. Can tolerate highly acid soils (Davies and Hutton, 1970), and nodulates at pH 4.0. It is not very tolerant of salinity.' 2)adapted to well-drained upland soils of the sand ridge

http://www.fao.org/ag/AGP/AGPC/doc/Gbase/DATA/Pf000070.htm 2)http://edis.ifas.ufl.edu/BODY_AA194

4.11

It is an erect leguminous herb with no evidence of it having a smothering habit

Humphreys, L. R. Environmental adaptation of tropical pasture plants. 1981. Macmillan publishers Ltd. London.

4.12

No evidence.

5.01

5.02

5.03

It is generally a herbaceous legume but older plants do become very woody at the base.

5.04

6.01

No evidence.

6.02

'Germination at 25 deg C for 10 d in light or darkness was markedly higher in seeds without a pericarp (53%) than in those with the pericarp removed manually (30%) and was lower still in those with a pericarp (22%).' - this suggests seed viability.

Delachiave, M. E. A.; Rodrigues, J. D.; Moraes, J. A. P. V. de; Pedras, J. F.; Rodrigues, S. D.; Boaro, C. S. F. 1988. Germination of seed of Stylosanthes guianensis. I. Imbibition and germination related to the adherent pericarp of seeds. Revista de Agricultura (Piracicaba), 1988, Vol.63, No.2, pp.179-188

6.03

No information.

6.04

Mode of reproduction is through self-fertilization.

Humphreys, L. R. Environmental adaptation of tropical pasture plants. 1981. Macmillan publishers Ltd. London.

6.05

No information. Probably not. The flower morphology does not reveal pollination by any special animals.

6.06

Propagation by seed.

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

6.07

Seeds were sown on 25 November and the appearance of flowers was first observed in the following February.

Ison, R. L. and Humphreys, L. R. 1983. Alltitudinal effects of Stylosanthes guianensis at low latitude site. I. Flowerig. Journal of Agriculture science. 101(1): 223-230.

7.01

The seeds are retained in the pods. 'It aids dispersal … and by being hooked, which enables it to be dispersed on animals' coats. Due to this hooked nature it is likely that the propagules may be dispersed unintentionally.

Burt, R. L., Rotar, P. P. , Walker, J. L. and Silvey, M. W. The Role of Centrosperma, Desmodium and Stylosanthes in improving tropical pastures. 1983. Westview Press. Boulder, Colorado.

7.02

Pasture and cover crop species

7.03

As the seeds are retained in the pod it is unlikely that the seeds are introduced as a produce contaminant.

7.04

7.05

7.06

7.07

The seeds are retained in the pods. 'It aids dispersal … and by being hooked, which enables it to be dispersed on animals' coats.

Burt, R. L., Rotar, P. P. , Walker, J. L. and Silvey, M. W. The Role of Centrosperma, Desmodium and Stylosanthes in improving tropical pastures. 1983. Westview Press. Boulder, Colorado.

7.08

Stylosanthes has indehiscent seeds that is they are retained in the pod. 'It aids seed dispersal by preventing total digestion by grazing animal and… '

Burt, R. L., Rotar, P. P. , Walker, J. L. and Silvey, M. W. The Role of Centrosperma, Desmodium and Stylosanthes in improving tropical pastures. 1983. Westview Press. Boulder, Colorado.

8.01

Perennial suberect herb about 1.2 m high. Pod a single ovoid joint 2.5-3mm X 2mm wide. Seeds 2mm long and 1.5 mm wide.

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

8.02

it is a legume with hard coated seeds that exhibit dormancy.Dark coloured seeds appeared to be more dormant than light coloured seeds. 2)70% of stylo seeds can be hardseeded and seeds may be viable up to 3 years in the soil

Erasmus-M; Pieterse-P-J. 2001.Improving seed germination of Stylosanthes guianensis by means of warm water treatment. South-African-Journal-of-Plant-and-Soil. [print] 2001; 18 (2): 85-86 2)http://www2.ctahr.hawaii.edu/sustainag/Stylo.htm

8.03

'Bailey (1964, 1965a) has shown that stylo has good tolerance to 2,4-D; from about six weeks of age, 1.65 kg. of acid equivalent per hectare can be used. Because stylo is well adapted to low fertility soils where bush regrowth is often troublesome, it is well to know the effect of 2,4,5-T, used in timber control, on this legume. Between 50 and 75 percent reduction in stylo can be expected 12 to 18 months after spraying with 2,4,5-T at 1.1 kg./ ha acid equivalent, mixed with water. Provided the associated grass is not too dense and stylo has set seed, regeneration occurs from both seed and surviving root stocks. Obviously, 2,4,5-T should be used in stylo pastures only in exceptional circumstances.' 

http://www.fao.org/ag/AGP/AGPC/doc/Gbase/DATA/Pf000070.htm

8.04

Seeds survive, however and fire stimulates new seedling growth by breaking seed dormancy. 2)Burning the pasture in February can enhance germination and establishment, but it will also likely kill any live-over plants. tolerant of very close grazing

http://www.fao.org/ag/AGP/AGPC/doc/Gbase/DATA/Pf000070.htm 2)http://edis.ifas.ufl.edu/BODY_AA194

8.05

highly susceptible to anthracnose fungus in wet lowlands

http://www.rlq.dcilgp.qld.gov.au/pastures/4484.html