Stylosanthes viscosa


Scientific name

Synonyms

Hedysarum hamatum L. var. viscosum L. (GRIN)
Stylosanthes glutinosa Kunth.
Stylosanthes prostrata M.E. Jones
Stylosanthes viscosa Sw. var. acutifolia Benth. (ILDIS)

Family/tribe

Family: Fabaceae (alt. Leguminosae) subfamily: Faboideae tribe: Aeschynomeneae subtribe: Stylosanthinae. Also placed in: Papilionaceae.

Common names

sticky stylo (Australia);  poor man's friend (Jamaica).

Morphological description

An erect, ascending, spreading or prostrate, multi-branched, perennial from 15 cm to 1 m tall.  Stems to 1 m long, densely pubescent with short viscid hairs.  Leaves trifoliolate, with leaflets ovate to lanceolate, to 25 mm long and 8 mm wide (usually smaller), acute or obtuse, shortly hairy, with two to four pairs of conspicuous veins;  petioles and stipule sheath shortly hairy, viscidInflorescence a small, crowded, viscid ovoid spike, with 2-5 (often pale) yellow flowers;  standard 4-7 mm long.  Loment usually with two fertile articles to 2.5 mm long, shortly hairy, reticulately nerved;  beak on terminal articulation, short, mostly coiled.  Seed size similar to that of S. scabra with 400,000-500,000 seed-in-pod and 600,000-800,000 de-hulled seed/kg.

Distribution

Native to:
North America:  Mexico, USA (southern Texas).
Mesoamerica:  Belize, El Salvador, Guatemala, Honduras, Nicaragua, Panama.
Caribbean:  Costa Rica, Cuba, Hispaniola, Jamaica.
South America:  Argentina, (Chaco), Bolivia, Brazil, Colombia, French Guiana, Guyana, Paraguay, Suriname, Venezuela.
Occurs mostly in open scrub, woodland or open, rocky savanna, usually in fully exposed positions.

Three ecotypes are recognised in Brazil:
1) Prostrate , densely hairy type with small leaves and inflorescences from Rio de Janeiro, Espirito Santo, and very dry caatinga area of Bahia.
2) Erect leafy type with small spikes, and anthocyanin in leaves, from western Minas Gerais.
3) Prostrate type, with large leaflets (no anthocyanin), and thick stems from southern and south-western Minas Gerais - most susceptible to anthracnose.

Naturalised in:
Now naturalised in Australia following evaluation.  Naturalised populations in Africa (Sierra Leone) may, in fact be S. fruticosa .  It is also uncertain whether certain of the above American populations are native or naturalised.

Uses/applications

S. viscosa has not been evaluated widely but may have a role in reducing tick populations (order Acarina) in grazing lands.  Generally considered too unpalatable to be successful in evaluations, but there may be more palatable and anthracnose resistant types should the need arise.

Ecology

Soil requirements

Occurs on soils with pH from 4-7.5 (mostly acid), often on sandy or sandy loam soils of sedimentary or granitic origin, but also on clays and clay loams.  Soils are generally well drained.  Tolerant of high soil Al+++ levels.

Moisture

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Average rainfall at collection sites varies from 230 mm in Baja California, Mexico, to 3,200 mm in Cayenne, French Guiana, often with long dry seasons.  Most accessions have been collected from sub-humid sites receiving 1,000-1,750 mm rain per year, with a 4-5 month dry season.  High level of drought tolerance, comparable with that of S. scabra .  Generally intolerant of waterlogging , particularly ecotypes from semi-arid tropics.

Temperature

Tropical to warm subtropical in distribution, from 29°S to 29°N, and from sea level to 2,000 m asl.  Ecotypic differences in frost tolerance .

Light

Mostly found in open situations suggesting low tolerance of shading.

Reproductive development

At about 20ºS, flowering commences from late February/early March to late May depending on ecotype.

Defoliation

Tolerant of heavy grazing, although grazing pressure often modified through low palatability of S. viscosa herbage.

Fire

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Fire tolerance varies with ecotype (e.g. CPI 34904 susceptible, CPI 38611 tolerant).

Agronomy

Establishment

Embryo dormancy in fresh seed declines rapidly.  The main restriction to germination is hard seededness, which is often high in freshly harvested seed.  Natural breakdown of hard seededness is brought about by exposure to soil surface temperatures of 50-55ºC.  In the seasonally dry tropics, dry season soil surface temperatures are sufficient to soften seed in readiness for the first rains.  When rapid germination and establishment of a proportion of the seed is desirable, various scarification treatments have been developed, often involving dry heat.  Recommendations vary from 1-2 hours at 85ºC in a heated oven, to 15-30 seconds on a hot surface at 140-150ºC, in each case cooling to ambient temperature.  Since heat treatments can damage seed, the safest and most practical way of scarifying seed is to use a hammer mill, which de-hulls and scarifies about 50% of the seed.  Seed is sown at 1-2 kg/ha.  Seedlings tend to be weak and slow growing during the first season.  Inoculation is not essential since S. viscosa nodulates readily with a wide spectrum of rhizobium strains, but use of CB 82 or CB 756, strains proven effective on this species, provides a measure of insurance.

Fertiliser

While able to establish and persist on low phosphate soils, S. viscosa responds to applications of 10-20 kg/ha P on such soils.  This is of benefit to both plant and animal.

Compatibility (with other species)

Once established, S. viscosa can persist with many of the grasses that grow in the same environment.  Also competes with many lower growing weed species, but not with taller-growing, unpalatable species.

Companion species

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Pests and diseases

Susceptibility to anthracnose caused by Colletotrichum gloeosporioides varies from highly susceptible to resistant, depending on genotype.  Fifty-six per cent of accessions tested were resistant to a mixture of races 1 and 2 of Type A of the organism.  Susceptible to blight caused by Sclerotium rolfsii as are many plant species.  Slightly affected by legume little leaf phytoplasma , but possibly not as severely as is S. scabra .  Some resistance to root knot nematode (Meloidogyne javanica), e.g. CPI 38611.

Ability to spread

Capable of spreading from plots.

Weed potential

The ability to set seed and the low palatability of herbage, combined with the ability to survive dry conditions in poor soils may confer weed potential on some accessions.

Feeding value

Nutritive value

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CP and P levels of mature herbage range from 6-12%, and 0.05-0.13% P respectively.

Palatability/acceptability

Generally considered unpalatable.  Low palatability compared with Centrosema acutifolium , Desmodium velutinum and Zornia glabra .

Toxicity

No information available.

Production potential

Dry matter

Generally not as productive as S. scabra .  Yields of the order of 1,500 kg/ha have been recorded.

Animal production

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No information available.  Appears to have little benefit on animal production.

Genetics/breeding

2n = 20.  Sporadic inter-specific crosses occur.  Evidence suggests that S. viscosa is the maternal parent of the allotetraploid , S. scabra , with S. seabrana the pollen parent.

Seed production

Seed production is difficult with this species due to the sticky nature of the inflorescence, leaves and stems.  The viscid substance, which is soluble in organic solvents but not water, is difficult to remove from equipment used in the harvesting process.

Herbicide effects

No information available.

Strengths

  • Drought tolerant.
  • Grows on poor soils.
  • Persistent.
  • Some resistance to anthracnose.
  • Acaricidal properties.

Limitations

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  • Unpalatable.
  • Susceptible to waterlogging .
  • Little benefit to animal production.

Other comments

Only a small fraction of the variation available has been tested to date and, with its wide range of adaptation, it should be much more closely examined, especially if the reasons for erratic palatability can be determined.  The majority of accessions conserved ex situ are of Brazilian and Venezuelan origin.  Areas in Central America and Mexico have been identified as possible sources of novel genetic variation and for conservation activities.  Acaricidal properties in some lines.

Selected references

Keller-Grein, G. and Schultze-Kraft, R. (1992) Preliminary agronomic evaluation of a Stylosanthes viscosa Sw. collection. Genetic Resources Communication Number 15. (CSIRO Division of Tropical Crops and Pastures, St Lucia, Queensland, Australia.)
Stace, H.M. and Edye, L.A. (eds) (1984) The biology and agronomy of Stylosanthes . (Academic Press: Sydney, Australia).

Internet links

Cultivars

Cultivars

Country/date released

Details

None released to date.      

Promising accessions

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Promising accessions

Country

Details

None reported.