Pueraria phaseoloides
(tropical kudzu)

P. phaseoloides is a vigorous fast-growing vine included in the Global Compendium of Weeds (Randall, 2012) and listed as one of the most aggressive weeds invading moist habitats in tropical and subtropical regions (USDA-ARS, 2012). It spreads by seeds and by runners (i.e., stolons) which are structures that enable plants to multiply rapidly and colonize entire forests very fast. This species has been extensively introduced in tropical and subtropical region of the world to be used as forage for livestock, to control soil erosion, and as a soil improvement species (Skerman et al., 1991; Cook et al., 2005). P. phaseoloides has the potential to degrade other plants by smothering them under a solid blanket of leaves, by girdling woody stems and tree trunks, and by breaking branches or uprooting entire trees and shrubs by the strength of its weight. Currently, this species is classified as a “noxious weed” in the United States (USDA-NRCS,2012) and as an invasive species in Costa Rica, Ecuador, Puerto Rico and Pacific Islands including Hawaii, Fiji, French Polynesia, Niue and New Caledonia (Soria et al., 2002; Acevedo-Rodríguez and Strong, 2012; Chacón and Saborio, 2012; PIER, 2012).

P. phaseoloides is native to wet tropical areas in southern China, Bangladesh, Bhutan, India, Nepal, Sri Lanka, Cambodia, Laos, Myanmar, Thailand, Vietnam, Brunei, Indonesia, Philippines, Malaysia, Papua New Guinea, and the Solomon Islands. It has been extensively introduced in tropical and subtropical areas to be used as a forage and soil improvement species and it can be found naturalized throughout the humid-tropics (Cook et al., 2005; Acevedo-Rodríguez and Strong, 2012; USDA-ARS, 2012; PIER, 2012). It is well adapted to Northern Australia, the Pacific Islands and tropical regions of Africa, North, Central and South America.

The risk of introduction of P. phaseoloides is very high. This species is an aggressive invasive vine widely cultivated in tropical and subtropical regions of the world and it has the capability to spread rapidly into natural forest, climbing into the canopy of mature trees and forming dense colonies (Cook et al., 2005; Acevedo-Rodríguez and Strong, 2012; USDA-ARS, 2012; PIER, 2012).

P. phaseoloides grows in semi-open to completely open areas at lower and middle elevations. It prefers annual rainfall regimes of >1500 mm, but will grow in the sub-humid tropics in 1000-1500 mm/year rainfall environments, particularly where temporary waterlogging occurs. It is an aggressive weed and can be found growing in pastures, grassland with a scattered shrub layer, riverbanks, coastal forests, disturbed forests, forest edges, along roadsides, waste sites, and even on fences (Soria et al., 2002; Acevedo-Rodríguez, 2005; PIER, 2012; Randall, 2012).

Genetics

The chromosome number for P. phaseoloides is 2n = 22 (Kumar and Hymowitz, 1989).

Physiology and Phenology

In Puerto Rico, P. phaseoloides has been observed flowering and fruiting from November to March (Acevedo-Rodríguez, 2005). In Brazil it has been observed flowering from April to May (Cook et al., 2005).

Associations

P. phaseoloides is widespread in moist open and semi-open areas, often degraded, at lower and middle elevations including pastures, grassland with a scattered shrub layer, and disturbed forests (Soria et al., 2002; PIER, 2012; Randall, 2012). In Puerto Rico, this species is a component of the weed community in roadsides, disturbed areas, and pastures in lower and middle elevations (Acevedo-Rodríguez, 2005). Like many legumes, P. phaseoloides is a nitrogen-fixing species and has root nodules housing Rhizobium bacteria (Skerman et al., 1991; Cook et al., 2005).

Environmental Requirements

P. phaseoloides grows in moist areas at low to middle elevations (from sea level to 1600m asl) with temperatures ranging from 15°C to 30°C, and high precipitation (>1500 mm annual rainfall). Ludlow and Wilson (1970) obtained only 8.3% of the dry matter, 24% of the relative growth rate, and 4% of the leaf area at 20°C as was produced at 30°C. This species grows well in a great variety of soil types (from sands to clay) with pH ranging from 4 to 6.5, but does not perform well on heavy clays (Cook et al., 2005). Landrau et al. (1953) found good growth at pH 4.5 on a lateritic soil, and at pH 4.6-5.1 in a clay soil. It is able to grow in very wet soils and it can survive short periods of flooding. P. phaseoloides does not tolerate salinity or frost conditions and it is not adapted to drought (Skerman et al., 1991; Cook et al., 2005). This species prefers to grow in fully sunlit open areas, but it is also adapted to partially shaded conditions (Cook et al., 2005).

Leaf spot (Pseudocercospora puerariae) is common throughout tropical America, causing defoliation under humid conditions. Anthracnose (Glomerella cingulata) has been reported in P. phaseoloides plants growing in Brazil, Colombia, Ecuador, Peru, Venezuela, and on some islands in the Caribbean. Under prolonged humid conditions P. phaseoloides can be defoliated by the foliar blight Thanatephorus cucumeris (Skerman et al., 1991; Cook et al., 2005).

Animal feed, fodder, forage

• Fodder/animal feed
• Forage

Environmental

• Erosion control or dune stabilization
• Soil improvement

Materials

• Fibre

P. phaseoloides is very similar to the real kudzu Pueraria montana var. lobata. These two species can be differentiated by their capability to produce underground tubers. The species P. phaseoloides does not produce any underground tubers and its fruits are relative narrow (about 5mm across). P. montana var. lobata produce large underground tubers (up to 1.8 m long and 15 cm wide) and its fruits are relatively wide (about 12 mm across; Queensland Department of Primary Industries and Fisheries, 2011).

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

While most growers are concerned to control other weeds to assist the establishment of P. phaseoloides, it can become necessary to control P. phaseoloides itself where it is a weed or invasive plant. This can be achieved with 2,4-D and related compounds. It is also susceptible to paraquat (Riepma, 1962). It recovers from glyphosate at 0.75 kg/ha and from mixtures of asulam with dalapon, triclopyr, etc. (Ikuenobe and Utulu, 1992). Chikoye et al. (2009) describe control in maize by atrazine, a mixture of atrazine and metolachlor, and a mixture of mesotrione, S-metolachlor and atrazine.

Tye (2007) reports the successful eradication of P. phaseoloides from Santa Cruz Island, Galapagos, in a programme that began within one year of its introduction at a single site. Most of the cost of eradication was for labour involved in searching for infestations.

22/07/13 Updated by:

Julissa Rojas-Sandoval, Department of Botany-Smithsonian NMNH, Washington DC, USA

Pedro Acevedo-Rodríguez, Department of Botany-Smithsonian NMNH, Washington DC, USA