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   Dioscorea bulbifera (herb, vine, climber)     
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      Dioscorea bulbifera foliage (Photo: James H. Miller, USDA Forest Service, Bugwood.org) - Click for full size   Dioscorea bulbifera foliage (Photo: Amy Ferriter, South Florida Water Management District, Bugwood.org) - Click for full size   Dioscorea bulbifera infestation (Photo: USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org) - Click for full size   Dioscorea bulbifera habit (Photo: Forest & Kim Starr, United States Geological Survey, Bugwood.org) - Click for full size   Dioscorea bulbifera bulbils (Photo: James H. Miller, USDA Forest Service, Bugwood.org) - Click for full size   Dioscorea bulbifera habit (Photo: Forest & Kim Starr, United States Geological Survey, Bugwood.org) - Click for full size
    Taxonomic name: Dioscorea bulbifera L.
    Synonyms: Dioscorea hoffa Cordem., Dioscorea tamnifolia Salisb., Dioscorea bulbifera L.  var. vera Prain & Burkill, Dioscorea crispata Roxb., Dioscorea dicranandra Donn.Sm., Dioscorea heterophylla Roxb., Dioscorea pulchella Roxb., Dioscorea tenuiflora Schltdl., Helmia bulbifera (L.) Kunth, Smilax decipiens Spreng.
    Common names: ‘oi (Cook Islands), aerial yam, air yam (English), air-potato, ápwereka (Chuuk Islands), belloi (Palauan-Palau Islands), bitter yam, Brotwurzel (German), cheeky yam (English), dau fasia (Solomon Islands), dau kwasi (Solomon Islands), ellal (Kosrae Island), hoei-oepas (India), hoi (Hawaiian-Hawaiian Islands), hoi (Niuean-Niue Island), hoi (Tongan-Tonga Islands), hoi (Tahiti Island), igname bulbifère (French), inhame (Portuguese-Brazil), kaile (Fijian-Fiji Islands), kaile manu (Fijian-Fiji Islands), kaile ndranu (Fijian-Fiji Islands), magnaheugo (Chamorro-Guam Island), mata (Marshallese-Marshall Islands), ñame de gunda (Spanish), palai (Pohnpei Island), papa voladora (Spanish), pi‘oi (Hawaiian-Kaua‘i Island), potato yam, pousse en l'air (French), pureka (Namoluk (Nómwunuuk) Atoll), puruka (Satawan Atoll), pwer (Satawan Atoll), pwereka (Chuuk Islands), pwerh (Puluwat (Pwonowót) Atoll), rook (Yapese-Yap (Waqab) Island), sarau (Fijian-Fiji Islands), soi (Samoan-American Samoa Islands), wild yam (English), yam (English), Yamswurzel (German), yoi (Yapese-Yap (Waqab) Island)
    Organism type: herb, vine, climber
    Dioscorea bulbifera is a highly invasive plant and presents a management problem in many parts of the world. Despite some medicinal and agricultural uses, D. bulbifera is widely characterized as an organism that outcompetes and smothers native vegetation.
    Description
    Dioscorea bulbifera is a monocotyledonus, dioecious, herbaceous perennial vine. Its annual stems, which arise from tubers, twine counterclockwise (Schultz, 1992). Langeland (undated) writes that "stems are round or slightly angled in cross section...[and] leaves are long petioled [with] blades to 8 in or more long." D. bulbifera has simple, alternate, obvate leaves, characterized by their distinct heart shape and veined pattern. Aerial tubers, or bulbils, arise from the axils of the plant and are usually smooth and subspherical. D. bulbifera is identifiable especially by its aggressively climbing, twining stems, which reaching lengths of 60 feet or more, and its "large heart shaped leaves...and potato like aerial tubers from the leaf stems" (Schultz, 1992).
    Similar Species
    Dioscorea alata, Dioscorea sansibarensis

    More
    Occurs in:
    ruderal/disturbed, urban areas
    Habitat description
    Dioscorea bulbiferademonstrates aggressive growth in a variety of mesic habitats, especially thickets, disturbed areas, fence rows, and hardwood hammocks. D. bulbifera does not inhabit coastal areas due to its salt intolerance, and it is rarely found in pinelands (Morisawa, 1999). In tropical hammocks, D. bulbifera's growth is most concentrated in canopy gaps (Shultz, 1992).
    General impacts
    As an invasive plant, Dioscorea bulbifera has a variety of negative impacts. D. bulbifera interrupts natural ecosystem function by forming a mat of vines impenetrable by other plants or sunlight. D. bulbifera can smother both seedlings as well as full grown trees (Shultz, 1992) D. bulbifera also impacts wildlife species dependant on native vegetation. Economically, extra taxes and fees sometimes must be levied to help pay for control and eradication efforts. (Invasive.org, 2002).
    Uses
    Schultz (1992) notes that "Dioscorea bulbifera is one of the most common and widespread food yams and can be found in every hot, humid tropical region of the world." D. bulbifera is high in diosgenin, and is collected in the wild for steroidal drug hormones. Chemicals derived from D. bulbifera are also used in contraceptive pills. (University of Wisconsin-Madison, 1999).
    Notes
    In an analysis of 4 wild Nepalese yam species, including Dioscorea bulbifera, Bahndari and Kawabata (2004) found that constituent chemicals in the yams "tend to imply that…wild yams may present a health hazard potential, which in turn demands propor processing before consumption to eliminate the effects of the antinutrients." Another study, by Beck et al (1984), evaluated traditional preparation methods of wild yams by Australian aboriginals. The process of baking, slicing, and leaching the yams overnight in running water removed the bitter compound diosbulbin D, making the yams palatable.
    Plant microfossil analysis from the Me' Aure' Cave in Moindou, New Caldaonia, and the Yuku rock sheltor in Papua New Guinea suggests that D. bulbifera or a closely related precursor was present in these regions between 2700-18000 YBP (Horrockset al, 2007a;Horrockset al, 2007b).
    Geographical range
    Native range: Africa; Asia (Alexander,et al, 1968); Australia (GRIN, 2007)
    Known introduced range: North America; South America (GRIN, 2007)
    Introduction pathways to new locations
    Floating vegetation/debris:
    Ignorant possession:
    Landscape/fauna "improvement":


    Local dispersal methods
    For ornamental purposes (local):
    Garden escape/garden waste:
    Horticulture (local):
    Management information
    Management of Dioscorea bulbifera is generally labor intensive, expensive, and requires multiple visits to control sites. Horvitz and Koop (2001) participated in a study which investigated the relationship between native and non-native vine behaviour in the Miami-Dade area. Their intensive control program for D. bulbifera included: pruning native vines for better access to non-natives; cutting non-native vines; hand application of herbicide to non-native vines; hand pulling non-native seedlings/tubers; and positioning and pruning native species to facilitate growth and canopy access. Sites were revisited within 6 months for recutting, reapplication of herbicides, and "hand removal of seedlings or other regenerative organs" (Horvitz and Koop, 2001). Horvitz and Koop (2001) note that "management significantly reduced seedling recruitment by non-native vines." Other researchers cite similar active management techniques for D. bulbifera, whose bulbils/tuber system is notoriously difficult to eradicate. Shultz (1992) notes the importance of disposing removed plant material in a secure location to avoid re-germination.

    Preventative measures: D. bulbifera should not be recommended as an ornamental plant. It is classified as a Class A Noxious Weed in Alabama and as a noxious weed in Florida (NRCS, 2007).

    Chemical: Morisawa (1999) writes that "RoundUp, a nonselective herbicide, will kill the vines but the tuber will most likely resprout...Garlon 4 applied at a 10% concentration provides good control when applied with the basal application method. Completely encircle the lowest 30-61cm of the stem or trunk with the herbicide and form a band at least 15cm wide. Garlon 4 (10% concentration) and Garlon 3A (50% concentration) provide excellent control when applied to a cut surface." Wound vines with a hatchet and apply herbicide during the growing season (Morisawa, 1999).

    Biological: An ongoing study by Sambura and Pemberton (ARS, 2007) seeks to identify natural insect herbivores of D. bulbifera in Nepal. So far the researchers' have identified a possible biological control agent in the Nepalese air potato beetle, Liliocerus spp.

    Reproduction
    Dioscorea bulbifera is vegetatively propagated. By producing an abundance of bulbils (aerial tubers) in its leaf axils, D. bulbifera assures its continuation, especially since soil contact is not necessary for stem production (Morisawa, 1999).
    Lifecycle stages
    Morisawa (1999) writes that tubers and bulbers of Dioscorea bulbifera usually sprout during spring, using dead vegetation from the previous years' growth to gain access to the canopy. Bulbils, which can lie dormant for up to a year, are produced in mid-summer and drop to the ground in the late summer/early fall (Schultz, 1992). Stems begin to die back in the early fall. Morisawa (1999) notes that "raccoons, wild hogs and other animals do not seem to feed upon the bulbils," a factor which contributes to D. bulbifera's rampant growth.
    Reviewed by: Forest Starr and Kim Starr, Botanical Research Associates United States Geological Survey Biological Resources Division Makawao, Maui, Hawaii USA
    Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
    Last Modified: Monday, 14 January 2008


ISSG Landcare Research NBII IUCN University of Auckland