A network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests.
PestNet is a network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests. It started in 1999. Anyone with an interest in plant protection is welcome to join. PestNet is free and is moderated, ensuring that messages are confined to plant protection.
May 2015. People were reportedly ill when they ate the yam in the images sent, and the id of the plant was requested. Recently, several families in Pohnpei become very sick (diarrhoea and vomiting) from eating the tuber. The yam is not D. alata because it has thorns on the stem; the flesh is yellowish. Unfortunately, the leaves have not been seen.
At first members said that it was Dioscorea bulbifera, but that was wrong. Most species of D. bulbifera need much processing, but they have not often been reported to be poisonous, although there are reports from Florida and Guam. The following reference from Guam states: Stone BC, The Flora of Guam, Vol. 6, 1970, pp. 127-128: “Tuberous vine, tubers usually globose or pear-shaped, sometimes lobed, some edible (in cultivated races), others (in wild races) causing nausea or fatal; flesh yellowish; stems generally bearing bulbils, twining to the left (clockwise); leaves broadly cordate… East Africa to Polynesia; the most widespread of all yams (Burkill).” D. dumentorium was also said to be a possibility as there are poisonous and non-poisonous types, and the tuber is yellow.
While D bulbifera certainly fits the bill as regards its tubers (“The very bitter underground tubers and the improperly prepared bulbils are poisonous” ), the problem is that all descriptions I’ve read report that its vines lack spines or thorns-(e.g. “The slender, twining, hairless, green to purple-flecked stems…. have no spines.” ,which Konrad’s photo show clearly.
Another member thought that the more likely candidate was Dioscorea hispida – in English sometimes known as “Bitter Yam,”- Not only are its tubers poisonous (requiring extensive preparatory soaking, etc. if eaten), but there are small spines/prickles/thorns on the main vine (see photo at: http://id.wikipedia.org/wiki/Gadung or in Jacques Barrau’s various illustrations). Barrau also reports this species as present on Ponape/Pohnpei, back in the 1950s – Barrau J (1962) Les plantes alimentaires de l’Océanie: origines, distribution et usages. Marseille, Faculté des Sciences de Marseille.p. 114).
There is another reference to the yam being on Pohnpei in Barrau, J. 1962. “Edible yams of the South Sea Islands, species present, vernacular names and distribution” In: The Secretariat, P.S.C. ed. Proceedings of the Ninth Pacific Science Congress of the Pacific Science Association 1957. Volume 4 Botany. Bangkok, Secretariat, Ninth Pacific Science Congress, pp.309-311. See p. 309: Dioscorea hispida Dennst…… “. This variety is to be found only in New Guinea and at Ponape, Caroline islands. I have found it in the cultivated state in the latter island.” Online at: http://www.archive.org/stream/proceedingsofthe029625mbp/proceedingsofthe029625mbp_djvu.txt
See also: Balick,MJ ed. (2009) Ethnobotany of Pohnpei: plants, people, and island culture. Honolulu /New York, University of Hawaii Press; New York Botanical Garden, xi, 585 p. for up-to-date information on this species. Alternatively, he early Bishop Museum Bulletin No 209: Glassman SF (1952) The flora of Ponape. 152 p.
In addition, there is an entry on ProMED mail Subject: PRO/EDR> Food poisoning, wild yams – Philippines. Archive Number: 20100409.1143FOOD POISONING, WILD YAMS – PHILIPPINES concerning people poisoned from eating D. hispida.
Illustrations from Barrau J (1962) Les plantes alimentaires de l’Océanie: origines, distribution et usages. Marseille, Faculté des Sciences de Marseille, p. 111) were also sent showing the differences between D. hispida and D. bulbifera.