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Crops > Roots & tubers > Yam > Yam borer, Solomon Is

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Yam borer, Solomon Islands

May 2005. Last month a group from Kastom Gaden Association – an NGO – and friends walked the south coast of Guadalcanal, Solomon Islands. It is called the weather coast, and not without reason: rainfall is between 5000 and 8000 mm a year, winds are strong, and without a fringing reef and with steeply descending shores, the seas are very rough indeed.

The area was famed for its taro and Dioscorea alata yams. In the last 25 years, both have been replaced by sweet potato and cassava. Everywhere taro is affected by alomae, a lethal virus disease (called chuaka locally), and yams have Pratylenchus coffeae nematode, pange.

In one village, the yams were riddled with holes made by the larva of an unknown insect (see photo). All the farmers could say was that the ‘worm’ was not new, but had got worse in recent years, and was destroying the crop. If anyone knows what it might be, please let me know. The width of the yam is about 10 cm.

There were four suggestions:

1. Papuana larvae or other Scarab larva [Papuana is known to attack yams] e.g., Elateridae – wireworm/click beetle – but the damage is not typical;
2. Elytroteinus – the weevil that causes damage in kava, ginger etc, – but the size of the damaged areas looks wrong for this;
3. Nematodes – the analogy given were the holes in Cyrtosperma made by the burrowing nermatode, Radopholus similis, in Yap, Federated States of Micronesia.

The damage might have occurred when the yam was smaller and increased as the yam grew in size –
this correlates with their being no larvae present.