Corm rot of giant swamp taro (Cyrtosperma merkusii) caused by the burrowing nematode Radopholus similis (Nematoda: Pratylenchidae) in the Pacific

Abstract

AbstractThe association between the burrowing nematode Radopholus similis and giant swamp taro is studied in detail for the first time in corms collected from swampy taro patches in Yap, one of the states of the Federated States of Micronesia. The R. similis population from Yap displays similar variation in morphometrics and morphology as reported in the literature. The rot caused by the nematodes is wet with a loose mass of brown dead tissues and a deep brown necrotic centre housing nematodes inside. Usually, the infected tissues spread a disgusting odour typical of this disease. The dead tissues progress into shallow to deep cavities that advance towards the edible, central portion of the corm giving a perforated appearance on the outside of the otherwise smooth corm. The disease becomes more severe as the age of the plant increases. Nematode-infected plants seldom show any above-ground symptoms. The market quality of the corm is greatly reduced by the nematode damage. The widespread occurrence of the disease and the type of damage R. similis causes to the corms pose a serious threat to giant swamp taro production, food security and the continuation of traditional customs on those islands where R. similis occurs.