Distribution of breeding and control of the filariasis vector Aedes samoanus in leaf axils of Pandanus in Samoa

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Abstract
Water in leaf axils of the screwpine Pandanus was sampled for mosquito immature stages at seventy villages in Upolu, fifty-five in Savai'i and three in Manono, the main islands of Samoa. Ten plants in every patch of Pandanus plantation were sampled at each village. Among 23,049 mosquito larvae collected from Upolu, 77% were the filariasis vector Aedes (Finlaya) samoanus, 17.7% were Ae. (Fin.) oceanicus and 5.3% were Ae. (Fin.) tutuilae. Out of 6981 larvae taken in Savai'i, 23.2% were Ae. samoanus, 67.6% Ae. oceanicus and 9.2% Ae.tutuilae. When larval counts per plant were analysed for each district, Ae. samoanus was found to predominate in Pandanus in Upolu and Ae. oceanicus in Savai'i. However, the adult density of Ae.samoanus was higher in Savai'i and this was attributed to the large areas of forests with Freycinetia for Ae.samoanus breeding. In Pandanus in Savai'i the number of Ae.samoanus was negligible. In Upolu, with more urbanization and larger plantations, there was greater breeding of Ae.samoanus in Pandanus. Two control trials were conducted against Ae.samoanus larvae in Pandanus, one using a sand culture of the parasitic nematode Romanomermis culicivorax and the other with temephos, an organophosphate insecticide. While R. culicivorax did not adapt to the leaf axil habitat, all plants were without larvae for 5 weeks after treatment with temephos.