Persistence of Vectobac WDG and Metoprag S-2G against Aedes aegypti larvae using a semi-field bioassay in Rio de Janeiro, Brazil

persistence of bacillus thuringiensis var. israelensis (vectobac wdg) and methoprene (metoprag s-2g) was evaluated against aedes aegypti late third instar larvae of the rockefeller strain in a semi-field bioassay. tests were performed in rio de janeiro, using containers made of plastic, iron, concrete and asbestos, placed in a shaded area. the formulations used were 0.2 g of vectobac-wdg and 1g of metoprag s-2g per 100 liters of water in house storage containers. vectobac wdg was tested twice, in march and in april/may, 2002. in march (temperature ranging from 21.5 to 39.3 oc), 70-100% mortality was observed by the 7th day and declined abruptly thereafter. no significant differences were observed among the container types. in april/may (18.6 to 34.8 oc) mortality was higher than 70% to 30-36 days in all cases, except in the iron container (40% mortality on the 12th day). metoprag s-2g was evaluated in april/may, 2002, and induced mortality higher than 70% up to 15 days in the plastic and iron containers and only seven days in the concrete container. in the asbestos container, maximal mortality was achieved on day one post-treatment (66%). our results point to a low persistence of both formulations in the weather conditions of rio de janeiro.