In Mambaí (Goiás) the population use various types of building materials. Since a variation in the persistence of BHC activity has been noted in different materiais, laboratory experiments were designed to investigate this aspect. The experiments employed a test kit of ten first instar Dipetalogaster maximus and verified the time necessary to achieve 50% mortality (LT50) after continuous contact with the sprayed surface. The tests were always done in duplicate with adequate Controls. Thirty-two surface from ten types of materials were tested at intervals up to 627 days after spraying. The results obtained can be summarized as follows: 1) the residual activity of BHC could be detected in ourtest system up to the final observation, 627 days after the test; 2) this activity variedgreatly among the different materiais 88 days after spraying. This variation was also related to variations in the atmospheric relative humidity; and 3) the capacity of the materiais to retain the residual activity of BHC in this system was the following in the order most efficient to least: adobe mud and unfired brick, tile, palm fronds and plaster without lime, straw and plaster with lime, fired brick and wood.
Insecticide; Residual activity; Triatomines; BHC