Field trial of permethrin for the control of Triatoma infestans.

Control of Chagas’ disease vectors in Central and South America has relied principally on repeated spraying of infested houses with benzene hexachloride (BHC) or dieldrin. Nevertheless, the continued use of these chlorinated hydrocarbon insecticides is currently under review. In Venezuela, strains of Rhodnius prolixus resistant to dieldrin and crossresistant to BHC have already emerged (1, Z), and several organophosphorus and carbamate insecticides are being evaluated as alternative control agents (3, 4). In Argentina, ultra-lowvolume application of malathion (5) has replaced BHC in a substantial part of the national campaign to control Chagas’ disease. It thus seems inevitable that BHC will eventually be replaced as the preferred insecticide for triatomine control in Brazil as well. Prolonged residua1 activity is considered an important feature of a triatomine control agent. For one thing, the bugs can remain hidden in deep wall-crevices many days before emerging to feed. Also, egg-laying sites are often virtually invulnerable to direct insecticide spraying, and eggs can normally take up to 20 days to hatch. Thus, to achieve effective population control it is desirable for the insec-