The susceptibility of Culex pipiens fatigans larvae to insecticides in Rangoon, Burma.

Since April 1963, the susceptibility to insecticides of larvae of Culex pipiens fatigans has been extensively studied by the WHO Filariasis Research Unit in Rangoon, Burma, as part of a programme of research aimed at establishing which compound or group of compounds could be used to control the vector of filariasis.Larvae from various localities in Rangoon showed wide variations in susceptibility to chlorinated hydrocarbons. There were also seasonal variations and it was difficult to standardize test conditions. Nevertheless, resistance to this group of compounds, especially DDT, sufficient to prevent control has been clearly demonstrated. As C. p. fatigans has never been subjected to intensive control by insecticides in Rangoon, the results confirm the findings made elsewhere that this mosquito is naturally resistant to chlorinated hydrocarbons.The larvae are, however, susceptible to organophosphorus compounds, especially fenthion and parathion.