The value of a spreading agent in larvicidal formulations containing DDT.

The value of a spreading agent in a 5% solution of DDT in oil was assessed under semifield conditions using third-stage laboratory-bred larvae of Anopheles gambiae. These larvae were treated with known dosages of the larvicide with and without the addition of spreading agent, and the mortalities produced by the two forms of the larvicide were compared. An attempt was also made to compare the efficacy of the two forms under field conditions. The trials described seem to have shown quite conclusively that, so far as a 5% solution of DDT in oil is concerned, there is no advantage to be gained by adding spreading agents to the larvicide.