Field Investigations on the Use of Heavy Dosages of Several Chlorinated Hydrocarbons as Mosquito Larvicides 1

Abstract

Summary Several of the newer chlorinated hydrocarbons were tested near Savannah, Georgia, at heavy dosages in an effort to establish a long period of effective control against mosquito larvae. In residual larvicidal tests in small landlocked ponds effective control for differing periods was obtained with heavy dosages of DDT, benzene hexachloride, toxaphene and dieldrin. Dieldrin was the most effective and at one pound per acre controlled breeding for 62–78 weeks. DDT at 3 pounds per acre was effective for only 13–23 weeks, and the addition of rosin did not significantly improve its action. The other two toxicants gave less enduring results. The effectiveness of DDT and BHC was greatly reduced by a constant flow of water into or through test ponds. Preflood applications, at 3 pounds per acre to dry ponds subsequently filled by rains, also showed the superiority of dieldrin, which controlled breeding for more than 18 weeks, closely followed by DDT and DDD which in some instances exhibited a residual action for more than 17 weeks. Five treatments per year with technical benzene hexachloride applied each summer for 3 consecutive years at the rate of 1 pound per acre to the ponds resulted in no fish injury which could be attributed to the effects of the BHC treatments. All other materials used in these tests were decidedly harmful to fish and other aquatic organisms and should never be applied in the above concentrations where these are of importance.