Larvicidal control of peridomestic mosquitoes

Abstract

The problem of mosquito breeding in peridomestic water containers is discussed, with special reference to conditions in Eastern Nigeria. An attempt at control by sealing water pots using local materials which was successful for a time, but later frustrated by local social custom, is described. Various applications of insecticides in solid preparations for the control of similar situations are reviewed. Experiments to evaluate the commoner synthetic insecticides are then described DDT, dieldrin, and BHC were tested against 4th-instar mosquito larvae of two species — A. aegypti and C. fatigans — in the form of alcoholic solutions, aqueous suspensions, and aqueous solutions.LD 50 values for the first two states are given, and it is concluded that for the preparation of larvicides in solid form the most effective toxicants will be dieldrin and gamma BHC, in the form of dieldrin and lindane powders. A series of field trials of various types of insecticidel briquettes and pellets for the control of A. aegypti in African water pots is described.Trials of pellets stabilized with plaster-of-Paris show these to be effective over a fair period, but unreliable due to disintegration. Sand cement pellets are found to be ineffective where DDT is used as the toxicant, but highly effective for a year or more when either dieldrin or lindane is used at 16 per cent. by weight.The possibility of controlling by similar means larger breeding places such as borrow pits is considered.