Efficacy of Vectobac DT and Culinexcombi Against Mosquito Larvae in Unused Swimming Pools in Malindi, Kenya

Abstract

The efficacy and persistence of 2 bacterial larvicides, Vectobac-DT (Bacillus thuringiensis israelensis [Bti]) and CulinexCombi (Bti and Bacillus sphaericus [Bs]), were tested against Anopheles gambiae and Culex quinquefasciatus in temporarily unused swimming pools with rainwater in Malindi, Kenya. Preand posttreatment larval densities were recorded by sampling with the standard WHO dipping technique for 8 consecutive days. The larvicides were applied to the pools with a knapsack sprayer. The data showed that Vectobac-DT was highly effective against early instars of An. gambiae with 89% reduction within 24 h but not as effective against the early stages of Cx. quinquefasciatus with reduction of only 46%. CulinexCombi resulted in high mortalities to early instars of both species with over 97% reduction within 24 h, but showed a drastic reduction 48 h after application. Both Vectobac-DT and CulinexCombi were highly effective against late instars of both species, whereby Vectobac-DT persisted much longer than CulinexCombi. Anopheles gambiae was found to be more susceptible to both larvicides than Cx. quinquefasciatus. By their high efficacy and good persistence against mosquito larvae, both Vectobac-DT and CulinexCombi can be recommended for use in integrated mosquito control programs.