Laboratory evaluation on the efficacy of Bacillus thuringiensis var. israelensis Berliner 1915 (Bacillaceae) on the instars of the dengue vector Aedes aegypti Linnaeus 1762 (Diptera: Culicidae) and against the adults of Diplonychus indicus Venk. & Rao (Hemiptera: Belostomatidae) as non-target organisma

Abstract

Mosquito control agents based on bacterial insecticides are the most widely used microbial pesticides as they are environment friendly alternatives to chemical insecticides and hold tremendous potential with improved efficacy. On the other hand, it is also necessary to preserve the non-target organisms, especially those that predate upon target mosquito larvae. Since, chemical larvicides are largely non-selective owing to their deleterious role on non-target organisms, bacterial insecticides when used do not cause harm to them. Therefore, in the present investigation, the toxicity of Bacillus thuringiensis var. israelensis was evaluated on all the larval instars of Aedes aegypti at concentrations of 0.1, 0.2, 0.3 and 0.4%. The LC50 values after 24, 48 and 72 hours against the first, second, third and fourth instars were 0.20, 0.19 and 0.17%; 0.16, 0.15 and 0.15%; 0.19, 0.18 and 0.16%; 0.14, 0.12 and 0.12% respectively. Further, the adults of Diplonychus indicus which were tested as the non-target organism was exposed to the same concentrations of bacterial formulation and the results indicated that they did not have toxic effect and that the treated adult bugs were normal with high predatory potential. The present research indicated that integration with appropriate biocides may not interfere with the biocontrol potential of the predator in controlling mosquitoes.