RESISTANCE TO BACILLUS-SPHAERICUS IN CULEX-QUINQUEFASCIATUS SAY 1823

Biological control of Culex quinquefasciatus using Bacillus sphaericus was considered a practical solution because of its specific and prolo nged killing action against mosquito larvae. To study the feasibility of B. sphaericus ('Spherix') in mesquites control, multicentric trials were undertaken. Initially,. B. sphaericus was very effective but wit hin a year, after 20-25 rounds of application, field populations of Cx . quinquefasciatus developed resistance up to 150-fold. Genetic studie s revealed that resistance was recessive, autosomal and controlled by more than one gene. This is the first report on nature and mode of inh eritance of resistance against B. sphaericus in mosquitoes.