Low-Level Resistance to Bacillus sphaericus in a Field-Treated Population of Culex quinquefasciatus (Diptera: Culicidae)

Abstract

A field-collected population of Crlex pipietls quinquefasciatus larvae from an urban area of Recife (Brazil), which has been treated for 2 yr with Bacillus sphaericus, was found to be ≈10-fold less susceptible than control field populations. Comparative in vitro binding experiments between the radiolabeled toxin from B. sphaericus and isolated midgut brush border membranes from the treated and the untreated larval populations, indicated no change in the affinity of the midgut receptor of the treated population for the toxin, and only a slight decrease in the receptor concentration.