Deltamethrin resistance in Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) in Brazil

摘要

The protectant insecticide deltamethrin has been ineffective against Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) pest in several parts of Brazil, even when used at high doses, showing the high level of pest resistance to this insecticide. Samples from some uncontrolled and other populations of R. dominica were collected to investigate the extent of their tolerance. Eleven strains were bioassayed with deltamethrin using the standard FAO method for resistance to pesticide. Ten strains, originating in Brazil, were designated BR1 to BRIO, and one originating in the United Kingdom was called UK1. Assessment of tolerance to deltamethrin revealed two very resistant strains, BR6 and BR7, and two susceptible strains, BR4 and UK1, while the remaining strains showed intermediate tolerance. Selection pressure (deltamethrin insecticide applied in the laboratory for 21 generations) increased the resistance of BR7 strain 29,937-fold. This work was considered the basic study for the implementation of anintegrated pest management programme in grain storage facilities in southern Brazil.