Interruption of chemical mosquito control and evolution of insecticide resistance genes in Culex pipiens (Diptera: Culicidae)

摘要

Within the Llobregat Delta, Barcelona, Spain, C. pipiens has been the target of organophosphate insecticide (OP) control for 10 years (1982-92). Between 1991 and 1992, OPs were replaced by Bacillus-based toxins in all the mosquito control programmeswithin >150 km of this area. The distribution of several OP-resistance genes was surveyed within the Llobregat Delta and neighbouring populations (<25 km distant) during the 2 years following this regional pesticide change to investigate how the changein selection pressure affected the dynamics of OP-resistance genes. The immigration failure of the A2-B2 resistant esterases and the observed difference in OP-resistance dynamics between isolated and nonisolated populations may indicate fitness disadvantages associated with OP-resistance genes, hence a tendency for a decrease in OP-resistance. In contrast, one OP-resistance gene further increased in frequency, whereas the frequencies of some others were maintained. These unexpected results question theimportance of pesticides from sources other than mosquito control, and the variability of pleiotropic fitness costs among pesticide resistance genes.