Evaluation of field resistance in field‐collected mosquito Culex quinquefasciatus Say through quantification of ULV permethrin/PBO formulation in field bioassays

Abstract

BACKGROUNDPyrethroids are among the most applied adulticides worldwide to control mosquito vectors for prevention of arboviral diseases transmission. However, pesticide resistance development in a mosquito population could lead to decreased control efficacy. While most studies investigate the resistant genotype (i.e. kdr, CYP450, etc.) as explanatory variables, few field efficacy studies have measured pesticide quantities deposited at different distances from the sprayer in association with observed mosquito mortality. The current study determined field delivered amounts of an applied ULV permethrin/PBO formulation (31% permethrin + 66% piperonyl butoxide) by GC/MS and estimated practical resistance ratios using caged mosquito females.RESULTSFor field samples, the extraction method recovered 78 ± 3.92–108 ± 8.97% of the permethrin/PBO formulation when utilizing the peaks of PBO from GC/MS to estimate the concentrations of adulticide deposited near the mosquito cages. The field bioassay showed that the spatial distribution of permethrin/PBO formulation was heterogeneous among three pseudo‐replicates within the same distance. Within the quantifiable permethrin/PBO range of 15.7–51.4 ng/cm2, field‐collected mosquito mortalities started at 64% and linearly increased reaching 100% only in two areas, while all Sebring susceptible mosquitoes died. The field LC95 resistance ratio (RR) of F0 Cx. quinquefasciatus ranged from 2.65–3.51, falling within the 95% CI of RR95 estimated by laboratory vial assays. Tests with and without PBO indicated P450's enzymes contributed to field resistance.CONCLUSIONResults showed the suitability of the collection and quantification method to estimate the field resistance ratio at the applied pesticide rate. Pesticide quantification would also allow the association of the known frequencies of resistance mechanisms (e.g. kdr, CYP450) with field mortalities to estimate the resistance level conferred by such mechanisms. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Isolation, characterization and functional analysis of a bacteriophage targeting Culex pipiens pallens resistance-associated Aeromonas hydrophila

“…pipiens pallens develops resistance to deltamethrin varies depending on the intensity of insecticide selection pressure [ 47 ], with target site mutations contributing significantly under low pesticide selection pressure and metabolic resistance playing a greater role under high pesticide selection pressure [ 47 ]. In the field, mosquitoes are exposed to insecticides at varying concentrations and durations, resulting in the synergistic action of multiple resistance mechanisms [ 48 ]. Previous research has identified widespread target gene mutations in Cx.…”

“…Previous research has identified widespread target gene mutations in Cx. pipiens in mosquito control operation areas [ 48 , 49 ]. Recent studies have indicated that symbiotic bacteria enhance mosquito resistance by directly breaking down the insecticide and increasing their metabolic enzyme activity [ 6 , 9 ].…”