title: Resistance development in Culex quinquefasciatus to spinosad: a preliminary report.
abstract: A Culex quinquefasciatus colony was established from surviving late instars and pupae from a semifield microcosm test with Natular XRG (a granular formulation containing 2.5% spinosad) applied at 14.2 kg/ha. The initial lethal concentrations for 50% and 90% of the population (LC50 and LC90) against Natular XRG were determined in the laboratory for the 1st generation progeny (F1). Selection was applied at LC70-90 levels to 10,000-15,000 of late 3rd and early 4th instars each generation. Susceptibility changes were determined every other generation and referenced to a susceptible laboratory colony as well as freshly collected wild populations of the same species concurrently. Tolerance to spinosad (resistance ratio < 5.0 fold) was observed up to F8 generation in the selected population. Thereafter, resistance ratios increased significantly from F10 to F16 generations, being 7.26- to 20.52-fold at the LC50 and 7.48- to 20.08-fold at the LC90 level.
authors.affiliation: West Valley Mosquito and Vector Control District, 1295 E Locust Street, Ontario, California 91763, USA.
authors.forename: Tianyun
authors.initials: T
authors.lastname: Su
authors.forename: Min-Lee
authors.initials: ML
authors.lastname: Cheng
mesh_terms: D000818:Animals; D003465:Culex / Q000187:drug effects* / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D007305:Insecticide Resistance / Q000235:genetics / Q000502:physiology*; D007306:Insecticides / Q000494:pharmacology*; D007928:Lethal Dose 50; D018942:Macrolides / Q000494:pharmacology*; D012641:Selection, Genetic
chemical_list: D004338:Drug Combinations; D007306:Insecticides; D018942:Macrolides; C415329:spinosad