title: Geographic Variation in Phosphine Resistance Among North American Populations of the Red Flour Beetle (Coleoptera: Tenebrionidae).
abstract: The red flour beetle, Tribolium castaneum (Herbst), is a common stored-product pest found worldwide. Phosphine, hydrogen phosphide (PH3), is the most commonly used fumigant for stored grains, for which genetically based resistance has been recorded for several pest species. This study assessed phosphine resistance in 25 T. castaneum populations from across the United States and Canada using a discriminating dose bioassay. Dose-mortality assays were conducted with adults from seven of these populations to categorize weak and strong resistance phenotypes. Phosphine resistance was detected in 12 out of the 25 populations, and the frequency of resistance within populations varied from 2% in Victoria, TX, to 100% in Red Level, AL. Two resistant populations from Kansas that had been sampled three years earlier were found to have similar resistance frequencies in the current study. None of the four Canadian populations had any detectable resistance among the insects tested. Resistance ratio calculations from LC50 value in resistant populations relative to the LC50 for the laboratory susceptible strain allowed resistance phenotypes to be assigned as either weak resistance, at 5- to 26-fold resistance relative to susceptible, or strong resistance at 95- to 127-fold relative to susceptible. This study suggests that proper resistance assessment techniques can help to determine occurrence of phosphine resistance in populations of T. castaneum and can further characterize the strength of resistance present. These data can be used to support resistance management programs that consider either cessation or modification of phosphine fumigation to control T. castaneum.
authors.affiliation: Department of Entomology, Kansas State University, Manhattan, KS 66506 ( ajcato@email.uark.edu ; twp1@ksu.edu ).|Present address: Department of Entomology, 319 Agriculture Building, University of Arkansas, Fayetteville, AR 72701.
authors.forename: A J
authors.initials: AJ
authors.lastname: Cato
authors.affiliation: Infestation Control and Sanitation, Canadian Grain Commission, 600-303 Main St., Winnipeg, Manitoba, Canada R3C 3G8 (Brent.Elliott@grainscanada.gc.ca).
authors.forename: Brent
authors.initials: B
authors.lastname: Elliott
authors.affiliation: Department of Agriculture and Fisheries, Queensland, Ecosciences Precinct, GPO Box 267, Brisbane, QLD 4001, Australia ( Manoj.Nayak@daf.qld.gov.au ).|Plant Biosecurity Cooperative Research Centre, GPO Box 5012, Bruce, ACT 2617, Australia.
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Nayak
authors.affiliation: Department of Entomology, Kansas State University, Manhattan, KS 66506 ( ajcato@email.uark.edu ; twp1@ksu.edu ).|Plant Biosecurity Cooperative Research Centre, GPO Box 5012, Bruce, ACT 2617, Australia.|Corresponding author, e-mail: twp1@ksu.edu.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Phillips
mesh_terms: D000818:Animals; D002170:Canada; D004305:Dose-Response Relationship, Drug; D005843:Geography; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology*; D010641:Phenotype; D010720:Phosphines / Q000494:pharmacology*; D014231:Tribolium / Q000187:drug effects* / Q000235:genetics; D014481:United States
chemical_list: D007306:Insecticides; D010720:Phosphines; C044646:phosphine
keywords: discriminating dose; fumigation; hydrogen phosphide; resistance frequency; stored product