title: Repellency of a wireworm, Agriotes obscurus (Coleoptera: Elateridae), on exposure to synthetic insecticides in a soil-less bioassay.
abstract: A soil-less bioassay arena to test repellency of wireworms (A. obscurus) to insecticides and carrier solvents is described. The bioassay and variables measured distinguish between shorter-range (contact and/or volatile) and longer-range (volatile) repellency. Wireworm positions are recorded every 3 s for 20 min, and average speed, rate of slowing, and longer- and shorter-range repellent behaviors calculated. Shorter-range repellency is determined with a Wireworm Repellency Score (WRS, range 0-100), calculated before contact and after contact with test chemicals. Of two carrier solvents tested, wireworms were strongly repelled by acetone (WRS = 57) but not by water (WRS = 1) when introduced to the bioassay arenas immediately after chemical inoculation. When bioassay arenas were assembled/sealed 2 min after inoculation, acetone elicited no repellency (WRS = 2). When dissolved in acetone in bioassays assembled with a 2-min delay, imidacloprid, chlorpyrifos, lindane, and tefluthrin elicited slight to moderate repellency at the highest concentrations tested (WRS = 30, 48, 42, and 49, respectively). Both longer- and shorter-range repellency increased over the duration of the observation period for lindane and tefluthrin, and shorter-range repellency also increased over the duration of the observation period for chlorpyrifos. Removal of volatiles in the bioassay arena by vacuum considerably affected wireworm movement in the arena, with the repellency elicited by acetone and lindane being significantly reduced. Clothianidin elicited no longer- or shorter-range repellency.
authors.affiliation: Agriculture and Agri-Food Canada, Pacific Agri-Food Research Center, Box 1000, 6947 No. 7 Highway, Agassiz, British Columbia V0M 1A0, Canada. vanherkw@agr.gc.ca
authors.forename: W G
authors.initials: WG
authors.lastname: van Herk
authors.forename: R S
authors.initials: RS
authors.lastname: Vernon
authors.forename: B D
authors.initials: BD
authors.lastname: Roitberg
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D001681:Biological Assay; D001517:Coleoptera / Q000187:drug effects* / Q000502:physiology*; D007302:Insect Repellents / Q000494:pharmacology*; D007306:Insecticides / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects
chemical_list: D007302:Insect Repellents; D007306:Insecticides