Journal of Medical Entomology (2014) 51, 638-643

M.K. Rust, R. Vetter, I. Denholm, B. Blagburn, M.S. Williamson, S. Kopp, G. Coleman, J. Hostetler, W. Davis, N. Mencke, R. Rees, S. Foit and K. Tetzner (2014)
Susceptibility of cat fleas (Siphonaptera: Pulicidae) to fipronil and imidacloprid using adult and larval bioassays
Journal of Medical Entomology 51 (3), 638-643
Abstract: The monitoring of the susceptibility of fleas to insecticides has typically been conducted by exposing adults on treated surfaces. Other methods such as topical applications of insecticides to adults and larval bioassays on treated rearing media have been developed. Unfortunately, baseline responses of susceptible strains of cat flea, Ctenocephalides felis (Bouchè), except for imidacloprid, have not been determined for all on-animal therapies and new classes of chemistry now being used. However, the relationship between adult and larval bioassays of fleas has not been previously investigated. The adult and larval bioassays of fipronil and imidacloprid were compared for both field-collected isolates and laboratory strains. Adult topical bioassays of fipronil and imidacloprid to laboratory strains and field-collected isolates demonstrated that LD₅₀s of fipronil and imidacloprid ranged from 0.11 to 0.40 nanograms per flea and 0.02 to 0.18 nanograms per flea, respectively. Resistance ratios for fipronil and imidacloprid ranged from 0.11 to 2.21. Based on the larval bioassay published for imidacloprid, a larval bioassay was established for fipronil and reported in this article. The ranges of the LC₅₀s of fipronil and imidacloprid in the larval rearing media were 0.07-0.16 and 0.11-0.21 ppm, respectively. Resistance ratios for adult and larval bioassays ranged from 0.11 to 2.2 and 0.58 to 1.75, respectively. Both adult and larval bioassays provided similar patterns for fipronil and imidacloprid. Although the adult bioassays permitted a more precise dosage applied, the larval bioassays allowed for testing isolates without the need to maintain on synthetic or natural hosts.
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Database assignments for author(s): Michael K. Rust, Ian Denholm, Martin S. Williamson

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ctenocephalides felis		Germany
	Ctenocephalides felis		U.S.A. (SW)
	Ctenocephalides felis		U.S.A. (mid N)
	Ctenocephalides felis		U.S.A. (mid S)
	Ctenocephalides felis		U.S.A. (NE)
	Ctenocephalides felis		U.S.A. (SE)
	Ctenocephalides felis		Australia (NT+QLD)