Journal of Medical Entomology (2005) 42, 631-636

M.K. Rust, I. Denholm, M.W. Dryden, P. Payne, B.L. Blagburn, D.E. Jacobs, N. Mencke, I. Schroeder, M. Vaughn, H. Mehlhorn, N.C. Hinkle and M. Williamson (2005)
Determining a diagnostic dose for imidacloprid susceptibility testing of field-collected isolates of cat fleas (Siphonaptera: Pulicidae)
Journal of Medical Entomology 42 (4), 631-636
Abstract: The susceptibility of four laboratory strains of cat fleas, Ctenocephalides felis (Bouché), to imidacloprid was determined by three different laboratories, by using a standardized bioassay protocol. The probit lines generated by the different laboratories were very similar, with LC₅₀ values ranging from 0.32 to 0.81 ppm. Based on these data, a diagnostic dose (DD) of 3 ppm imidacloprid in larval rearing media was provisionally identified for detecting shifts in tolerance, possibly as a consequence of incipient imidacloprid resistance. None of the larvae from the susceptible laboratory strains survived the DD. Eighteen field-collected isolates were evaluated for their susceptibility to imidacloprid and to validate a DD of 3 ppm. Probit lines from 18 field-collected isolates were very similar, with LC₅₀ values ranging from 0.14 to 1.52 ppm. When exposed to the DD, between 3 and 10% of the exposed larvae emerged as adults from only three of the 18 isolates. All other field isolates gave 100% mortality at the DD. Under the criteria established (>5% survivorship at 3 ppm), two isolates would be established on mammalian hosts and more extensive tests conducted to exclude or confirm the presence of resistance. The DD of 3 ppm is robust enough to eliminate most of the susceptible isolates collected until today, yet low enough to identify possible isolates for further testing.
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Database assignments for author(s): Michael K. Rust, Ian Denholm, Patricia A. Payne, Martin S. Williamson

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

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Ctenocephalides felis