title: Chronology of permethrin resistance in a southern Illinois population of the horn fly (Diptera: Muscidae) during and after selection by pyrethroid use.
abstract: From 1985 through 1988, horn flies (Haematobia irritans (L)) collected at the Dixon Springs Agricultural Center (DSAC) in southern Illinois were tested in 22 h bioassays for permethrin resistance with residues on cotton cloths. The LC90 for a susceptible field population collected in June 1985 was 0.19 micrograms/cm2. In comparison, flies collected from pyrethroid-tagged cattle in 1985 and 1986 exhibited 25- to 116-fold resistance to permethrin. A 25-fold level of resistance allowed survival on treated cattle 8 wk after pyrethroid tag application. Flies representing the local background population were collected periodically from an untreated herd 2.4 km from the nearest cattle treated with a pyrethroid; these flies exhibited up to 18-fold resistance. Although pyrethroids were not used on DSAC animals after October 1986, all bioassays done in 1987 and 1988 indicated resistance levels of greater than or equal to 7-fold. The 95% confidence intervals for LC90s from all 1987 bioassays overlapped the confidence interval from the corresponding July 1986 estimate for resistant flies collected from pyrethroid-tagged cattle. Although some decline in resistance was evident in 1988, bioassays done at the end of the season produced resistance ratios of 7.4 and 15.3. Survivorship at a diagnostic dose indicated that resistance frequencies remained at 4-8% throughout 1988. Two years' abstinence from pyrethroid use was insufficient to allow an adequate decline in resistance levels.
authors.affiliation: Office of Agricultural Entomology, University of Illinois, Champaign 61820.
authors.forename: R A
authors.initials: RA
authors.lastname: Weinzierl
authors.forename: C D
authors.initials: CD
authors.lastname: Schmidt
authors.forename: D B
authors.initials: DB
authors.lastname: Faulkner
authors.forename: G F
authors.initials: GF
authors.lastname: Cmarik
authors.forename: G D
authors.initials: GD
authors.lastname: Zinn
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000517:prevention & control*; D004478:Ectoparasitic Infestations / Q000517:prevention & control / Q000662:veterinary*; D007087:Illinois; D007305:Insecticide Resistance; D007306:Insecticides; D009117:Muscidae; D026023:Permethrin; D011722:Pyrethrins
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D026023:Permethrin