title: Pyrethroid resistance in Phytoseiulus macropilis (Acari: Phytoseiidae): cross-resistance, stability and effect of synergists.
abstract: Phytoseiulus macropilis Banks (Acari: Phytoseiidae) is an effective predator of Tetranychus urticae Koch (Acari: Tetranychidae). The objectives of this research were to study the stability of fenpropathrin resistance and the cross-resistance relationships with different pyrethroids, and also to evaluate the effect of synergists [piperonyl butoxide (PBO), diethyl maleate (DEM) and S,S,S-tributyl phosphorotrithioate (DEF)] on fenpropathrin resistant and susceptible strains of this predaceous mite. The stability of fenpropathrin resistance was studied under laboratory conditions, using P. macropilis populations with initial frequencies of 75 and 50% of resistant mites. The percentages of fenpropathrin resistant mites were evaluated monthly for a period of up to 12 months. A trend toward decreased resistance frequencies was observed only during the first 3-4 months. After this initial decrease, the fenpropathrin resistance was shown to be stable, maintaining constant resistance frequencies (around 30%) until the end of the evaluation period. Toxicity tests carried out using fenpropathrin resistant and susceptible strains of P. macropilis indicated strong positive cross-resistance between fenpropathrin and the pyrethroids bifenthrin and deltamethrin. Bioassays with the synergists DEM, DEF and PBO were also performed. The maximum synergism ratio (SR = LC50 without synergist/LC50 with synergist) detected for the three evaluated synergists (PBO, DEM, DEF) was 5.86 (for DEF), indicating low influence of enzyme detoxification processes in fenpropathrin resistance.
authors.affiliation: Instituto Biológico, APTA, Rodovia Heitor Penteado km 3.5, Caixa Postal 70, Campinas, SP, 13001-970, Brazil. crisviquei@gmail.com.
authors.forename: Maria Cristina Vitelli
authors.initials: MC
authors.lastname: Queiroz
authors.affiliation: Instituto Biológico, APTA, Rodovia Heitor Penteado km 3.5, Caixa Postal 70, Campinas, SP, 13001-970, Brazil.
authors.forename: Mario Eidi
authors.initials: ME
authors.lastname: Sato
mesh_terms: D056810:Acaricides / Q000494:pharmacology*; D000818:Animals; D004351:Drug Resistance; D004357:Drug Synergism; D008298:Maleates / Q000494:pharmacology; D008925:Mites / Q000187:drug effects*; D009570:Nitriles / Q000494:pharmacology*; D063086:Organothiophosphates / Q000494:pharmacology; D010882:Piperonyl Butoxide / Q000494:pharmacology; D011722:Pyrethrins / Q000494:pharmacology*
chemical_list: D056810:Acaricides; D008298:Maleates; D009570:Nitriles; D063086:Organothiophosphates; D011722:Pyrethrins; C017180:decamethrin; C006863:butyl phosphorotrithioate; C099952:bifenthrin; C044267:fenpropathrin; C014476:diethyl maleate; D010882:Piperonyl Butoxide
keywords: Biological control; IPM; Integrated pest management; Pesticide resistance