title: Spinosad resistance, esterase isoenzymes and temporal synergism in Frankliniella occidentalis (Pergande) in Australia.
abstract: Spinosad has been widely used in Australia to control western flower thrips Frankliniella occidentalis (Pergande) but spinosad usefulness is now compromised by resistance. Here we studied a highly spinosad resistant strain of F. occidentalis to explore if esterases had a role in spinosad resistance. Enhanced esterase activity in pressured spinosad-resistant F. occidentalis was confirmed via PAGE electrophoresis and estimated to be approximately three times higher than that in a susceptible strain. Spinosad-esterase inhibition data in the resistant strain, showed a concentration effect with significant esterase-spinosad binding occurring at spinosad concentrations from 6.2× 10(-7) to 1.5× 10(-5) M. Similarly, a spinosad-piperonyl butoxide (PBO) inhibition curve showed a concentration effect, with significant esterase-PBO binding occurring in the resistant strain at PBO concentrations between 3.3× 10(-5) M and 8.4× 10(-4) M. No binding of esterase to spinosad or PBO occurred in the susceptible strain. Results of bioassays in which spinosad resistant F. occidentalis were sprayed with a 4h delayed release formulation of cyclodextrin-complexed spinosad with immediately available PBO demonstrated that spinosad resistance was significantly reduced from 577 to 72-fold. With further development the PBO synergism of spinosad using a delayed release formulation, similar to that used here, may provide effective control for spinosad resistant F. occidentalis. Temporal synergism of spinosad may prove to be effective tactic for the control of spinosad resistant F. occidentalis where the main resistance mechanism involved has been confirmed to be esterase based.
authors.affiliation: NSW DPI, PMB 4008, Narellan 2567, Australia. Electronic address: grant.herron@dpi.nsw.gov.au.
authors.forename: Grant A
authors.initials: GA
authors.lastname: Herron
authors.affiliation: NSW DPI, 4 Marsden Park Road, Calala 2340, Australia.
authors.forename: Robin V
authors.initials: RV
authors.lastname: Gunning
authors.affiliation: TecMAC Pty Ltd, Spring Terrace Road, Forest Reefs 2798, Australia.
authors.forename: Emma L A
authors.initials: EL
authors.lastname: Cottage
authors.affiliation: Endura Fine Chemicals, Viale Pietramella 5, 40121 Bologna, Italy.
authors.forename: Valerio
authors.initials: V
authors.lastname: Borzatta
authors.affiliation: Endura Fine Chemicals, Viale Pietramella 5, 40121 Bologna, Italy.
authors.forename: Carlotta
authors.initials: C
authors.lastname: Gobbi
mesh_terms: D000818:Animals; D001315:Australia; D004338:Drug Combinations; D004950:Esterases / Q000378:metabolism*; D005260:Female; D007305:Insecticide Resistance / Q000502:physiology; D007306:Insecticides / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology*; D010574:Pesticide Synergists / Q000494:pharmacology*; D010882:Piperonyl Butoxide / Q000494:pharmacology*; D061149:Thysanoptera / Q000187:drug effects / Q000201:enzymology*
chemical_list: D004338:Drug Combinations; D007306:Insecticides; D007527:Isoenzymes; D018942:Macrolides; D010574:Pesticide Synergists; D004950:Esterases; D010882:Piperonyl Butoxide; C415329:spinosad
keywords: Esterase; Piperonyl butoxide; Resistance management; Temporal synergism; Western flower thrips