title: Esterase inhibition by synergists in the western flower thrips Frankliniella occidentalis.
abstract: BACKGROUND
  Western flower thrips (WFT), Frankliniella occidentalis (Pergande), is among the most important crop pests in the south-eastern region of Spain. Its increasing resistance to insecticides constitutes a serious problem, and understanding the mechanisms involved is therefore of great interest. Use of synergists to inhibit the enzymes involved in insecticide detoxification is widely used to determine their responsibility for insecticide resistance. However, they do not always act as intended or expected, and caution must be exercised when interpreting synergist results.
  
  
  RESULTS
  Laboratory-selected strains of WFT were used to analyse the effects of the synergists piperonyl butoxide (PBO), S,S,S-tributyl phosphorotrithioate (DEF) and methiocarb on total esterase activity. Significant differences were found, indicating esterase activity inhibition by DEF, a lower effect for methiocarb and a small inhibition of the activity by PBO. Esterase isoenzyme inhibition by these compounds showed a similar result; this assay revealed an extreme sensitivity of Triplet A (resistance-associated esterases) to DEF. In an in vivo assay carried out with these compounds at different incubation times, only DEF caused posterior in vitro esterase activity inhibition, with a maximum effect 1 h after treatment.
  
  
  CONCLUSIONS
  In this work, only DEF shows true synergistic inhibition of WFT esterases.
authors.affiliation: Departament de Biologia Funcional i Antropologia Física, Universitat de València, Burjassot, Valencia, Spain. neus.lopez@uv.es
authors.forename: Neus
authors.initials: N
authors.lastname: López-Soler
authors.forename: Amelia
authors.initials: A
authors.lastname: Cervera
authors.forename: Vicente
authors.initials: V
authors.lastname: Quinto
authors.forename: Jaime
authors.initials: J
authors.lastname: Abellán
authors.forename: Pablo
authors.initials: P
authors.lastname: Bielza
authors.forename: Rafael
authors.initials: R
authors.lastname: Martínez-Pardo
authors.forename: Maria Dolores
authors.initials: MD
authors.lastname: Garcerá
mesh_terms: D000818:Animals; D002219:Carbamates / Q000494:pharmacology; D004789:Enzyme Activation; D057075:Enzyme Assays; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D004950:Esterases / Q000378:metabolism*; D007305:Insecticide Resistance; D007306:Insecticides / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism; D008714:Methiocarb / Q000494:pharmacology; D063086:Organothiophosphates / Q000494:pharmacology; D010574:Pesticide Synergists / Q000494:pharmacology*; D011722:Pyrethrins / Q000494:pharmacology; D061149:Thysanoptera / Q000187:drug effects* / Q000201:enzymology; D013997:Time Factors; D005466:Fluorocarbons
chemical_list: D002219:Carbamates; D004791:Enzyme Inhibitors; D004950:Esterases; D007306:Insecticides; D007527:Isoenzymes; D008714:Methiocarb; D063086:Organothiophosphates; D010574:Pesticide Synergists; D011722:Pyrethrins; C006863:butyl phosphorotrithioate; C100163:formetanate; C119568:acrinathrin; D005466:Fluorocarbons