title: Pyrethroid resistance in the tomato red spider mite, Tetranychus evansi, is associated with mutation of the para-type sodium channel.
abstract: BACKGROUND
  The tomato red spider mite, Tetranychus evansi (Baker and Pritchard), is a serious pest of solanaceous crops in many African countries. In this study an investigation has been conducted to establish whether mutation of the para-type sodium channel underlies pyrethroid resistance in T. evansi strains collected in Southern Malawi.
  
  
  RESULTS
  Two T. evansi strains from Malawi showed tolerance to the organophosphate chlorpyrifos and resistance (20-40-fold) to the pyrethroid bifenthrin, but were susceptible to two contemporary acaricides (abamectin and fenpyroximate) in insecticide bioassays. Cloning of a 3.1 kb fragment (domains IIS5 to IVS5) of the T. evansi para gene from pyrethroid-resistant and pyrethroid-susceptible strains revealed a single non-synonymous mutation in the resistant strains that results in an amino acid substitution (M918T) within the domain II region of the channel. Although novel to mites, this mutation confers high levels of resistance to pyrethroids in several insect species where it has always been associated with another mutation (L1014F). This is the first report of the M918T mutation in the absence of L1014F in any arthropod species. Diagnostic tools were developed that allow sensitive detection of this mutation in individual mites.
  
  
  CONCLUSIONS
  This is the first study of pyrethroid resistance in T. evansi and provides contemporary information for resistance management of this pest in Southern Malawi.
authors: The College of Medicine, Malawi-Liverpool Wellcome Trust, Clinical Research Programme, Chichiri, Blantyre, Malawi.
authors: Benjamin N
authors: BN
authors: Nyoni
authors: Kevin
authors: K
authors: Gorman
authors: Themba
authors: T
authors: Mzilahowa
authors: Martin S
authors: MS
authors: Williamson
authors: Maria
authors: M
authors: Navajas
authors: Linda M
authors: LM
authors: Field
authors: Chris
authors: C
authors: Bass
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D003001:Cloning, Molecular; D005260:Female; D007305:Insecticide Resistance / Q000235:genetics; D007306:Insecticides; D008297:Male; D008969:Molecular Sequence Data; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D011722:Pyrethrins; D017422:Sequence Analysis, DNA; D015222:Sodium Channels / Q000235:genetics*; D040102:Tetranychidae / Q000235:genetics*
chemical_list: D007306:Insecticides; D011722:Pyrethrins; D015222:Sodium Channels; C099952:bifenthrin