title: Cross-resistance relationships between neonicotinoids and pymetrozine in Bemisia tabaci (Hemiptera: Aleyrodidae).
abstract: BACKGROUND
  Although cross-resistance between compounds in the same insecticide group is a frequently observed phenomenon, cross-resistance between groups that differ in structural and functional characteristics can be extremely unpredictable. In the case of controlling the whitefly, Bemisia tabaci Gennadius, neonicotinoids and the pyridine azomethine antifeedant pymetrozine represent independent lines of discovery that should be suited for alternation to avoid prolonged selection for the same resistance mechanism. Reports of an association between responses to neonicotinoids and pymetrozine were investigated by resistance profiling of seven B. tabaci strains and complementary reciprocal selection experiments.
  
  
  RESULTS
  All strains demonstrated a consistent correlation between responses to three neonicotinoid compounds: thiamethoxam, imidacloprid and acetamiprid. Responses to neonicotinoids for six field strains clearly correlated with responses to pymetrozine. Reciprocal selection experiments confirmed an unexpected case of intergroup cross-resistance. A seventh strain exhibited a so far unique phenotype of strong resistance to pymetrozine but full susceptibility to neonicotinoids. Selection experiments confirmed that in this strain the mechanism of pymetrozine resistance is specific and has no implications for neonicotinoids.
  
  
  CONCLUSIONS
  Cross-resistance between neonicotinoids and pymetrozine in B. tabaci probably reflects the overexpression of a cytochrome-P450-dependent monooxygenase capable of metabolising both types of compound in spite of their apparent structural dissimilarity. Given the predominance of this mechanism in B. tabaci, both can contribute to resistance management but should be placed within the same treatment 'window'.
authors.affiliation: Rothamsted Research, Harpenden, Hertfordshire, UK. kevin.gorman@bbsrc.ac.uk
authors.forename: Kevin
authors.initials: K
authors.lastname: Gorman
authors.forename: Russell
authors.initials: R
authors.lastname: Slater
authors.forename: James D
authors.initials: JD
authors.lastname: Blande
authors.forename: Alison
authors.initials: A
authors.lastname: Clarke
authors.forename: Jodie
authors.initials: J
authors.lastname: Wren
authors.forename: Alan
authors.initials: A
authors.lastname: McCaffery
authors.forename: Ian
authors.initials: I
authors.lastname: Denholm
mesh_terms: D000818:Animals; D003368:Gossypium; D006430:Hemiptera / Q000187:drug effects*; D007093:Imidazoles / Q000737:chemistry / Q000494:pharmacology; D007305:Insecticide Resistance; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D007928:Lethal Dose 50; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000737:chemistry / Q000494:pharmacology; D010078:Oxazines / Q000737:chemistry / Q000494:pharmacology; D018515:Plant Leaves; D011725:Pyridines / Q000737:chemistry / Q000494:pharmacology; D000077922:Thiamethoxam; D013844:Thiazoles / Q000737:chemistry / Q000494:pharmacology; D014227:Triazines / Q000737:chemistry / Q000494:pharmacology
chemical_list: D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010078:Oxazines; D011725:Pyridines; D013844:Thiazoles; D014227:Triazines; C082359:imidacloprid; C464485:acetamiprid; D000077922:Thiamethoxam; C480311:pymetrozine