1. Academic Validation
  2. The mode of action of isocycloseram: A novel isoxazoline insecticide

The mode of action of isocycloseram: A novel isoxazoline insecticide

  • Pestic Biochem Physiol. 2022 Oct:187:105217. doi: 10.1016/j.pestbp.2022.105217.
Judith Blythe 1 Fergus G P Earley 2 Katarzyna Piekarska-Hack 1 Lucy Firth 1 Julia Bristow 1 Elizabeth A Hirst 1 James A Goodchild 1 Elke Hillesheim 3 Andrew J Crossthwaite 1
Affiliations

Affiliations

  • 1 Syngenta, Bioscience, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK.
  • 2 Syngenta, Bioscience, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK. Electronic address: fergus.earley@syngenta.com.
  • 3 Syngenta Crop Protection AG, Research Biology, Schaffhauserstrasse 101, CH-4332 Stein, Switzerland.
Abstract

Isocycloseram is a novel isoxazoline insecticide and acaricide with activity against lepidopteran, hemipteran, coleopteran, thysanopteran and dipteran pest species. Isocycloseram selectively targets the invertebrate Rdl GABA Receptor at a site that is distinct to fiproles and organochlorines. The widely distributed cyclodiene resistance mutation, A301S, does not affect sensitivity to isocycloseram, either in vitro or in vivo, demonstrating the suitability of isocylsoseram to control pest infestations with this resistance mechanism. Detailed studies demonstrated that the binding sites relevant to the insecticidal activity of avermectins and isocycloseram are distinct. Isocycloseram was shown to compete for binding with metadiamide insecticides related to broflanilide. In addition, a G335M mutation in the third transmembrane domain of the Rdl GABA Receptor, impaired the ability of both isocycloseram and metadiamides to block the GABA mediated response. As such the Insecticides Resistance Action Committee (IRAC) has classified isocycloseram in Group 30 "GABA-Gated Chloride Channel Allosteric Modulators".

Keywords

Avermectin; Cyclodiene resistance; GABA gated chloride channel; Isocycloseram; Isoxazoline insecticides; Metadiamide insecticides.

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