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Harpenden, United Kingdom

Philippou D.,Rothamsted Research | Borzatta V.,Endura SpA | Capparella E.,Endura SpA | Moroni L.,Endura SpA | And 3 more authors.
Pest Management Science | Year: 2013

BACKGROUND: It has been reported previously that piperonyl butoxide (PBO) can inhibit both P450 and esterase activity. Although the method by which PBO combines with cytochrome P450 has been identified, the way in which it acts as an esterase inhibitor has not been established. This paper characterises the interactions between PBO and the resistance-associated esterase in Myzus persicae, E4. RESULTS: After incubation with PBO/analogues, hydrolysis of 1-naphthyl acetate by E4 is increased, but sequestration of azamethiphos is reduced. Rudimentary in silico modelling suggests PBO docks at the lip of the aromatic gorge. CONCLUSIONS: PBO binds with E4 to accelerate small substrates to the active-site triad, while acting as a blockade to larger, insecticidal molecules. Structure-activity studies with analogues of PBO also reveal the essential chemical moieties present in the molecule. © 2012 Society of Chemical Industry.

Durmusolu E.,Ege University | Hatipolu A.,Ege University | Gurkan M.O.,Ankara Ileri Teknoloji Yatirimlari A.S. | Moores G.,ApresLabs Ltd
Turkiye Entomoloji Dergisi | Year: 2015

The European Grapevine Moth [Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae)] is a major pest in vineyards and insecticides are heavily used in its management. Currently, there is no IRAC approved bioassay method for L. botrana, so this study aimed to develop a suitable susceptibility test. For this purpose, 10 different populations were cultured from Manisa (Turkey) that province an important place in the world of viticulture. Diet-incorporation, topical application and diet covering methods selected as potential methods. Three different bioassay techniques (diet-incorporation, diet covering and topical application) were compared using indoxacarb, deltamethrin, spinosad and chlorpyrifos-ethyl on three different populations. Results revealed that the dietincorporation by mixing was the most appropriate method for testing insecticide resistance against the European Grapevine Moth.

Erdogan C.,Plant Protection Central Research Institute | Velioglu A.S.,BASF | Gurkan M.O.,Ankara University | Denholm I.,Rothamsted Research | And 2 more authors.
Pesticide Biochemistry and Physiology | Year: 2012

Resistance to the organophosphate chlorpyrifos ethyl was investigated in greenhouse populations of Trialeurodes vaporariorum from Turkey using both bioassay and biochemical studies. These populations were collected from Antalya, Izmir, and Mersin. LC50 values to chlorpyrifos ethyl were determined for all populations using leaf dip bioassay. Resistance ratios (RRs) were calculated from these LC50 values relative to the susceptible BCP population. Bioassay results from all populations revealed varying levels of resistance to chlorpyrifos ethyl with resistance ratios between 7.16- and 12.89-fold in the greenhouse whitefly populations from Turkey. Results revealed the first documented cases of insecticide resistance in this species in Turkey. Biochemical assays on acetylcholinesterase (AChE) sensitivity in individual greenhouse whitefly were conducted to explore the role of this enzyme in conferring resistance to this insecticide. AChE insensitivity in individual greenhouse whitefly was determined. This is believed to be the first record of sensitive and insensitive AChE variants to be identified according to their sensitivities to chlorpyrifos ethyl-oxon and pirimicarb. © 2012 Elsevier Inc.

Carvalho R.,Rothamsted Research | Yang Y.,Nanjing Agricultural University | Field L.M.,Rothamsted Research | Gorman K.,Rothamsted Research | And 4 more authors.
Pesticide Biochemistry and Physiology | Year: 2012

The tomato red spider mite, Tetranychus evansi is an invasive pest of many African countries where it causes significant damage to a range of solanaceous crops. In Malawi the control of T. evansi relies heavily on the use of chemical pesticides and this species has evolved resistance to members of the pyrethroid and organophosphate (OP) classes. In this study the molecular mechanisms underlying resistance to the organophosphate chlorpyrifos were investigated in two resistant strains of T. evansi from Malawi and France. Cloning and sequencing of the gene encoding the OP target (. ace-1) revealed an amino acid substitution at just one of the positions (331) previously implicated in OP resistance across a range of different insect and mite species. The amino acid residue usually found at this position in susceptible insects and mites is a phenylalanine (F) but was a tyrosine (Y) in all sequenced clones of the France strain and a tyrosine or tryptophan (W) in sequenced clones of the Malawi strain. Additionally we found evidence that the ace-1 locus is amplified in the resistant strains, with direct measurement of gene copy number by quantitative PCR showing there are around 8-10 copies of the gene in both the France and the Malawi strain. Sequencing of clones of ace-1 from the Malawi strain indicated that individual mites have fewer copies of the W331 allele than the Y331 allele. The enhanced copy number of the ace-1 gene in T. evansi and copy number variation of the two alleles seen in the Malawi strain may be a mechanism to compensate for fitness costs associated with the mutant alleles as has been proposed for T. urticae. © 2012.

Bingham G.,Rothamsted Research | Bingham G.,Vestergaard Frandsen SA. | Alptekin S.,Rothamsted Research | Delogu G.,CNR Institute of Biomolecular Chemistry | And 3 more authors.
Pest Management Science | Year: 2014

BACKGROUND: It has been demonstrated previously that cis-jasmone acts as an elicitor of plant defence mechanism(s) by inducing secondary metabolism. It has also been demonstrated that temporal synergism can result in hypersensitive insect pests due to the inhibition of metabolic enzymes. RESULTS: Laboratory bioassays demonstrated that pre-exposure of insects by piperonyl butoxide followed by cis-jasmone treatment of crops, reduced Aphis gossypii on cotton by 80% and Myzus persicae on sweet pepper by 90%. By microencapsulating the cis-jasmone and combining with piperonyl butoxide, Bemisia tabaci on tomatoes was reduced by 99%. A field trial with microencapsulated cis-jasmone combined with piperonyl butoxide resulted in a comparable reduction of whitefly egg numbers to that given by the registered rate of imidacloprid, with efficacy of 89% and 93%, respectively. CONCLUSIONS: If insect defence enzymes are compromised by piperonyl butoxide whilst plant defence is primed by cis-jasmone, there are possibilities of an insecticide-free method of controlling insect pests. The success seems largely dependent upon the toxicity of the plants' secondary chemistry. © 2013 Society of Chemical Industry.

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