Harpenden, United Kingdom
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Nicholls C.,AHDBStoneleigh ParkKenilworth Warwickshire UK | Paine M.J.I.,Liverpool UK | Moores G.D.,ApresLabs Ltd
Insect Molecular Biology | Year: 2016

Honey bees, Apis mellifera, are markedly less sensitive to neonicotinoid insecticides containing a cyanoimino pharmacophore than to those with a nitroimino group. Although previous work has suggested that this results from enhanced metabolism of the former by detoxification enzymes, the specific enzyme(s) involved remain to be characterized. In this work, a pretreatment of honey bees with a sublethal dose of thiacloprid resulted in induced insensitivity to the same compound immediately following thiacloprid feeding. A longer pretreatment time resulted in no, or increased, sensitivity. Transcriptome profiling, using microarrays, identified a number of genes encoding detoxification enzymes that were over-expressed significantly in insecticide-treated bees compared with untreated controls. These included five P450s, CYP6BE1, CYP305D1, CYP6AS5, CYP315A1, CYP301A1, and a carboxyl/cholinesterase (CCE) CCE8. Four of these P450s were functionally expressed in Escherichia coli and their ability to metabolize thiacloprid examined by liquid chromatography-mass spectrometry (LC-MS) analysis. © 2016 The Royal Entomological Society.


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.


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.


Philippou D.,Rothamsted Research | Borzatta V.,Endura SpA | Capparella E.,Endura SpA | Moroni L.,Endura SpA | And 2 more authors.
Pest Management Science | Year: 2016

BACKGROUND: Derivatives of piperonyl butoxide with alkynyl side chains were tested in vitro and in vivo against pyrethroid-resistant Meligethes aeneus and imidacloprid-resistant Myzus persicae. RESULTS: Synergists with the alkynyl side chain were more effective inhibitors of P450 activity in vitro than piperonyl butoxide, and demonstrated high levels of synergism in vivo, with up to 290-fold synergism of imidacloprid against imidacloprid-resistant M. persicae. CONCLUSIONS: These ‘second-generation’ synergists could overcome metabolic resistance in many pest species and possibly enable reduced rates of insecticide application in some cases. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry


Durmusolu E.,Ege University | Hatipolu A.,Ege University | Gurkan M.O.,Ankara Ileri Teknoloji Yatirimlari A.S. | Moores G.,Apres Labs 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.


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.


Alptekin S.,Rothamsted Research | Philippou D.,Rothamsted Research | Field L.,Rothamsted Research | Wegorek P.,Institute Plant Protection | And 2 more authors.
Outlooks on Pest Management | Year: 2015

An increasing global population (estimated at over 9 billion by the year 2050) brings the problem of maintaining a sustainable agricultural system, with the constraints on land-use and environmental protection that such a process incurs. One acute problem is that of arthropod pests, chemical control of which remains the foundation of pest control for growers today, and for the foreseeable future. Insecticide resistance continues both to increase and broaden; a situation that will be exacerbated by the withdrawal of some older insecticidal actives under the EU’s Pesticide Framework Directive. One possible solution that has been advocated is the use of synergists, especially if coupled with ‘temporal synergism’,a concept reported previously in Outlooks on Pest Management(Moores et al., 2005), whereby a synergist contacts a pest some hours before the insecticide component of the treatment. For example, when crop pests were exposed to piperonyl butoxide (PBO) several hours before pyrethroid, carbamate or neonicotinoid insecticides, inhibition of the metabolic enzymes (P450s and esterases) that would normally degrade these insecticides occurred, leaving the insect pests in a hypersensitive state before exposure to the insecticide (Bingham et al., 2007; 2008). However, it may be that not just the target insects would be exposed to both synergists and insecticides, beneficial insects such as bees would potentially also be at risk. The honey bee (Apis mellifera) (Hymenoptera: Apidae) is a global pollinator of many crop plants, encountering various challenges such as disease, parasites and both intended and unintended insecticide exposure. Although, as mentioned earlier, chemical control is currently an indispensable input for global agriculture, pesticides have been suspected by some to be involved in the disappearance of honey bees since the first report of colony collapse disorder in 2006. As with other insects, honey bees use their metabolic enzymes to detoxify insecticides and although their genome contains a smaller number of genes encoding detoxification enzymes (as judged by comparison with the published genomes of other insects), the literature indicates that a lower number of detoxification genes does not necessarily correspond to a lower detoxification activity (Johnson et al, 2012; Claudianos et al. 2006). So, will a regime to control insect pests by inhibition of their detoxifying enzymes also penalise honey bees in the same way? Before advocating widespread use of synergists such as PBO, it is essential that studies are performed to characterise their effects against the defence enzymes of the honey bee, both in terms of potency and to identify which defence enzymes (P450s and /or esterases) are inhibited. The synthetic pyrethroid, tau-fluvalinate, is used widely as an acaricide treatment against the bee parasite Varroa destructor in apiculture. It has been reported that the reason for tau-fluvalinate’s lower toxicity to the bees themselves is due to rapid metabolism by their P450s. If this is correct, and PBO inhibits this honey bee defence system, it could be expected that exposure to this pyrethroid would result in high mortality, rendering this insecticide of no value impotent for parasite control. © 2015 Research Information Ltd. All rights reserved.


PubMed | Catholic University of the Sacred Heart, Rothamsted Research, ApresLabs Ltd and Endura SpA
Type: Journal Article | Journal: Pest management science | Year: 2016

Piperonyl butoxide (PBO) is a well-known insecticide synergist capable of interacting with phase 1 metabolic enzymes, specifically esterases and cytochrome P450s. In this study, structure-activity relationship analyses were used to characterise the interaction of around 30 analogues of PBO with the esterase FE4 and the P450 CYP6CY3 from insecticide-resistant Myzus persicae (Sulzer), in order to predict the synthesis of more potent inhibitors.Enzyme inhibition studies were performed against esterase and oxidase activities and, together with in silico modelling, key activity determinants of the analogues were identified and optimised. Novel analogues were then designed and synthesised, some of which showed greater inhibition against both enzymatic systems: specifically, dihydrobenzofuran moieties containing an alkynyl side chain and a butyl side chain against FE4, and benzodioxole derivatives with a propyl/butyl side chain and an alkynyl ether moiety for CYP6CY3.In vitro assays identified potential candidate synergists with high inhibitory potency. The in vivo confirmation of such results will allow consideration for a possible use in agriculture. 2016 Society of Chemical Industry.


PubMed | Rothamsted Research, ApresLabs Ltd and Endura SpA
Type: Journal Article | Journal: Pest management science | Year: 2016

Derivatives of piperonyl butoxide with alkynyl side chains were tested in vitro and in vivo against pyrethroid-resistant Meligethes aeneus and imidacloprid-resistant Myzus persicae.Synergists with the alkynyl side chain were more effective inhibitors of P450 activity in vitro than piperonyl butoxide, and demonstrated high levels of synergism in vivo, with up to 290-fold synergism of imidacloprid against imidacloprid-resistant M. persicae.These second-generation synergists could overcome metabolic resistance in many pest species and possibly enable reduced rates of insecticide application in some cases. 2016 Society of Chemical Industry.

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