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1.
BACKGROUND: Bicyclophosphorothionates (2,6,7‐trioxa‐1‐phosphabicyclo[2.2.2]octane‐1‐sulfides) are blockers (or non‐competitive antagonists) of γ‐aminobutyric acid (GABA) receptor channels. Twenty‐two bicyclophosphorothionates with different 3‐ and 4‐substituents were synthesised, and [3H]4′‐ethynyl‐4‐n‐propylbicycloorthobenzoate (EBOB) binding assays were performed to evaluate their affinities for housefly and rat GABA receptors. RESULTS: Introduction of an isopropyl group at the 3‐position enhanced the affinity of bicyclophosphorothionates for housefly GABA receptors and reduced the affinity towards rat GABA receptors. The 4‐isopentyl‐3‐isopropylbicyclophosphorothionate showed the highest affinity for housefly GABA receptors (IC50 = 103 nM ) among the analogues tested, while the 4‐cyclohexylbicyclophosphorothionate showed the highest affinity for rat GABA receptors (IC50 = 125 nM ). Among the bicyclophosphorothionates synthesised to date, the former analogue exhibited the highest selectivity for housefly GABA receptors, with an IC50rat/IC50fly ratio of approximately 97. Three‐dimensional GABA receptor models successfully explained the structure–activity relationships of the bicyclophosphorothionates. CONCLUSION: The results indicate that minor structural modifications of blockers can change their selectivity for insect versus mammalian GABA receptors. The substituent at the 3‐position of the bicyclophosphorothionates dictates selectivity for housefly versus rat GABA receptors. This information should prove useful for the design of safer insecticides and parasiticides. Copyright © 2010 Society of Chemical Industry  相似文献   

2.
Monoterpenoids and their derivatives from plant essential oils showed good insecticidal activities in previous studies, but the mechanisms of their action as natural insecticides are not known yet. In the present work, we evaluated the pharmacological action of five monoterpenoids (α-terpineol, carvacrol, linalool, pulegone, and thymol) on native insect GABA receptors from house flies and American cockroaches using radiotracer methods. In the [3H]-TBOB binding assay, carvacrol, pulegone, and thymol all enhanced the [3H]-TBOB binding to membrane preparation of house fly heads with EC50 values of 48 μM, 432 μM, and 6 mM, respectively. Moreover, these three monoterpenoids at concentrations of 500 μM and 1 mM also significantly increased the 36Cl− uptake induced by GABA in membrane microsacs prepared from American cockroach ventral nerve cords. These results revealed that carvacrol, pulegone, and thymol are all positive allosteric modulators at insect GABA receptors. The other two monoterpenoids that were tested, α-terpineol and linalool, showed little or no effect in both the [3H]-TBOB binding and 36Cl− uptake assays.  相似文献   

3.
BACKGROUND: The housefly, Musca domestica L., and stable fly, Stomoxys calcitrans (L.) are cosmopolitan pests of both farm and home environments. Houseflies have been shown to be resistant to a variety of insecticides, and new chemistries are slow to emerge on the market. Toxicities of selected semiochemicals with molecular structures indicative of insecticidal activity were determined against adults from an insecticide‐susceptible laboratory strain of houseflies. The three most active semiochemicals were also evaluated against recently colonized housefly and stable fly strains. RESULTS: Nineteen semiochemicals classified as aliphatic alcohols, terpenoids, ketones and carboxylic esters showed toxicity to houseflies and stable flies. Rosalva (LC50 = 25.98 µg cm?2) followed by geranyl acetone and citronellol (LC50 = 49.97 and 50.02 µg cm?2) were identified as the most toxic compounds to houseflies. Permethrin was up to 144‐fold more toxic than rosalva on the susceptible strain. However, it was only 35‐fold more toxic to the insecticide‐tolerant field strain. The compounds generated high toxicity to stable flies, with LC50 values ranging from 16.30 to 40.41 µg cm?2. CONCLUSION: Quantification of LC50 values of rosalva, citronellol and geranyl acetone against susceptible housefly and field‐collected housefly and stable fly strains showed that semiochemicals could serve as potent insecticides for fly control programs. Copyright © 2010 Society of Chemical Industry  相似文献   

4.
BACKGROUND: Vector‐borne diseases continue to present significant threats to human, animal and plant health. Mosquitoes, houseflies, sand flies and stable flies are well‐known vectors of several human and animal pathogens. The toxicity of selected semiochemicals with molecular structures indicative of insecticidal activity was determined against these insect species with the aim of developing novel insecticides toxic to multiple insect species. RESULTS: Three semiochemicals, namely beta‐damascone, cyclemone A and melafleur, showed remarkable toxicity to three mosquitoes, Aedes aegypti L., Ae. albopictus (Skuse) and Anopheles quadrimaculatus Say, the housefly, Musca domestica L., the stable fly, Stomoxys calcitrans L., and the sand fly, Lutzomyia shannoni (Dyar). The chemicals were equally toxic to several field‐collected permethrin‐tolerant housefly strains. When formulated as 500 mL L?1 emulsifiable concentrates, the chemicals demonstrated stability and toxicity on filter paper and camouflage military fabrics, with persistence up to 8 days under laboratory conditions. The chemicals were equally effective under field conditions when evaluated on unpainted plywood panels, although a higher dosage was required under field conditions to achieve similar efficacy. CONCLUSION: Laboratory quantification of LC50 values and field efficacy of three semiochemicals as formulated compounds on mosquitoes, houseflies, stable flies and sand flies showed that these semiochemicals could serve as potent insecticides for multiple insect species. Copyright © 2010 Society of Chemical Industry  相似文献   

5.
2,6,7-Trioxa-1-phosphabicyclo[2.2.2]octane 1-sulfides (bicyclophosphorothionates) with various C1–4 alkyl groups at the 3- and 4-positions were synthesized and tested for their ability to compete with [3H]4′-ethynyl-4-n-propylbicycloorthobenzoate (EBOB), a non-competitive antagonist of γ-aminobutyric acid (GABA) receptors, for specific binding to rat-brain and housefly-head membranes, and for their insecticidal activity against houseflies. Among the 3,4-substituted analogues, 20 compounds were selectively active for housefly GABA receptors versus rat GABA receptors. The 3-alkyl groups of C3 length and the 4-alkyl groups of C4 length were tolerated in housefly receptors, whereas such bulky substituents were deleterious in rat receptors. The 4-isobutyl-3-isopropyl analogue was the most potent in housefly receptors (IC50 = 45.2 nM ), and tert-butylbicyclophosphorothionate (TBPS), with the 4-tert-butyl group and no 3-substituent, was the most potent in rat receptors (IC50 = 62.2 nM ). Their receptor selectivities (rat IC50/housefly IC50) were 52 and 0.038, respectively. The insecticidal activity (LD50) of 20 active analogues was well correlated with their potency (IC50) in inhibiting [3H]EBOB binding to housefly-head membranes (r = 0.93). The results obtained in the present study indicate that the introduction of appropriate alkyl groups into the 3- and 4-positions of bicyclophosphorothionate leads to non-competitive antagonists with increased affinity and selectivity for housefly ionotropic GABA receptors versus rat GABAA receptors. © 1999 Society of Chemical Industry  相似文献   

6.
γ-Aminobutyric acid (GABA) receptors (GABARs) are an important target for existing insecticides such as fiproles. These insecticides act as noncompetitive antagonists (channel blockers) for insect GABARs by binding to a site within the intrinsic channel of the GABAR. Recently, a novel class of insecticides, 3-benzamido-N-phenylbenzamides (BPBs), was shown to inhibit GABARs by binding to a site distinct from the site for fiproles. We examined the binding site of BPBs in the adult housefly by means of radioligand-binding and electrophysiological experiments. 3-Benzamido-N-(2,6-dimethyl-4-perfluoroisopropylphenyl)-2-fluorobenzamide (BPB 1) (the N-demethyl BPB) was a partial, but potent, inhibitor of [3H]4′-ethynyl-4-n-propylbicycloorthobenzoate (GABA channel blocker) binding to housefly head membranes, whereas the 3-(N-methyl)benzamido congener (the N-methyl BPB) had low or little activity. A total of 15 BPB analogs were tested for their abilities to inhibit [3H]BPB 1 binding to the head membranes. The N-demethyl analogs, known to be highly effective insecticides, potently inhibited the [3H]BPB 1 binding, but the N-methyl analogs did not even though they, too, are considered highly effective. [3H]BPB 1 equally bound to the head membranes from wild-type and dieldrin-resistant (rdl mutant) houseflies. GABA allosterically inhibited [3H]BPB 1 binding. By contrast, channel blocker-type antagonists enhanced [3H]BPB 1 binding to housefly head membranes by increasing the affinity of BPB 1. Antiparasitic macrolides, such as ivermectin B1a, were potent inhibitors of [3H]BPB 1 binding. BPB 1 inhibited GABA-induced currents in housefly GABARs expressed in Xenopus oocytes, whereas it failed to inhibit l-glutamate-induced currents in inhibitory l-glutamate receptors. Overall, these findings indicate that BPBs act at a novel allosteric site that is different from the site for channel blocker-type antagonists and that is probably overlapped with the site for macrolides in insect GABARs.  相似文献   

7.
Variously substituted benzyl derivatives of chloronicotinyl insecticides were synthesized with a wide range of substituents including halogens, NO2, CN, CF3 and small alkyl and alkoxy groups at the ortho, meta and para positions, as well as multiple‐substituted benzyl analogues. Their binding activity to the α‐bungarotoxin binding site in housefly (Musca domestica) head membrane preparations was measured. Among the compounds tested, the activity of the meta‐CN derivative was the highest, being 20–100 times higher than those of imidacloprid, acetamiprid and nitenpyram. The synergized insecticidal activity against houseflies was also measured for selected compounds with the metabolic inhibitor, NIA16388 (propargyl propyl phenylphosphonate). For the nitromethylene analogues, including both benzyl and pyridylmethyl analogues, higher binding activity usually resulted in higher insecticidal activity. © 2000 Society of Chemical Industry  相似文献   

8.
BACKGROUND: The housefly, Musca domestica L., continues to be a major pest of confined livestock operations. Houseflies have developed resistance to most chemical classes, and new chemistries for use in animal agriculture are increasingly slow to emerge. Five adult housefly strains from four Florida dairy farms were evaluated for resistance to four insecticides (beta‐cyfluthrin, permethrin, imidacloprid and nithiazine). RESULTS: Significant levels of tolerance were found in most field strains to all insecticides, and in some cases substantial resistance was apparent (as deduced from comparison with prior published results). At the LC90 level, greater than 20‐fold resistance was found in two of the fly strains for permethrin and one fly strain for imidacloprid. Beta‐cyfluthrin LC90 resistance ratios exceeded tenfold resistance in three fly strains. The relatively underutilized insecticide nithiazine had the lowest resistance ratios; however, fourfold LC90 resistance was observed in one southern Florida fly strain. Farm insecticide use and its impact on resistance selection in Florida housefly populations are discussed. CONCLUSION: Housefly resistance to pyrethroids is widespread in Florida. Imidacloprid resistance is emerging, and tolerance was observed to both imidacloprid and nithiazine. If these insecticides are to retain efficacy, producer use must be restrained. Copyright © 2009 Society of Chemical Industry  相似文献   

9.
Toxicity tests revealed up to 40-fold resistance to a number of cyclodiene insecticides in a laboratory-reared, cyclodiene-resistant (CYW) housefly strain (Musca domestica L.). Using [35S] TBPS as a probe for convulsant sites in insects, saturable specific binding was detected in thorax and abdomen membranes prepared from housefly strains susceptible (CSMA) and resistant (CYW) to cyclodienes. Scatchard analysis of[35S] TBPS binding data to CSMA and CYW membranes failed to provide evidence for significant differences between the two strains in either the affinity (Kd) or density (Bmax) of saturable binding sites. For several polychlorocycloalkane insecticides, the ligand displacement profile of [35S] TBPS binding was almost identical for the CSMA and CYW houseflies. Therefore, using [35S] TBPS as a probe for convulsant sites, a 40-fold resistance to cyclodienes in the CYW housefly strain cannot be accounted for only in terms of alterations in TBPS binding sites.  相似文献   

10.
Xie W  Wang S  Wu Q  Feng Y  Pan H  Jiao X  Zhou L  Yang X  Fu W  Teng H  Xu B  Zhang Y 《Pest management science》2011,67(1):87-93
BACKGROUND: The polyphagous B‐biotype Bemisia tabaci (Gennadius) has developed a high resistance to commonly used insecticides in China. To illustrate the induced changes by host plant, bioassay and biochemical research on five different host populations were investigated. RESULTS: Except for bifenthrin, all tested insecticides showed lower toxicity to the B. tabaci poinsettia population compared with other host populations. Moreover, four insecticides, the exceptions being abamectin and fipronil, showed highest toxicity towards the tomato population. The LC50 values of the poinsettia population, particularly towards acetamiprid, were 14.8‐, 10.3‐ and 7.29‐fold higher than those of tomato, cucumber and cabbage respectively. The CarE activities of B. tabaci cabbage and cucumber populations were all significantly higher than those of poinsettia, cotton and tomato populations. The ratio of the cabbage population was 1.97‐, 1.79‐ and 1.30‐fold higher than that of poinsettia, cotton and tomato respectively. The frequency profiles for this activity also have obvious differences. The GST and P450 activities of the cucumber population were the lowest in the five host populations. CONCLUSION: Long‐term induction of host plants for B‐biotype B. tabaci could influence their susceptibilities to several insecticides. Rational selection and usage of insecticides for particular hosts will be helpful for resistance management and control of this species. Copyright © 2010 Society of Chemical Industry  相似文献   

11.
BACKGROUND: Phthalic acid diamide derivatives are among the most important classes of synthetic insecticides. In this study, a 3,3‐dichloro‐2‐propenyloxy group, the essential active group of pyridalyl derivatives, was incorporated into phthalic acid diamide derivatives with the aim of combining the active groups to generate more potent insecticides. RESULTS: Thirty‐one new phthalic acid diamides were obtained, and these were characterised by 1H and 13C NMR. The structure of N2‐[1,1‐dimethyl‐2‐(methoxy)ethyl]‐3‐iodo‐N1‐[4‐(3,3‐dichloro‐2‐propenyloxy)‐3‐(trifluoromethyl)phenyl]‐1,2‐benzenedicarboxamide was determined by X‐ray diffraction crystallography. The insecticidal activities of the compounds against Plutella xylostella were evaluated. The title compounds exhibited excellent larvicidal activities against P. xylostella. Structure‐activity relationships revealed that varying the combination of aliphatic amide and aromatic amide moieties, or the nature and position of substituent Y on the aniline ring, could aid the design of structures with superior performance. CONCLUSION: A series of novel phthalic acid diamides containing a 3,3‐dichloro‐2‐propenyloxy group at the 4‐position of the aniline ring were designed and synthesised. Structure‐activity relationships with the parent structure provided information that could direct further investigation on structure modification. Copyright © 2012 Society of Chemical Industry  相似文献   

12.
BACKGROUND: Certain bisacylhydrazine compounds such as tebufenozide (RH5992) have been shown to act as order‐specific insecticides. Their compatibility with predatory Heteroptera, which are used as biological control agents, has also been demonstrated. However, the molecular mode of action of these ecdysone agonists has not been explored in a heteropteran, much less one that is a significant agricultural pest, such as Nezara viridula. RESULTS: Alternatively spliced ligand‐binding regions of the N. viridula ecdysone receptor were expressed, purified and characterised by 2D gel analysis, mass spectrometry, homology modelling and competitive binding of a bisacylhydrazine insecticidal compound (RH5992) and various ecdysteroids. Ligand binding by the two splice isoforms was indistinguishable, and relative affinities were found to occur in the order muristerone A > ponasterone A > 20‐hydroxyecdysone > inokosterone > RH5992 > α‐ecdysone. CONCLUSION: The predicted difference in amino acid sequence between the ligand‐binding domains of the N. viridula ecdysone receptor splice variants was verified by mass spectrometry. Both splice variant isoforms exhibit a greater affinity for the bisacylhydrazine insecticide RH5992 than do the other hemipteran ecdysone receptors characterised to date. Their affinities for a range of ecdysteroids also distinguish them from the ecdysone receptors of other Hemiptera characterised thus far. Homology models of both N. viridula receptor isoforms provide further insight into the bisacylhydrazine‐ and ecdysteroid‐binding properties of these receptors, including their similar affinity for 20‐hydroxyecdysone and the postulated pentatomomorphan moulting hormone makisterone A. Copyright © 2011 Society of Chemical Industry  相似文献   

13.
BACKGROUND: Application of insecticides in modern agriculture in order to enhance legume production has led to their accumulation in soils to levels that adversely affect soil microflora such as rhizobia and exert a negative impact on the physiological activities associated with them. This study was therefore designed to identify rhizobial strains expressing higher tolerance to insecticides fipronil and pyriproxyfen and synthesising plant growth regulators even amid insecticide stress. RESULTS: The fipronil‐ and pyriproxyfen‐tolerant Rhizobium sp. strain MRL3 produced plant‐growth‐promoting substances in substantial amounts, both in the presence and in the absence of the insecticides. In general, both insecticides at recommended and higher rates reduced plant dry biomass, symbiotic properties, nutrient uptake and seed yield of lentil plants. Interestingly, when applied with any concentration of the two insecticides, Rhizobium sp. strain MRL3 significantly increased the measured parameters compared with plants grown in soils treated solely with the same concentration of each insecticide but without inoculant. CONCLUSION: This study suggests that Rhizobium strain MRL3 may be exploited as a bioinoculant to augment the efficiency of lentil exposed to insecticide‐stressed soils. Copyright © 2010 Society of Chemical Industry  相似文献   

14.
Monoterpenoid derivatives were synthesized and their insecticidal activities were evaluated against red flour beetles, Tribolium castaneum (Herbst), in fumigant bioassays and against house flies Musca domestica (L.) in topical, fumigant, and ovicidal bioassays. Acetate derivatives and haloacetate derivatives were compared with each other, and with the parent monoterpenoid to determine structure-activity relationships. Acetate derivatives were more active than the propionate derivatives of cyclic monoterpenoids in the topical, fumigant, and ovicidal bioassays. Pivalates were topically more insecticidal than acetates to adult house flies, while the acetates had the greater ovicidal activity. Acetates and pivalates were more effective than haloacetates in the topical, red flour beetle fumigation and ovicidal bioassays. Fluoroacetates of cyclic monoterpenoids were the most effective house fly fumigants, followed by acetates, and trichloroacetates. Several derivatives were produced that displayed enhanced activity relative to the parent alcohols or phenols.  相似文献   

15.
BACKGROUND: The moulting accelerating compounds (MACs) or ecdysteroid agonists represent a selective group of insecticides acting upon binding to the ecdysteroid receptor (EcR) and leading to lethal premature moulting in larval stages and aborted reproduction in adults. Psyttalia concolor Szèpl. is a useful parasitic wasp attacking important tephritid pests such as the medfly and olive fruit fly. RESULTS: Contact and oral exposure in the laboratory of female parasitic wasps to the dibenzoylhydrazine‐based methoxyfenozide, tebufenozide and RH‐5849 did not provoke negative effects. No mortality and no reduction in beneficial capacity were observed. The ligand‐binding domain (LBD) of the EcR of P. concolor was sequenced, and a homology protein model was constructed which confirmed a cavity structure with 12 α‐helices, harbouring the natural insect moulting hormone 20‐hydroxyecdysone. However, a steric clash occurred for the MAC insecticides owing to a restricted extent of the ligand‐binding cavity of the PcLBD‐EcR, while they did dock well in that of susceptible insects. CONCLUSIONS: The insect toxicity assays demonstrated that MACs are selective for P. concolor. The modelling/docking experiments are indications that these insecticides do not bind with the LBD‐EcR of P. concolor and support the theory that they show no biological effects in the parasitic wasp. These data may help in explaining the compatible use of MACs together with parasitic wasps in IPM programmes. Copyright © 2012 Society of Chemical Industry  相似文献   

16.
BACKGROUND: Glutathione S‐transferases (GSTs) have received considerable attention in insects for their roles in insecticide resistance. Laodelphax striatellus (Fallén) is a serious rice pest. L. striatellus outbreaks occur frequently throughout eastern Asia. A key problem in controlling this pest is its rapid adaptation to numerous insecticides. In this research, nine cDNAs encoding GSTs in L. striatellus were cloned and characterised. RESULTS: The cloned GSTs of L. striatellus belonged to six cytosolic classes and a microsomal subgroup. Exposure to sublethal concentrations of each of the six insecticides, DDT, chlorpyrifos, fipronil, imidacloprid, buprofezin and beta‐cypermethrin, quickly induced (6 h) up‐expression of LsGSTe1. The expression of LsGSTs2 was increased by chlorpyrifos, fipronil and beta‐cypermethrin. Furthermore, exposure of L. striatellus to fipronil, imidacloprid, buprofezin and beta‐cypermethrin increased the expression of the LsGSTm gene after 24 or 48 h. CONCLUSION: This work is the first identification of GST genes from different GST groups in Auchenorrhyncha species and their induction characteristics with insecticide types and time. The elevated expression of GST genes induced by insecticides might be related to the enhanced tolerance of this insect to insecticides and xenobiotics. Copyright © 2012 Society of Chemical Industry  相似文献   

17.
Little information is available on the actions of β-carboline convulsants on insect GABA receptors or their potential as insecticides. Accordingly, two compounds (3-ethoxy-β-carboline, 3-EBC; dimethoxy-β-carboline-3-methyl ester, DMCM) were studied for their effects on Drosophila melanogaster larval neuron discharge and also in lethality bioassays on adult female D. melanogaster and adult male Blattella germanica. Recordings of nerve spiking in the isolated larval central nervous system showed that 3-EBC and DMCM inhibited nerve discharge, and this inhibitory effect was not additive with that of GABA, confirming that the inhibition was expressed through an action on the GABA receptor. Nerve blockage induced by β-carbolines could not be reversed by picrotoxinin, indicating that there may exist some overlap or negative allosteric coupling between the picrotoxinin and β-carboline binding sites. DMCM and 3-EBC effectively antagonized the effects of exogenously applied GABA in nerve preparations from insecticide-susceptible larvae. In contrast, preparations from the rdl strain of D. melanogaster, which possesses a GABA receptor that is highly resistant to cyclodienes and related convulsants, were less sensitive to the GABA antagonist effect of DMCM. Neither of the β-carbolines produced any appreciable mortality in insects, even when synergized with piperonyl butoxide or S,S,S-tributyl phosphorotrithioate, The toxicity of the β-carbolines is probably limited by their relatively weak effects on the GABA receptor and perhaps also by pharmacokinetic factors. These considerations, coupled with the cross-resistance observed in cyclodiene-resistant insects, suggest that the currently available β-carbolines are not viable as lead compounds for insecticide screening efforts. © 1997 SCI.  相似文献   

18.
BACKGROUND: Developing scientifically valid, economically acceptable insecticide resistance management (IRM) programs is critical for sustainable insect management. The diamondback moth, Plutella xylostella (L.), has demonstrated an ability to develop resistance to many different classes of insecticides, including proteins produced by the bacterium Bacillus thuringiensis Berliner (Bt). Recently it has developed resistance to the novel compounds spinosad and indoxacarb. In greenhouse cage experiments, a laboratory‐selected population of P. xylostella resistant to spinosad, indoxacarb and Bt was used to compare population growth and resistance evolution if these three insecticides were rotated or used in a mosaic fashion. RESULTS: The average population density through nine generations was lowest in the treatment in which the insecticide was rotated every generation (R‐1) (x? = 20.7 ± 3.20) compared with the treatment in which the insecticide was rotated every third generation (R‐3) (x? = 41.4 ± 17.6) or where the insecticides were applied as a mosaic (M) (x? = 41.8 ± 6.53). After nine generations, the survival of resistant individuals increased for each insecticide (7.2–73.5%) compared with the population without selection (CK) (0.73–3.1%). Survival on spinosad was significantly lower (23.7%) in the single‐generation rotation than for the other two treatments, both of which exceeded 72%. The calculated survival on all three insecticides treated simultaneously, according to the survival on each insecticide, was 0.26, 0.81 and 1.6% for R‐1, R‐3 and M treatments respectively. CONCLUSION: Results of both population density and resistance development indicated that insecticide rotation every generation was better for IRM than if the insecticide was rotated every third generation or if the three insecticides were applied as a mosaic. Copyright © 2010 Society of Chemical Industry  相似文献   

19.
BACKGROUND: Laodelphax striatellus (Fallén) is a major pest of cultivated rice and is commonly controlled in China with the organophosphate insecticides. To develop a better resistance management strategy, a chlorpyrifos‐resistant strain of L. striatellus was selected in the laboratory, and its cross‐resistance to other insecticides and possible mechanisms of the chlorpyrifos resistance were investigated. RESULTS: After 25 generations of selection with chlorpyrifos, the selected strain of L. striatellus developed 188‐fold resistance to chlorpyrifos in comparison with the susceptible strain, and showed 14‐ and 1.6‐fold cross‐resistance to dichlorvos and thiamethoxam respectively. There was no apparent cross‐resistance to abamectin. Chlorpyrifos was synergised by the inhibitor triphenyl phosphate; the carboxylesterase synergistic ratio was 3.8 for the selected strain, but only 0.92 for the susceptible strain. The carboxylesterase activity of the selected strain was approximately 4 times that of the susceptible strain, whereas there was no significant change in the activities of alkaline phosphatase, acid phosphatase, glutathione S‐transferase and cytochrome P450 monooxygenase between the strains. The Michaelis constant of acetylcholinesterase, maximum velocity of acetylcholinesterase and median inhibitory concentration of chlorpyrifos‐oxon on acetylcholinesterase were 1.7, 2.5 and 5 times higher respectively in the selected strain. CONCLUSION: The high cross‐resistance to the organophosphate dichlorvos in the chlorpyrifos‐resistant strain suggests that other non‐organophosphate insecticides would be necessary to counter resistance, should it arise in the field. Enhanced activities of carboxylesterase and the acetylcholinesterase insensitivity appear to be important mechanisms for chlorpyrifos resistance in L. striatellus. Copyright © 2010 Society of Chemical Industry  相似文献   

20.
BACKGROUND: Knowledge of pesticide selectivity to natural enemies is necessary for a successful implementation of biological and chemical control methods in integrated pest management (IPM) programmes. Diacylhydrazine (DAH)‐based ecdysone agonists, also known as moulting‐accelerating compounds (MACs), are considered to be a selective group of insecticides, and their compatibility with predatory Heteroptera, which are used as biological control agents, is known. However, their molecular mode of action has not been explored in beneficial insects such as Orius laevigatus (Fieber) (Hemiptera: Anthocoridae). RESULTS: In this project, in vivo toxicity assays demonstrated that the DAH‐based RH‐5849, tebufenozide and methoxyfenozide have no toxic effect against O. laevigatus. The ligand‐binding domain (LBD) of the ecdysone receptor (EcR) of O. laevigatus was sequenced, and a homology protein model was constructed that confirmed a cavity structure with 12 α‐helices, harbouring the natural insect moulting hormone 20‐hydroxyecdysone. However, docking studies showed that a steric clash occurred for the DAH‐based insecticides owing to a restricted extent of the ligand‐binding cavity of the EcR of O. laevigatus. CONCLUSIONS: The insect toxicity assays demonstrated that MACs are selective for O. laevigatus. The modelling/docking experiments are indications that these pesticides do not bind with the LBD‐EcR of O. laevigatus and support the supposition that they show no biological effects in the predatory bug. These data help in explaining the compatible use of MACs together with predatory bugs in IPM programmes. Copyright © 2012 Society of Chemical Industry  相似文献   

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