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Robert M Hollingworth - One of the best experts on this subject based on the ideXlab platform.
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metabolic mechanisms of Indoxacarb resistance in field populations of choristoneura rosaceana harris lepidoptera tortricidae
Pesticide Biochemistry and Physiology, 2020Co-Authors: Abdulwahab M Hafez, D Motasanchez, Robert M HollingworthAbstract:Abstract Synergism and metabolic studies were conducted to identify the resistance mechanism against Indoxacarb in two Choristoneura rosaceana (Harris) field populations compared to a susceptible population. The synergism study was carried out using diet incorporation bioassay for Indoxacarb and the three synergists PBO, DEM, and DEF. The metabolic study consists of Indoxacarb in vitro reaction with fifth instar larvae 12,000 g midgut supernatant or with pre-inhibited (in vivo by the esterases inhibitor DEF) fifth instar larvae 12,000 g midgut supernatant at different incubation times. In both susceptible and cherry populations, only DEF significantly synergized Indoxacarb with a synergism ratio (SR) of 6.5 and 22.6-fold respectively indicating an involvement of esterases in the both populations. In the apple population, all synergists PBO, DEM, and DEF significantly synergized Indoxacarb with SR of 9.6, 7.7, and 285.6-fold respectively indicating a complex resistance case with the possible involvement of all three metabolic resistance mechanisms with the central role of esterase enzymes. In vitro, the Indoxacarb (DPX-JW062) was very rapidly metabolized within 5 min into small molecules in the lower portion of the metabolic pathway when it reacted with the midgut supernatant of each population. None of the metabolites in the upper portion of the metabolic pathway were detected at any incubation time including the potent sodium channel blocker DCJW metabolite. The two field populations showed significantly higher rates of metabolism of DPX-JW062 compared to the susceptible population at five min of incubation and that may explain the presence of Indoxacarb resistance. In the second part of the in vitro study, the bio-transformation of DPX-JW062 was remarkably decreased when it reacted with the pre-inhibited (by DEF) midgut supernatant of each population. Additionally, the degradation of metabolites in the upper portion of the metabolic pathway remarkably decreased, which resulted in accumulation of DCJW and MP819 metabolites. The accumulation of DCJW metabolite under the pre-inhibited midgut supernatants treatment provided a persuasive explanation of the synergistic impact of esterase inhibitor DEF on Indoxacarb in C. rosaceana.
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synergism of insecticides provides evidence of metabolic mechanisms of resistance in the obliquebanded leafroller choristoneura rosaceana lepidoptera tortricidae
Pest Management Science, 2004Co-Authors: Mushtaq Ahmad, Robert M HollingworthAbstract:The interactions between six insecticides (Indoxacarb, cypermethrin, chlorpyrifos, azinphosmethyl, tebufenozide and chlorfenapyr) and three potential synergists, (piperonyl butoxide (PBO), S,S,S-tributyl phosphorotrithioate (DEF) and diethyl maleate (DEM)) were studied by dietary exposure in a multi-resistant and a susceptible strain of the obliquebanded leafroller, Choristoneura rosaceana (Harris). The synergists did not produce appreciable synergism with most of the insecticides in the susceptible strain. Except for tebufenozide, PBO synergized all the insecticides to varying degrees in the resistant strain. A very high level of synergism by PBO was found with Indoxacarb, which reduced the resistance level from 705- to 20-fold when PBO was administered alone and to around 10-fold when used in combination with DEF. DEF also synergized Indoxacarb, cypermethrin, chlorpyrifos, azinphosmethyl and tebufenozide in the resistant strain. DEM produced synergism of Indoxacarb, chlorpyrifos, azinphos-methyl and chlorfenapyr in the resistant strain. DEM was highly synergistic to cypermethrin, and to some extent to tebufenozide in both the susceptible and resistant strains equally, implying that detoxification by glutathione S-transferases was not a mechanism of resistance for these insecticides. The high level of synergism seen with DEM in the case of cypermethrin may be due to an increase in oxidative stress resulting from the removal of the antioxidant, glutathione. These studies indicate that enhanced detoxification, often mediated by cytochrome P-450 monooxygenases, but with probable esterase and glutathione S-transferase contributions in some cases, is the major mechanism imparting resistance to different insecticides in C. rosaceana.
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broad spectrum insecticide resistance in obliquebanded leafroller choristoneura rosaceana lepidoptera tortricidae from michigan
Pest Management Science, 2002Co-Authors: Mushtaq Ahmad, Robert M HollingworthAbstract:Nineteen insecticides, belonging to nine chemical classes, were bioassayed by dietary exposure against two strains of obliquebanded leafroller, Choristoneura rosaceana, collected from Michigan apple orchards. Berrien is a putatively organophosphate-resistant strain from a commercial orchard with a history of insecticide use, and Kalamazoo a susceptible strain from an isolated and unsprayed orchard. The Berrien strain was moderately resistant (about 25-fold) to organophosphates such as azinphos-methyl and chlorpyrifos. Very low resistance ( 700-fold) to Indoxacarb, which has never been used in Michigan to control this insect pest. The active metabolite of Indoxacarb, DCJW, was considerably more toxic than the parent compound, but the resistance against DCJW was comparable to that seen with Indoxacarb. This indicates that a failure to activate Indoxacarb was not the mechanism of resistance in Berrien. The low level of resistance to several chemistries recorded in Michigan C rosaceana can be managed at this stage by adopting a rotation of chemistries having different modes of action. © 2002 Society of Chemical Industry
Mushtaq Ahmad - One of the best experts on this subject based on the ideXlab platform.
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resistance to new insecticides and their synergism in spodoptera exigua lepidoptera noctuidae from pakistan
Crop Protection, 2018Co-Authors: Mushtaq Ahmad, Abid Farid, Muhammad SaeedAbstract:Abstract The beet armyworm Spodoptera exigua (Hubner) is an important pest of field and vegetable crops in Pakistan. Due to persistent use of insecticides, it developed high levels of resistance to organophosphates and pyrethroids in the mid 2000s and farmers then switched to new chemistries. In the present study, its resistance to new chemistries such as Indoxacarb, spinosad, chlorfenapyr, methoxyfenozide and avermectins was monitored from 1998 to 2017 using a leaf-dip bioassay. There was generally a very low to low resistance to these insecticides during the first 11 years of their introduction (1998-2008). Resistance to methoxyfenozide remained very low throughout the 20 years of monitoring. A moderate resistance was recorded to Indoxacarb (2011-2015), spinosad (2009-2012), chlorfenapyr (2011-2017), abamectin (2016-2017) and emamectin benzoate (2010-2013). A high resistance was found to Indoxacarb during 2016–2017, spinosad during 2013–2017 and emamectin benzoate during 2014–2017. A rotation of diverse chemistries, having novel modes of action, along with other integrated pest management tactics, is recommended for the management of insecticide resistance in S. exigua.
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synergism of insecticides provides evidence of metabolic mechanisms of resistance in the obliquebanded leafroller choristoneura rosaceana lepidoptera tortricidae
Pest Management Science, 2004Co-Authors: Mushtaq Ahmad, Robert M HollingworthAbstract:The interactions between six insecticides (Indoxacarb, cypermethrin, chlorpyrifos, azinphosmethyl, tebufenozide and chlorfenapyr) and three potential synergists, (piperonyl butoxide (PBO), S,S,S-tributyl phosphorotrithioate (DEF) and diethyl maleate (DEM)) were studied by dietary exposure in a multi-resistant and a susceptible strain of the obliquebanded leafroller, Choristoneura rosaceana (Harris). The synergists did not produce appreciable synergism with most of the insecticides in the susceptible strain. Except for tebufenozide, PBO synergized all the insecticides to varying degrees in the resistant strain. A very high level of synergism by PBO was found with Indoxacarb, which reduced the resistance level from 705- to 20-fold when PBO was administered alone and to around 10-fold when used in combination with DEF. DEF also synergized Indoxacarb, cypermethrin, chlorpyrifos, azinphosmethyl and tebufenozide in the resistant strain. DEM produced synergism of Indoxacarb, chlorpyrifos, azinphos-methyl and chlorfenapyr in the resistant strain. DEM was highly synergistic to cypermethrin, and to some extent to tebufenozide in both the susceptible and resistant strains equally, implying that detoxification by glutathione S-transferases was not a mechanism of resistance for these insecticides. The high level of synergism seen with DEM in the case of cypermethrin may be due to an increase in oxidative stress resulting from the removal of the antioxidant, glutathione. These studies indicate that enhanced detoxification, often mediated by cytochrome P-450 monooxygenases, but with probable esterase and glutathione S-transferase contributions in some cases, is the major mechanism imparting resistance to different insecticides in C. rosaceana.
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broad spectrum insecticide resistance in obliquebanded leafroller choristoneura rosaceana lepidoptera tortricidae from michigan
Pest Management Science, 2002Co-Authors: Mushtaq Ahmad, Robert M HollingworthAbstract:Nineteen insecticides, belonging to nine chemical classes, were bioassayed by dietary exposure against two strains of obliquebanded leafroller, Choristoneura rosaceana, collected from Michigan apple orchards. Berrien is a putatively organophosphate-resistant strain from a commercial orchard with a history of insecticide use, and Kalamazoo a susceptible strain from an isolated and unsprayed orchard. The Berrien strain was moderately resistant (about 25-fold) to organophosphates such as azinphos-methyl and chlorpyrifos. Very low resistance ( 700-fold) to Indoxacarb, which has never been used in Michigan to control this insect pest. The active metabolite of Indoxacarb, DCJW, was considerably more toxic than the parent compound, but the resistance against DCJW was comparable to that seen with Indoxacarb. This indicates that a failure to activate Indoxacarb was not the mechanism of resistance in Berrien. The low level of resistance to several chemistries recorded in Michigan C rosaceana can be managed at this stage by adopting a rotation of chemistries having different modes of action. © 2002 Society of Chemical Industry
Michael E Scharf - One of the best experts on this subject based on the ideXlab platform.
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Indoxacarb biotransformation in the german cockroach
Pesticide Biochemistry and Physiology, 2016Co-Authors: Ameya D Gondhalekar, Ernesto S Nakayasu, Isabel Silva, Bruce A Cooper, Michael E ScharfAbstract:Insecticides that are used for pest control undergo physical and biological (enzymatic) degradation. Indoxacarb is an oxadiazine class sodium channel blocker insecticide used for German cockroach (Blattella germanica L.) control. At present, no information is available on enzymatic biotransformation or metabolism of Indoxacarb in this important urban pest. We studied the biotransformation pathways of Indoxacarb in one susceptible and three field strains with varying susceptibility levels using liquid chromatography and high-resolution mass spectrometry. As shown in other insect species we found evidence for hydrolase-based bioactivation of Indoxacarb to a toxic decarbomethoxylated metabolite, DCJW. In addition, both Indoxacarb and DCJW were further metabolized to hydroxy, oxadiazine ring-opened and hydroxylated ring-opened metabolites. In general, higher Indoxacarb disappearance, increased formation of DCJW and the above-mentioned metabolites were observed in the three field strains. In vitro biotransformation studies showed that hydroxylated and oxadiazine ring-opened metabolite formation is NADPH/cytochrome P450-dependent. Bioassays and in vivo metabolism experiments using the enzyme-inhibiting insecticide synergists, piperonyl butoxide (PBO) and S,S,S,-tributyl phosphorotrithioate (DEF), provided insights into potential Indoxacarb resistance mechanisms that may proliferate in German cockroach field strains following unchecked selection pressures. The information presented here is an essential step toward developing Indoxacarb resistance management programs and also reveals mechanisms of secondary/tertiary Indoxacarb toxicity.
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implementation of an Indoxacarb susceptibility monitoring program using field collected german cockroach isolates from the united states
Journal of Economic Entomology, 2013Co-Authors: Michael E Scharf, Ameya D Gondhalekar, Clay W Scherer, Raj K SaranAbstract:Indoxacarb, a sodium channel-blocking insecticide, has been in widespread use for German cockroach control in the United States since 2006. A two-tiered Indoxacarb susceptibility monitoring strategy was previously developed as a first step toward determining Indoxacarb susceptibility levels in German cockroach field populations. This strategy entails: (tier 1) testing field-collected populations in vial bioassays at two diagnostic concentrations; and (tier 2) testing populations at three diagnostic doses in oral (feeding) bioassays with treated bait matrix. In the current study the two-tiered technique was implemented to evaluate field (n = 14) and susceptible laboratory (n = 2) strains collected from 13 different U.S. locations. Our hypothesis was that at least some of the field-collected populations would display significant survivorship in both bioassays relative to susceptible laboratory populations. In agreement with this hypothesis, significantly reduced susceptibility was detected in 13 and 7 field strains with vial and feeding bioassays, respectively. In general, the lower number of strains displaying reduced susceptibility in feeding bioassays (seven strains) supports previous findings that Indoxacarb is more toxic via ingestion. Although these findings suggest a reduced risk for resistance selection via feeding on Indoxacarb-containing baits, they also suggest a need for proactive resistance management with respect to both spray and bait products.
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development of strategies for monitoring Indoxacarb and gel bait susceptibility in the german cockroach blattodea blattellidae
Pest Management Science, 2011Co-Authors: Ameya D Gondhalekar, Cheol Song, Michael E ScharfAbstract:BACKGROUND: Advion® cockroach gel bait (6 g kg−1 Indoxacarb) is in widespread use for Blattella germanica (L.) control in the United States. However, baseline susceptibility levels to Indoxacarb in German cockroach field populations are not known. Hence, this research sought to develop monitoring strategies to estimate the susceptibility of German cockroach populations to Indoxacarb. RESULTS: Four bioassays were evaluated: topical lethal dose (LD), formulated gel bait lethal time (LT), vial lethal concentration (LC) and gel bait matrix LD. Of these methods, the vial LC and gel bait matrix LD bioassays were the most economical and relevant assessment strategies. For Indoxacarb susceptibility monitoring, a two-tiered approach was developed that utilizes diagnostic concentrations and doses in vial LC (30 and 60 µg vial−1) and gel bait matrix LD (1.0, 1.5 and 2.5 µg insect−1) formats. CONCLUSIONS: A two-tiered susceptibility monitoring strategy was developed that includes testing field populations at diagnostic concentrations and doses in first-tier vial LC bioassays and second-tier gel bait matrix LD bioassays. The vial method facilitates rapid identification of field strains with reduced susceptibility. The feeding bioassay effectively simulates field exposure to Advion® and therefore has utility for secondary confirmation of susceptibility shifts and identification of behavioral resistance (i.e. bait aversion). Copyright © 2010 Society of Chemical Industry
Lisa J Bird - One of the best experts on this subject based on the ideXlab platform.
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linkage mapping an Indoxacarb resistance locus in helicoverpa armigera lepidoptera noctuidae by genotype by sequencing
Pest Management Science, 2020Co-Authors: Yizhou Chen, Lisa J Bird, Lauren K Woolley, Tom Walsh, K D Gordon, Grant A HerronAbstract:Background A major challenge to sustainable agricultural pest control is the rapid evolution of insecticide resistance. This is caused by mechanisms that reduce insecticide efficacy. Understanding the genetic mechanisms of resistance is essential for DNA-based monitoring of resistance in field populations. One such insecticide is Indoxacarb, an important selective control option for Helicoverpa armigera in a range of crops including grain, horticulture and cotton. Recently, a strain of H. armigera (GY7-39) resistant to Indoxacarb (198-fold) was isolated from field-collected moth. Results To identify the Indoxacarb resistance locus, GY7-39 was backcrossed for six generations to susceptible strain New GR. In each generation, only resistant males were used to cross back to New GR. Genotype-by-sequencing was carried out on 95 H. armigera samples. In total, 13 203 tags with 8697 unique locations on the H. armigera genome were obtained. The Indoxacarb resistance locus in strain GY7-39 was mapped to a 2.6 Mbp region on chromosome 16. In this region, two closely linked loci (IndoR1 and IndoR2) were found to be associated with Indoxacarb resistant GY7-39. Conclusions We mapped Indoxacarb resistance in GY7-39 to two closely linked loci IndoR1 and IndoR2 in a narrowed 2.6 Mbp region of H. armigera chromosome 16. The results provide essential background data for future genetic investigations including fine mapping of the Indoxacarb resistance gene and the eventual development of an effective DNA-based diagnostic to support resistance management. © 2019 Society of Chemical Industry.
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baseline susceptibility of helicoverpa punctigera lepidoptera noctuidae to Indoxacarb emamectin benzoate and chlorantraniliprole
Journal of Economic Entomology, 2019Co-Authors: Lisa J Bird, P W WalkerAbstract:Susceptibility in Helicoverpa punctigera (Wallengren) to emamectin benzoate, chlorantraniliprole, and Indoxacarb was established from feeding assays on insecticide-incorporated artificial diet in the laboratory. The variation in dose responses was examined in H. punctigera field populations collected in eastern Australia between September 2013 and January 2016 and compared with a laboratory strain. Chlorantraniliprole was the most toxic insecticide with an average LC50 of 3.7 µg of insecticide per liter of diet (n = 12 field strains). The average LC50 for emamectin benzoate was 5.6 µg of insecticide per liter of diet (n = 11 field strains), whereas Indoxacarb had the lowest toxicity with an average LC50 of 172 µg of insecticide per liter of diet (n = 14 field strains). Variation in susceptibility between field strains was low at 1.9-, 2.4-, and 2-fold for chlorantraniliprole, emamectin benzoate, and Indoxacarb, respectively. Narrow ranges of intra-specific tolerance, high slopes, and goodness-of-fit to a probit binomial model suggested feeding bioassays using insecticide-incorporated diet were a more effective laboratory method for measuring dose responses of these insecticides in H. punctigera than traditional topical bioassays. We propose discriminating concentrations of 0.032, 0.026, and 4 µg of insecticide/ml of diet for chlorantraniliprole, emamectin benzoate, and Indoxacarb, respectively, to monitor insecticide resistance in H. punctigera. Although the potential for H. punctigera to develop insecticide resistance is considered low based on historical records, recent changes in population dynamics of this species in eastern Australia may have increased the risk of resistance development.
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genetics cross resistance and synergism of Indoxacarb resistance in helicoverpa armigera lepidoptera noctuidae
Pest Management Science, 2017Co-Authors: Lisa J BirdAbstract:BACKGROUND The cotton bollworm Helicoverpa armigera is a global pest of field and horticultural crops and has developed resistance to insecticides from many chemical classes. Indoxacarb is an important option for selective control of H. armigera in a range of crops that play host to this species. A strain of H. armigera resistant to Indoxacarb (designated GY7-39) was detected from the field by F2 screening and characterised by comparison with a near-isogenic Indoxacarb-susceptible laboratory strain to determine inheritance, cross-resistance profile and synergism of Indoxacarb resistance. RESULTS The level of Indoxacarb resistance in the GY7-39 strain was 139–198-fold compared with the susceptible strain. Genetic analysis showed that resistance was autosomal, incompletely dominant and conferred by one or a few closely linked loci. Indoxacarb resistance in the GY7-39 strain did not confer cross-resistance to chlorantraniliprole. The GY7-39 strain was more susceptible to emamectin benzoate, fenvalerate, Cry1Ac and Cry2Ab compared with the susceptible strain. Indoxacarb resistance was synergised by the metabolic inhibitor PBO. CONCLUSIONS Rapid selection of Indoxacarb resistance in the GY7-39 strain indicates the potential risk of resistance development to Indoxacarb in field populations of H. armigera. Lack of cross-resistance indicates that resistance could be managed effectively by the use of rotational strategies that incorporate transgenic technologies. Synergism studies indicate the potential involvement of metabolic detoxification enzymes as the mechanism of resistance to Indoxacarb. © 2016 Society of Chemical Industry
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baseline susceptibility of helicoverpa armigera lepidoptera noctuidae to Indoxacarb emamectin benzoate and chlorantraniliprole in australia
Journal of Economic Entomology, 2015Co-Authors: Lisa J BirdAbstract:ABSTRACT Baseline susceptibility of Helicoverpa armigera (Hubner) to emamectin benzoate, chlorantraniliprole, and Indoxacarb was determined in feeding assays on insecticide-incorporated artificial diet in the laboratory. The intraspecific variation of H. armigera was established from field populations collected between September 2012 and March 2013, primarily from commercial farms across eastern Australia. Emamectin benzoate had the highest toxicity with a median lethal concentration (LC50) of 0.01 µg/ml diet (n = 20 strains). The LC50 for chlorantraniliprole was 0.03 µg/ml diet (n = 21 strains), while Indoxacarb had the lowest relative toxicity with an average LC50 of 0.3 µg/ml diet (n = 22 strains). Variation in susceptibility amongst field strains was 2.3-fold for emamectin benzoate and 2.9-fold for chlorantraniliprole and Indoxacarb. Discriminating concentrations of 0.2, 1, and 12 µg of insecticide per milliliter of diet for emamectin benzoate, chlorantraniliprole, and Indoxacarb, respectively, were c...
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baseline susceptibility of helicoverpa armigera lepidoptera noctuidae to Indoxacarb emamectin benzoate and chlorantraniliprole in australia
Journal of Economic Entomology, 2015Co-Authors: Lisa J BirdAbstract:Baseline susceptibility of Helicoverpa armigera (Hubner) to emamectin benzoate, chlorantraniliprole, and Indoxacarb was determined in feeding assays on insecticide-incorporated artificial diet in the laboratory. The intraspecific variation of H. armigera was established from field populations collected between September 2012 and March 2013, primarily from commercial farms across eastern Australia. Emamectin benzoate had the highest toxicity with a median lethal concentration (LC50) of 0.01 µg/ml diet (n=20 strains). The LC50 for chlorantraniliprole was 0.03 µg/ml diet (n=21 strains), while Indoxacarb had the lowest relative toxicity with an average LC50 of 0.3 µg/ml diet (n=22 strains). Variation in susceptibility amongst field strains was 2.3-fold for emamectin benzoate and 2.9-fold for chlorantraniliprole and Indoxacarb. Discriminating concentrations of 0.2, 1, and 12 µg of insecticide per milliliter of diet for emamectin benzoate, chlorantraniliprole, and Indoxacarb, respectively, were calculated from toxicological data from field H. armigera strains as a first step in resistance management of these classes of insecticide in Australia. The low intraspecific tolerance, high slope values, and goodness-of-fit to a probit binomial model obtained in this study suggest that a feeding assay using diet incorporated insecticide is an effective laboratory method for measuring the dose-responses of these classes of insecticides in H. armigera.
Ali H Sayyed - One of the best experts on this subject based on the ideXlab platform.
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cross resistance and genetics of resistance to Indoxacarb in spodoptera litura lepidoptera noctuidae
Journal of Economic Entomology, 2008Co-Authors: Ali H Sayyed, Munir Ahmad, Mushtaq A SaleemAbstract:Bioassays (at generation G1) with a newly collected field population of Spodoptera litura (F.) (Lepidoptera: Noctuidae) from Multan, Pakistan, showed resistance ratios of 15, 23, 37, and 16 for Indoxacarb, spinosad, abamectin, and emamectin, respectively, compared with a laboratory susceptible population, Lab-PK. At G1, the field population was selected with Indoxacarb by using single pair crosses. For Indoxa-SEL, bioassay at G4 found that selection increased resistance ratio to 95 for Indoxacarb compared with Lab-PK. Selection with Indoxacarb significantly increased resistance to spinosad and emamectin; however, resistance to abamectin was observed to drop. A significant reduction in the resistance to Indoxacarb was observed in Indoxa-SEL at G9, indicating unstable resistance to Indoxacarb; however, it was stable for fipronil. Synergism tests with microsomal oxidase and esterase-specific inhibitors suggested that the Indoxacarb resistance was associated with microsomal oxidase. Reciprocal genetic crosses between Indoxa-SEL and Lab-PK populations indicated that resistance was autosomal and incompletely dominant. Tests of monogenic inheritance suggested that resistance to Indoxacarb was controlled by more than one locus.
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genetics and evidence for an esterase associated mechanism of resistance to Indoxacarb in a field population of diamondback moth lepidoptera plutellidae
Pest Management Science, 2006Co-Authors: Ali H Sayyed, Denis J WrightAbstract:Bioassays (at generation G2) with a newly collected field population (designated CH3) of Plutella xylostella L. from farmers' fields in the Cameron Highlands, Malaysia, indicated resistance ratios of 813-, 79-, 171-, 498- and 1285-fold for Indoxacarb, fipronil, spinosad, deltamethrin and Bacillus thuringiensis toxin Cry1Ac respectively compared with a laboratory susceptible population (Lab-UK). At G2 the field-derived population was divided into two subpopulations: one was selected (G2 to G7) with Indoxacarb (indoxa-SEL), while the second was left unselected (UNSEL). A significant reduction in the resistance ratio for each compound was observed in UNSEL at G8. For indoxa-SEL, bioassays at G8 found that selection with Indoxacarb gave a resistance ratio of 2594 compared with Lab-UK and of 90 compared with UNSEL. The toxicity of fipronil, spinosad and deltamethrin was not significantly different in indoxa-SEL at G8 compared with G2 but was significantly greater than UNSEL at G8. The toxicity of Cry1Ac was significantly reduced in indoxa-SEL at G8 compared with G2 but was also significantly greater than UNSEL at G8. This suggests that Indoxacarb selection maintained resistance to these compounds in the indoxa-SEL population. Synergist studies indicated that resistance to Indoxacarb in indoxa-SEL was esterase associated. Logit regression analysis of F1 reciprocal crosses between indoxa-SEL and Lab-UK indicated that resistance to Indoxacarb was inherited as an autosomal, incompletely recessive (DLC = 0.35) trait. Tests of monogenic inheritance suggested that resistance to Indoxacarb was controlled by a single locus. Copyright © 2006 Society of Chemical Industry
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could resistance to insecticides in plutella xylostella lep plutellidae be overcome by insecticide mixtures
Journal of Applied Entomology, 2006Co-Authors: M N R Attique, A Khaliq, Ali H SayyedAbstract:To investigate if synergism occurs between pyrethroids, organophosphates and new insecticides, we tested representatives of these compounds (bifenthrin, chlorpyrifos, spinosad, Indoxacarb and emamectin) against the diamondback moth (Plutella xylostella). Larvicidal activity of these insecticides was assessed separately and together on a susceptible strain (Lab-UK) of P. xylostella as well as a field population collected from Multan. The field population showed significant resistance to chlorpyrifos (331 100-fold), bifenthrin (45 200-fold), emamectin (1800-fold), spinosad (11-fold) and Indoxacarb (5600-fold) when compared with the Lab-UK population. When insecticides were mixed based on LC50 and tested at serial concentrations against Lab-UK, significant synergy (CI < 1) occurred between bifenthrin, spinosad and emamectin. In contrast, the interaction between bifenthrin and Indoxacarb was additive (CI B< 1). The toxicity of bifenthrin against the field population increased significantly (P < 0.01) when combined with spinosad, emamectin and Indoxacarb. Synergistic effects could be attributed to the complementary modes of action by these insecticide classes acting on different components of nerve impulse transmission (which are not identical forbifenthrin and Indoxacarb either). However, chlorpyrifos/bifenthrin mixture was not significantly different either from bifenthrin or chlorpyrifos alone, indicating an additive affect. In combination with spinosad and emamectin, tested against the resistant field population, the toxicity of chlorpyrifos increased significantly and even more so with Indoxacarb. Mixtures could also give rise to multiple resistance that may extend across other chemical classes and thus become difficult to manage. Therefore, alternative strategies such as mosaics or rotations should be considered. That is, though synergistic effects have been found, this should not be followed up as a strategy to manage resistant field populations.
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fipronil resistance in the diamondback moth lepidoptera plutellidae inheritance and number of genes involved
Journal of Economic Entomology, 2004Co-Authors: Ali H Sayyed, Denis J WrightAbstract:Bioassays (at generation 1, G1) using fipronil, spinosad, Indoxacarb, and Bacillus thuringiensis toxins Cry1Ac and Cry1Ca with a newly collected field population of Plutella xylostella (L.) from farmers fields in the Cameron Highlands, Malaysia, indicated a resistance ratio of approximately 400-, 1,170-, 330-, 2,840-, and 1,410-fold, respectively, compared with a laboratory-susceptible population of P. xylostella (ROTH). At G3, the field-derived population was divided into two subpopulations, one was selected (G3 to G7) with fipronil (fip-SEL), whereas the second was left unselected (UNSEL). Bioassays at G8 found that selection with fipronil gave a resistance ratio of approximately 490 compared with UNSEL and approximately 770 compared with ROTH. The resistance ratio for fipronil, spinosad, Indoxacarb, Cry1Ac, and Cry1Ca in the UNSEL population declined significantly by G8. Logit regression analysis of F1 reciprocal crosses between fip-SEL (at G8) and UNSEL indicated that resistance to fipronil in the fip-SEL population was inherited as an autosomal, incompletely recessive (D(LC) = 0.37) trait. At the highest dose of fipronil tested, resistance was completely recessive, whereas at the lowest dose it was incompletely recessive. A direct test of monogenic inheritance based on a backcross of F1 progeny with fip-SEL suggested that resistance to fipronil was controlled by a single locus. The fip-SEL population at G8 showed little change in its response to spinosad and Indoxacarb compared with G1, whereas its susceptibility to Cry1Ac and Cry1Ca increased markedly over the selection period. This suggests that there may be some low level of cross-resistance between fipronil, spinosad, and Indoxacarb.