Susceptibility of house flies (Diptera: Muscidae) exposed to commercial insecticides on painted and unpainted plywood panels

House flies were collected from dairies in New York state and the levels of resistance to commercially available insecticide formulations were measured on painted and unpainted plywood panels. Dimethoate was ineffective on all surfaces. The wettable powder permethrin formulation was more toxic than the emulsifiable concentrate formulation. The wettable powder cyfluthrin formulation was also more toxic than the recently developed liquid formulation. In general, the best house fly control was obtained on flat latex painted plywood panels and the poorest control on gloss latex painted panels. It is highly unlikely that producers obtain adequate control with dimethoate and permethrin.     

Insecticide resistance in house flies from caged‐layer poultry facilities

The frequency of resistance of eight strains of house flies, Musca domestica L., collected from caged‐layer poultry facilities across New York state, to nine insecticides (dimethoate, tetrachlorvinphos, permethrin, cyfluthrin, pyrethrins, methomyl, fipronil, spinosad and cyromazine) was measured relative to a laboratory susceptible strain. Percentage survival was evaluated at five diagnostic concentrations: susceptible strain LC₉₉, 3 × LC₉₉, 10 × LC₉₉, 30 × LC₉₉ and 100 × LC₉₉. The highest levels of resistance were noted for tetrachlorvinphos, permethrin and cyfluthrin. There was substantial variation in the levels of resistance to the different insecticides from one facility to another, independent of their geographical location. There was very little cross‐resistance detected in these populations to either fipronil or spinosad. Overall, there was a good correlation between insecticide use histories and the levels of resistance. The apparent isolation of fly populations within poultry facilities suggests that there are good opportunities for the implementation of successful resistance management strategies at these facilities. Differences between these results and those of a resistance survey on New York dairy farms in 1987 are discussed. © 2000 Society of Chemical Industry     

Insecticide resistance in house flies from the United States: Resistance levels and frequency of pyrethroid resistance alleles

Although insecticide resistance is a widespread problem for most insect pests, frequently the assessment of resistance occurs over a limited geographic range. Herein, we report the first widespread survey of insecticide resistance in the USA ever undertaken for the house fly, Musca domestica, a major pest in animal production facilities. The levels of resistance to six different insecticides were determined (using discriminating concentration bioassays) in 10 collections of house flies from dairies in nine different states. In addition, the frequencies of Vssc and CYP6D1 alleles that confer resistance to pyrethroid insecticides were determined for each fly population. Levels of resistance to the six insecticides varied among states and insecticides. Resistance to permethrin was highest overall and most consistent across the states. Resistance to methomyl was relatively consistent, with 65–91% survival in nine of the ten collections. In contrast, resistance to cyfluthrin and pyrethrins + piperonyl butoxide varied considerably (2.9–76% survival). Resistance to imidacloprid was overall modest and showed no signs of increasing relative to collections made in 2004, despite increasing use of this insecticide. The frequency of Vssc alleles that confer pyrethroid resistance was variable between locations. The highest frequencies of kdr, kdr-his and super-kdr were found in Minnesota, North Carolina and Kansas, respectively. In contrast, the New Mexico population had the highest frequency (0.67) of the susceptible allele. The implications of these results to resistance management and to the understanding of the evolution of insecticide resistance are discussed.     

Indoxacarb resistance in the house fly, Musca domestica

Indoxacarb (DPX-MP062) is a recently introduced oxadiazine insecticide with activity against a wide range of pests, including house flies. It is metabolically decarbomethoxylated to DCJW. Selection of field collected house flies with indoxacarb produced a New York indoxacarb-resistant (NYINDR) strain with >118-fold resistance after three generations. Resistance in NYINDR could be partially overcome with the P450 inhibitor piperonyl butoxide (PBO), but the synergists diethyl maleate and S,S,S-tributyl phosphorothioate did not alter expression of the resistance, suggesting P450 monooxygenases, but not esterases or glutathione S-transferases are involved in the indoxacarb resistance. Conversely, the NYINDR strain showed only 3.2-fold resistance to DCJW, and this resistance could be suppressed with PBO. Only limited levels of cross-resistance were detected to pyrethroid, organophosphate, carbamate or chlorinated hydrocarbon insecticides in NYINDR. Indoxacarb resistance in the NYINDR strain was inherited primarily as a completely recessive trait. Analysis of the phenotypes vs. mortality data revealed that the major factor for indoxacarb resistance is located on autosome 4 with a minor factor on autosome 3. It appears these genes have not previously been associated with insecticide resistance.     

Biochemical and molecular analyses to determine pyrethroid resistance in Aedes aegypti

Dengue fever is an important mosquito-borne viral disease in Taiwan. Insecticide resistance has been shown to significantly reduce the efficacy of vector control interventions. The detection of insecticide resistance is an important component in mosquito abatement programs. In this study, we used the insecticide-impregnated papers bioassay method to reveal high levels of resistance to permethrin in the LYPR and field strains of Aedes aegypti. We used the standard glass cylinder method to observe the knockdown effect of paralysis within 2 to 4 minutes after exposing mosquitoes to pyrethroid vapors. Biochemical assays showed elevated detoxification enzyme activities. Glutathione S-transferases, monooxygenases and β-esterases were the enzymes predominantly responsible for the permethrin resistance of Ae. aegypti in Taiwan. Molecular screening for common insecticide target-site mutations revealed the presence of V1023G and D1794Y mutations. Pearson’s correlation analysis was used to investigate the correlations between the allelic frequency of kdr mutation associated increase with the LC50 values of permethrin and the KT50 values of pyrethroid vaporizers. These findings will be used to assess resistance levels, estimate resistance potential, and formulate monitoring and resistance management strategies.     

Association between insecticide use and greenhouse whitefly (Trialeurodes vaporariorum westwood) resistance to insecticides in hawaii

Susceptibility to acephate, methomyl, and permethrin was determined with laboratory bioassays for adults of greenhouse whitefly, Trialeurodes vaporariorum Westwood, from 12 to 14 sites in Hawaii. Comparisons at LC₅₀ showed up to 42-fold resistance to acephate, 36-fold resistance to methomyl, and 8-fold resistance to permethrin. Higher levels of resistance to acephate and methomyl than to permethrin are consistent with greater use of organophosphates and carbamates than pyrethroids by growers. Insecticide use varied from 1 to 98 insecticide sprays per site per season. Significant positive associations between LC₅₀ for each insecticide and frequency of application of the same insecticide were found across sites. This finding suggests that local variation in insecticide use was an important cause of variation in susceptibility.     

Lack of cross-resistance to indoxacarb in insecticide-resistant Spodoptera frugiperda (Lepidoptera: Noctuidae) and Plutella xylostella (Lepidoptera: Yponomeutidae)

Two field strains of the fall armyworm, Spodoptera frugiperda (JE Smith), collected from corn in north Florida showed high resistance to carbaryl (626- and 1159-fold) and moderate resistance to parathion-methyl (30- and 39-fold) as compared with a laboratory susceptible strain. A field strain of the diamondback moth, Plutella xylostella (L.) collected from cabbage in north Florida and selected for 20 generations with permethrin showed high resistance to permethrin (987-fold) as compared with a susceptible strain. However, in all instances, no cross-resistance to indoxacarb, a novel oxidiazine insecticide, was observed in these two species. Biochemical studies revealed that, in S. frugiperda, activities of detoxification enzymes (microsomal oxidase, glutathione S-transferase and general esterase) were significantly higher in the field strains than in the susceptible strain, indicating that these detoxification enzymes were not actively involved in the resistance to indoxacarb. The lack of cross-resistance between indoxacarb and permethrin in P. xylostella further supports the notion that the mode of action of these insecticides on the insect sodium channel is different.     

Resistance to cyfluthrin and tetrachlorvinphos in the lesser mealworm, Alphitobius diaperinus, collected from the eastern United States

The lesser mealworm, Alphitobius diaperinus (Panzer), is an important pest in poultry facilities. The toxicity of cyfluthrin and tetrachlorvinphos to five strains of the lesser mealworm was compared with the toxicity to a susceptible laboratory strain. Bioassays were carried out with both larvae and adults. For the susceptible strain, cyfluthrin and tetrachlorvinphos had similar toxicity to adults, but cyfluthrin was 5 times more toxic to larvae when compared with tetrachlorvinphos. High levels of resistance to tetrachlorvinphos in two beetle strains were detected in both larvae and adults, although these strains were heterogeneous and still contained susceptible individuals. Resistance to cyfluthrin ranged from 1.7- to 9.5-fold for adults and from 0.5- to 29-fold for larvae at the LC(95). Overall, the patterns of resistance did not mirror the insecticide use patterns reported at these facilities. The implications of these results to management of the lesser mealworms are discussed.     

Report of resistance to the neonicotinoid insecticide imidacloprid in Trialeurodes vaporariorum (Hemiptera: Aleyrodidae)

Susceptibilities of UK and mainland European samples of Trialeurodes vaporariorum (Westwood) to the neonicotinoid insecticide imidacloprid were investigated over a 7 year period. All 24 strains collected between 1997 and 2003 showed similar baseline levels of susceptibility to that of a known susceptible laboratory strain when exposed to a diagnostic concentration (128 mg L(-1)) of formulated imidacloprid. Two samples collected during 2004, one from the UK and one from The Netherlands, demonstrated reduced susceptibility at this concentration. Using dose-response assays, the presence of resistant individuals was disclosed in both these strains; some individuals were unaffected at doses high enough to induce phytotoxic effects. This report represents the first confirmed cases of neonicotinoid resistance inducing control failures in T. vaporariorum, and highlights a need for careful vigilance to sustain the effectiveness of imidacloprid and related neonicotinoid insecticides.     

The A302S mutation in Rdl that confers resistance to cyclodienes and limited cross-resistance to fipronil is undetectable in field populations of house flies from the USA

Fipronil is a relatively new insecticide with great potential for insect control, however widespread use of cyclodiene insecticides has selected for an A302S mutation in the Rdl (GABA gated chloride channel) allele. This mutation gives resistance to cyclodienes and limited cross-resistance to fipronil. Given the concern over the possible reduction in efficacy and/or lifetime that fipronil might be used for pest control (given the extensive use of cyclodienes in the past), it is important to know the frequency of the A302S Rdl mutation in field populations. To ascertain the relative frequency of the A302S Rdl mutation in house fly populations we used three experimental approaches. First, we attempted to select for fipronil resistance by initially treating 33,100 field collected flies and selecting 14 additional generations. We were unable to produce a highly resistant strain. Second, we directly sequenced field collected flies. Third, we tested field collected house flies with a diagnostic dose of dieldrin and then genotyped the survivors. Out of the 4750 flies tested, there were no Rdl resistance alleles detected. We conclude that the resistant Rdl allele is rare in house flies in the US due to decades without cyclodiene use and a fitness disadvantage (in the absence of cyclodienes) of the 302S Rdl allele. The limited cross-resistance provided by the cyclodiene resistant Rdl allele, combined with the very low frequency of this allele in field populations, suggests that fipronil could be a promising insecticide for house fly control.     

Insecticide resistance in the tropical bedbug Cimex hemipterus

Insecticide resistance in the bedbug Cimex hemipterus was investigated using 4211 bedbugs collected from three districts of Sri Lanka. Insecticide bioassays were carried out with discriminating dosages of deltamethrin, permethrin, DDT, malathion, and propoxur. Activity levels of insecticide metabolizing enzymes and the insecticide target site acetylcholinesterase were monitored using biochemical assays. Percentage survivals after DDT, malathion, and propoxur exposure were 41-88%, 18-64%, and 11-41%, respectively. For deltamethrin and permethrin, KT₅₀/KT₉₀ (time to knock-down 50%/90% of the population) values were 0.5-24/1.0-58 and 1.3-10/2.5-47 h, respectively. Both elevated esterase and malathion carboxylesterase mechanisms were present in bedbug populations. Monooxygenase levels were heterogeneous. Organophosphate and carbamate target site acetylcholinesterase, was insensitive in 29-44% of the populations. High DDT resistance was probably due to glutathione S-transferases. Malathion carboxylesterases are mainly responsible for high malathion resistance. High tolerance to both DDT and pyrethroids suggests the presence of ‘kdr’ type resistance mechanism in one population.     

Evolutionary plasticity of monooxygenase-mediated resistance

The cytochrome P450 monooxygenases are an important metabolic system involved in the detoxification of xenobiotics, and are thus one of the major mechanisms by which insects evolve insecticide resistance. However, comparatively little is known about the evolutionary constraints of this insecticide resistance mechanism. We investigated the genetic basis of resistance in a strain of house fly (NG98) from Georgia, USA that had evolved 3700-fold resistance to the pyrethroid insecticide permethrin, and compared this to other permethrin resistant strains of house flies from the US and Japan. Resistance in NG98 was due to kdr on autosome 3 and monooxygenase-mediated resistance on autosomes 1, 2, and 5. These results indicate that the genes which evolve to produce monooxygenase-mediated resistance to permethrin are different between different populations, and that the P450 monooxygenases have some degree of plasticity in response to selection. Monooxygenase-mediated resistance appears to evolve using different P450s, and possibly different regulatory signals controlling P450 expression, even in strains selected with the same insecticide.     

Susceptibility of lesser mealworm (Coleoptera: Tenebrionidae) adults and larvae exposed to two commercial insecticides on unpainted plywood panels

BACKGROUND: The susceptibilities of adult and larval lesser mealworms, Alphitobius diaperinus (Panzer), to two commercially formulated insecticides, cyfluthrin and tetrachlorvinphos, were examined through exposure on treated plywood panels. Lesser mealworms were collected from four caged-layer poultry farms, three in New York and one in Maine. An additional strain was obtained from an infestation occurring in a cricket colony.RESULTS: In all poultry farm derived strains, a portion of the population (1.8-16.2%) survived cyfluthrin exposure. The Maine and cricket colony strains were tolerant of tetrachlorvinphos exposure as both larvae and adults, with 55-74% mortality, whereas nearly 100% mortality was observed with New York strains. The cricket colony adult beetles were highly susceptible to cyfluthrin, with 100% mortality following exposure, but larvae were considerably less susceptible (87.7%). Pesticide use histories for the poultry farms and their impact on the results are discussed.CONCLUSION: The results document that tetrachlorvinphos, an active ingredient with a long use history, may be losing its effectiveness against lesser mealworms in some poultry operations; however, it is still effective in many others.     

Laboratory studies on the mechanisms of resistance to permethrin in a field-selected strain of house flies

Enhanced oxidative metabolism appeared to be a major factor involved in resistance to permethrin in a field strain of house flies, selected with permethrin over 4 years. This was shown in the 7.8-fold synergism by piperonyl butoxide which reduced the resistance ratio from 97 to 15. The rate of permethrin detoxication was significantly higher (P=0.05) in the resistant flies compared with a susceptible strain or resistant flies pretreated with piperonyl butoxide. The esterase inhibitor S,S,S-tributyl phosphorotrithioate did not reduce the level of resistance to permethrin in the resistant strain, although some hydrolytic metabolism was apparent. Rates of penetration were similar in susceptible and resistant flies and in resistant flies pre-treated with piperonyl butoxide. A minor unidentified resistance factor, possibly reduced sensitivity of the nervous system, may also have been present in the resistant strain.     

The pyrethroid resistance status and mechanisms in Aedes aegypti from the Guerrero state,Mexico

Dengue is one of the most important vector-borne diseases worldwide and is a public health problem in Mexico. Most programs in dengue endemic countries rely on insecticides for Aedes control. In Mexico, pyrethroid insecticides (mainly permethrin and deltamethrin) have been extensively used over a decade as adulticides and represented a strong selection for insecticide resistance for dengue vectors in several parts of the country. We studied the type, frequency and distribution of insecticide resistance mechanisms in Aedes aegypti from six municipalities in the state of Guerrero selected on the basis of historically intense chemical control and a high risk for dengue transmission. Ae. aegypti eggs were collected from October 2009 to January 2010 using ovitraps. F₁ adults, emerged from these collections, were exposed to permethrin, deltamethrin and DDT in WHO diagnostic tests and showed high resistance levels to both pyrethroids and DDT. This was consistent with the presence of increased metabolic enzyme activities and target site insensitivity due to kdr mutations. Biochemical assays showed elevated esterase and glutathione S-transferase activities in the six municipalities. The V1016I kdr mutation on the IIS6 domain of the sodium channel gene was present in an overall frequency of 0.80. A second mutation, F1534C on the IIIS6 domain of the same gene was also detected, being the first report of this mutation in Guerrero. The multiple resistance mechanisms present in Ae. aegypti from Guerrero state represent a warning for the efficacy of the pyrethroid usage and consequently for the success of the dengue control program.     

Field and laboratory selection of Frankliniella occidentalis (Pergande) for resistance to insecticides

Response of western flower thrips, Frankliniella occidentalis (Pergande), to selection for resistance to insecticides commonly used to control this pest in Murcia (south-east Spain) was studied under field and laboratory conditions. In the field, plots within sweet pepper crops in commercial and experimental greenhouses were treated under different selection strategies: insecticide rotation versus formetanate reiteration, formetanate reiteration versus acrinathrin reiteration, and formetanate reiteration versus methiocarb reiteration. Thrips populations were sampled monthly and bioassayed against methiocarb, methamidophos, acrinathrin, endosulfan, deltamethrin and formetanate. In the laboratory, F occidentalis strains were selected against each insecticide for several generations. To evaluate cross-resistance, each selected strain was bioassayed with the other insecticides. Frankliniella occidentalis populations showed a rapid development of acrinathrin resistance, reaching high levels in field and laboratory conditions. Formetanate and methiocarb resistance were also observed, although development was slower and at moderate levels. Cross-resistances between acrinathrin/deltamethrin and acrinathrin/formetanate were detected under field and laboratory conditions. Formetanate/methiocarb cross-resistance was suspected in laboratory selections, but not in field assays. Simultaneous moderate resistance levels to the three specific insecticides against thrips (formetanate, methiocarb and acrinathrin) were shown in laboratory selection strains, indicating a general mechanism of resistance, probably metabolic.     

Various mechanisms responsible for permethrin metabolic resistance in seven field-collected strains of the German cockroach from Iran, Blattella germanica (L.) (Dictyoptera: Blattellidae)

Insecticide resistance in the German cockroach can be mediated by a number of mechanisms, the most common being enhanced enzymatic metabolism. Seven field-collected strains of German cockroach, Blattella germanica (L.) with various levels of resistance to pyrethroids, five out of which were also cross-resistant to DDT were used in this study. The investigation of possible mechanisms responsible for permethrin resistance was carried out using the synergists PBO, DEF and DMC and biochemical assays, including general esterases, glutathione S-transeferases and monooxygenases assays, using an automated microtitre plate reader. PBO and DEF, the inhibitors of cytochrome p450 monooxygenases and general esterases, respectively, affected permethrin resistance to varying degrees depending on the strain. DDT resistance in five strains were not completely eliminated by the synergist DMC, an inhibitor of glutathione S-transferase enzymes, suggesting that a further non-metabolic resistance mechanism such as kdr-type may be present. This suggestion was further supported by GST assay data, where a little elevation in GST activity was detected in only two strains. The synergist data supported by biochemical assays implicated that cytochrome p450 monooxygenases or hydrolases are involved in permethrin resistance in some strains. However, these results implicated both enhanced oxidative and hydrolytic metabolism of permethrin as resistance mechanism in the other strains. The results of synergist and biochemical studies implicated that all the field-collected permethrin resistant strains have developed diverse mechanisms of resistance, although these strains have been collected from the same geographic area. The change in resistance ratios of some strains by using PBO or DEF is discussed. It is of interest to note that because resistance to permethrin was not completely eliminated by DEF and PBO, it is likely that one or more additional mechanisms are involved in permethrin resistance in every strain studied.     

Genetics of Pyrethroid Resistance in a Strain (ALHF) of House Flies (Diptera: Muscidae)

Five house fly lines were derived from crosses of the pyrethroid-resistant ALHF (wildtype) and the susceptible aabys (bearing recessive morphological markers on each of five autosomes) strains. Each line was homozygous for one mutant-type marker from aabys. The level of resistance to permethrin was measured for each line to determine the genetic linkage of pyrethroid resistance in ALHF. Permethrin resistance in ALHF was 6600-fold compared with that in aabys. Resistance in flies bearing a mutant-type marker on autosome 4 was similar to that in ALHF. Flies with mutant-type markers on autosomes 1 and 2 had relatively lower resistance than ALHF; flies with mutant-type markers on autosomes 3 and 5 had much lower levels of resistance. These results demonstrated that factors on autosomes 3 and 5 play very important roles in pyrethroid resistance, whereas factors on autosomes 1 and 2 may have relatively small roles in resistance. Piperonyl butoxide (PBO) increased toxicity of permethrin in strains with mutant-type markers on autosomes 3 and 4 similar to that in ALHF. Slightly decreased synergism ratios in strains with autosomes 1 and 2 mutant-type markers compared with ALHF indicated that factors on autosomes 1 and 2 might make a small contribution in P450 monooxygenase-mediated resistance. However, when the autosome 5 mutant-type marker was present, PBO did not substantially decrease resistance, suggesting that the factor(s) on autosome 5 plays the most important role in P450 monooxygenase-mediated resistance. The resistance ratios of permethrin + PBO in strains with mutant-type markers on autosomes 1, 2, and 5 were significantly lower than those in ALHF, suggesting that factors on autosomes 1, 2, and 5 might be involved in pyrethroid resistance mechanisms other than P450-mediated detoxication. Injection did not change levels of resistance in the house flies tested, revealing that decreased rate of cuticular penetration (pen) probably does not play an important role in pyrethroid resistance in ALHF. The interaction and regulation of different mechanisms and/or factors involved in pyrethroid resistance in house flies are discussed.     

First report of cyromazine resistance in a population of UK house fly (Musca domestica) associated with intensive livestock production

BACKGROUND: House fly control in livestock‐rearing facilities is heavily reliant on the use of the larvicide cyromazine. While extensive use of this compound has led to the development of resistance in several countries, no elevated tolerance has so far been reported from the United Kingdom. RESULTS: Tolerance to cyromazine in larvae derived from a field strain collected at an intensive pig unit was significantly elevated over that of insects taken from a susceptible laboratory strain. Resistance factors (RFs) of 2.9 and 2.4 were returned for assays initiated with eggs and neonate larvae respectively. The RF for field strain larvae exposed from neonate increased significantly to 3.9 and 5.6 following rounds of selection at 1.0 and then 1.5 mg kg^?1 cyromazine. CONCLUSION: Low‐level resistance to cyromazine in UK house flies is reported here for the first time. The geographic extent of this resistance is unknown but, if widespread, may lead to control failures in the future, and indicates that careful stewardship of this compound in the United Kingdom is now required. © Crown copyright 2010. Reproduced with permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Cross‐resistance between azinphos‐methyl and acetamiprid in populations of codling moth,Cydia pomonella (L.) (Lepidoptera: Tortricidae), from Washington State

BACKGROUND: Codling moth, Cydia pomonella (L.), has been intensely managed with the organophosphate insecticide azinphos‐methyl for 50 years, and populations have developed resistance. New management programs have been developed and implemented that rely more heavily on other classes of insecticides. A prerequisite for developing effective resistance management strategies for these compounds is to establish their current levels of effectiveness. Adult and neonate larval assays were conducted to assess the response of field‐collected codling moth populations from apple in Washington State. RESULTS: Male codling moth populations exhibited a range of responses to a discriminating concentration of azinphos‐methyl in a survey of 20 populations. Populations from certified organic orchards were more susceptible than those from conventional orchards. Mean fecundity was inversely related to azinphos‐methyl tolerance. Male responses to azinphos‐methyl and acetamiprid varied significantly among populations and were correlated. The residual effectiveness of field applications of both insecticides varied significantly against neonate larvae. Neonate bioassays with insecticide‐dipped fruit found significant differences among populations with azinphos‐methyl, acetamiprid, methoxyfenozide and spinosad, but not with esfenvalerate. CONCLUSION: These results support a concern that alternation of insecticides with different modes of action may not be a sufficient strategy to avoid the evolution of broad‐spectrum insecticide resistance by codling moth. Published 2010 by John Wiley & Sons, Ltd.