Insecticide resistance in Musca domestica L. from Eastern England

Strains of houseflies were obtained from a refuse tip and 34 farms selected at random from Eastern England in 1984. Resistance was assessed to four insecticides that had been in use for fly control in the UK. Dose-response data were obtained by topical application of the insecticides and, in addition, a resistance test method was used in which flies were allowed to feed on sugar coated with either methomyl or azamethiphos. For both methods, the knock-down (KD) after 48 h was used as a measure of response. The ranges of resistance factors for the topical application method were, for methomyl, 1·1–15·9 at KD₅₀ and 2·1–17·0 at KD₉₅; for azamethiphos, 2·2–36·9 at KD₅₀ and 4·5–88·2 at KD₉₅; for pyrethrins + piperonyl butoxide, 0·9–6·8 at KD₅₀ and 1·4–13·4 at KD₉₅; and for permethrin, 1·7–34·8 at KD₅₀ and 2·2–112·5 at KD₉₅. The ranges of the resistance factors for the feeding tests were, for methomyl, 2·1–39·8 at KD₅₀ and 2·4–64·0 at KD₉₅, and, for azamethiphos, 5·6–51·7 at KD₅₀ and 8·8–92·0 at KD₉₅.     

The current status of insecticide resistance in Musca domestica in England and Wales and the implications for housefly control in intensive animal units

Following the 1984–85 housefly (Musca domestica L.) resistance survey, a similar survey was carried out between January 1990 and April 1992 in order to monitor changes in UK housefly resistance. Samples of fly populations were collected from 35 farms throughout England and Wales. Dose-response data were obtained by topical application and feeding test methods. For both methods the knockdown (KD) after 48 h was used for all the dose-response comparisons. The ranges of resistance factors for the topical application method were for methomyl, 1·6–20·0 at KD₅₀ and 4·5–34·4 at KD₉₅; for azamethiphos, 2·5–58·5 at KD₅₀ and 5·0–2604 at KD₉₅; for pyrethrins+piperonyl butoxide, 1·2–9·6 at KD₅₀ and 1·6–14·7 at KD₉₅; and for permethrin, 2·2–118·8 at KD₅₀ and 4·3–200·0 at KD₉₅. The ranges of the resistance factors for the feeding tests were for methomyl, 1·2–56·1 at KD₅₀ and 3·1–80·0 at KD₉₅, and for azamethiphos, 3·9–125·0 at KD₅₀ and 4·4–380·0 at KD₉₅. The means of resistance factors for all of the insecticides showed increases over those obtained in a previous survey carried out in 1984–85. The significance of the results for housefly control in intensive animal units in the UK is discussed.     

The cross-resistance to pyrethrins and eight synthetic pyrethroids,of an organophosphorus-resistant strain of the rust-red flour beetle Tribolium castaneum (herbst)

Comparisons with standard susceptible insects showed that a strain of Tribolium castaneum, with a specific resistance to malathion and its carboxylic ester analogues, had no cross-resistance to topical applications of natural pyrethrins. Another strain of T. castaneum, showing resistance to many organophosphorus (OP) insecticides, was cross-resistant to pyrethrins ( × 34) and eight synthetic pyrethroids also applied topically; least cross-resistance occurred with resmethrin ( × 2.2), bioresmethrin ( × 3.3) and phenothrin ( × 4.0). Generally larger resistance factors were recorded with formulations synergised by piperonyl butoxide (PB). The greatest cross-resistance encountered was with unsynergised tetramethrin ( × 338). Apart from tetramethrin, factors of synergism did not exceed 5.7 with either the susceptible or multi-OP resistant strains. PB antagonised six of the nine pyrethroids against the multi-OP resistant strain. Antagonism also occurred with two of these six, permethrin (cis: trans ratio 1:3) and 5-prop-2-ynylfurfuryl ( 1RS)-cis,trans-chrysanthemate (‘Prothrin’), against the susceptible strain. Considering only formulations without the synergist, the most effective compounds against the susceptible strain, relative to pyrethrins, were bioresmethrin (2.7) and permethrin (2.4). Similarly with the multi-OP resistant strain the most effective compounds were bioresmethrin (28), resmethrin (14) and permethrin (6.6). Thus the LD₅₀ (the dose required to kill 50% of the test species) for bioresmethrin against the resistant strain (0.14 μg) only slightly exceeded the LD₅₀ for pyrethrins against the susceptible strain (0.12 μg).     

Changes in cross-resistance patterns of houseflies selected with natural pyrethrins or resmethrin (5-benzyl-3-furylmethyl (±)-cis-trans-chrysanthemate)

A pyrethrins-resistant strain of houseflies, 213ab, previously selected with a 1:10 (by wt.) mixture of natural pyrethrins and piperonyl butoxide, was further selected either with natural pyrethrins alone (strain NPR) or with resmethrin (strain 104). After 50 generations the two populations differed in their resistance to the natural and synthetic esters. Both were resistant to all pyrethroids. Part of strain NPR was immune and very much more resistant than strain 104 to the natural pyrethrins and allethrin, but it was only 2–3 times more resistant than strain 104 against the new synthetic esters resmethrin (5-benzyl-3-furylmethyl (±)-cis-trans-chrysanthemate), bio-resmethrin (5-benzyl-3-furylmethyl (+)-trans-chrysanthemate), pyresmethrin (5-benzyl-3-furylmethyl pyrethrate) and 5B2Me3FC (5-benzyl-2-methyl-3-furylmethyl (±)-cis-trans-chrysanthemate). Pretreatment of both strains with sesamex diminished but did not eliminate resistance. Synergism was greater in strain NPR, especially with natural pyrethrins and allethrin. Both strains had great resistance to DDT indicating that resistance to DDT and pyrethroids is linked. Differences in resistance to different compounds suggest that at least three factors can confer resistance, one of which, pen, delays penetration and two others involve detoxication, one py a on the acid side of the ester linkage and the other, py b, on the alcohol side. Natural pyrethrins and resmethrin select for different groupings of these factors. Treatment with resmethrin does not select for py b presumably because this mechanism cannot attack the resmethrin molecule. Similarly when piperonyl butoxide is added to the natural pyrethrins py b is inhibited and so removed from selection pressure. Under these conditions, the strain produced contains the same factors as one selected by resmethrin and so shows the same small resistance to natural pyrethrins alone.     

A comparison of permethrin and methomyl insecticides for the control of a multiresistant strain of houseflies (Musca domestica)

A methomyl sugar bait formulation and permethrin residual spray were compared for the control of a multi-insecticide resistant strain of housefly in a UK pig farm. The methomyl was applied as a granular scatter bait at the manufacturer's recommended rate of 25 mg m^?2 active ingredient (a.i.) to the treated floor area. Permethrin was applied at 32, 64 and 128 mg m^?2 a.i. to structural surfaces. The highest deposit rate of permethrin used was four times that recommended by the manufacturer for the control of flying insects. The methomyl bait gave effective control but the permethrin spray failed at all deposit rates tested. The use of permethrin increased resistance to this compound at the KD50 level from x 13 to x 560 within 10 weeks and significantly increased the proportion of flies resistant to natural pyrethrins synergised with piperonyl butoxide (P<0.01).     

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     

Genetics of resistance of pyrethroid-selected houseflies,Musca domestica L.

Four resistance factors were isolated genetically from the NPR strain of houseflies (Musca domestica L.), which resists natural pyrethrins, and were characterised toxicologically. The four factors were : pen, which reduces the rate of penetration of insecticides through the cuticle; kdr-NPR, a general pyrethroid resistance mechanism unaffected by the synergist sesamex; py-ses, a mechanism of resistance to natural pyrethrins that can be suppressed by sesamex; and py-ex, a factor that gives strong resistance to synergised natural pyrethrins and to the new synthetic esters, e.g. resmethrin, but little or none to natural pyrethrins alone.     

药剂对小菜蛾抗性及敏感品系乙酰胆碱酯酶抑制作用比较

采用浸叶法测定了云南通海、元谋和澜沧的小菜蛾plutella xylostella田间种群对常用杀虫剂的抗药性。结果表明,云南上述地区小菜蛾田间种群对各类杀虫剂均产生了不同程度的抗性。对有机磷类药剂的抗药性为1.74~31.1倍;对菊酯类药剂的抗药性为7.41~764倍;对阿维菌素类药剂则产生了 5.60~4.06×104倍的抗性。通过离体和活体试验测定了药剂对小菜蛾头部乙酰胆碱酯酶(AChE)的抑制作用。敌敌畏和灭多威对通海抗性品系AChE离体和活体内的抑制中浓度(I50)分别是敏感品系的209、26.5倍和2.21、2.16倍;敌敌畏对通海小菜蛾种群的离体和活体内抑制中时间(IT50)小于敏感品系,分别是敏感品系的0.32和0.17倍;而灭多威对通海小菜蛾种群的离体和活体内抑制中时间(IT50)则大于敏感品系,分别是敏感品系的1.37和1.74倍。     

Susceptibility to thiamethoxam of Musca domestica from Danish livestock farms

BACKGROUND: Neonicotinoid baits are currently replacing anticholinesterase baits for control of adult houseflies (Musca domestica L.). Introduction of new insecticides includes evaluation of their cross-resistance potential, which was assessed for thiamethoxam in field populations from Denmark. RESULTS: In feeding bioassay with a susceptible strain, thiamethoxam LC(50) at 72 h was 1.7 microg thiamethoxam g(-1) sugar, making it 19-fold, 11-fold and threefold more toxic to houseflies than azamethiphos, methomyl and spinosad respectively. The field populations were 6-76-fold resistant to thiamethoxam. There was no correlation between the toxicities of thiamethoxam and spinosad, dimethoate, methomyl, bioresmethrin or azamethiphos. The toxicity in feeding bioassay at 72 h of imidacloprid in a susceptible strain was 32 microg imidacloprid g(-1) sugar at LC(50), making it 19-fold less toxic to houseflies than thiamethoxam. There was a strong significant correlation between the toxicities of thiamethoxam and imidacloprid in field populations.CONCLUSION: Neonicotinoid-resistant houseflies were present at a detectable and noticeable level before thiamethoxam and imidacloprid were introduced for housefly control in Denmark. The toxicity of thiamethoxam is explained by other parameters than the toxicities of spinosad, dimethoate, methomyl, bioresmethrin or azamethiphos. The cross-resistance between thiamethoxam and imidacloprid indicates a coincidence of mechanism of the toxicity and resistance in the field populations.     

Variation of Musca domestica L. acetylcholinesterase in Danish housefly populations

Anti-cholinesterase resistance is in many cases caused by modified acetylcholinesterase (MACE). A comparison was made of toxicological data and AChE activity gathered from 21 field populations and nine laboratory strains of houseflies, Musca domestica L., to elucidate the best way of generating data to provide advice for management strategies and gathering information for resistance risk assessment on the organophosphates azamethiphos and dimethoate and the carbamate methomyl, which have been the primary insecticides used against adult houseflies in Denmark. Cluster analysis was performed and > 2000 houseflies were assigned to one of three phenotypes based on total acetylcholinesterase activity as well as inhibition by azamethiphos, methomyl or omethoate. A cluster, i.e. a phenotype, with high total AChE activity and high sensitivity to azamethiphos and less sensitivity to inhibition by methomyl and omethoate was shown to be linked to methomyl resistance. It was not possible to define any clusters that could be linked to azamethiphos or dimethoate resistance. The five mutations V180L, G262A, G262V, F327Y and G365A causing anticholinesterase resistance in houseflies were all identified in the Danish housefly strains. The data are very heterogeneous, and a correlation of molecular genetic background and resistance of phenotypes is not obvious with the available data.     

DDT-resistant mosquito strains with cross-resistance to pyrethroids

Various DDT-resistant strains of mosquito, comprising 8 strains of Aedes aegypti from the Neotropics (tropical and South America) and one each of Anopheles gambiae and An. quadrimaculatus were tested for resistance to pyrethroids. Susceptibility was measured by LT₅₀ values, after exposure to impregnated papers in the cylinders used in the WHO standardised test for adult mosquitoes. DDT-resistance levels (by comparison with susceptible strains) ranged from × 2 to × 73, with simultaneous low resistance to permethrin (× 1.4 to × 3.4) except in one strain from Guyana which reached × 30. Further comparisons were made with this Guyana strain and one from Salvador with similar DDT-resistance (about × 70) but low permethrin-resistance. Tests with methoxychlor and I,I-di-(4-chlorophenyl)-2-nitropropane and with the synergist I,I-di-(4-chlorophenyl)-2,2,2-trifluoroethanol suggested that a considerable part of the DDT-resistance of both strains was due to a dehydrochlorination mechanism. Tests with the synergist piperonyl butoxide (PB) suggested that microsomal oxidase systems were also involved, especially in the Guyana strain. The cross-resistance in both strains extended to 3 other pyrethroids. Addition of the synergist PB had little effect on the Salvador strain, but substantially reduced permethrin-resistance in the Guyana strain. It is concluded that an unknown mechanism associated with DDT-resistance confers a low level cross-tolerance to pyrethroids; this can be substantially augmented by the development of a microsomal oxidase mechanism, as in the Guyana strain.     

Genetic and biochemical studies of resistance to permethrin in a pyrethroid-resistant strain of the housefly (Musca domestica L.)

One or more weak factors of resistance on autosome 2, and barely detectable resistance on autosome 3, confer moderate resistance to several pyrethroids (5–13-fold) in the field-collected Ipswich strain of houseflies. In these flies, which unlike other pyrethroid-resistant strains lack kdr or super-kdr, pyrethroid resistance probably developed in response to prolonged treatment of buildings for animals with pyrethrins synergised with piperonyl butoxide. Substrains, isolated genetically from Ipswich flies and with resistance only on autosome 2, degraded permethrin more rapidly than susceptible flies and produced larger amounts of very polar metabolites. In this, they differed from flies with kdr or super-kdr which resembled susceptible flies in their metabolism of permethrin. NIA 16388 (propyl prop-2-ynyl phenylphosphonate) was a better synergist and reduced the metabolism of permethrin more than piperonyl butoxide in both the susceptible and resistant insects. The slight increase in synergism and minimal decrease in metabolism when piperonyl butoxide was applied with NIA 16388 indicated that the latter also inhibited detoxication that was sensitive to piperonyl butoxide.     

Resynthesis of multiple resistance to organophosphorus insecticides from strains with factors of resistance isolated from the SKA strain of house flies

Individual factors of resistance to insecticides attributable to chromosomes II, III and ^V of the SKA strain of houseflies (Musca domestica L) were combined in pairs to determine how their presence affects resistance. The re-synthesised strains with resistance factors on chromosomes II and V, and on chromosomes III and V, were tested with several organophosphorus insecticides and DDT. The penetration delaying mechanism Pen on chromosome III, which alone gives little or no resistance, slightly increased the resistance of flies with the microsomal detoxifying factor Ses on chromosome V to diazinon and malaoxon-ethyl (c. × 1.5), but was more effective in increasing resistance to DDT (× 6). There was no effect on the response to other insecticides tested. The combined effect of the mechanisms of resistance on chromosome II (glutathione S-ethyl transferase and phosphatase) and on chromosome V (microsomal detoxication) approximated to the product of the resistance conferred by each of these mechanisms singly, suggesting that the mechanisms of resistance on the two chromosomes act independently. Therefore, most of the strong resistance to organophosphorus insecticides in the SKA strain results from the interaction between delayed penetration (chromosome III) and the factors of resistance on chromosome II, and the independent action of the resistance factors on chromosomes II and V.     

Laboratory assessment of different methods of applying a commercial granular bait formulation of methomyl to control adult houseflies (Musca domestica l.) in intensive animal units

Female houseflies (Musca dornestica L.) from a susceptible and a multiinsecticide-resistant strain were used to evaluate the toxicity of a granular insecticide bait formulation of the carbamate insecticide methomyl. The bait was either applied to a polystyrene bait target, or scattered over the floor of the fly treatment cages. Targets were treated with methomyl granules dissolved in water with and without apaste carrier or the granules were applied directly to the target using an adhesive. Scattered methomyl granules proved the most effective of the various treatments assessed. Based on the KT₉₀ values, the most effective suspended bait treatments against susceptible or resistant flies were water as a carrier, and egg or ‘Lap’ wallpaper paste as adhesives; the least effective were ‘Polycell’ regular wallpaper paste as an adhesive and carboxymethylcellulose as a carrier. A proportion of flies from both the susceptible and the resistant strain recovered from knockdown; most of these lost their ability to fly (‘hoppers’) and subsequently survived the treatments. When bait targets treated with methomyl granules were fixed at right angles to the wall/floor junction of the treatment cages most of the recovered flies fed again on the bait and received a lethal dose. The mortality of flies exposed to suspended bait targets was influenced by the level of light. For both strains of fly, mortality decreased as the light intensity was lowered; this effect was more pronounced with the resistant strain. The implication of these results for the application of methomyl bait is discussed.     

Potential of piperonyl butoxide‐synergised pyrethrins against psocids (Psocoptera: Liposcelididae) for stored‐grain protection

BACKGROUND: Piperonyl butoxide (PB)‐synergised natural pyrethrins (pyrethrin:PB ratio 1:4) were evaluated both as a grain protectant and a disinfestant against four Liposcelidid psocids: Liposcelis bostrychophila Badonnel, L. entomophila (Enderlein), L. decolor (Pearman) and L. paeta Pearman. These are key storage pests in Australia that are difficult to control with the registered grain protectants and are increasingly being reported as pests of stored products in other countries. Firstly, mortality and reproduction of adults were determined in wheat freshly treated at 0.0, 0.75, 1.5, 3 and 6 mg kg^?1 of pyrethrins + PB (1:4) at 30 ± 1 °C and 70 ± 2% RH. Next, wheat treated at 0.0, 1.5, 3 and 6 mg kg^?1 of pyrethrins + PB (1:4) was stored at 30 ± 1 °C and 70 ± 2% RH and mortality and reproduction of psocids were assessed after 0, 1.5, 3 and 4.5 months of storage. Finally, the potential of synergised pyrethrins as a disinfestant was assessed by establishing time to endpoint mortality for adult psocids exposed to wheat treated at 3 and 6 mg kg^?1 of synergised pyrethrins after 0, 3, 6, 9 and 12 h of exposure. RESULTS: Synergised pyrethrins at 6 mg kg^?1 provided 3 months of protection against all four Liposcelis spp., and at this rate complete adult mortality of these psocids can be achieved within 6 h of exposure. CONCLUSION: Piperonyl butoxide‐synergised pyrethrins have excellent potential both as a grain protectant and as a disinfestant against Liposcelidid psocids. Copyright © State of Queensland, Department of Employment, Economic Development and Innovation, 2010. Published by John Wiley and Sons, Ltd.     

The status and development of insecticide resistance in Danish populations of the housefly Musca domestica L

Samples of housefly (Musca domestica) field populations were collected from Danish livestock farms in 1997. The tolerance of the first‐generation offspring was determined for a number of insecticides. Dose‐response values were obtained by topical application for the pyrethroids bioresmethrin and pyrethrum, both synergised with piperonyl butoxide, and the organophosphate dimethoate. The organophosphates azamethiphos and propetamphos and the carbamate methomyl were tested in discriminating dose feeding bioassays. Resistance was low to moderate in most of the populations for most of the compounds tested, but this study also revealed the existence of high resistance to pyrethroid, organophosphate and carbamate insecticides in some populations. The resistance factors at LD₅₀ for bioresmethrin/piperonyl butoxide ranged between 2 and 98, and for pyrethrum/piperonyl butoxide between 2 and 29. Our results indicate that pyrethroid resistance in Denmark is increasing, since four of the 21 farms showed more than 100‐fold resistance at LD₉₅, a level of resistance only observed once before. Resistance factors at LD₅₀ for dimethoate ranged from 9 to 100, and showed two distinct trends: populations with either decreasing or increasing resistance. Resistance to azamethiphos was found to be widespread and high. Although two strains with high methomyl and propetamphos resistance were observed, methomyl and propetamphos resistance is moderate and appears not to be increasing. © 2001 Society of Chemical Industry     

The joint action of insect growth regulators and insecticides on strains of Spodoptera littoralis Boisd. That are susceptible or resistant to aminocarb

An investigation was made of the action of the juvenile hormone analogues (JHAs) methoprene (ZR-515) and 3-[5-(4-ethylphenoxy)-3-methylpent-3-enyl]-2, 2-dimethyloxirane (R-20458), and the insecticides chlorpyrifos and methomyl, when applied, separately or in combination, to the late insect stages of susceptible (S) and aminocarb-resistant (R_m) strains of Spodoptera littoralis Boisd. Sixth-instar larvae of the R_m strain showed detectable levels of cross-resistance to chlorpyrifos, methomyl and R-20458. However, cross-resistance to methoprene was less pronounced in the R_m strain. Treatment of the same instar with the ED₅₀ of methoprene produced an appreciable level of sterility in the S strain, but this level decreased in the R_m strain. Similar treatment with R-20458 caused a lower level of sterility in the S strain and the R_m strain was less affected. In the S strain, the ED₂₅ of either chlorpyrifos or methomyl when applied simultaneously with the ED₂₅ of R-20458, produced an antagonistic effect and the R_m strain was more capable of resisting the joint action of these compounds. The treatment, ED₂₅ chlorpyrifos + ED₂₅ methoprene produced an additive effect on the S strain, while the R_m strain tolerated their combined action. Nevertheless, the treatment, ED₂₅ methomyl + ED₂₅ methoprene produced additive effects on both the S and R_m strains. The prepupae of the R_m strain tolerated the action of the insecticides methomyl and chlorpyrifos. A similar pattern of cross-resistance was also detected against the action of the two hormones at the ED₂₅ level, while at the ED₂₅ level, both the S and R_m strains were almost equally sensitive to the action of the two juvenoids. Chlorpyrifos-JHA combinations produced additive effects on prepupae of the S strain while the R_m strain completely resisted their joint action. Methomyl-JHA combinations produced high potentiation in the S strain, but the R_m strain remained insensitive to their joint action. Detectable levels of tolerance to the action of chlorpyrifos and methomyl at the ED₂₅ and ED₅₀ levels were indicated in 2-day-old pupae of the R_m strain. This was less evident in the case of JHAs, particularly methoprene, which was to some extent equally effective on both strains; the reproductive ability of the S and R_m strains was highly affected by this compound. The pupae of the R_m strains were equally as affected as those of the S strain by the combination ED₂₅ chlorpyrifos+ ED₂₅ R-20458. Nevertheless, the two strains showed antagonism to the action of chlorpyrifos with methoprene. A high level of potentiation was produced in the S strain to the combination of methomyl and R-20458 but the R_m strain was able to withstand their combined action. Of interest in this respect was the action of the combination of methomyl and methoprene, for which high levels of potentiation were detected in pupae of the S and R_m strains. This combination also Produced a high percentage of sterility in mated females of the R_m strain.     

The pattern of cross-resistance to insecticides and juvenile hormone analogues in a diflubenzuron-resistant strain of the cotton leaf worm Spodoptera littoralis boisd

The rate of development of resistance to diflubenzuron in a laboratory susceptible strain of the cotton leafworm Spodoptera littoralis Boisd., the pattern of cross-resistance exhibited by the resistant strain to several insecticides and juvenile hormone analogues, as well as the synergistic action of piperonyl butoxide (PB) and S, S, S-tributyl phosphorotrithioate (TBP) with insecticides or diflubenzuron on both strains, were investigated. Resistance to diflubenzuron increased slightly in the first eight selected generations and was enhanced by further selection until in generation 30, the selected strain attained the high level of resistance of 290.7-fold, compared with the parent strain. The resistant strain when challenged with either insecticides or juvenile hormone analogues at selected generations (5, 10, 15, 20, 25 and 30) exhibited different levels of resistance to several insecticides representing organochlorine and organo-phosphorus compounds, carbamates and pyrethroids, but a clear case of negative correlation was indicated between resistance to diflubenzuron and juvenile hormone analogues. With regard to the synergistic action of PB and TBP on the toxicity of either diflubenzuron or insecticides against the fourth-instar larvae of the susceptible strain, methomyl showed slight levels of synergism when it was combined with them. With the exception of cypermethrin, which was not affected by the two synergists, lower levels of synergism were observed with the compounds endrin, diflubenzuron and fenvalerate when they were combined with the same synergists. These two synergists however, antagonised the toxic action of the organophosphorus compounds phosfolan and chlorpyrifos. Against the resistant strain, endrin was moderately synergised by TBP but only slightly by PB. Slight levels of synergism were observed when methomyl, phosfolan and diflubenzuron were combined with either synergist, but both antagonised chlorpyrifos and fenvalerate. Resistance to diflubenzuron and to the other tested chemicals in the resistant strain was scarcely affected by the two synergists.     

Potentiation of Super-kdr resistance to deltamethrin and other pyrethroids by an intensifier (factor 161) on autosome 2 in the housefly (Musca domestica L.)

An intensifier (factor 161) identified on the second autosome in a pyrethroid-resistant strain of houseflies (Musca domestica L.) was isolated and introduced into a strain with super-kdr. Unlike E_0.39, which on its own also confers very weak (< × 3) resistance to pyrethroids, factor 161 very strongly intensified super-kdr resistance to pyrethroids. Together, factor 161 and super-kdr conferred immunity to deltamethrin in female houseflies (LD₅₀ > 20 μg fly^?1) but produced much less intensification of resistance to WL 48281, the (1R)cis (αS) isomer of cypermethrin, which differs from deltamethrin only in having chlorine instead of bromine substituents in the acid side-chain. Intensification was strongly decreased by piperonyl butoxide and propyl prop-2-ynylphenylphosphonate (NIA) but was unaffected by S,S,S-tributyl phosphorotrithioate (DEF). This synergism suggests involvement of oxidative rather than esteratic metabolism in the intensification of super-kdr by factor 161.     

三种增效剂对棉铃虫增效作用

用３个不同地区的棉铃虫田间种群分别测定了３种增效剂对３种杀虫剂的增效作用。结果表明ＰＢ对氯氟氰菊酯,ＤＥＦ对辛硫磷,ＰＢ和ＴＰＰ对灭多威增效较好,而且棉铃虫的抗性水平越高,增效剂的增效作用越突出。