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.     

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     

Insensitive acetylcholinesterase,high glutathione-S-transferase,and hydrolytic activity as resistance factors in a tetrachlorvinphos-resistant strain of house fly

The gene producing insensitive acetylcholinesterase in a tetrachlorvinphos-resistant strain of house fly was introduced into the genome of a susceptible strain. The resistance to a number of organophosphorus insecticides, which was high in the original strain (234- and more than 800-fold for paraoxon and tetrachlorvinphos, respectively), was much lower in the resulting strain, ranging from 53-fold for paraoxon to 3.9-fold for tetrachlorvinphos. Synergists further decreased these factors. The reduction in sensitivity of the acetylcholinesterase in vitro was about 20-fold for both inhibitors. The Michaelis parameters for hydrolysis of acetylcholine and acetylthiocholine of the mutant and normal acetylcholinesterase showed only minor differences. An increased rate of metabolism of the insecticides was found in the original strain. In vitro, glutathione-dependent detoxication was from 9- to 120-fold that of a susceptible strain, depending on the insecticide and the conditions used. The enzyme de-alkylated parathion and methylparaoxon, but there was no de-arylation of parathion, although it is important in other strains. In vitro, paraoxon and methylparaoxon were also hydrolysed, and this is not so in the susceptible strain. The high resistance present in the original strain seems to be due to joint action of at least three mechanisms.     

Effect of a mixture of iprobenfos and malathion on the development of malathion resistance in the mosquito Culex pipiens pallens Coq

A malathion-resistant (RM) strain of Culex pipiens pallens Coq was obtained by successively selecting a field population with malathion in the laboratory. The synergistic effect of iprobenfos on malathion toxicity and alpha-naphthyl acetate (alpha-NA) esterase assay revealed that malathion resistance in the RM strain was associated with increased alpha-NA esterase activity and the synergism was mainly due to the inhibition by iprobenfos of this activity. There was no difference in alpha-NA esterase activity between the larvae and female adults in the susceptible (S) strain, but the activity in the adults was 13-fold higher than in the larvae of the RM strain. To understand the effect of the application of a mixture of iprobenfos and malathion on the evolution of malathion resistance, an artificial strain (Syn) was generated by mixing the RM and S strains with 0.1 frequency of the malathion-resistant individuals. The offspring of the Syn strain were divided into two sub-strains, Rm and Rm+ibp, which were successively treated with, respectively, malathion alone and malathion + iprobenfos (1:2) at LC70. In the mixture, the fungicide iprobenfos acted as a synergist of malathion. After treatment for 10 generations, the resistance level to malathion was 317.4-fold for the Rm sub-strain, whereas for the Rm+ibp sub-strain it was only 38.9-fold, compared with the Syn strain. Similar results were obtained by measurement of alpha-NA esterase activity from both larvae and female adults. The alpha-NA esterase activities in larvae and female adults at F10 generation were 2.6- and 10.9-fold from the Rm+ibp sub-strain and 5.7- and 98.5-fold from the Rm sub-strain, respectively, compared with the Syn strain. The above results suggested that iprobenfos, although it cannot completely stop or prevent the onset of malathion resistance, could dramatically delay its evolution.     

Multiple Resistance in the Larger House Fly Musca domestica in Germany

Populations of the housefly Musca domestica isolated from farms in different German districts with strong resistance problems were compared to laboratory strains with varying resistance spectra. Resistance against pyrethroids, organophosphates and carbamates was tested using impregnated filter papers, and by topical application using a susceptible housefly strain (origin WHO) for comparison. The multi-resistant fly strains tested had a strong resistance against these insecticide groups, ranging from 37- to >10000-fold for organophosphates and 150- to >6600-fold for pyrethroids. The constituent enantiomer pairs of the α-cyano-pyrethroid cyfluthrin were tested, as was beta-cyfluthrin. With respect to multi-resistant fly strains, the isomers II and IV had the best activity, with LD₅₀ values of 0·012 and 0·014 μg per fly, respectively. In addition, different groups of insect growth regulators (juvenile hormone analogues, chitin synthesis inhibitors and one triazine derivative) were tested in a special larvicidal test. The chitin synthesis inhibitors were quite effective against multi-resistant M. domestica strains except for one strain with strong resistance against chitin synthesis inhibitors, developed after extensive treatments with benzoylphenylureas for several years. The fly strains tested were not resistant against cyromazine. Additionally, the insecticides were combined with the synergists piperonyl butoxide, tributylphosphorotrithioate (DEF) and Cibacron blue and tested against the fly strain with the strongest resistance spectrum (‘Grimm’) in comparison to the susceptible strain (‘WHO-N’). Piperonyl butoxide had the greatest effect on the efficacy of cyfluthrin followed by Cibacron blue and DEF. In a parallel investigation with susceptible and resistant house fly strains, different enzyme activities related with resistance mechanisms were tested, e.g. glutathione S-transferase (3·5-fold) and mixed-function oxidase (2·3-fold). Implications of these results for management of insecticide resistance in M. domestica are discussed.     

Efficacy of current and potential grain protectant insecticides against a fenitrothion-resistant strain of the sawtoothed grain beetle,Oryzaephilus surinamemis L

The responses of a highly fenitrothion-resistant and a susceptible strain of Oryzaephilus surinamensis L. from Australia were measured against a range of alternative grain protectants using impregnated-paper and treated-grain assays. The R-strain was also highly resistant to carbaryl, moderately resistant to malathion and pirimiphos-methyl and showed low-level resistance to methacrifos, chlorpyrifos-methyl, bioresmethrin, permethrin, cyfluthrin, cypermethrin and dichlorvos. There was marginal resistance to deltamethrin. Methoprene, to which there was no resistance, was the most effective material at suppressing progeny production of the resistant strain. At current commercial application rates chlorpyrifos-methyl was the only compound of those tested that would completely control both adults and larvae of resistant O. surinamensis for a storage period of nine months. Overall, the homogeneity of response of both strains to insecticides using the treated-grain assay was as good as the response from impregnated-paper assays. The latter also tended to exaggerate resistance factors compared to the treated-grain assays.     

荧光增白剂对Cry1Ac抗感棉铃虫围食膜的影响及增效作用

为了提高Bt的杀虫活性,运用扫描电镜、SDS-PAGE电泳和生物测定技术,研究了荧光增白剂FB28对棉铃虫Cry1Ac抗性和敏感品系围食膜的影响及对Cry1Ac杀虫蛋白的增效作用。结果表明,正常棉铃虫围食膜表面光滑致密,没有空洞和缝隙。用含1%FB28的人工饲料饲喂刚蜕皮的5龄棉铃虫幼虫2 h后,抗感棉铃虫围食膜表面均出现许多空洞,且敏感棉铃虫的空洞明显大于抗性棉铃虫;随着处理时间的延长,围食膜上的空洞逐渐变小,13 h后恢复正常。用1%FB28离体或活体处理抗、感品系棉铃虫,均可造成围食膜蛋白被降解。用1%FB28与Cry1Ac杀虫蛋白混合饲喂抗、感棉铃虫初孵幼虫,可明显提高棉铃虫的死亡率,且对抗性品系的增效作用明显大于敏感品系,对敏感和抗性品系棉铃虫的增效比分别为2.23和9.34;1%FB28还可以明显增加对抗、感品系3龄棉铃虫幼虫的生长抑制作用。     

Comparative toxicity of two ecdysteroid agonists,RH-2485 and RH-5992, on susceptible and pyrethroid-resistant strains of the Egyptian cotton leafworm,Spodoptera littoralis

The comparative toxicity of two non-steroidal ecdysteroid agonists, RH-2485 and RH-5992 (tebufenozide), on development stages, fecundity and egg viability of a susceptible laboratory strain and a pyrethroid-resistant field strain ofSpodoptera littoralis (Boisduval) was evaluated. Taking the LC₅₀s as the criterion, RH-2485 was 3–7-fold more potent than RH-5992 against the susceptible and 7–14-fold more against the field strain. The LC₅₀ of RH-2485 in the 1st and 6th instars of the susceptible strain was 0.32 and 0.57 mg a.i./l, respectively. The field strain showed a mild cross-resistance of about threefold to both compounds in 1st instars and to a lesser extent in 6th instars. A considerable increase in fecundity (~3-fold) and no effect on egg viability was observed when 6th instars were fed on cotton leaves treated with 0.25 mg a.i./l RH-2485 (~LC₄₀). Our results indicate that both compounds are potentially potent insecticides for controllingS. littoralis larvae, being 10-60-fold more potent than a previous ecdysteroid agonist, RH-5849.     

Juvenile hormone analogs: Toxicity and cross-resistance in the housefly

The toxicity of several juvenile hormone analogs (JHAs) to susceptible and insecticide-resistant housefly (Musca domestica L.) strains was determined by an assay procedure in which larvae were exposed to residues of JHAs in glass vials. All JHAs tested were toxic and the most active compound, isopropyl 11-methoxy-3, 7, 11-trimethylododeca-2, 4-dienoate, was 100 times as toxic to the susceptible Orlando Regular strain as methyl parathion and 600 times as toxic as DDT.A 5- to 30-fold tolerance to the different JHAs was present in an insecticide resistant strain in which resistance is associated with a high level of NADPH-dependent microsomal oxidase activity controlled by a gene(s) on chromosome II. Cross-resistance was less marked in a strain with a chromosome V high oxidase gene and absent in strains with other resistance mechanisms.The data indicate that cross-resistance to JHAs in insects may occur in certain strains with high levels of oxidative detoxifying activity. Even so, the most active JHA was far more toxic to both susceptible and resistant strains than methyl parathion or DDT.     

Delayed cuticular penetration and enhanced metabolism of deltamethrin in pyrethroid-resistant strains of Helicoverpa armigera from China and Pakistan

The penetration and metabolism of [14C]deltamethrin was studied in susceptible and resistant Chinese and Pakistani strains of Helicoverpa armigera (Hübner), which were resistant to deltamethrin by 330- and 670-fold, respectively. The penetration of deltamethrin into resistant individuals was significantly slower than into susceptible individuals over a 24-h period. The time taken for 50% penetration of the applied deltamethrin was 1 h for the susceptible strain and 6 h for both of the resistant strains. The internal radioactivity was reduced by the larvae of resistant strains much faster than by the susceptible larvae. After 48 h, 40% of the penetrated deltamethrin was still inside the larvae of the susceptible strain, in comparison with 1.5-5% in the Pakistani strain and 8-14% in the Chinese strain. Both of the resistant strains produced methanol-soluble and water-soluble metabolites, but the susceptible strain produced methanol-soluble metabolites only. By 12, 24 and 48 h after dosing, the amount of methanol-soluble metabolites excreted by the resistant strains was almost double that of the susceptible strain. Both of the resistant strains also excreted 5-7% of the penetrated dose as a water-soluble metabolite after 48 h. In comparison with the Chinese strain, the Pakistani strain exhibited slower penetration, lower internal content and faster excretion of deltamethrin, which correlated with the higher resistance of the Pakistani strain. These findings show that the resistant Pakistani and Chinese strains of H. armigera possess mechanisms of reduced cuticular penetration and enhanced metabolism of deltamethrin and perhaps other pyrethroids.     

Cross-resistance potential of fipronil in Musca domestica

The toxicity of fipronil to insecticide-susceptible houseflies and the cross-resistance potential of fipronil were determined for six insecticide-resistant laboratory housefly strains by topical application and feeding bioassay. The insecticide-resistant strains represented different levels and patterns of resistance to pyrethroids, organophosphates, carbamates and organochlorines. Five strains were almost susceptible to fipronil in feeding bioassay with resistance factors at LC50 between 0.36 and 3.0. Four of these strains were almost susceptible to topically applied fipronil (resistance factors at LD50 were 0.55, 0.83, 3.3 and 2.5, respectively), whereas one strain was 13-fold resistant to topically applied fipronil. A highly gamma-HCH-resistant strain, 17e, was 430-fold resistant to fipronil in topical application bioassay and 23-fold resistant in feeding bioassay at LD50/LC50. We also tested the toxicity of fipronil in a feeding bioassay and gamma-HCH in topical application bioassay on thirteen housefly field populations. Eleven of the field populations had resistance factors for fipronil ranging from 0.98 to 2.4 at LC50, whereas two populations were 4.0- and 4.6-fold resistant to fipronil. The resistance level to gamma-HCH at LD50 in the field populations ranged from 1.8- to 8.1-fold. The two strains showing fipronil resistance were 3.4- and 8.1-fold resistant to gamma-HCH. Fipronil and gamma-HCH toxicities were positively correlated in the field populations. Biochemical assays of esterase, glutathione S-transferase and cytochrome P450 monooxygenase indicated that the low fipronil resistance observed in laboratory and field strains could be caused by elevated detoxification or be due to a target-site resistance mechanism with cross-resistance to gamma-HCH.     

Stability and Biological Activity of Cyfluthrin Isomers

A GC-MS method capable of completely separating the four pairs of diastereoisomers of cyfluthrin is presented and the method used to show that isomerisation of the cyfluthrin enantiomers occurs in methanol. This methanol-induced isomerisation could also be demonstrated by bioassays using water fleas. The biological activities of the various cyfluthrin isomers contained in the commercial products cyfluthrin and beta-cyfluthrin were assayed using several strains of lepidopteran larvae including Plutella xylostella, Heliothis virescens and Spodoptera frugiperda. With the susceptible strains, the efficiencies of the isomers mixtures of cyfluthrin and beta-cyfluthrin were shown to obey the rules of additivity. However, in tests with a resistant strain of P. xylostella originating from Thailand, the ‘inactive’ isomer III acted synergistically with the active isomer IV. Resistance factors in strains of H. virescens and P. xylostella were found to be higher with cis than with trans isomers. This probably contributes to the superior action of cyfluthrin and beta-cyfluthrin against various pests of agricultural importance since the commercial products contain a high content of trans isomers (‘high trans pyrethroids’).     

棉铃虫对久效磷抗性的毒理学机制

就棉铃虫田间种群对久效磷抗性的毒理学机制进行了研究。久效磷对敏感品系和高抗品系的乙酰胆碱酯酶抑制率存在显著差异,在同等剂量浓度下,对敏感品系的抑制率为７３．４８％,对高抗品系的抑制率仅为５９．６７％,说明棉铃虫对久效磷产生高水平抗性与乙酰胆碱酯酶不敏感性有关。在不同田间抗性品系中,ＰＢＯ和ＴＰＰ对久效磷均具有明显的增效作用,增效比分别为５．６～２３．４倍和２．９～４．６倍;而相应地ＢＰＯ和ＴＰＰ对     

The role of metabolic enzymes in insecticide-resistant colorado potato beetles

Several metabolic enzymes were assayed in susceptible and insecticide-resistant (R-mfo and R-AchE) strains of the Colorado potato beetle (Leptinotarsa decemlineata Say). We compared the activities of esterases, glutathione transferases and mixed function oxidases, and measured in-vivo metabolism of carbofuran to determine the contributions of metabolic factors to the observed resistance. There were no substantial differences between strains in α- or β-naphthylacetate hydrolysis, or in glutathione transferase activity. Compared to the susceptible strain, the R-mfo strain showed 4-fold higher activity in both ethoxyresorufin-O-dealkylase, and pentoxyresorufin-O-dealkylase activity. The R-AChE strain had a 1.5-fold higher level of ethoxyresorufin-O-dealkylase activity. Correspondingly, the in-vivo metabolism of carbofuran was highest in the R-mfo strain, and the R-AChE strain was slightly higher than the susceptible strain. These results are discussed in relation to other resistance mechanisms which we have examined in these strains.     

In-vivo and in-vitro studies on DDT uptake and metabolism in susceptible and resistant strains of the mosquito Aedes aegypti L.

Twelve strains of Aedes aegypti have been compared for resistance to pp′-DDT, uptake of pp′-DDT, and dehydrochlorination of pp′-DDT to pp′-DDE in vivo and in vitro both at the larval and adult stages. Resistant larvae were shown to contain significantly more pp′-DDE than susceptible larvae after a standard exposure to pp′-DDT but also substantially more pp′-DDT in an unmetabolised state. There was a small increase in the percentage dehydrochlorinated in vivo in the resistant strains compared with the susceptible strains, but this was not correlated with the level of resistance nor with dehydrochlorination in vitro. However, dehydrochlorination in vitro was correlated with resistance. Adult resistance was correlated positively with dehydrochlorination, both in vivo and in vitro, but the resistant adults did not contain increased levels of unmetabolised DDT. By comparing resistance levels at the two stages, it was found that there were two kinds of resistant strain: four strains of Asian origin and one from West Africa were highly resistant as larvae but showed almost no resistance as adults; five strains from Central and South America were highly resistant at both stages. The different mechanisms of resistance in adults and larvae are discussed in relation to genetic studies.     

Mechanism of resistance to spinosyn in the tobacco budworm, Heliothis virescens

Topical laboratory selection of tobacco budworm larvae, Heliothis virescens, with technical spinosad for multiple generations resulted in larvae 1068-fold resistant to topical applications of the insecticide and 316.6-fold resistant to insecticide treated diet as compared to the parental strain. The penetration of 2′-O-methyl[¹⁴C]spinosyn A across the cuticle of the susceptible (parental) and selected (resistant) tobacco budworms increased with time 3-12 h after application. A trend of reduced penetration in the resistant strain was found but the differences were not statistically significant. 2′-O-methyl[¹⁴C]spinosyn A when injected into the hemocoel was not metabolized 96 h after treatment in both the susceptible and resistant strain, suggesting that a change in metabolism was not the mechanism of resistance. Electrophysiological studies indicated that dose-dependent spinosyn A-induced currents occurred in neurons from spinosyn resistant and susceptible (adult) tobacco budworms. At both 10 and 100 nM spinosyn A, however, the amplitude of these currents in the resistant insects was significantly smaller than the amplitude of currents observed from neurons from susceptible tobacco budworm adults. This suggests that neurons from resistant insects have decreased sensitivity to spinosyn A. However, the reduced inward currents in the resistant strain may or may not be related to the mode of action of the spinosyns. No statistically significant cross-resistance was noted for the spinosad resistant tobacco budworms for topical applications of permethrin (Pounce^®), profenofos (Curacron^®), emamectin benzoate (Denim^®), or indoxacarb (Steward^®). A statistically significant reduction in susceptibility to acetamiprid (Mospilan^®) in artificial diet as determined from a resistance ratio of 0.482 was found.     

Monitoring insecticide resistance in house flies (Diptera: Muscidae) from New York dairies

House flies were collected from dairies across New York state and the levels of resistance to seven insecticides were measured using standard laboratory assays with three to five diagnostic concentrations. The highest levels of resistance were found for tetrachlorvinphos, permethrin and cyfluthrin. Although levels of resistance to methomyl were somewhat lower, they were among the highest ever reported for field‐collected house flies. Resistance to pyrethrins was limited primarily to the lowest diagnostic concentration. House flies were susceptible to fipronil at all dairies, suggesting that this material would be highly effective for fly control. The levels of resistance were similar at all the dairies, irrespective of their insecticide use, suggesting substantial movement of flies between facilities. Relative to resistance levels found at New York dairies in 1987, resistance levels had increased for permethrin, were unchanged for tetrachlorvinphos and had decreased for dimethoate. To identify a single diagnostic concentration that could be used in the laboratory assays to assess accurately resistance levels in future studies, we carried out a ‘simulated’ field bioassay using formulated materials. A diagnostic concentration for each insecticide is proposed on the basis of a comparison of our bioassays. © 2001 Society of Chemical Industry     

Monitoring of insecticide resistance in damson hop aphid,Phorodon humuli Schrank (Hemiptera: Aphididae) from German hop gardens

The damson hop aphid, Phorodon humuli (Schrank) (Hemiptera: Aphididae), is one of the most important sucking pests of many hop-growing areas world-wide. In this study we determined the efficacy of several insecticides against strains collected throughout the year 2001. All strains were collected in different hop gardens in the Hallertau (Bavaria), Germany, the largest hop-growing area of the world. First of all we established a leaf dip bioassay, carried out using six-well tissue culture plates and appropriate for monitoring susceptibility against imidacloprid, oxydemeton-methyl, cyfluthrin, amitraz, pymetrozine and pirimicarb. Four of these compounds, imidacloprid, cyfluthrin, pymetrozine and amitraz, are currently registered for the control of sucking pests in German hop gardens and are useful against P. humuli. The leaf-dip bioassay system turned out to be very reliable and robust. Ten P. humuli strains were collected in May 2001 and maintained in the laboratory to assess their resistance to the different insecticides in comparison with two laboratory reference strains (H2 and H5). Using diagnostic concentrations, resistance monitoring for imidacloprid and cyfluthrin was investigated during July and August 2001 on 53 populations from 30 sites around the Hallertau, an area of ca 2500 km2. Resistance to diagnostic concentrations (LC95 for reference strains) of imidacloprid, amitraz and pymetrozine was not detected in any strain received in 2001, but late-season (August) populations seemed to respond more heterogeneously than those collected mid-season (July). Overall composite mean mortalities to diagnostic concentrations of imidacloprid (13 mg litre(-1)) in collections from May, July and August were 95 (+/-2.5), 98 (+/-2.3) and 87 (+/-5.9)%, respectively. Moderate resistance to pyrethroids was observed in all strains collected in May and August using a diagnostic concentrations of 10 mg litre(-1) cyfluthrin (LC95 of the susceptible reference strain H5). Slight to moderate resistance to diagnostic concentrations of oxydemeton-methyl and pirimicarb was observed in some, but not all, strains collected early season. The results are discussed in terms of the implemention of hop aphid resistance management strategies in German hop-cultivation areas.