Monitoring for imidacloprid resistance in the tobacco‐adapted form of the green peach aphid,Myzus persicae (Sulzer) (Hemiptera: Aphididae), in the eastern United States

BACKGROUND: Imidacloprid is the primary insecticide for controlling the tobacco‐adapted form of the green peach aphid (TGPA), Myzus persicae (Sulzer), a major pest of tobacco worldwide. This study used leaf‐dip bioassays to assess TGPA resistance to imidacloprid in the eastern United States from 2004 through 2007. RESULTS: When combined over the 4 year study, 18, 14 and 3% of the TGPA had imidacloprid resistance ratios (RRs) of 10–20‐fold, 20–30‐fold and 30–90‐fold, respectively, compared with the most susceptible colony tested. This indicates that some colonies have developed moderate levels of resistance to imidacloprid. A colony collected near Clayton, North Carolina, had the highest RR of 91 (LC₅₀ value = 31 mg L^?1). This resistance declined for six tests over a 3 year period in the laboratory culture from >130‐fold RR (LC₅₀ = 48 mg L^?1) to 40‐fold RR (LC₅₀ = 15 mg L^?1). Over the same period, the most susceptible colony and a standard colony not exposed to imidacloprid for over 7 years had consistently low LC₅₀ values. CONCLUSION: Moderate levels of resistance to imidacloprid are noticed among TGPA colonies from the eastern United States. The variation in resistance indicates that the factors responsible are present in the populations at low frequencies and are just not enough to cause field failures yet. Copyright © 2010 Society of Chemical Industry     

Insecticide resistance status of Bemisia tabaci Q‐biotype in south‐eastern Spain

BACKGROUND: Bemisia tabaci Gennadius Q‐biotype has readily developed resistance to numerous insecticide classes. Studies in the Mediterranean area are needed to clarify the resistance status and cross‐resistance patterns in this invasive whitefly biotype. The levels of resistance in nymphs of seven strains of B. tabaci Q‐biotype from south‐eastern Spain to representative insecticides were determined. RESULTS: Six populations had low to moderate levels of resistance to azadirachtin (0.2‐ to 7‐fold), buprofezin (11‐ to 59‐fold), imidacloprid (1‐ to 15‐fold), methomyl (3‐ to 55‐fold), pyridaben (0.9‐ to 9‐fold), pyriproxyfen (0.7‐ to 15‐fold) and spiromesifen (1‐ to 7‐fold), when compared with a contemporary Spanish Q‐biotype reference population (LC₅₀ = 2.7, 8.7, 15.2, 19.9, 0.34, 20.9 and 1.1 mg L^?1 respectively). A single population collected from a greenhouse subject to intensive insecticide use exhibited generally higher resistance levels to the same array of compounds (31‐, 1164‐, 3‐, 52‐, 9‐, 19‐ and 3‐fold respectively). Pyridaben and spiromesifen were extremely effective against nymphs of all strains, with LC₅₀ values significantly below recommended application rates. CONCLUSION: In contrast to previous reports, high rates of efficacy exist for numerous insecticide classes against B. tabaci Q‐biotype populations in these intensive agricultural regions of south‐eastern Spain. This probably reflects the recent and significant reductions in exposure that have resulted from a wider uptake of IPM technologies and strategies. However, the continued presence of resistance genes also suggests that a reversion to levels of high insecticide exposure could result in a rapid selection for resistance. Copyright © 2009 Society of Chemical Industry     

Genetic analysis of abamectin resistance in Tetranychus cinnabarinus

The carmine spider mite is the most serious crop mite pests in China. Abamectin has been used to control insects and mites worldwide but carmine spider mites, Tetranychus cinnabarinus, had developed resistance to it. Genetic research on insecticide resistance has been fundamental for understanding the resistance development, studying resistance mechanisms, and designing appropriate resistance management strategies to control insect pests. A resistant colony of T. cinnabarinus, RRG42, was established to examine the inheritance of abamectin resistance in T. cinnabarinus. The females of T. cinnabarinus were selected for bioassay using a slide dip method. After 42 generations of selection, the RRG42 strain was 8.7-fold resistant to abamectin compared with the susceptible strain (SS). The logarithm (log) concentration–probit response curve for F₁s from reciprocal crosses, of F₁RS and F₁SR, were inclined to that for SS and the degree of dominance (D) values for F₁s were −0.81 and −0.17. There was a significant difference in values of LC₅₀ and slope of log concentration–probit lines between F₁RS and F₁SR. The observed mortalities of BC1 (F₁RS♀ × RRG42♂) and BC1′ (F₁SR♀ × SS♂) were significantly different from the expected mortalities based on a monogenic resistance in the chi-square tests. The inheritance of abamectin resistance in T. cinnabarinus is incompletely recessive and may be controlled by more than one gene. The maternal or cytoplasmic effect may exist in the inheritance of resistance to abamectin in T. cinnabarinus.     

Beet armyworm (Spodoptera exigua) resistance to spinosad

Susceptibility to spinosad (Success®/Tracer®) of beet armyworm (Spodoptera exigua) from the southern USA and Southeast Asia was determined through exposure of second‐ and third‐instar larvae to dipped cotton leaves. LC₅₀ estimates of susceptibility of second‐ and third‐instar larvae of field populations ranged from 0.279 to 6.14 and 0.589 to 14.0 mg spinosad litre⁻¹, respectively. A Thailand population was 22‐ and 24‐fold less susceptible than the six other US field populations evaluated, and 85‐ and 58‐fold less susceptible than a reference laboratory population, respectively. From these results, we initiated experiments to test the hypothesis that the Thailand population was resistant to spinosad. F₁ crosses between the resistant Thailand population and a susceptible reference strain yielded individuals that were 22‐fold less sensitive to spinosad than the susceptible parent. This same resistant strain exhibited significantly greater survivorship on plants treated with spinosad in the field. Lastly, selection of an Arizona population resulted in a significant reduction in susceptibility to spinosad, further substantiating the hypothesis of a genetic basis for resistance to spinosad. These findings indicate a vulnerability of this new insecticide to resistance development in beet armyworm and should serve as a warning against excessive use of it. © 2000 Society of Chemical Industry     

姜黄素异噁唑和吡唑衍生物的合成及杀螨活性

为了寻求和开发新的基于天然产物的杀螨剂,在明确姜黄素具有杀螨活性,且其结构中的双羰基并非杀螨活性关键基团的基础上,设计并合成了15个姜黄素异噁唑和吡唑衍生物,其结构均经红外光谱、核磁共振氢谱和质谱分析确认。生物活性测定结果表明:几乎所有的目标化合物对朱砂叶螨Tetranychus cinnabarinus和柑橘全爪螨Panonychus citri均表现出了比先导化合物姜黄素更优异的触杀活性,其中化合物 4和11 的活性最为突出。处理48 h后,化合物 4 对朱砂叶螨和柑橘全爪螨的LC50值分别为333.0和156.0 mg/L,其毒力是姜黄素的6.35和4.56倍, 11 的LC50值分别为478.4和144.7 mg/L,毒力是姜黄素的4.42和4.92倍;相应地处理72 h后, 4 的LC50值分别为115.0和84.9 mg/L,其毒力是姜黄素的5.02和1.43倍, 11 的LC50值分别为91.0和68.7 mg/L,毒力是姜黄素的6.35和1.77倍。化合物 4和11 可作为进一步开发研究的具有杀螨活性的候选化合物。     

Genetic analysis of abamectin resistance in Tetranychus cinnabarinus

The carmine spider mite is the most serious crop mite pests in China. Abamectin has been used to control insects and mites worldwide but carmine spider mites, Tetranychus cinnabarinus, had developed resistance to it. Genetic research on insecticide resistance has been fundamental for understanding the resistance development, studying resistance mechanisms, and designing appropriate resistance management strategies to control insect pests. A resistant colony of T. cinnabarinus, RRG42, was established to examine the inheritance of abamectin resistance in T. cinnabarinus. The females of T. cinnabarinus were selected for bioassay using a slide dip method. After 42 generations of selection, the RRG42 strain was 8.7-fold resistant to abamectin compared with the susceptible strain (SS). The logarithm (log) concentration–probit response curve for F₁s from reciprocal crosses, of F₁RS and F₁SR, were inclined to that for SS and the degree of dominance (D) values for F₁s were −0.81 and −0.17. There was a significant difference in values of LC₅₀ and slope of log concentration–probit lines between F₁RS and F₁SR. The observed mortalities of BC1 (F₁RS♀ × RRG42♂) and BC1′ (F₁SR♀ × SS♂) were significantly different from the expected mortalities based on a monogenic resistance in the chi-square tests. The inheritance of abamectin resistance in T. cinnabarinus is incompletely recessive and may be controlled by more than one gene. The maternal or cytoplasmic effect may exist in the inheritance of resistance to abamectin in T. cinnabarinus.     

Pyrethroid insecticide resistance in British populations of the cabbage whitefly, Aleyrodes proletella

BACKGROUND: The cabbage whitefly, Aleyrodes proletella L., is emerging as a significant pest of field brassica crops in certain regions of the United Kingdom. In order to investigate the contribution of pesticide resistance to this phenomenon, A. proletella populations were sampled from five different areas in England in 2008 and 2009. Adult residual leaf‐dip bioassays were carried out using pyrethroid and neonicotinoid insecticides. RESULTS: Significant resistance to pyrethroids was found in multiple samples collected from two areas. No evidence of cross‐resistance to neonicotinoids was found in a subset of the pyrethroid‐resistant populations. While the patterns of resistance to different pyrethroids were broadly correlated, the magnitude of resistance factors differed substantially. Survival of strains at a putative diagnostic concentration of lambda‐cyhalothrin was found to provide a guide to their LC₅₀. Significant differences in LC₅₀ were found when different brassica crops were used in the bioassay, although the resistance patterns between strains were maintained. CONCLUSION: Reduced susceptibility to multiple pyrethroid insecticides exists in populations of A. proletella in the United Kingdom, corresponding to recent major outbreaks. The mechanism(s) of resistance are yet to be determined, but molecular structural differences in pyrethroids probably influence the magnitude of cross‐resistance within this group of insecticides. Copyright © 2011 Society of Chemical Industry     

Multiple resistance across glufosinate,glyphosate, paraquat and ACCase‐inhibiting herbicides in an Eleusine indica population

An Eleusine indica population was previously reported as the first global case of field‐evolved glufosinate resistance. This study re‐examines glufosinate resistance and investigates multiple resistance to other herbicides in the population. Dose–response experiments with glufosinate showed that the resistant population is 5‐fold and 14‐fold resistant relative to the susceptible population, based on GR₅₀ and LD₅₀ R/S ratio respectively. The selected glufosinate‐resistant subpopulation also displayed a high‐level resistance to glyphosate, with the respective GR₅₀ and LD₅₀ R/S ratios being 12‐ and 144‐fold. In addition, the subpopulation also displayed a level of resistance to paraquat and ACCase‐inhibiting herbicides fluazifop‐P‐butyl, haloxyfop‐P‐methyl and butroxydim. ACCase gene sequencing revealed that the Trp‐2027‐Cys mutation is likely responsible for resistance to the ACCase inhibitors examined. Here, we confirm glufosinate resistance and importantly, we find very high‐level glyphosate resistance, as well as resistance to paraquat and ACCase‐inhibiting herbicides. This is the first confirmed report of a weed species that evolved multiple resistance across all the three non‐selective global herbicides, glufosinate, glyphosate and paraquat.     

Monitoring of resistance to spirodiclofen and five other acaricides in Panonychus citri collected from Chinese citrus orchards

BACKGROUND: Citrus red mite, Panonychus citri (McGregor), is one of the most important pesticide‐resistant pests in China. In order better to understand its resistance status, six populations of the mite were collected from Chinese citrus orchards for monitoring of resistance to spirodiclofen and another five acaricides. RESULTS: All the samples collected in the field in 2006 were susceptible to spirodiclofen. However, the LC₅₀ values in populations sampled in 2009 ranged from 3.29 to 418.24 mg L^?1 spirodiclofen, a 127‐fold difference between the least and most sensitive populations. Compared with a susceptible strain, 50‐fold and 90.8‐fold resistance to spirodiclofen was detected in populations sampled from Pinghe and Fuzhou in 2009, as well as cross‐resistance to spirotetramat. The LC₅₀ values for abamectin, fenpropathrin, hexythiazox and pyridaben in the collected samples ranged from 0.041 to 3.52 mg L^?1, from 23.91 to 696.16 mg L^?1, from 13.94 to 334.19 mg L^?1 and from 48.90 to 609.91 mg L^?1 respectively. CONCLUSION: Great variations in resistance to the tested acaricides were observed among the sampled populations. The Pinghe population developed resistance to all the acaricides tested. The Jianning population was susceptible to most acaricides tested, except pyridaben. Resistance management strategies were conducted on the basis of these observations. Copyright © 2010 Society of Chemical Industry     

Cross‐resistance study and biochemical mechanisms of thiamethoxam resistance in B‐biotype Bemisia tabaci (Hemiptera: Aleyrodidae)

BACKGROUND: B‐biotype Bemisia tabaci (Gennadius) has invaded China over the past two decades. To understand the risks and to determine possible mechanisms of resistance to thiamethoxam in B. tabaci, a resistant strain was selected in the laboratory. Cross‐resistance and the biochemical mechanisms of thiamethoxam resistance were investigated in the present study. RESULTS: A 66.3‐fold thiamethoxam‐resistant B. tabaci strain (TH‐R) was established after selection for 36 generations. Compared with the susceptible strain (TH‐S), the selected TH‐R strain showed obvious cross‐resistance to imidacloprid (47.3‐fold), acetamiprid (35.8‐fold), nitenpyram (9.99‐fold), abamectin (5.33‐fold) and carbosulfan (4.43‐fold). No cross‐resistance to fipronil, chlorpyrifos or deltamethrin was seen. Piperonyl butoxide (PBO) and triphenyl phosphate (TPP) exhibited significant synergism on thiamethoxam effects in the TH‐R strain (3.14‐ and 2.37‐fold respectively). However, diethyl maleate (DEM) did not act synergistically with thiamethoxam. Biochemical assays showed that cytochrome P450 monooxygenase activities increased 1.21‐ and 1.68‐fold respectively, and carboxylesterase activity increased 2.96‐fold in the TH‐R strain. However, no difference was observed for glutathione S‐transferase between the two strains. CONCLUSION: B‐biotype B. tabaci develops resistance to thiamethoxam. Cytochrome P450 monooxygenase and carboxylesterase appear to be responsible for the resistance. Reasonable resistance management that avoids the use of cross‐resistance insecticides may delay the development of resistance to thiamethoxam in this species. Copyright © 2009 Society of Chemical Industry     

Pyrethroid tolerance in Culex pipiens pipiens var molestus from Marin County, California

In May 2001 a sample of Culex pipiens pipiens variety molestus Forskål from Marin County, California, collected as larvae and reared to adults, was found to show reduced resmethrin and permethrin knock‐down responses in bottle bioassays relative to a standard susceptible Cx pipiens quinquefasciatus Say colony (CQ1). Larval susceptibility tests, using CQ1 as standard susceptible, indicated that the Marin mosquitoes had LC₅₀ resistance ratios of 18.3 for permethrin, 12 for deltamethrin and 3.3 for pyrethrum. A colony of Marin was established and rapidly developed higher levels of resistance in a few generations after exposure to permethrin as larvae. These selected larvae were shown to cross‐resist to lambda‐cyhalothrin as well as to DDT. However, adult knock‐down time in the presence of permethrin, resmethrin and pyrethrum was not increased after increase in tolerance to pyrethroids as larvae. Partial and almost complete reversion to susceptibility as larvae was achieved with S, S, S‐tributylphosphorotrithioate and piperonyl butoxide (PBO), respectively, suggesting the presence of carboxylesterase and P450 monooxygenase mediated resistance. Insensitive target site resistance (kdr) was also detected in some Marin mosquitoes by use of an existing PCR‐based diagnostic assay designed for Cx p pipiens L mosquitoes. Carboxylesterase mediated resistance was supported by use of newly synthesized novel pyrethroid‐selective substrates in activity assays. Bottle bioassays gave underestimates of the levels of tolerance to pyrethroids of Marin mosquitoes when compared with mortality rates in field trials using registered pyrethroid adulticides with and without PBO. This study represents the first report of resistance to pyrethroids in a feral population of a mosquito species in the USA. Copyright © 2003 Society of Chemical Industry     

Characterization of field‐evolved resistance to Bacillus thuringiensis‐derived Cry1F δ‐endotoxin in Spodoptera frugiperda populations from Argentina

BACKGROUND

Transgenic maize (Zea mays L.) event TC1507 (Herculex^® I insect protection), expressing Cry1F δ‐endotoxin derived from Bacillus thuringiensis var. aizawai, was commercialized in 2003 in the Americas. Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) susceptibility to Cry1F was monitored annually across several regions in Argentina using diagnostic concentration bioassays. Reduced performance of TC1507 maize against S. frugiperda was reported in 2013. A resistant population was established in the laboratory and the dominance of Cry1F resistance was characterized.

RESULTS

During 2012–2015, high‐survivorship of several populations was observed in the resistance monitoring program. Reciprocal crosses of a Cry1F‐resistant population with a Cry1F‐susceptible population were evaluated to calculate effective dominance (D_ML) based on mortality levels observed at 100 µg/ml Cry1F. Two additional dominance levels (D_LC and D_EC) were calculated using lethal (LC₅₀) or effective concentration (EC₅₀) derived from concentration–response bioassays. Estimates indicated that Cry1F resistance in S. frugiperda in Argentina was either highly recessive (D_ML = 0.005) or incompletely recessive (D_LC < 0.26 and D_EC < 0.19).

CONCLUSION

This study is the first documented confirmation and characterization of S. frugiperda Cry1F field‐evolved resistance in Argentina. The resistance to Cry1F in S. frugiperda populations collected in Argentina, is autosomal and incompletely recessive similar to the resistance reported in Brazil. © 2017 The Authors. Pest Management Science published by John Wiley © Sons Ltd on behalf of Society of Chemical Industry.     

Nicotinoid and pyrethroid insecticide resistance in houseflies (Diptera: Muscidae) collected from Florida dairies

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

Buprofezin susceptibility survey, resistance selection and preliminary determination of the resistance mechanism in Nilaparvata lugens (Homoptera: Delphacidae)

BACKGROUND: Buprofezin has been used for many years to control Nilaparvata lugens (Stål). Assessment of susceptibility change in the insect is essential for maintaining control efficiency and resistance management. RESULTS: Eleven‐year surveys showed that most field populations were susceptible before 2004. However, substantially higher levels of resistance (up to 28‐fold) were found in most of the rice fields in China after 2004. A field population was collected and periodically selected for buprofezin resistance in the laboratory. After 65 generations (56 were selected), the colony successfully obtained 3599‐fold resistance to buprofezin. Synergism tests showed that O,O‐diethyl‐O‐phenyl phosphorothioate (SV1), piperonyl butoxide (PBO) and diethyl maleate (DEM) increased buprofezin toxicity in the resistant strain by only 1.5–1.6 fold, suggesting that esterases, P450‐monooxygenases and glutathione S‐transferases had no substantial effect on buprofezin resistance development. CONCLUSION: The results from this study indicate that N. lugens has the potential to develop high resistance to buprofezin. A resistance management program with rotation of buprofezin and other pesticides may efficiently delay or slow down resistance development in the insect. Further investigation is also necessary to understand the resistance mechanisms in N. lugens. Copyright © 2008 Society of Chemical Industry     

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     

Cross‐resistance,mode of inheritance and stability of resistance to emamectin in Spodoptera litura (Lepidoptera: Noctuidae)

BACKGROUND: Spodoptera litura (F.) is a cosmopolitan pest that has developed resistance to several insecticides. The aim of the present study was to establish whether an emamectin‐selected (Ema‐SEL) population could render cross‐resistance to other insecticides, and to investigate the genetics of resistance. RESULTS: Bioassays at G₁ gave resistance ratios (RRs) of 80‐, 2980‐, 3050‐ and 2800‐fold for emamectin, abamectin, indoxacarb and acetamiprid, respectively, compared with a laboratory susceptible population Lab‐PK. After three rounds of selection, resistance to emamectin in Ema‐SEL increased significantly, with RRs of 730‐fold and 13‐fold compared with the Lab‐PK and unselected (UNSEL) population respectively. Further studies revealed that three generations were required for a tenfold increase in resistance to emamectin. Resistance to abamectin, indoxacarb, acetamiprid and emamectin in UNSEL declined significantly compared with the field population at G₁. Furthermore, selection with emamectin reduced resistance to abamectin, indoxacarb and acetamiprid on a par with UNSEL. Crosses between Ema‐SEL and Lab‐PK indicated autosomal and incomplete dominance of resistance. A direct test of a monogenic model and Land's method suggested that resistance to emamectin was controlled by more than one locus. CONCLUSION: Instability of resistance and lack of cross‐resistance to other insecticides suggest that insecticides with different modes of action should be recommended to reduce emamectin selection pressure. Copyright © 2010 Society of Chemical Industry     

Inheritance of resistance to a new non‐steroidal ecdysone agonist,fufenozide, in the diamondback moth,Plutella xylostella (Lepidoptera: Plutellidae)

BACKGROUND: The diamondback moth (DBM), Plutella xylostella (L.), is a cosmopolitan pest of cruciferous crops. Fufenozide, a novel non‐steroidal ecdysone agonist, exhibits good efficacy and plays an increasingly important role in the control of Lepidopterous pests in China. A laboratory strain of DBM was selected for resistance to fufenozide, and the genetic basis of resistance was studied. RESULTS: The resistant strain, selected under laboratory conditions, exhibited a higher level of resistance to fufenozide (302.8‐fold based on LC₅₀s) than the laboratory susceptible strain. Mortality data from the testing of F₁ progeny of reciprocal crosses of resistant and susceptible DBM indicated that resistance was autosomal and incompletely recessive with a degree of dominance of ?0.664. Chi‐square analysis from responses of a backcross of crossed F₁ progeny and the resistant strain and F₂ progeny were highly significant, suggesting that the resistance was probably controlled by more than one gene. The estimated realised heritability (h²) of fufenozide resistance was 0.08, indicating that diamondback moth may have a lower chance of developing resistance to fufenozide than other kinds of insecticide. CONCLUSION: The resistance of DBM to fufenozide might be autosomal and incompletely recessive, and the resistance is probably controlled by more than one gene. These results provide the basic information for pest management programmes. Copyright © 2009 Society of Chemical Industry     

The toxicity of formetanate and chlorphenamidine to resistant fruit tree red spider mite,Panonychus ulmi (Koch)

Formetanate was found to be somewhat less effective on three strains of Panonychus ulmi (Koch) resistant to organophosphorus compounds (O.P.'s), and on two others multi-resistant to O.P.'s and tetradifon, than on susceptible mites; the LC₅₀'s in tests on larvae or adult mites were two to three times greater. Chlorphenamidine was as effective on O.P.-resistant mites as on susceptibles; but on the multi-resistant strains it was more effective, the ratio of LC₅₀'s, R/S, in assays on larvae being ×0.37. However, it has not been shown that resistance to tetradifon confers true (pleiotropic) negative cross-resistance to chlorphenamidine.     

Pyrethroid resistance and cross‐resistance in the German cockroach,Blattella germanica (L)

A German cockroach (Blatella germanica (L)) strain, Apyr‐R, was collected from Opelika, Alabama after control failures with pyrethroid insecticides. Levels of resistance to permethrin and deltamethrin in Apyr‐R (97‐ and 480‐fold, respectively, compared with a susceptible strain, ACY) were partially or mostly suppressed by piperonyl butoxide (PBO) and S,S,S,‐tributylphosphorotrithioate (DEF), suggesting that P450 monooxygenases and hydrolases are involved in resistance to these two pyrethroids in Apyr‐R. However, incomplete suppression of pyrethroid resistance with PBO and DEF implies that one or more additional mechanisms are involved in resistance. Injection, compared with topical application, resulted in 43‐ and 48‐fold increases in toxicity of permethrin in ACY and Apyr‐R, respectively. Similarly, injection increased the toxicity of deltamethrin 27‐fold in ACY and 28‐fold in Apyr‐R. These data indicate that cuticular penetration is one of the obstacles for the effectiveness of pyrethroids against German cockroaches. However, injection did not change the levels of resistance to either permethrin or deltamethrin, suggesting that a decrease in the rate of cuticular penetration may not play an important role in pyrethroid resistance in Apyr‐R. Apyr‐R showed cross‐resistance to imidacloprid, with a resistance ratio of 10. PBO treatment resulted in no significant change in the toxicity of imidacloprid, implying that P450 monooxygenase‐mediated detoxication is not the mechanism responsible for cross‐resistance. Apyr‐R showed no cross‐resistance to spinosad, although spinosad had relatively low toxicity to German cockroaches compared with other insecticides tested in this study. This result further confirmed that the mode of action of spinosad to insects is unique. Fipronil, a relatively new insecticide, was highly toxic to German cockroaches, and the multi‐resistance mechanisms in Apyr‐R did not confer significant cross‐resistance to this compound. Thus, we propose that fipronil could be a valuable tool in integrated resistance management of German cockroaches. © 2001 Society of Chemical Industry     

High level methoprene resistance in the mosquito Ochlerotatus nigromaculis (Ludlow) in central California

In the summer of 1998, failures of methoprene field applications to control the mosquito Ochlerotatus nigromaculis (Ludlow) were noticed in several pastures in the outskirts of Fresno, California, USA. Effective control with methoprene had been achieved for over 20 years prior to this discovery. Susceptibility tests indicated that the Fresno Oc nigromaculis populations had developed several thousand‐fold higher LC₅₀ and LC₉₀ tolerance levels to methoprene compared with methoprene‐naïve populations. The synergists piperonyl butoxide (PBO), S,S,S‐tributyl phosphorotrithioate and 3‐octylthio‐1,1,1‐trifluoro‐2‐propanone had little synergistic effect, suggesting that the mechanism of methoprene tolerance was not mediated by P450 monooxygenase or carboxylesterase enzyme degradation. As part of initiating a resistance management strategy, partial reversion back to methoprene susceptibility was achieved in a resistant population after six consecutive applications of Bacillus thuringiensis israelensis Goldberg & Marga coupled with two oil and two pyrethrum + PBO applications. © 2002 Society of Chemical Industry