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BACKGROUND The seasonal long-distance migration of pests amongst different seasonal habitats may encounter different degrees of insecticides' selection pressure, but the knowledge on the evolution of resistance and the underlying mechanisms remains little. Here, we show that the development of resistance of the oriental armyworm Mythimna separata (Walker), a notorious agricultural pest that migrates between northern and northeast China seasonally across the Bohai Gulf, is influenced by seasonal migration. RESULTS There are two conspicuous migrations of M. separata, the northeastwards population in the second half of May and the returning population in the second half of August, between northern and northeast China per year, and the abundance values of migrants from April to October are significantly different. The resistance levels of seasonal migratory populations to λ-cyhalothrin vary in different months, and the resistance levels and estimated frequency of the resistance allele of the first northeastward population (second half of May, May.-2) in spring are significantly higher than those of the returning populations in autumn. Moreover, resistance decline was observed in migrating population Jul.-2, with the resistance levels in the F1 progeny higher than those in their F2 progeny. Synergism tests indicate that cytochrome P450 monooxygenases (P450s) play a major role in resistance. Enzymatic assays show that the P450 activity is significantly correlated with resistance levels in migratory populations, indicating that increased P450 activity is the main mechanism of resistance. The expression levels and correlation analysis of the relative expression of P450s with resistance levels show that 3 (i.e. CYP9A144, CYP9G40, and CYP6B79) out of 23 genes from CYP6 and CYP9 subfamilies are potentially involved in resistance to λ-cyhalothrin. CONCLUSION Our results show that the resistance of M. separata to λ-cyhalothrin is unstable and likely to be metabolically driven by enhanced P450 activity mediated by the overexpression of multiple P450 genes. Notably, the development of resistance is probably affected by seasonal migration. This article is protected by copyright. All rights reserved.

Background Recent work has shown that two codling moth (Cydia pomonella) glutathione S-transferase genes (GSTs), CpGSTd1 and CpGSTd3, can metabolize λ-cyhalothrin, one of the recommended insecticides for C. pomonella control worldwide. However, systematical characterization of delta and epsilon GSTs, especially their potential contributions in the metabolism of λ-cyhalothrin, is currently still lacking in C. pomonella. Results In this study, a total of nine cDNA sequences were identified in C. pomonella, including four in the delta and five in the epsilon subclasses. RT-qPCR showed that seven GSTs were ubiquitously expressed at all developmental stages, and CpGSTe2, CpGSTe3, and CpGSTe4 were mainly expressed in larvae. The mRNA levels of CpGSTd2, CpGSTd4, and CpGSTe5 were significantly higher in male than in female adults. Tissue-specific expression analysis revealed that the CpGSTe2, CpGSTe3, and CpGSTe4 were highly expressed in the midgut while CpGSTd2 and CpGSTd4 were predominantly expressed in the Malpighian tubules. The transcripts of these GSTs (except CpGSTe1) were co-expressed following exposure to LD10 of λ-cyhalothrin for 3 h. Recombinant CpGSTd4, CpGSTe2, and CpGSTe3 proteins expressed in Escherichia coli displayed glutathione-conjugating activity toward 1-chloro-2,4-dinitrobenzene. In addition, λ-cyhalothrin could inhibit the activity of recombinant CpGSTd4, CpGSTe2, and CpGSTe3 enzymes, but only recombinant CpGSTe3 showed λ-cyhalothrin metabolic capacity, with 21.88 ± 1.09% of parental compound being depleted within 1 h. Conclusion These data show that CpGSTe3 is a third GST gene, encoding an enzyme that metabolizes λ-cyhalothrin in C. pomonella. © 2019 Society of Chemical Industry.

In accordance with Article 6 of Regulation (EC) No 396/2005, the applicant Syngenta Agro GmbH submitted a request to the competent national authority in Germany to modify the existing maximum residue level (MRL) for the active substance lambda‐cyhalothrin in seed and fruit spices. The data submitted in support of the request were found to be sufficient to derive MRL proposals in seed spices and in fruit spices. Since the general data gap related to toxicity of degradation products formed under sterilisation conditions and identified in the framework of the MRL review has not yet been addressed, a risk management decision is required whether it is appropriate to take over the proposed MRLs in the MRL legislation. Adequate analytical enforcement methods are available to control the residues of lambda‐cyhalothrin in the commodities under consideration. Based on the risk assessment results, EFSA concluded that the short‐term and long‐term intake of residues resulting from the use of lambda‐cyhalothrin on spices according to the reported agricultural practice is unlikely to present a risk to consumer health. However, the consumer exposure calculation shall be considered provisional, pending the toxicological assessment of the compounds formed under sterilisation conditions.

Background Pesticide is an important agricultural necessity to control plant diseases and pests, ensuring safe production of food. However, the low efficacy, large dosage and high-frequency use of conventional pesticide formulation seriously induced food safety and ecological environment issues. In this research, lambda-cyhalothrin solid nanodispersion (LCSND) was developed by a self-dispersing method. Results The mean particle size of the lambda-cyhalothrin solid nanodispersion was 32.7 ± 1.1 nm. It exhibited excellent dispersibility, wettability and stability, especially the improved bioavailability compared to the commercial formulations. Notably, the solid nanodisperison had a small particle size and large specific surface area. The solid nanodispersion without organic solvents can minimize the environment pollution and overcome the instability characteristic of the liquid formulations. Conclusion Therefore, lambda-cyhalothrin solid nanodispersion has broad application prospects in agricultural production and environmental protection. © 2018 Society of Chemical Industry.

In this study, a sensitive and fast procedure of ultrasonic-assisted dispersive liquid-liquid microextraction (UADLLME) coupled with gas chromatography-tandem mass spectrometry (GC-MS/MS) for the determination of major pyrethroid pesticides (permethrin, tetramethrin, bifenthrin, fenvalerate, flucythrinate, fluvalinate, fenpropathrin, deltamethrin, and cyhalothrin) in blood samples was developed. Response surface methodology (RSM) combined with Box-Behnken design (BBD) and ANOVA function was used to optimize key factors affecting the extraction efficiency of UADLLME procedure. Target compounds were analyzed by GC-MS/MS. Under the optimal conditions, good linearity (R2 >0.99) was achieved for all the analytes in the concentration range of 0.5 to 100 μg L-1 . The recoveries for spiked samples at 3 concentration levels were between 70.2 and 91.8%, with relative standard deviations (RSD) lower than 10%. Very low limits of detection (LODs) and limits of quantification (LOQs) ranging from 0.01 to 0.1 μg L-1 and from 0.03 to 0.3 μg L-1 were achieved. This method was successfully applied to the determination of low concentration of pyrethroids in blood samples from real forensic cases. High sensitivity, fast determination, simplicity in operation, small sample volume, and low usage of organic solvents are the advantages of this method. This methodology is of important value for sensitive and quick determination of residue pesticides and metabolites, study of residue pesticides behavior in human body, as well as application in real forensic cases.

In accordance with Article 6 of Regulation (EC) No 396/2005, the applicant Syngenta Crop Protection AG submitted a request to the competent national authority in Greece to modify the existing maximum residue levels (MRLs) for lambda‐cyhalothrin in celeries, fennel and rice. The data submitted in support of the request were found to be sufficient to derive tentative MRL proposals for the concerned crops. They are tentative as formally the general data gap identified in the MRL review for further investigations of the toxicological properties of the compounds formed under sterilisation conditions has not yet been addressed. Adequate analytical enforcement methods are available to control the residues of lambda‐cyhalothrin in the commodities under consideration. Based on the risk assessment results, EFSA concluded that the short‐term and long‐term intake of residues resulting from the uses of lambda‐cyhalothrin according to the reported agricultural practices is unlikely to present a risk to consumer health. The consumer risk assessment presented might need to be reconsidered in the light of the confirmatory data requested following the renewal of the approval and the review of the existing MRLs.

In this study, the molecular interactions between pepsin and three pyrethroid insecticides, including fenvalerate, cyhalothrin and deltamethrin, were investigated by multi-spectroscopic and molecular docking methods under mimic physiological pH conditions. The results indicated that all of these insecticides could interact with pepsin to form insecticide-pepsin complexes. The binding constants, number of binding sites and thermodynamic parameters measured at different temperatures indicated that these three pyrethroid insecticides could spontaneously bind with pepsin mainly through electrostatic forces and hydrophobic interactions with one binding site. According to the theory of Foster's non-radioactive energy transfer, the distance (r) between pepsin and three pyrethroid insecticides were all found to be less than 7 nm, which implied that the energy transfer occurred between pepsin and these insecticides, leading to the quenching of pepsin fluorescence. Synchronous and three-dimensional fluorescence, CD spectra and molecular docking results indicated that all tested pyrethroid insecticides bound directly into the enzyme cavity site and the binding of insecticides into the cavity influenced the microenvironment of the pepsin activity site which resulted in the extension of peptide strands of pepsin with loss of α-helix structures.Copyright © 2016 John Wiley & Sons, Ltd.

Heat shock cognate protein 70 (Hsc70) is a very important stress-resistance protein of insects against environmental stresses. We employed fluorescent real-time quantitative polymerase chain reaction and Western-blot techniques to analyze the transcriptional and translational expression profiles of AlHSC70 under extreme temperature (4°C and 40°C) or 4 pesticide stresses in Apolygus lucorum. The results showed that the expression of AlHSC70 were significantly induced by cyhalothrin or extremely high temperature (40°C) in both transcriptional and translational levels (P < 0.05), while the transcriptional and translational level of AlHSC70 decreased significantly in treatments of chlorpyrifos or extreme cold temperature (4°C) (P < 0.05). Moreover, after Apolygus lucorum treated by imidacloprid or emamectin benzoate, the expression of AlHSC70 was only up-regulated significantly at the transcriptional level (P < 0.05), although obviously up-regulated at the translational level of AlHSC70. Therefore, this study confirmed that the Alhsc70 gene played important roles in response to both temperature and pesticide stresses, especially for cyhalothrin or extremely high temperature (40°C). In addition, the significant polynomial regression correlations between temperature and the Alhsc70 expression level were shown in all the nymph and adult stages (P < 0.01), indicating temperature was an important factor to affect the relative expression of Alhsc70.

BACKGROUND Pyrethroids are one of the most widespread and commonly used classes of insecticide and are used in multiple roles, including protecting potato crops from virus vector aphids. Resistance in some genotypes of a few species is now widespread, but most species remain susceptible. The rate of virus transmission by two genotypes of the peach potato aphid, Myzus persicae, fed on potato virus Y (PVY)-infected leaves of potato treated with the pyrethroid λ-cyhalothrin was evaluated. RESULTS The susceptible genotype, type J, was significantly inhibited from transmitting virus to uninfected seedlings. A genotype containing the M918L super knockdown resistance mutation conferring resistance to pyrethroids, type O, showed no inhibition of transmission. However, when survival of the aphids after exposure was compared, the pyrethroid had not killed the type J aphids. CONCLUSIONS λ-Cyhalothrin in a commercial formulation disrupts PVY transmission by disorienting aphid vectors for a sufficient time for the virus to lose its transmissibility. However, M. persicae genotypes carrying the M918L mutation are not prevented from transmitting. © 2014 Society of Chemical Industry

BACKGROUND: The withdrawal of malathion in the European Union in 2009 resulted in a large increase in lambda-cyhalothrin applications for the control of the Mediterranean fruit fly, Ceratitis capitata, in Spanish citrus crops. RESULTS: Spanish field populations of C. capitata have developed resistance to lambda-cyhalothrin (6–14-fold), achieving LC50 values (129–287 ppm) higher than the recommended concentration for field treatments (125 ppm). These results contrast with the high susceptibility to lambda-cyhalothrin found in three Tunisian field populations. We have studied the mechanism of resistance in the laboratory-selected resistant strain W-1K�� (205-fold resistance). Bioassays with synergists showed that resistance was almost completely suppressed by the P450 inhibitor PBO. The study of the expression of 53 P450 genes belonging to the CYP4, CYP6, CYP9 and CYP12 families in C. capitata revealed that CYP6A51 was overexpressed (13–18-fold) in the resistant strain. The W-1K�� strain also showed high levels of cross-resistance to etofenprox (240-fold) and deltamethrin (150-fold). CONCLUSION: Field-evolved resistance to lambda-cyhalothrin has been found in C. capitata. Metabolic resistance mediated by P450 appears to be the main resistance mechanism in the resistant strain W-1K�� . The levels of cross-resistance found may compromise the effectiveness of other pyrethroids for the control of this species. © 2014 Society of Chemical Industry Supporting information may be found in the online version of this article.

In compliance with Article 43 of Regulation (EC) No 396/2005, the European Food Safety Authority (EFSA) received from the European Commission a mandate to provide its reasoned opinion on the existing maximum residue levels (MRLs) for lambda‐cyhalothrin which might lead to consumers intake concerns on the basis of the new toxicological reference values for gamma‐cyhalothrin and of the data currently available to EFSA for lambda‐cyhalothrin. In order to identify the MRLs of potential concern that require a more detailed assessment, EFSA performed a conservative risk assessment screening taking into account the crops for which MRLs were proposed in the framework of the Article 12 and the Article 43 of Regulation (EC) No 396/2005 reflecting the use of lambda‐cyhalothrin and the new toxicological reference values for gamma‐cyhalothrin.

The Cache Slough complex is an area of tidal sloughs in the Sacramento–San Joaquin River Delta of California (USA), and is surrounding by irrigated agricultural lands. Among the species of concern in the area is the delta smelt (Hypomesus transpacificus), a federally listed threatened species. Releases of the organophosphate insecticide chlorpyrifos and pyrethroid insecticides were examined to determine whether they represented a threat to the copepods on which delta smelt feed (Eurytemora affinis and Pseudodiaptomus forbesi) and to aquatic life in general, represented by the standard testing organism, Hyalella azteca. There was a single incident of toxicity to H. azteca as a result of discharge of agricultural irrigation water containing chlorpyrifos. Pyrethroids were not found in samples collected during the dry season. Following rain events, however, the waters of western Cache Slough repeatedly became toxic to H. azteca because of the pyrethroids bifenthrin and cyhalothrin. The 96‐h median lethal concentrations (LC50s) for E. affinis and P. forbesi for the pyrethroids bifenthrin and cyhalothrin were 16.7 ng/L to 19.4 ng/L when tested at 20 °C. However, their LC50s may be 5 mg/L to 10 ng/L at in situ temperatures of the Cache Slough, comparable to the peak bifenthrin concentration observed. The dominant pyrethroid source appeared to be urban runoff entering a creek 21 km upstream of Cache Slough. Pyrethroids of urban origin were supplemented by agricultural inputs of pyrethroids and chlorpyrifos as the creek flowed toward Cache Slough. Environ Toxicol Chem 2014;33:920–929. © 2014 SETAC

The authors investigated whether and how 2 environmental factors could influence the toxicity of a pyrethroid to 2 representatives of an important group of soil organisms. The impacts of different temperatures (20 °C and 26 °C) and soil moisture levels (30%, 50%, and 70% of water holding capacity) were investigated in combination with the insecticide λ-cyhalothrin on the reproduction success of Folsomia candida and Sinella curviseta in a full factorial design. Testing was based on the standard collembolan reproduction test (Organisation for Economic Co-operation and Development, guideline 232) following an effect concentration design. The results showed an effect of environmental and chemical factors on the number of juveniles of these animals. Particularly in dry soil, the reproduction of both species was reduced, while higher soil moisture levels influenced the number of juveniles positively compared with the middle soil moisture level. In general, however, higher soil moisture led to increased sensitivity to λ-cyhalothrin. In both organisms, temperature affected the toxicity of the pesticide but in different directions: high temperature led to higher toxicity in F. candida but to lower toxicity in S. curviseta.

The present study examined the acute neurotoxic effects of three different pyrethroids, allethrin, cyhalothrin, and deltamethrin on the release of serotonin (5-HT) and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the striatum of conscious rats using microdialysis. Allethrin 10 mg/kg reduced extracellular levels of 5-HT to 46%, whereas 20 and 60 mg/kg increased the release to 177% and 243% of baseline, respectively. Cyhalothrin increased 5-HT release to 145–204% and deltamethrin decreased to 58–32% of baseline in a dose-dependent manner. None of the pyrethroids tested altered extracellular levels of 5-HIAA. Local infusion of the voltage-gated sodium channel antagonist tetrodotoxin (TTX) into striatum completely prevented the effects of allethrin, cyhalothrin, and deltamethrin (10 and 20 mg/kg) on 5-HT release. The effect of deltamethrin at 60 mg/kg was completely abolished by striatal infusion of nimodipine (L-type Ca++ channel antagonist) with TTX. These findings suggest that pyrethroids disrupt the serotonergic neurotransmission in striatum in a dose-related manner with Na+ and Ca2+ channel-dependent mechanisms. © 2012 Wiley Periodicals, Inc. J BiochemMol Toxicol 27:150-156, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.21450

1 The present study assessed the fitness of a lambda-cyhalothrin-resistant population of Eriopis connexa (Germar) with respect to development, reproduction, survival under prey scarcity and prey consumption. 2 Nontreated resistant females (R0) and females recovered after the topical application of 0.05, 0.10 and 0.25 mg active ingredient/mL of lambda-cyhalothrin (R0.05, R0.10 and R0.25) produced, on average, 50% less eggs than susceptible females (S0), irrespective of the applied dose. All of the other traits evaluated remained similar. With respect to developmental characteristics, the larval viability and weight of adult male R0.25 progeny were statistically lower compared with the R0 and S0 progenies. Prey scarcity between days 3 and 13 of adulthood did not affect R0 and R0.25 survival, although egg production was significantly lower for R0 females, followed by R0.25 females, compared with S0 females. 3 The mean consumption of cotton aphids Aphis gossypii Glover over 5 consecutive days was significantly higher for S0, followed by R0 and R0.25, up to day 3 of observation. However, after day 4, prey consumption was similar among the three populations. 4 The results obtained in the present study show that resistant females have a lower reproductive output than susceptible females and that this is not related to the knockdown effect; however, the costs of recovering from knockdown interfere with the survival of offspring and also slightly with prey consumption. Thus, we conclude that the lambda-cyhalothrin-resistant E. connexa population exhibits an egg production disadvantage relative to the susceptible population and that this is increased when the population is subjected to prey scarcity.

Lambda-cyhalothrin (LCT) is a widely used broad-spectrum pyrethroid insecticide. Oral LCT administration to adult male mice at 3 doses (0.2, 0.4, and 0.8 mg/kg/day) for 6 weeks caused a significant reduction in the weight of the seminal vesicles. The epididymal sperm count was lower in mice that received at the highest dose than in control mice. However, the proportions of live and motile spermatozoa were reduced at both the medium and the high doses compared with control mice. All doses induced an increase in the number of morphologically abnormal spermatozoa. Histopathological observations of the testes, liver, kidneys, and spleen showed dose-related degenerative damage in LCT-treated mice. The results indicate that LCT has reproductive toxicity, hepatotoxicity, nephrotoxicity, and splenotoxicity in male mice at the tested doses. © 2012 Wiley Periodicals, Inc. Environ Toxicol 29: 750-762, 2014.

γ-Cyhalothrin is a single isomer, synthetic pyrethroid insecticide. This material was originally developed and marketed by Pytech Chemicals, a joint venture between Dow AgroSciences and Cheminova A/S. Cheminova A/S now wholly owns Pytech Chemical. As a part of registration studies, there was a need for a stable isotope of γ-cyhalothrin to serve as an internal standard. This paper will discuss the 11-step synthesis that was used to prepare an M + 7 stable isotope of γ-cyhalothrin by utilizing triethyl phosphonoacetate-d2 and acetone-d6 to incorporate deuterium into the molecule. In the end, the diastereomers were separated by preparative reverse-phase HPLC to give γ-cyhalothrin-d7 in an overall yield of 6%. Copyright © 2012 John Wiley & Sons, Ltd.

Liriomyza trifolii is an important pest of vegetables and ornamental crops around the world. This pest is attacked by many parasitoid species. The principal management tactic used against L. trifolii is insecticide application. Insecticides vary in their effects on parasitoid species and insecticides that have less harmful effects should be preferred for the control of this pest. In this study, novaluron, abamectin, λ-cyhalothrin and spinetoram were investigated for their lethal effects on adults of Neochrysocharis formosa and Ganaspidium nigrimanus, two important parasitoids of L. trifolii. Three different bioassays were used on adult parasitoids: direct insecticide application, insecticide intake and insecticide residue. Adult parasitoid response to novaluron exhibited the least lethal effects among the bioassays and insecticides tested. Abamectin had significant mortality to both parasitoid species in the direct application and insecticide intake bioassays and mortality were high for G. nigrimanus in the residue bioassay. Spinetoram was the most harmful insecticide to the adult parasitoids in all three bioassays. λ-cyhalothrin effects varied between the two parasitoids. In the direct application, it was harmful to G. nigrimanus and had no effect on N. formosa. In the insecticide intake bioassay λ-cyhalothrin had no effect in survival of either species, and in the residue bioassay it reduced parasitoid survival of both species. Potential tolerance of N. formosa to λ-cyhalothrin is discussed.

Pyrethroid insecticide use in California, USA, is growing, and there is a need to understand the fate of these compounds in the environment. Concentrations and toxicity were assessed in streambed sediment of the San Joaquin Valley of California, one of the most productive agricultural regions of the United States. Concentrations were also measured in the suspended sediment associated with irrigation or storm-water runoff, and mass loads during storms were calculated. Western valley streambed sediments were frequently toxic to the amphipod, Hyalella azteca, with most of the toxicity attributable to bifenthrin and cyhalothrin. Up to 100% mortality was observed in some locations with concentrations of some pyrethroids up to 20 ng/g. The western San Joaquin Valley streams are mostly small watersheds with clay soils, and sediment-laden irrigation runoff transports pyrethroid insecticides throughout the growing season. In contrast, eastern tributaries and the San Joaquin River had low bed sediment concentrations (

The susceptibility of members of the Anopheles sinensis Group in Korea to insecticides was evaluated under laboratory conditions using 15 insecticides currently used by local public health centers in Korea. The insecticides included eight pyrethroids, six organophosphates and a pyrazol analogue. Based on their LC50 values, the order of susceptibility of An. sinensis larvae to the insecticides was bifenthrin, chlorfenapyr, α-cypermethrin and λ-cyhalothrin, with values of 0.009, 0.04, 0.06 and 0.08 p.p.m., respectively. The least susceptibility was obtained with fenitrothion, with an LC50 of 7.7 p.p.m. In the comparative resistance test, the resistance ratios (RR) of 14 insecticides were compared to each other using two strains of members of the An. sinensis Group collected in the locality in 2001 and 2008. Anopheles spp. demonstrated higher RR to organophosphates such as fenthion, and low RR for the pyrethroids. Among the organophosphates, fenthion had the highest RR of 33.3 and 270.0 fold differences for LC50 and LC90 values, respectively. Among the pyrethroids, permethrin was observed to have the highest RR of 3.8 and 1.8 fold differences for LC50 and LC90 values, respectively. However, there were no significant differences in susceptibility to chlorfenapyr, chlorpyrifos, deltamethrin and fenitrothion. An. sinensis s. l. was more susceptible to the six insecticides bifenthrin, λ-cyhalothrin, α-cypermethrin, cypermethrin, cyfluthrin and pyridafenthion, showing 0.03, 0.06, 0.3, 0.3, 0.4 and 0.4 fold differences in resistance rates (RR LC50), respectively.

The principal goal of this work was to develop an efficient method for the simultaneous determination of four pyrethroid (PYR) insecticides, cyfluthrin, cyhalothrin, cypermethrin, and deltamethrin, in porcine muscle and pasteurized milk using liquid-liquid extraction (LLE). Sample extraction was carried out with and without additional column cleanup procedures, and the final determination was made using GC with electron-capture detector (ECD). The pesticide identity was confirmed using GC-MS in the SIM mode. Since there were minor differences between the extraction procedures, extraction without the additional cleanup procedure was used throughout the work. The method was validated by fortifying blank samples with half, two, and four times the maximum residue limit (MRL) of each PYR. The average recoveries (n = 6) ranged from 83.5 to 99.2% and 82.9 to 109% in porcine muscle and pasteurized milk, respectively. The repeatability of measurements expressed as RSDs, was in the range of 1.7-11.9 and 1.5-10.3% in porcine muscle and pasteurized milk, respectively. The LODs ranged from 3.3 to 9 and 3 to 8.1 ppm, whereas the LOQs ranged from 10 to 27.4 and 9 to 24.6 ppm, in porcine muscle and pasteurized milk, respectively. The applicability of the method was demonstrated by analyzing real samples collected from major cities in the Republic of Korea. No residues of the selected pesticides were detected in any of the samples.

Pertussis toxin (PTX) inhibits the activation of the α-subunit of the inhibitory heterotrimeric G-proteins (Gαi./o) and modulates voltage-gated sodium channels, which may be one of the primary targets of pyrethroids. To investigate the potential mechanisms of agricultural pests resistance to pyrethroid insecticides, we examined the modulations by PTX on sodium channels in the central neurons of the 3rd—4th instar larvae of cyhalothrin-resistant (Cy-R) and cyhalothrin-susceptible (Cy-S) Helicoverpa armigera by the whole-cell patch-clamp technique. The isolated neurons were cultured for 12—16 h in an improved L15 insect culture medium with or without PTX (400 ng/mL). The results showed that both the Cy-R and Cy-S sodium channels exhibited fast kinetics and tetrodotoxin (TTX) sensitivity. The Cy-R sodium channels exhibited not only altered gating properties, including a 8.88-mV right shift in voltage-dependent activation (V0.5act) and a 6.54-mV right shift in voltage-dependent inactivation (V0.5inact), but also a reduced peak in sodium channel density (Idensity) (55.2% of that in Cy-S neurons). Cy-R sodium channels also showed low excitability, as evidenced by right shift of activation potential (Vacti) by 5—10 mV and peak potential (Vpeak) by 20 mV. PTX exerted significant effects on Cy-S sodium channels, reducing sodium channel density by 70.04%, right shifting V0.5act by 14.41 mV and V0.5inact by 9. 38 mV. It did not cause any significant changes of the parameters mentioned above in the Cy-R sodium channels. The activation time (Tpeak) from latency to peak at peak voltage and the fast inactivation time constant (τinact) in both Cy-S and Cy-R neurons were not affected. The results suggest that cotton bollworm resistant to pyrethroid insecticides involves not only mutations and allosteric alterations of voltage-gated sodium channels, but also might implicate perturbation of PTX-sensitive Gαi./o-coupled signaling transduction pathways.

γ-Cyhalothrin (1a), (S)-cyano(3-phenoxyphenyl)methyl (1R,3R)-3-[(1Z)-2-chloro-3,3,3-trifluoro-1-propenyl]-2,2-dimethylcyclopropanecarboxylate, is a single-isomer, synthetic pyrethroid insecticide marketed by Pytech Chemicals GmbH, a joint venture between Dow AgroSciences and Cheminova A/S. As a part of the registration process there was a need to incorporate a carbon-14 label into the cyclopropyl ring of this molecule. A high yielding radiochemical synthesis of γ-cyhalothrin was developed from readily available carbon-14 labeled N-t-Boc protected glycine. This seven step synthesis, followed by a preparative normal phase HPLC separation of diastereomers, provided 21.8 mCi of γ-cyhalothrin-1-14C (1b) with >98% radiochemical purity. Copyright © 2007 John Wiley & Sons, Ltd.

The response of the large pine weevil ( Hylobius abietis ) to the pesticide lambda-cyhalothrin, a pyrethroid, is investigated. Both behavioural (feeding prefer- ences) and nutritional and physiological (lipid content) responses are recorded. Hylobius abietis shows both a significant avoidance of pesticide-treated food sources and a decrease in lipid content after exposure, but a full recovery after feeding on untreated food. It is proposed that the mechanism for the pesticide avoidance and altered lipid levels is due to an anti-feedant effect of the pesticide. Implications for pest management programmes are described.

The effects of cyhalothrin on the transient outward potassium current in central neurons of Helicoverpa armigera were studied by using the patch clamp techniques. The results showed that before using cyhalothrin (10−5 mmol/L), activation potential was approximately -40 mV, after application of the drug, the activation potential shifted roughly 10 mV to the negative potential direction, so channels can be activated more easily. Before and after cyhalothrin application, the change of current amplitude was insignificant. The value of V1/2 and k of activation curves did not change significantly, however, the V1/2 of the inactivation curves changed significantly. Inactivation curves significantly shifted to a negative direction, so that inactivation of the channels was hastened. It is indicated that there may exit a primary way in which cyhalothrin provides neurotoxicity to the nervous system through the regulation of activation potentials and inactivation state of IA channels.

Residues of the pesticides chlorpyrifos, dimethoate, cyhalothrin, cypermethrin, fenvalerate, deltamethrin and chlorothalonil in the autumn Chinese cabbage (Brassica chinensis L.) were studied using gas chromatography. The results indicated that the residues were dependent on the frequency and rate of pesticide application and on the weather conditions immediately following spraying. When the Chinese cabbages were treated once at normal rates, the half-lives of the seven pesticides in the vegetable were 4.7, 5.3, 2.9, 3.5, 5.4, 4.3 and 4.0 days respectively. Thus, based on the recommended preharvest intervals, the residual levels of all pesticides were within the national standards. When the Chinese cabbages were treated four times at maximal rates at 5 day intervals, the half-lives of chlorpyrifos, cypermethrin and chlorothalonil in the vegetable were 3.6, 2.9 and 5.9 days respectively, so that, based on the recommended preharvest intervals, the residual levels of chlorpyrifos and chlorothalonil exceeded the national standards for pollution-free vegetables, but the residual level of cypermethrin was within the national standard. Effects of rain on pesticide final residues in plants treated four times were more significant than in those treated once.

The relativecontribution of oxidasesand esterasesto pyrethroidresistance was studiedin a YS-FPstrainof Helicoverpaarmigerafrom China.The YS-FPstrainwas derivedfrom a field-collectedstrain (YS) by 16 generationsof selectionwith a mixtureof fenvalerateand phoxim.Compared with theYS strain,the YS-FPstrain showed 1850- to >7140-foldresistance to fourester-bondedphenoxybenzyl alcohol pyrethroids (fenvalerate, deltamethrin, cypermeth- rinand cyhalothrin), >205-fold resistance toa non-esterphenoxybenzyl alcohol pyrethroid (etofenprox) and only 19-foldresistance toan ester-bondedmethylated biphenyl alcohol pyrethroid (bifenthrin). Theoxidase inhibitor piperonylbutoxide eliminated most of theresistance tofenvalerate, deltamethrin, cypermethrin, cyhalothrin and etofenprox,whereas the esteraseinhibitor S,S,S -tributylphosphorothioatehad a smallsynergisticeffect forfenvalerate andcyhalothrinonly. Thissuggeststhat theresistanceto thesepyrethroidsin theYS-FPstrainwasmainlybecause of enhancedoxidative detoxification. The monooxygenaseactivities of themidgutsof sixth-instarlarvae of theYS-FP strainto substratesp-nitroanisole, ethoxycoumarin andmethoxycoumarin were3.7-, 4.7- and 10-fold, respectively, comparedwith that of theYS strain.Glutathione S-transferase activity and esterase activity were not significantly alteredin the YS-FPstrain.Thisconfirmsthatenhancedoxidativedetoxification was a majormechanismcontributing to pyrethroidresistance in theYS-FPstrain. Key words: Helicoverpa armigera, esterases, glutathione S-transferases, oxidases, pyrethroids, resistance

Outdoor experimental channels were used to study the behavioral changes of stream macroinvertebrates exposed to a pulse of the pyrethroid insecticide lambda-cyhalothrin. The primary end point was the number of macroinvertebrates drifting, but the mobility of macroinvertebrates caught in the drift also was assessed. A specified number of two insect species, Baetis rhodani and Leuctra fusca/digitata, and of the amphipod Gammarus pulex were introduced into small replicated subsections of the experimental channels. Macroinvertebrates were allowed to acclimatize for 26 h prior to a 60-min pulsed exposure to lambda-cyhalothrin. Measurement was initiated 2 h before pesticide application and continued for the following 24 h. Pulse concentrations of lambda-cyhalothrin of 0.001, 0.01, 0.1, and 1.0 microg L(-1) were applied, and each experiment was replicated 8 times. All three species responded to the pesticide pulse with catastrophic drift. The 0.001 microg L(-1) treatment caused a significant increase in the drift of Gammarus, whereas the drift response threshold was 0.01 microg L(-1) for the two insect species. Drift response onset followed the applied pulse concentration, with the highest concentrations resulting in more individuals of all species entering drift at an early stage. The majority of individuals caught in drift samples during low concentrations showed no change in mobility. At the two highest concentrations, however, both Baetis and Leuctra were in the process of being immobilized, with Leuctra the more sensitive of the two. In contrast, only a few of the Gammarus individuals caught showed changes in mobility after the high-concentration treatments. The present study shows that lambda-cyhalothrin is a potential hazard for macroinvertebrate populations in headwater streams. The clear species-specific responses indicate that sublethal doses have the potential to change the macroinvertebrate community structure.

In laboratory, greenhouse and field tests, we determined the effects of combining full rates of the defoliants tribufos and thidiazuron and the herbicide thifensulfuron-methyl with half rates of the insecticides lambda-cyhalothrin or azinphos-methyl, and the combination of tribufos and thidiazuron, both in half rates, on mortality of the boll weevil, Anthonomus grandis grandis Boheman and on the quality of defoliation. Tribufos, 0.47kgha −1 and tribufos, 0.235kgha −1 + thidiazuron, 0.125kgha −1 exhibited a slightly toxic effect to boll weevil, while tribufos, 0.47kgha −1 + lambda − cyhalothrin, 0.019kgha −1 ,t ribufos, 0.47kgha −1 + azinphos − methyl, 0.14kgha −1 , and tribufos, 0.235kgha −1 + thidiazuron, 0.125kgha −1 + azinphos − methyl, 0.14kgha −1 , provided control of boll weevil as good as or better than full-rate azinphos-methyl or lambda-cyhalothrin alone owing to synergistic effects. Thidiazuron or thifensulfuron-methyl alone or in combination with insecticides did not affect boll weevil mortality. Treatment with tribufos + thidiazuron, both at half rate, significantly increased defoliation compared to full rates of tribufos or thidiazuron alone, and provided adequate defoliation for approximately the same cost per hectare. Published in 2004 for SCI by John Wiley & Sons, Ltd.

Use of the insecticide lambda-cyhalothrin in agriculture may result in the contamination of water bodies, for example by spray drift. Therefore, the possible exposure of aquatic organisms to this insecticide needs to be evaluated. The exposure of the organisms may be reduced by the strong sorption of the insecticide to organic materials and its susceptibility to hydrolysis at the high pH values in the natural range. In experiments done in May and August, formulated lambda-cyhalothrin was mixed with the water body of enclosures in experimental ditches containing a bottom layer and macrophytes (at different densities) or phytoplankton. Concentrations of lambda-cyhalothrin in the water body and in the sediment layer, and contents in the plant compartment, were measured by gas-liquid chromatography at various times up to 1 week after application. Various water quality parameters were also measured. Concentrations of lambda-cyhalothrin decreased rapidly in the water column: 1 day after application, 24-40% of the dose remained in the water, and by 3 days it had declined to 1.8-6.5%. At the highest plant density, lambda-cyhalothrin residue in the plant compartment reached a maximum of 50% of the dose after 1 day; at intermediate and low plant densities, this maximum was only 3-11% of the dose (after 1-2 days). The percentage of the insecticide in the ditch sediment was 12% or less of the dose and tended to be lower at higher plant densities. Alkaline hydrolysis in the water near the surface of macrophytes and phytoplankton is considered to be the main dissipation process for lambda-cyhalothrin.

In many parasitoid species, the recognition of chemical signals is essential to find specific hosts. This function is often impaired by exposure to insecticides that are usually neurotoxic. The behaviour of the Hymenopterous parasitoid Aphidius ervi (Haliday) (Hymenoptera:Aphidiinae) after surviving low doses of the pyrethroid lambda-cyhalothrin was examined in laboratory conditions. The host aphid was Myzus persicae (Sulzer) (Homoptera:Aphididae) on oilseed rape. Parasitoid females were exposed by contact with dry residues of the active ingredient at a lethal dose, LD20, and a sub-lethal dose, LD0.1. In a four-armed olfactometer, untreated and inexperienced females were attracted by the odour of M persicae-infested plants and previous oviposition experience increased the duration of the attraction response. The response of inexperienced females decreased after an exposure to LD0.1 but not to LD20. No effect was observed when females had an oviposition experience prior to the olfactometer test. The oviposition activity was significantly decreased in the LD20-treated group but not in the LD0.1-treated one. All effects disappeared within 24 h. Our work shows that orientation and oviposition behaviours may be impaired by low doses of lambda-cyhalothrin, depending on the dose, the parasitoid experience and the type of behaviour. Copyright © 2004 Society of Chemical Industry

The application aspects of chemicals which attract the forest cockchafer, Melolontha hippocastani F., were investigated in field and laboratory experiments. Previous studies have shown that males of M. hippocastani are attracted by a synthetic mixture of green leaf volatiles (GLV) and the sex pheromone 1,4-benzoquinone (BQ), that synergistically enhances the male response to GLV. In the present study, we demonstrated that BQ also synergised the male response to one single component of the GLV mixture, the leaf alcohol (Z)-3-hexen-1-ol (Z-3-ol). BQ enhanced the attractiveness of Z-3-ol at doses between 0.05 and 5 mg per trap, reaching a maximum at 5 × 10−1 mg day−1. The addition of an insecticide (cyhalothrin) to traps baited with BQ and Z-3-ol did not affect the lures’ attractiveness. However, when a conidiospore formulation of the entomopathogenic fungus Beauveria brongniartii (Saccardo) Petch was added, the attractiveness of baited traps was significantly reduced. Furthermore, two types of dispensers baited with a solution of BQ in Z-3-ol at 20 mg ml−1 were tested over the entire 4-week flight season. Both a membrane dispenser and a dispenser based on a porous polyethylene (PPE) absorbent disk attracted more males than controls over the entire 4 weeks. The membrane dispenser attracted as many males each week as a reference formulation that was renewed daily. Furthermore, the membrane dispenser attracted more males than the PPE dispenser in weeks 2–4, although laboratory experiments showed that the latter released even higher or at least equal amounts of the joined lure over the entire 4 weeks. However, estimation of the BQ/Z-3-ol ratios of the released material by solid phase microextraction (SPME) and coupled gas chromatography–mass spectrometry (GC-MS) revealed that the membrane dispenser released a higher proportion of BQ than the PPE dispenser in weeks 2–4. Therefore, a higher BQ/Z-3-ol ratio might be responsible for the advantage of the membrane dispenser in the field.

In this paper, we reported the differences in susceptibility to insecticides between adults and larvae of housefly, Musca domestica (L.), and the mechanisms for the differences. The larvae of housefly were much more tolerant to insecticides than the adults, and the tolerance ratio to cyhalothrin was as high as 205.5 for susceptible strain. Mechanism studies showed that higher GST activity was associated with higher insecticide tolerance in the larvae. The co-toxicity coefficient of the mixture of cyhalothrin and methylene dithiocyanate(4:1) on pyrehid-resistant houseflies was 188.

The genetic inheritance of resistance to cyhalothrin in housefly, Musca domstica (L) was investigated. Reciprocal crosses between susceptible (S) and resistant (R) strains were used to determine the characteristics of resistance. Analysis of probit line from the F1 generation and F2 generation obtained by inbreeding the F1 hybrids indicated that cyhalothrin resistance was controlled by more than one factors and degree of resistance dominance to cyhalothrin was -0.10, indicating cyhalothrin resistance is conferred by incompletely recessive gene(s). The realized heritability of resistance to cyhalothrin cyhalothrin calculated from data collected routinely from laboratory selection was 0.12.

The effects of the insecticide lambda-cyhalothrin (Karate) on non-target arthropods in winter wheat were studied throughout two successive seasons in 1998 and 1999. The study particularly focussed on the crop in the growing season after insecticide application (also winter wheat) for detection of potential long-term effects and for determination of the suitability of different sampling methods. The investigations were based on the assumption that arthropod immigration from surrounding areas is limited in large fields. For this reason a simple approach seemed to be feasible. Two plots of equal size (10 ha, adjusted to each other) were defined in a 100 ha field and designated control and treatment plots. Ten sampling points were established on each plot. The following monitoring methods were utilised: visual counting, sweep netting and pitfall trapping. In the first year of investigation, countings and catches were carried out 2 days prior to insecticide application and 2, 16, 30 and 44 days after application. In the next year, they were carried out 365 days and 384 days after insecticide application in the successive crop of winter wheat. At the time of the first sampling prior to insecticide application, the two plots showed significant differences with respect to arthropod density or activity, particularly in visual counting and to a minor degree to sweep netting and pitfall trapping. Lower densities or activities were observed in the plot reserved for treatment. Measures for mathematical equalisation of the results of population densities before pesticide treatment should be considered. After insecticide application, the densities or activities of non-target arthropods decreased, particularly in visual counting and sweep netting. After one year, these effects disappeared to a large extent. Several groups of arthropods reached even higher levels in the treated plot than in the untreated one. The pitfall traps revealed weak activity-decreasing effects in carabids and spiders in the treated plot, but the opposite tendency for staphylinids. Hence, it seems that the conditions in a large field are less homogeneous, and that smaller scale conditions can support processes of recovery in non-target populations.

Preliminary risk characterisation for the pyrethroid insecticide lambda-cyhalothrin identifies potential concerns for fish and aquatic invertebrates. Here we describe additional ecotoxicological studies for lambda-cyhalothrin generated to refine the aquatic risk assessment. These include tests conducted under more realistic exposure conditions (i.e. accounting for the rapid adsorption of lambda-cyhalothrin to sediments), studies on sediment toxicity and bioavailability, tests on a range of fish and invertebrate species in order to characterise sensitivity distributions, and field studies which have examined effects on invertebrate communities and fish populations under semi-natural conditions. Fish are generally less sensitive to lambda-cyhalothrin than are aquatic invertebrates, and fish species tend to be similar to each other in their sensitivities. Adsorption of lambda-cyhalothrin reduces exposure and hence the apparent toxicity of the compound to fish, and under field conditions no adverse effects on fish have been observed even at concentrations approaching the water solubility. For aquatic invertebrates, there is a wider range of sensitivities, with the Crustacea and Insecta predictably being the more sensitive taxa. Again, adsorption reduces the exposure of the chemical, and under field conditions no ecologically adverse effects have been observed at concentrations of c.0·02 μg litre−1. © 1998 Society of Chemical Industry

To study the impact of residual pyrethroid insecticide on the abundance and distribution of peridomestic Lutzomyia longipalpis, the sandfly vector of visceral leishmaniasis in Brazil, lambda-cyhalothrin was applied at 20 mg a.i.m-2 in the following interventions: (i) spraying of all animal pens in a village (blanket coverage); (ii) treatment of a subset of animal pens, either by spraying, or by installation of insecticide-impregnated 1 m2 cotton sheets as ‘targets’ (focal coverage). By sampling with CDC light traps, and using a novel analytical approach, we detected a 90% reduction in Lu. longipalpis abundance in sprayed sheds of the focal intervention. However, there was no discernible effect on the abundance of other phlebotomines trapped in sheds, or on the abundance of Lu. longipalpis in untreated dining-huts and houses. This differential impact on Ludongipalpis abundance is explained in terms of the disruption of male pheromone production. Treated targets were approximately half as effective as residual spraying in reducing the abundance of Lu.longipalpis in sheds. Following blanket intervention, the abundance of Lu.longipalpis in traps fell by only 45% (not significant): catches at untreated dining-huts actually increased, possibly because the blanket coverage diverted Lu. longipalpis away from major aggregation sites at animal pens. It is recommended that care be taken during vector control programmes to ensure that all potential aggregation sites are treated. The possible consequences of leaving some sites untreated include poor control of peridomestic sandfly abundance and an increase in the biting rate on dogs and humans.

Pyrethroids are widely used insecticides, but minimal information has been published on their presence in municipal wastewater in the United States. Pyrethroids in wastewater from the Sacramento, California, USA, area consisted of permethrin, bifenthrin, cypermethrin, and cyhalothrin, with a combined concentration of 200 ng/L to 500 ng/L. Sampling within the wastewater collection system leading to the treatment plant suggested pyrethroids did not originate primarily from urban runoff, but could be from any of several drain disposal practices. Wastewater from residential areas was similar in pyrethroid composition and concentration to that from the larger metropolitan area as a whole. Secondary treatment removed approximately 90% of pyrethroids, but those remaining exceeded concentrations acutely toxic to sensitive species. Toxicity to the amphipod, Hyalella azteca, was consistently evident in the final effluent. The large river into which this particular plant discharged provided sufficient dilution such that pyrethroids were undetected in the river, and there was only slight toxicity of unknown cause in 1 river sample, but effects in receiving waters elsewhere will be site-specific. Environ Toxicol Chem 2013;32:2460–2468. © 2013 SETAC

Insecticidal dipping fluid emulsions, mixed in vitro in dam water containing suspended clay particles and 1% w/v zinc sulphate, were analysed to determine rates of settling of diazinon, cyhalothrin and cypermethrin. Fifteen minutes after mixing, the concentration of the insecticides 5 cm below the surface had declined by 72.5%, 72.8% and 89.4%, respectively. On remixing, the concentration of insecticide in suspension was close to or greater than the initial concentration. In 2 trials, lice were eradicated from sheep showered with dip wash mixed in cloudy dam water to which 1% w/v of zinc sulphate was added. In 12 flock treatments in which 1000 to 2000 sheep were dipped with added zinc sulphate, the concentration of insecticide remained above the minimum lethal for susceptible strains of lice. However, lice were still present 6 months later in 8 of these flocks. When zinc sulphate is added to dip wash, agitation is needed to maintain the insecticide in suspension.

The interactions of the synthetic pyrethroid, lambda-cyhalothrin and malathion were studied with purines, pyrimidines, caffeine and some other related nitrogenous compounds in resistant and susceptible strains of Tribolium castaneum (Herbst.) The results were compared with those obtained with a known synergist, piperonyl butoxide (PBO) and precocene I. Adenine, cytosine, guanine, thymine and uracil synergised lambda-cyhalothrin, especially in the susceptible strain, with maximum effect at a 1:1 mass ratio, with the effect decreasing with increasing proportion of the heterocycle. The order of synergism of lambda-cyhalothrin was; precocene I>PBO>the nitrogenous compounds, in both resistant and susceptible strains. On the other hand, caffeine (lethal effect increased about twice), barbital (about twice), isobarbituric acid (less than twice) and bromacil (up to eight times) synergised malathion in malathion-resistant strains and antagonised in the susceptible strains. Total in-vivo esterases, carboxylesterases and cytochrome P 450 of susceptible and resistant strains showed significantly increased activity or content when treated with either insecticide plus a heterocyclic compound. Exceptions were with bromacil and malathion and for the malathion-specific strain, Kano-C with malathion and the N-heterocycles

Synthetic pyrethroid (SP) resistance has developed in Australian field populations of the sheep body louse, Bovicola (Damalinia) ovis. Laboratory bioassays were used to measure the susceptibility of lice to cypermethrin and the other registered SPs. Results of these bioassays indicated resistance to cypermethrin, deltamethrin, cyhalothrin and alphacypermethrin. So far, high-level resistance has been diagnosed in only a few strains. The toxicological responses of these strains were clearly separated from those of the majority of louse strains tested. Furthermore, these strains had survived immersion in commercial SP dips. The level of resistance described in some strains was sufficient to cause pour-on products to fail despite the fact that the LC50s of these strains fell within the normal range of field responses.

Piperonyl butoxide (PBO) synergised the synthetic pyrethroids (SPs) cypermethrin, deltamethrin, cyhalothrin and alpha-cypermethrin in a concentration-dependent manner in susceptible and both low-and high-SP-resistant strains of the sheep body louse Bovicola ovis. Synergism ratios as high as 23 x were recorded when 200 mg/L PBO was mixed with deltamethrin in bioassays with the highly resistant Hartley strain. High PBO synergism implicates mono-oxygenase detoxification of SPs as a major cause of SP resistance in B. ovis. the possibility of mixing PBO with existing SP lousicide products to control pyrethroid resistant lice is discussed.

SUMMARY Lice were found in samples of baled wool from 198 of 464 flocks treated to eliminate an Infestation in the period July 1988 to June 1990. In 287 flocks the Insecticide was applied as a backline treatment and in 177 flocks a shower dip was used. Of these flocks, 41.5% and 44.6%, respectively, were found to be infested at the following shearing. After adjusting for the accuracy of the test, It was estimated that infestation in 2 consecutive 12-month periods occurred in 52.6% of flocks with a real incidence rate of 27.4%. Using these estimates, it was calculated that in 34.7% of infested flocks treatment did not kill all lice. There were no differences in the proportion of consecutive infestations between flocks treated with any of the 3 chemicals applied as backline treatments. Among flocks treated In a shower dip, 68.4% using coumaphos, 37.8% using diazlnon and 41.5% using cyhalothrin had consecutive Infestations (P < 0.05). The detection of lice in 63.2% of flocks that were treated with magnesium fluosilicate was, in part, attributed to the application of this chemical by one operator.

The persistence patterns of three synthetic pyrethroids—fenvalerate, tau-fluvalinate, lambda-cyhalothrin—and an organophosphorus insecticide, monocrotophos, on eggplant (Solanum melongena L.) have been evaluated. The extractable residues ranged from 0.05 to 0.45, 0.01 to 0.40, 0.003 to 0.09 and 0.09 to 0.32 μg g−1 for fenvalerate, tau-fluvalinate, lambda-cyhalothrin and monocrotophos, respectively. Fenvalerate was the most persistent among the four, followed by monocrotophos, lambda-cyhalothrin and tau-fluvalinate. The Maximum Residue Limit (MRL) of these pesticides on S. melongena has not yet been documented. The present data may be useful for establishing MRL and assessing the amount of pesticide residues in this vegetable.

Simulation modelling was undertaken to investigate the likely practical benefits of more persistent formulations of a synthetic pyrethroid for control of Heliothis sp. on cotton. A model was built describing mortality to first-instar Heliothis larvae on cotton during the period following a spray application and used to evaluate the influence of formulation type on persistence of effect. The product used in the study was lambda-cyhalothrin. Data for the model were gathered principally from published and unpublished reports. Two parameters were used to describe a formulation; the half-life of the biologically active residue, and the toxicity relative to a standard formulation. To achieve a 50% increase in persistence of effect, defined as days' mortality above 50%. it was necessary to treble the values of both parameters. Persistence of effect was more sensitive to the way in which larvae were distributed over the plant than to the growth rate of the plant but the relative increase in persistence of effect from improved formulation was robust to changes in larval distribution and plant growth.

This paper describes the development of methods suitable for the sampling and analysis of the pyrethroid insecticides lambda-cyhalothrin and cypermethrin in natural waters. A solid-phase water-sampling method which avoids the requirement for transport and storage of large volumes of water is described. This method is shown to be capable of extracting trace levels (ng litre−-1) of the title compounds from natural waters with efficiencies of at least 80%. Chromatographic analysis of processed samples by gas chromatography–electron capture detection enables determination of residues at levels of 1–2 ng litre−-1 in water.

The pyrethroid insecticide lambda-cyhalothrin was evaluated in field trials against Glossina f.fuscipes and sleeping sickness transmission in Iyolwa sub-county, Tororo District, Uganda. The insecticide was applied selectively to the resting-sites of tsetse, by bush-spraying, using 10% wettable powder (10WP) formulation at an application rate of 11.6 g a.i./ha over an area of 28 km2, or by a 2% Electrodyn formulation (2ED) applied at 0.9 g a.i./ha over 30 km2. In a third trial area of 32 km2, 215 pyramidal traps treated with lambda-cyhalothrin 100 mg/m2 were set. The best impact was obtained with 10WP lambda-cyhalothrin which eliminated tsetse within 1-2 months, whereas G.f.fuscipes persisted at very low density in part of the area treated with 2ED lambda-cyhalothrin. In both treated areas the numbers of human sleeping sickness cases fell to no more than one per month, compared with four to twelve per month previously. The overall rate of cattle trypanosomiasis (T.brucei and T.vivax) was also reduced slightly. Insecticide-treated traps remained fully effective for at least 6 months under field conditions and catches were reduced 20-90-fold. These results in the control of tsetse and trypanosomiasis transmission lead us to recommend lambda-cyhalothrin for tsetse control operations.

The effects of dissolved organic carbon (DOC) in the form of Aldrich humic acid on the accumulation and acute toxicities of three synthetic pyrethroids — fenvalerate, deltamethrin, and cyhalothrin—to Daphnia magna in laboratory experiments were investigated. Concentrations of DOC as low as 2.6 mg/L, 3.2 mg/L, and 3.1 mg/L for deltamethrin, fenvalerate, and cyhalothrin, respectively, resulted in a significant decrease in bioaccumulation. Acute toxicities of all three pyrethroids were found to decrease as DOC concentrations increased; e.g., at a DOC concentration of 15.5 mg/L, the acute toxicity of fenvalerate was reduced by a factor of 17. The percentages of deltamethrin and fenvalerate bound to DOC increased as DOC concentrations increased after 2-h and 24-h contact times. At low concentrations of DOC (e.g., 1.7 mg/L), as much as 40% of fenvalerate and 20% of deltamethrin were found sorbed to the dissolved material. After 24-h contact times, 76.4 and 80.8% of fenvalerate and deltamethrin, respectively, were bound to DOC. Reverse-phase partition coefficients (Krp) for both fenvalerate and deltamethrin were found to vary with DOC concentrations and were in the range 1.0 to 4.8 × 105 L/kg for fenvalerate and 0.9 to 5.6 × 105 L/kg for deltamethrin.