Insecticidal anthranilic diamides: a new class of potent ryanodine receptor activators

Synthesis and insecticidal activities of 2,3-dihydroquinazolin-4(1H)-one derivatives targeting calcium channel

A series of compounds containing dihydroquinazolinone moiety was designed and synthesized. Amine bridge part was changed in comparison with known anthranilic diamides insecticides. Their insecticidal activities against oriental armyworm (Mythimna separata) indicated that most of the compounds showed moderate to high activities at the tested concentrations. In particular, compounds 5a and 5k showed 80% larvicidal activities against oriental armyworm at the concentration of 5mg/L. The present study also explored the possible effects of target compounds on the high voltage-gated calcium channel and the calcium channels in the endoplasmic reticulum in the central neurons isolated from the third instar larvae of Spodoptera exigua using whole-cell patch clamp and calcium imaging technique. The results showed that compound 5a activated the high voltage-gated calcium channel in the central neurons of S. exigua weakly. The peak currents only increased by 6% of the initial value at the end of the 10-min recording after treated with 0.22μM 5a, while chlorantraniliprole has an opposite effect. The effects of 5a on the intracellular calcium ion concentration ([Ca(2+)]i) in neurons were well investigated. The experimental results indicated that these novel compounds have different mechanism compared with chlorantraniliprole.

Toxicity of insecticides to populations of tomato borer Tuta absoluta (Meyrick) from Greece

BACKGROUND

Tuta absoluta (Meyrick), in only a few years, has become a serious threat to global tomato production. Depending on the cropping system and infestation pressure, T. absoluta control may rely heavily on insecticide applications. By means of a validated IRAC bioassay method, the toxicity of all insecticides registered for T. absoluta control in Greece has been estimated. A non-registered pyrethroid insecticide was also included in this study.

RESULTS

Low heterogeneity was detected in the populations tested with most insecticides. The LC50 ranged from 0.31 to 1.31 mg L(-1) for flubendiamide, from 0.12 to 0.53 mg L(-1) for chlorantraniliprole, from 0.03 to 0.12 mg L(-1) for emamectin benzoate, from 0.08 to 0.26 mg L(-1) for spinosad, from 31.8 to 159.5 mg L(-1) for metaflumizone, from 1.73 to 17.5 mg L(-1) for indoxacarb, from 530 to 2038 mg L(-1) for chlorpyriphos and finally from 475 to 794 mg L(-1) for cypermethrin. The variability of the LC50 values among the tested populations was low (RR under 5×), except for indoxacarb (RR = 10×). In the absence of a reference strain, comparisons with the recommended label rates were performed. Evidence of potential control failures was detected using probit analysis estimates for cypermethrin, chlorpyriphos and metaflumizone.

CONCLUSIONS

For most registered insecticides, a solid set of baseline data has been presented that can be used in future resistance monitoring studies. The interaction of metaflumizone with T. absoluta has been discussed, and for chlorpyriphos it is suspected that the resistance level is underestimated with the present dataset. Finally, it has been demonstrated that the pyrethroid cypermethrin would provide insufficient control of the pest.

Synthesis, insecticidal activities, and SAR studies of novel pyridylpyrazole acid derivatives based on amide bridge modification of anthranilic diamide insecticides

Anthranilic diamides are one of the most important classes of modern agricultural insecticides. To discover new structure-modified compounds with high activity, series of novel carbonyl thioureas, carbonyl ureas, oxadiazoles, carbonyl thiophosphorylureas, oxadiazole-containing amides, and thiazoline-containing amides were designed through the modification of the amide bridge based on the structure of chlorantraniliprole and were synthesized, and bioassays were carried out. The compounds were characterized and confirmed by melting point, IR, (1)H NMR, and elemental analyses or HRMS. Preliminary bioassays indicated that some compounds exhibited significant insecticidal activities against oriental armyworm, diamondback moth, beet armyworm, corn borer, and mosquito. Among them, trifluoroethoxyl-containing carbonyl thiourea 20a showed best larvicidal activity against oriental armyworm, with LC50 and LC95 values of 0.1812 and 0.7767 mg/L, respectively. Meanwhile, 20c and 20e showed 86 and 57% death rates against diamondback moth at 0.005 mg/L, and the LC50 values of the two compounds were 0.0017 and 0.0023 mg/L, respectively, which were lower than that of the control chlorantraniliprole. The relationship between structure and insecticidal activity was discussed, and the HF calculation results indicated that the carbonyl thiourea moiety plays an important role in the insecticidal activity. The present work demonstrated that the trifluoroethoxyl-containing carbonyl thioureas can be used as lead compounds for further development of novel insecticides.

Characterisation of field-evolved resistance to chlorantraniliprole in the diamondback moth, Plutella xylostella, from China

BACKGROUND

Chlorantraniliprole and flubendiamide belong to the new chemical class of diamide insecticides. High levels of resistance to chlorantraniliprole rapidly evolved in field populations of Plutella xylostella from southern China. An investigation was made of diamide cross-resistance, as well as inheritance, stability and metabolic mechanisms of chlorantraniliprole resistance in field populations of P. xylostella from southern China.

RESULTS

Three field populations of P. xylostella collected from southern China in 2011 showed high levels of cross-resistance between chlorantraniliprole (18-1150-fold) and flubendiamide (15-800-fold) when compared with a susceptible reference strain. Genetic analysis showed that chlorantraniliprole resistance in the ZC population was autosomal and incompletely recessive. In the absence of selection pressure, resistance to chlorantraniliprole in the ZC population declined from 2040-fold (G1 ) to 25-fold (G7 ). The ZC-R strain (derived by selection from ZC) exhibited 670-fold resistance to chlorantraniliprole, which is synergised by known metabolic inhibitors such as PBO, DEM and DEF at low levels.

CONCLUSION

Field-evolved resistance to chlorantraniliprole in P. xylostella confers strong cross-resistance to flubendiamide, so both compounds should be well separated and not alternated in resistance management strategies. High-level resistance to chlorantraniliprole in the ZC population was incompletely recessive and not stable. Metabolic detoxification was involved in chlorantraniliprole resistance in the ZC-R strain to some extent, but target-site resistance could not be excluded. © 2012 Society of Chemical Industry.

Nicotinic acetylcholine receptors: a comparison of the nAChRs of Caenorhabditis elegans and parasitic nematodes

Nicotinic acetylcholine receptors (nAChRs) play a key role in the normal physiology of nematodes and provide an established target site for anthelmintics. The free-living nematode, Caenorhabditis elegans, has a large number of nAChR subunit genes in its genome and so provides an experimental model for testing novel anthelmintics which act at these sites. However, many parasitic nematodes lack specific genes present in C. elegans, and so care is required in extrapolating from studies using C. elegans to the situation in other nematodes. In this review the properties of C. elegans nAChRs are reviewed and compared to those of parasitic nematodes. This forms the basis for a discussion of the possible subunit composition of nAChRs from different species of parasitic nematodes. Currently our knowledge on this is largely based on studies using heterologous expression and pharmacological analysis of receptor subunits in Xenopus laevis oocytes. It is concluded that more information is required regarding the subunit composition and pharmacology of endogenous nAChRs in parasitic nematodes.

The story of a new insecticidal chemistry class: the diamides

This paper describes the story of the invention of the diamides, a novel chemical class of insecticides. It starts with the pioneering work by Nihon Nohyaku researchers, who developed a herbicide lead with weak insecticidal activity to flubendiamide, a highly potent lepidoptericide. The journey continues with Nissan's isoxazolines and the invention of the anthranilamides by DuPont, culminating in the discovery of the blockbuster chlorantraniliprole and its analogue cyantraniliprole. The next steps are Syngenta's sulfoximines and bicyclic anthranilamides, Ishihara Sangyo Kaisha's cyclopropylamides, Sumitomo's hydrazides, Bayer's pyrazoles and tetrazoles, BASF's sulfoximines and more recent contributions from Chinese agrochemical companies and academic institutions. The diamides affect calcium homeostasis by binding to ryanodine receptors and releasing calcium from the intracellular stores. Investigations at Nihon Nohyaku, DuPont and Bayer on the action of the diamides on ryanodine receptors will be briefly reported.

2-Amino-N,3-dimethylbenzamide

In the title compound, C₉H₁₂N₂O, the mean plane through the amide group and the benzene ring form a dihedral angle of 33.93 (7)°. An intra­molecular N—H⋯O hydrogen bond is present. In the crystal, mol­ecules are linked by N—H⋯N and N—H⋯O hydrogen bonds, forming double-stranded chains parallel to the b axis.

Synthesis and bioactivity study of 2-acylamino-substituted N'-benzylbenzohydrazide derivatives

The discovery of new safe and effective pesticides is one of the main means of providing eco-friendly agricultural agents for modern crop protection. To identify new biological molecules based of the anthranilic diamide skeleton of the novel pesticide chlorantraniliprole, which acts on the ryanodine receptor and functional groups in acyl hydrazine insect growth regulators, more than 40 new compounds of 2-acylamino-substituted N'-benzylbenzohydrazide derivatives were designed and synthesized. The structures of the new compounds were characterized using (1)H nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), or electron impact mass spectrometry (EI-MS), and their biological activities at a concentration of 600 mg L(-1) were determined against cotton aphid (Aphis gossypii Glover), carmine spider mite (Tetranychus cinnabarinus), and diamondback moth (Plutella xylostella). The results of a preliminary assay showed that compounds 6a-I-2 and 6d-III-4 maintained the lethal activity of anthranilic diamide against P. xylostella; compounds 6c-II-4, 6d-I-7, 6d-II-1, and 6d-III-5 exhibited good lethal activity against A. gossypii; and compounds 6a-II-1, 6a-III-1, 6b-I-7, 6c-I-1, and 6c-III-5 retained promising larvicidal activities against T. cinnabarinus. In subsequent further tests against T. cinnabarinus, compounds 6a-II-1, 6a-III-1, 6c-I-1, and 6c-III-5 showed an LC(50) value of <90 mg L(-1); especially, the LC(50) of compound 6a-III-1 was only 27.9 mg L(-1). In conclusion, the introduction of the functional fragment-substituted acyl hydrazine improved the acaricidal activity of the anthranilic diamide skeleton, and the halogen atom at X position and the methyl group at R(1) play crucial roles in the biological activities of the compounds.

Determination of residual flubendiamide in the cabbage by QuEChERS-liquid chromatography-tandem mass spectrometry

Flubendiamide, which belongs to the new chemical class of phthalic acid diamides, is widely used against lepidopteron pests in a variety of vegetable and rice pests. It provides superior plant protection against a broad range of economically important lepidopterous pests, including Spodoptera exigua and Plutella xylostella. A determination method of flubendiamide in the cabbage was established in this paper. Flubendiamide in the cabbage was extracted with acetonitrile and ultrasonic extraction, and was purified by QuEChERS and analyzed by LC-MS/MS (liquid chromatography-tandem mass spectrometry). The results indicated that the average recovery of flubendiamide in the cabbage was 81.27%-91.45%, the coefficient of variation was 1.79%-4.81%, and the lowest detection concentration was 0.3 μg/kg. The extraction of flubendiamide from the cabbage and its analysis was in accordance with the pesticide residue criterion, i.e., simple, rapid, accurate, reproducible, stable, separatory, and convenient. It identifies and quantifies trace-level flubendiamide residues in the cabbage extracts using LC-MS/MS in the ESI negative mode coupled with the QuEChERS method.

Synthesis, crystal structure and biological activity of novel anthranilic diamide insecticide containing alkyl ether group

In searching for environmentally benign insecticides with high activity, low toxicity and low residue, two series of novel anthranilic diamide containing methyl ether and isopropyl ether group were designed and synthesized. All of the compounds were characterized by (1)H NMR spectroscopy, (13)C NMR spectroscopy and elemental analysis. The single crystal structure of 19j was determined by X-ray diffraction. The insecticidal activities of the new compounds were evaluated. The results showed that some compounds exhibited excellent insecticidal activities against Lepidoptera pests. Among this series, compound, 18l showed 100 % larvicidal activity against Mythimna separate Walker, Plutella xylostella Linnaeus and Laphygma exigua Hubner at the test concentration, which was equal to the available chlorantraniliprole.

Modulation of the expression of ryanodine receptor mRNA from Plutella xylostella as a result of diamide insecticide application

Ryanodine receptors (RyRs), members of the largest family of calcium channel proteins, have been studied because of their key roles in calcium signalling within cells. With the development of diamide insecticides that exhibit a novel mode of action on the RyRs from Lepidoptera, research on insect RyRs has become more attractive in the field of plant protection. To enhance our understanding of the effects of diamides on RyRs, we cloned the Plutella xylostella RyR gene (Px-RyR), which is the most serious pest of Brassicaceae plants throughout the world. Furthermore, we investigated the modulation of the expression of Px-RyR as a result of the application of diamide insecticides. The full-length cDNAs of Px-RyR contain an open reading frame (ORF) of 15,372bp with a predicted protein consisting of 5123 amino acids. Px-RyR possesses a high level of overall amino acid homology with other isoforms (77-92% identity with insect isoforms and 45-47% identity with vertebrate isoforms). The weight of Px. gradually decreased as the concentration of the diamides increased. However, the relative expression levels of the RyRs from larvae were dependent on the insecticide concentration and gradually increased with increasing insecticide concentrations.

Effect of biochar amendment on the bioavailability of pesticide chlorantraniliprole in soil to earthworm

To evaluate the effect of biochar amendment on the bioavailability of chlorantraniliprole (CAP) in soils with different physico-chemical properties, the uptake of CAP from various soils by earthworms was studied. It was observed that the biochar amendment of the soils affected the sorption of CAP, but the magnitude of the sorption enhancement by biochar amendment among the soils was varied, presumably due to the attenuation of the sorptivity of the biochar when amended in the soil. The amendment with biochars leads to a decrease in the bioavailability of CAP in the soils to earthworms, and more prominent for biochar BC850 amendment. In the soil with a CAP concentration of 10 mg kg(-1), the residue of CAP in the earthworm tissues was found to be 9.65 mg kg(-1), in comparison with that the CAP residue was 4.05 mg kg(-1) in BC450 amended soil and 0.59 mg kg(-1) in BC850, respectively. The degree of bioavailability reduction by same level of biochar amendment was different among soils with different properties. The results demonstrate that the properties of soils are important to performance of biochar in soil.

Synthesis, structure and insecticidal activities of some novel amides containing N-pyridylpyrazole moeities

In our search for environmentally benign insecticides with high activity, low toxicity and low residue, a novel series of amides containing N- pyridylpyrazole moieties were designed and synthesized. The structures of the title compounds were characterized and confirmed by 1H-NMR and elemental analysis. Furthermore, the structure of compound 7l was determined by single crystal X-ray diffraction. The preliminary bioassay tests showed that some of them exhibited good insecticidal activities against Mythimna separata Walker, Plutella xylostella (Linnaeus, 1758) and Laphygma exigua Hübner.

Synthesis and insecticidal activities of novel anthranilic diamides containing acylthiourea and acylurea

Two series of anthranilic diamides containing acylthiourea and acylurea linkers were designed and synthesized, with changed length and flexibility of the linkers to compare to known anthranilic diamide insecticides. In total, 26 novel compounds were synthesized, and all compounds were characterized by (1)H nuclear magnetic resonance and high-resolution mass spectrometry. Their insecticidal activities against oriental armyworm (Mythimna separata), mosquito larvae (Culex pipiens pallens), and diamondback moth (Plutella xylostella) were evaluated. The larvicidal activities against oriental armyworm indicated that the introduction of acylthiourea into some structures could retain their insecticidal activity; 8 of the 15 compounds (13a-13e, 14a-14e, and 15a-15e) exhibited 100% larvicidal activity at 10 mg/L. However, the introduction of acylurea decreased the insecticidal activity; only 3 of the 11 compounds (17a-17k) exhibited 100% larvicidal activity at 200 mg/L. The whole-cell patch-clamp technique indicated that compound 13b and chlorantraniliprole exhibited similar effects on the voltage-gated calcium channel. The calcium-imaging technique was also applied to investigate the effects of compounds 13b and 15a on the intracellular calcium ion concentration ([Ca(2+)](i)), which indicated that they released stored calcium ions from endoplasmic reticulum. Experimental results denoted that several new compounds are potential activators of the insect ryanodine receptor (RyR).

Residual toxicity and sublethal effects of chlorantraniliprole on Plutella xylostella (lepidoptera: plutellidae)

BACKGROUND

The diamondback moth (DBM), Plutella xylostella (L.), is the most important pest of cruciferous vegetables in the world. Chlorantraniliprole is a novel anthranilic diamide insecticide registered for the control of lepidopteran pests. The dose response, residual toxicity and sublethal effects of chlorantraniliprole applied for 48 h at LC₁₀ (0.02 mg L(-1) ) and LC₂₅ (0.06 mg L(-1) ) on P. xylostella were investigated.

RESULTS

Leaf-dip bioassays showed that chlorantraniliprole had a high level of toxicity against larvae of P. xylostella, and the 48 h LC₅₀ values were 0.23 and 0.25 mg L(-1) for a susceptible and field strain respectively. Chlorantraniliprole also had a long-lasting effect when the larvae were exposed to chlorantraniliprole field sprayed on radish seedlings. Sublethal effects of chlorantraniliprole were indicated by reduced pupation, pupal weight and adult emergence rates. There was also an increase in the duration of female preoviposition period, decreased fecundity and egg hatch and decreased survival rates of the offspring. The mean values of the net reproductive rate (R₀), intrinsic rate of increase (r(m)), finite rate of increase (λ) were significantly lower in the treatment than in control groups.

CONCLUSIONS

These results indicate that chlorantraniliprole is effective against P. xylostella. The sublethal concentrations of chlorantraniliprole may reduce the population growth of P. xylostella by decreasing its survival and reproduction, and by delaying its development.

Molecular characterization of a ryanodine receptor gene in the rice leaffolder, Cnaphalocrocis medinalis (Guenée)

Ryanodine receptors (RyRs) are the targets of two novel classes of synthetic insecticidal chemicals, phthalic acid diamides and anthranilic diamides. Isolation of full-length RyR cDNAs is a critical step towards the structural and functional characterization of insect RyRs and an understanding of the molecular mechanisms underlying the species selective toxicity of diamide insecticides. However, there has been little research on the insect RyR genes due to the high molecular weight of the RyR proteins. In this study, we isolated a full-length RyR cDNA (named as CmRyR) from Cnaphalocrocis medinalis, an important rice pest throughout Southeast Asia. The composite CmRyR gene contains an ORF of 15264 bp encoding a protein of 5087 amino acid residues, which shares 79% overall identity with its Drosophila melanogaster homologue. All hallmarks of the RyR proteins are conserved in the CmRyR protein, suggesting that CmRyR is a structural and functional analogue of known RyRs. A multiple sequence alignment illustrates that the insect RyRs share high levels of amino acid sequence identity at the the COOH-terminal region. However, the amino acid residues analogous to the CmRyR residues N⁴⁹²², N⁴⁹²⁴, N⁴⁹³⁵, L⁴⁹⁵⁰, L⁴⁹⁸¹, N⁵⁰¹³ and T⁵⁰⁶⁴ are unique to lepidopteran RyRs compared with non-lepidopteran insect RyRs. This finding suggests that these residues may be involved in the differences in channel properties between lepidopteran and non-lepidopteran insect RyRs and in the species selective toxicity of diamide insecticides. Furthermore, two alternative splicing sites were identified in the CmRyR gene, one of which was located in the central part of the predicted second SPRY domain. Diagnostic PCR showed that the inclusion frequencies of two mutually exclusive exons (a/b) and one optional exon (c) differed between developmental stages or adult anatomical regions. Our results imply that alternative splicing may be a major means of generating functional diversity in C. medinalis RyR channel.

Design, synthesis and insecticidal activities of novel pyrazole amides containing hydrazone substructures

BACKGROUND

Pyrazole and hydrazone derivatives possess good insecticidal activities; their substructural units are widely used in pesticide design. In an effort to discover new molecules with good insecticidal activities, a series of pyrazole amide derivatives containing hydrazone substructures were synthesised and bioassayed.

RESULTS

Bioassays demonstrated that some of the title compounds exhibited notable control of Plutella xylostella (Linnaeus), Helicoverpa armigera (Hübner), Culex pipiens pallens, Laphygma exigua (Hübner), Spodoptera litura (Fabricius), Nilaparvata lugens (Stål) and Rhopalosiphum maidis (Fitch) at 5, 10, 0.25, 200, 20, 100 and 500 mg L(-1) respectively. Comparative molecular field analysis (CoMFA) based on the bioactivities for P. xylostella was studied; the values of q(2) and r(2) for the CoMFA model were 0.701 and 0.964 respectively.

CONCLUSION

Some of the title compounds displayed good and broad-spectrum insecticidal activities against different insect species; the CoMFA model revealed that a bulky and negatively charged group at the 4-position of benzene could enhance insecticidal activity. These results could provide useful information for the design of novel insecticide containing substructural units of pyrazole amide and hydrazone.

Non-nucleoside inhibitors of the measles virus RNA-dependent RNA polymerase: synthesis, structure-activity relationships, and pharmacokinetics

The measles virus (MeV), a member of the paramyxovirus family, is an important cause of pediatric morbidity and mortality worldwide. In an effort to provide therapeutic treatments for improved measles management, we previously identified a small, non-nucleoside organic inhibitor of the viral RNA-dependent RNA polymerase by means of high-throughput screening. Subsequent structure-activity relationship (SAR) studies around the corresponding pyrazole carboxamide scaffold led to the discovery of 2 (AS-136a), a first generation lead with low nanomolar potency against life MeV and attractive physical properties suitable for development. However, its poor water solubility and low oral bioavailability (F) in rat suggested that the lead could benefit from further SAR studies to improve the biophysical characteristics of the compound. Optimization of in vitro potency and aqueous solubility led to the discovery of 2o (ERDRP-00519), a potent inhibitor of MeV (EC(50) = 60 nM) with an aqueous solubility of approximately 60 μg/mL. The agent shows a 10-fold exposure (AUC/C(max)) increase in the rat model relative to 2, displays near dose proportionality in the range of 10-50 mg/kg, and exhibits good oral bioavailability (F = 39%). The significant solubility increase appears linked to the improved oral bioavailability.

Susceptibility of standard clones and European field populations of the green peach aphid, Myzus persicae, and the cotton aphid, Aphis gossypii (Hemiptera: Aphididae), to the novel anthranilic diamide insecticide cyantraniliprole

BACKGROUND

Parthenogenetic clones of the green peach aphid, Myzus persicae (Sulzer), and the cotton aphid, Aphis gossypii Glover, were tested with the anthranilic diamide insecticide cyantraniliprole (i.e. DuPont(™) Cyazypyr(™) ) in systemic-uptake bioassays to investigate potential for cross-resistance conferred by mechanisms of insecticide resistance to organophosphates, carbamates and pyrethroids and, in the case of M. persicae, reduced sensitivity to neonicotinoids. These data were compared with the response of field samples of M. persicae and A. gossypii collected from around Europe.

RESULTS

Cyantraniliprole was not cross-resisted by any of the known insecticide resistance mechanisms present in M. persicae or A. gossypii. The compound was equally active against resistant and susceptible aphid strains. The responses of the M. persicae field samples were very consistent with a maximum response ratio of 2.9 compared with a standard laboratory clone. The responses of the A. gossypii field samples were more variable, although a majority of the responses were not statistically different.

CONCLUSION

Cyantraniliprole is currently the only anthranilic diamide (IRAC MoA 28) insecticide targeting aphid species such as M. persicae and A. gossypii. There is no evidence to suggest that the performance of this compound is affected by commonly occurring mechanisms that confer resistance to other insecticide chemistries. Cyantraniliprole is therefore a valuable tool for managing insecticide resistance in these globally important pests.

Selection for resistance, reversion towards susceptibility and synergism of chlorantraniliprole and spinetoram in obliquebanded leafroller, Choristoneura rosaceana (Lepidoptera: Tortricidae)

BACKGROUND

Obliquebanded leafroller, Choristoneura rosaceana (Harris), is an economic pest of pome fruits throughout North America. Repeated applications of broad-spectrum insecticides have resulted in the development of resistance, cross-resistance and multiple resistance in this pest. Studies were conducted to determine the possibility of resistance evolution, stability of resistance and the effect of metabolic synergists on toxicity of new reduced-risk insecticides chlorantraniliprole and spinetoram in C. rosaceana.

RESULTS

Larvae of C. rosaceana were selected for resistance to chlorantraniliprole and spinetoram in the laboratory. Significant levels of resistance to each insecticide were observed after 12 generations of selection. In the absence of selection pressure, susceptibility of a subset of larvae from both chlorantraniliprole- and spinetoram-selected populations reverted to preselection levels after five and six generations respectively, indicating that resistance to both chlorantraniliprole and spinetoram was unstable in C. rosaceana. In synergist bioassays performed after 12 generations of selection, S,S,S-tributylphosphoro trithioate (DEF) and piperonyl butoxide (PBO) synergized the toxicity of chlorantraniliprole and spinetoram respectively, suggesting the involvement of esterases in chlorantraniliprole resistance and the involvement of mixed-function oxidases in spinetoram resistance.

CONCLUSION

These findings suggest that chlorantraniliprole and spinetoram could be incorporated into C. rosaceana resistance management programs by using rotational strategies.

Baseline susceptibilities of B- and Q-biotype Bemisia tabaci to anthranilic diamides in Arizona

BACKGROUND

Development of pyriproxyfen and neonicotinoid resistance in the B-biotype whitefly and recent introduction of the Q biotype have the potential to threaten current whitefly management programs in Arizona. The possibility of integrating the novel anthranilic diamides chlorantraniliprole and cyantraniliprole into the current program to tackle these threats largely depends on whether these compounds have cross-resistance with pyriproxyfen and neonicotinoids in whiteflies. To address this question, the authors bioassayed a susceptible B-biotype strain, a pyriproxyfen-resistant B-biotype strain, four multiply resistant Q-biotype strains and 16 B-biotype field populations from Arizona with a systemic uptake bioassay developed in the present study.

RESULTS

The magnitude of variations in LC(50) and LC(99) among the B-biotype populations or the Q-biotype strains was less than fivefold and tenfold, respectively, for both chlorantraniliprole and cyantraniliprole. The Q-biotype strains were relatively more tolerant than the B-biotype populations. No correlations were observed between the LC(50) (or LC(99)) values of the two diamides against the B- and Q-biotype populations tested and their survival rates at a discriminating dose of pyriproxyfen or imidacloprid.

CONCLUSION

These results indicate the absence of cross-resistance between the two anthranilic diamides and the currently used neonicotinoids and pyriproxyfen. Future variation in susceptibility of field populations to chlorantraniliprole and cyantraniliprole could be documented according to the baseline susceptibility range of the populations tested in this study.

Assessment of resistance risk in Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) to chlorantraniliprole

BACKGROUND

Beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), is a major pest of numerous cultivated crops. Chlorantraniliprole, the first commercialised ryanodine receptor insecticide from the anthranilic diamide class, has exceptional insecticidal activity on a range of lepidopteran pests. The aim of this study was to assess the resistance of S. exigua to chlorantraniliprole in the laboratory.

RESULTS

A field-collected population of S. exigua was selected after repeated exposure to chlorantraniliprole to determine the risk of resistance evolution. After 22 generations of selection, there was a 12.0-fold increase in LC(50) . The realised heritability (h(2)) of resistance was estimated as 0.1082 by using threshold trait analysis. The projected rate of resistance evolution indicated that, if h(2) = 0.1082 and 70% of the population was killed at each generation, then a tenfold increase in LC(50) would be expected in 21.7 generations for chlorantraniliprole.

CONCLUSION

These results show that the risk of resistance development to chlorantraniliprole exists in S. exigua after continuous application.

Fast extraction and dilution flow injection mass spectrometry method for quantitative chemical residue screening in food

A prototype multiresidue method based on fast extraction and dilution of samples followed by flow injection mass spectrometric analysis is proposed here for high-throughput chemical screening in complex matrices. The method was tested for sulfonylurea herbicides (triflusulfuron methyl, azimsulfuron, chlorimuron ethyl, sulfometuron methyl, chlorsulfuron, and flupyrsulfuron methyl), carbamate insecticides (oxamyl and methomyl), pyrimidine carboxylic acid herbicides (aminocyclopyrachlor and aminocyclopyrachlor methyl), and anthranilic diamide insecticides (chlorantraniliprole and cyantraniliprole). Lemon and pecan were used as representative high-water and low-water content matrices, respectively, and a sample extraction procedure was designed for each commodity type. Matrix-matched external standards were used for calibration, yielding linear responses with correlation coefficients (r) consistently >0.99. The limits of detection (LOD) were estimated to be between 0.01 and 0.03 mg/kg for all analytes, allowing execution of recovery tests with samples fortified at ≥0.05 mg/kg. Average analyte recoveries obtained during method validation for lemon and pecan ranged from 75 to 118% with standard deviations between 3 and 21%. Representative food processed fractions were also tested, that is, soybean oil and corn meal, yielding individual analyte average recoveries ranging from 62 to 114% with standard deviations between 4 and 18%. An intralaboratory blind test was also performed; the method excelled with 0 false positives and 0 false negatives in 240 residue measurements (20 samples × 12 analytes). The daily throughput of the fast extraction and dilution (FED) procedure is estimated at 72 samples/chemist, whereas the flow injection mass spectrometry (FI-MS) throughput could be as high as 4.3 sample injections/min, making very efficient use of mass spectrometers with negligible instrumental analysis time compared to the sample homogenization, preparation, and data processing steps.

Laboratory assays of select candidate insecticides for control of Dendroctonus ponderosae

BACKGROUND

The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae), is the most destructive bark beetle in western North America. Dendroctonus ponderosae can be prevented from successfully colonizing and killing individual trees by ground-based sprays of insecticides applied directly to the tree bole. However, the future availability of several active ingredients, including carbaryl which is most commonly used in the western United States, is uncertain. Two novel insecticides, cyantraniliprole [Cyazypyr(™)-OD (oil dispersion) and Cyazypyr(™)-SC (suspension concentrate)] and chlorantraniliprole (Rynaxypyr(®)), and carbaryl were assayed in both filter paper and topical assays.

RESULTS

Compared with 20,000 mg L(-1) carbaryl (i.e. the maximum label rate for solutions applied to conifers for protection from bark beetle attack in the western United States), cyantraniliprole OD caused similar rates of mortality in D. ponderosae adults at 400-fold weaker concentrations in both bioassays, while cyantraniliprole SC caused similar rates of mortality at 40-fold weaker concentrations. Probit analyses confirmed that D. ponderosae is most sensitive to cyantraniliprole OD, while chlorantraniliprole was effective at concentrations similar to carbaryl.

CONCLUSIONS

These results suggest that lower concentrations of carbaryl have merit for field testing than have been previously considered. While cyantraniliprole and chlorantraniliprole have similar modes of action, cyantraniliprole OD appears to have greater promise for protecting individual trees from mortality attributed to D. ponderosae attack and should be evaluated in field studies.

QuEChERS multiresidue method validation and mass spectrometric assessment for the novel anthranilic diamide insecticides chlorantraniliprole and cyantraniliprole

The gas-phase dissociation reactions of chlorantraniliprole (Rynaxypyr) and cyantraniliprole (Cyazypyr) have been studied in triple-quadrupole, ion trap, and orbitrap mass spectrometers equipped with electrospray and desorption electrospray ion sources, revealing the formation of odd-electron fragment ions, the structures of which were elucidated. The odd-electron fragments were unusually abundant, and their formation is proposed to occur via a tricyclic intermediate. The applicability of the QuEChERS multiresidue method for the quantitation of chlorantraniliprole and cyantraniliprole was also assessed in this study. Four matrices representative of oily, watery, acidic, and dry crop groups were tested, with a targeted limit of quantitation (LOQ) of 0.01 mg/kg. Average recoveries ranged between 87 and 107%, with relative standard deviations (RSD) of ≤ 8%. Linear calibration functions with correlation coefficients r > 0.99 were obtained. The study provides an expansion of the QuEChERS method to include anthranilic diamides and a mass spectrometric assessment for these two novel agrochemical active ingredients.

Synthesis and insecticidal activities of novel anthranilic diamides containing modified N-pyridylpyrazoles

In order to look for novel insecticides targeting the ryanodine receptor, four new series of anthranilic diamides containing modified N-pyridylpyrazoles were designed and synthesized. All of the compounds were characterized and confirmed by (1)H NMR, (13)C NMR, and HRMS. The single crystal structure of 10c was determined by X-ray diffraction. Their insecticidal activities against oriental armyworm (Mythimna separata) and diamondback moth (Plutella xylostella) indicated that most of the compounds showed moderate to high activities at the tested concentration, while compound 19 showed comparable higher activity at the concentration of 0.125 mg/L. The preliminary structure-activity relationship (SAR) was discussed.

Assessment of resistance risk in obliquebanded leafroller (Lepidoptera: Tortricidae) to the reduced-risk insecticides chlorantraniliprole and spinetoram

Obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), is a major pest of pome fruit in Washington. The use of broad-spectrum insecticides for decades has led to the development of insecticide resistance in C. rosaceana. Recently registered insecticides with novel modes of action, such as chlorantraniliprole and spinetoram, have provided effective C. rosaceana control, but resistance remains a threat. The risk of insecticide resistance development in a pest can be assessed by artificial selection in the laboratory. Subsequently, this information can be valuable in developing strategies to retain susceptibility in the field. A laboratory population of C. rosaceana was selected after repeated exposure to chlorantraniliprole and spinetoram to determine the risk of resistance evolution. After six generations of selection, 6.58- and 3.64-fold increases in LC50 were recorded for chlorantraniliprole and spinetoram, respectively. The realized heritability (h2) of resistance was estimated as 0.17 for chlorantraniliprole and 0.18 for spinetoram by using threshold trait analysis. The rates of resistance development were compared using the response quotient (Q), which was estimated as 0.11 and 0.07 for chlorantraniliprole and spinetoram, respectively. Projected rates of resistance evolution indicated that if h2 = 0.2 and 80% of the population was killed at each generation, then a 10-fold increase in LC50 would be expected in less than six generations for chlorantraniliprole and 10 generations for spinetoram. These results indicate that the risk of resistance development in C. rosaceana exists to both of these insecticides but that resistance development in C. rosaceana would be slower against spinetoram than chlorantraniliprole.

Toxicity and residual efficacy of chlorantraniliprole, spinetoram, and emamectin benzoate to obliquebanded leafroller (Lepidoptera: Tortricidae)

Studies were conducted to determine the residual toxicity of spinetoram, chlorantraniliprole, and emamectin benzoate to obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae). Larvae were exposed to apple (Malus spp.) foliage collected at different intervals after an airblast sprayer application at the manufacturer-recommended field rate and half the field rate. A mortality of 100% was recorded at field rate applications of spinetoram, chlorantraniliprole, and emamectin benzoate through 59, 38, and 10 d after treatment (DAT), respectively. Significantly less foliage was consumed by C. rosaceana larvae surviving in the emamectin, chlorantraniliprole, and spinetoram treatments compared with those exposed to untreated foliage. Third-instar C. rosaceana exposed to fresh residues on terminal foliage showed 100% mortality after 5-d exposure to spinetoram residues and after 10-d exposure to chlorantraniliprole and emamectin benzoate. The effects of larval movement from foliage with fresh residues was examined by transferring neonate larvae from foliage treated with spinetoram, chlorantraniliprole, or emamectin benzoate to untreated foliage after various exposure intervals. An exposure of 1, 3, and 6 d was required for spinetoram, chlorantraniliprole, and emamectin benzoate to cause 100% mortality at the field rate, respectively. The higher the concentration of chlorantraniliprole and emamectin benzoate, the less exposure time was necessary to cause high levels of mortality in C. rosaceana neonates. Our results indicate that these novel insecticides are highly toxic to C. rosaceana larvae. Implications of these results for C. rosaceana management programs are discussed.

Baseline susceptibility of the diamondback moth (Lepidoptera: Plutellidae) to chlorantraniliprole in China

Diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), has evolved resistance to various kinds of insecticides in the field. Chlorantraniliprole, which is a new pesticide of the anthranilic diamide group, provides potent and broad-spectrum activity within the insect order Lepidoptera. This insecticide provides a new option for control of P. xylostella populations resistant to other chemicals. The susceptibility of 16 field populations and seven laboratory maintained strains of P. xylostella to chlorantraniliprole were determined through leaf dip bioassay. The susceptibility variation among 16 field populations was low (five-fold), with median lethal concentrations (LC50 values) varying from 0.221 to 1.104 mg/liter. However, wider ranges of variation in LC50 values (10-fold) were observed among seven laboratory strains. Low level tolerance (six- to 10-fold) was detected in two laboratory-selected strains and three field-collected populations when compared with the susceptible Roth strain. A discriminating concentration (15 mg/liter) was calibrated from pooled toxicological data of the 16 field populations, as an important first step in resistance management, for the routine monitoring of resistance in the future. When assessed at the established discriminating dose 15 mg/liter, seven laboratory strains and five field populations showed an average mortality of 99.75% (from 98 to 100%). Synergism assays showed metabolic enzymes might be involved in chlorantraniliprole detoxification in the susceptible Roth strain, but not in the additional observed tolerance of strains selected for resistance with other insecticides.

3D-QSAR studies of insecticidal anthranilic diamides as ryanodine receptor activators using CoMFA, CoMSIA and DISCOtech

To explore the three-dimensional quantitative structure-activity relationships (3D-QSAR) and the pharmacophore model of a new class of potent activators of the anthranilic diamide ryanodine receptor (RyR), comparative molecular field analysis (CoMFA), comparative molecular similarity indices analysis (CoMSIA) and distance comparison technique (DISCOtech) were performed on 38 anthranilic diamides. Successful CoMFA and CoMSIA models yielded "leave-one-out" (LOO) cross-validated correlation coefficient (q(2)) values of 0.785 and 0.788 and non-cross-validated correlation coefficient (r(2)) values of 0.958 and 0.981, respectively. Results were graphically interpreted in terms of field contribution maps. A DISCOtech pharmacophore model containing an aromatic ring center, a hydrophobic ring center, a hydrogen bond-donor and a hydrogen bond-acceptor was constructed. This model indicated that hydrophobic interaction and hydrogen bonds have important roles in the interactions between activators and RyRs, which was consistent with CoMSIA results. The information obtained from CoMFA, CoMSIA and DISCOtech models enabled interpretation of the structure-activity relationships of anthranilic diamides. Based on the constructed models, some vital features for the interaction of anthranilic diamides with RyRs were identified, which may prove helpful in designing more potent RyR activators.

Molecular characterization of flubendiamide sensitivity in the lepidopterous ryanodine receptor Ca(2+) release channel

Flubendiamide is a benzenedicarboxamide derivative that shows selective insecticidal activity against lepidopterous insects. The specific modulatory effects of flubendiamide on ryanodine binding in insect muscle microsomal membranes suggest that the ryanodine receptor (RyR) Ca(2+) release channel is a primary target of flubendiamide. However, the molecular mechanisms underlying the species-specific action of flubendiamide are unclear. We have cloned cDNA encoding a novel RyR from the lepidopterous silkworm RyR (sRyR) and tested the sensitivity to flubendiamide of the recombinant sRyR in HEK293 cells. Confocal localization studies and Ca(2+) imaging techniques revealed that sRyRs form Ca(2+) release channels in the endoplasmic reticulum. Importantly, flubendiamide induced release of Ca(2+) through the sRyR, but not through the rabbit RyR isoforms. Photoaffinity labeling of sRyR deletion mutants using a photoreactive derivative revealed that flubendiamide is mainly incorporated into the transmembrane domain (amino acids 4111-5084) of the sRyR. The rabbit cardiac muscle isoform RyR2 (rRyR2) and the RyR mutant carrying a replacement of the transmembrane domain (residues 4084-5084) with its counterpart sequence from rRyR2 (residues 3936-4968) were not labeled by the photoreactive compound. This replacement in the sRyR significantly impaired the responses to flubendiamide but only marginally reduced the sensitivity to caffeine, a general RyR activator. Furthermore, deletion of the N-terminal sequence (residues 183-290) abolished the responses of the sRyR to flubendiamide but not the sensitivity to caffeine. Our results suggest that the transmembrane domain plays an important role in the formation of an action site for flubendiamide, while the N-terminus is a structural requirement for flubendiamide-induced activation of the sRyR.

Feeding cessation effects of chlorantraniliprole, a new anthranilic diamide insecticide, in comparison with several insecticides in distinct chemical classes and mode-of-action groups

BACKGROUND

Chlorantraniliprole is a novel anthranilic diamide insecticide, efficacious for control of lepidopteran insect pests, as well as some species in the orders Coleoptera, Diptera and Hemiptera. In this study, the speed of action of chlorantraniliprole was compared with that of seven commercial insecticides by means of ingestion bioassays against larvae of Plutella xylostella L., Trichoplusia ni (Hübner), Spodoptera exigua (Hübner) and Helicoverpa zea (Boddie).

RESULTS

Based on feeding cessation and reduction in feeding damage, chlorantraniliprole is among the fastest-acting insecticides available for control of lepidopteran pests, comparable in speed of action with methomyl, lambda-cyhalothrin and esfenvalerate, and faster than emamectin benzoate, indoxacarb, methoxyfenozide and metaflumizone.

CONCLUSION

The speed of action of chlorantraniliprole against target pest species, based on time for feeding cessation and reduction in feeding damage, is significantly greater than that of most recently developed insecticides and comparable only with the speed of action of the fast-acting carbamates and pyrethroids. In addition, chlorantraniliprole has a favorable toxicological and ecotoxicological profile. It belongs to a new chemical class with a novel mode of action and is effective against insect populations that have developed resistance to other insecticide groups, thus representing an attractive new tool for integrated pest management programs.