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The brown planthopper (BPH), Nilaparvata lugens (Stål), is one of the most destructive pests that seriously threatens the high-quality and safe production of rice. However, due to the unscientific use of chemical insecticides, N. lugens has developed varying levels of resistance to insecticides, including nitenpyram and clothianidin. The ATP-binding cassette (ABC) transporter plays a nonnegligible role in phase III of the detoxification process, which may play an important role in insecticide resistance. In the present study, NlABCG3 was significantly overexpressed in both the NR and CR populations compared with susceptible populations. Silencing NlABCG3 significantly increased the susceptibility of BPH to nitenpyram and clothianidin. In addition, RNAi-mediated knockdown of three key genes in the miRNA biogenesis pathway altered the level of NlABCG3. Subsequently, the luciferase reporter assays demonstrated that novel_268 binds to the NlABCG3 coding region and downregulates its expression. Furthermore, injection of miRNA inhibitors or mimics of novel_268 significantly altered the susceptibility of N. lugens to nitenpyram and clothianidin. These results suggest that miRNA novel_268 targeting NlABCG3 is involved in nitenpyram and clothianidin resistance in N. lugens. These findings may help to enhance our knowledge of the transcriptional regulation of the ABC transporter that mediate insecticide resistance in N. lugens., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Odorant binding protein (OBP) can interact with small-molecule compounds insecticides and thereby modulate variation in insecticide susceptibility in insects. However, the regulatory mechanism of OBP-mediated insecticide resistance in Nilaparvata lugens, a destructive rice pest in Asia, remains unclear. Here, we explored the role of NlOBP3 in the resistance of N. lugens to nitenpyram and sulfoxaflor. The results showed that NlOBP3 was overexpressed in association with nitenpyram and sulfoxaflor resistance, and NlOBP3 silencing significantly increased the mortality of N. lugens to nitenpyram and sulfoxaflor, suggesting that NlOBP3 may be associated with nitenpyram and sulfoxaflor resistance in N. lugens. OBP localization revealed that NlOBP3 was highly expressed in all nymph stages and was enriched in the antennae, legs, body wall, and fat body. RT-qPCR analyses showed that the mRNA levels of NlOBP3 were significantly affected by nitenpyram and sulfoxaflor. Additionally, molecular docking predicted that there were multiple binding sites that may played key roles in the binding of NlOBP3 with nitenpyram and sulfoxaflor. The current study identifies a previously undescribed mechanism of insecticide resistance in N. lugens, showing that NlOBP3 is likely to be involved in the evolution of nitenpyram and sulfoxaflor resistance in N. lugens., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The evolution of nitenpyram resistance has been confirmed to be related to overexpression of two key metabolic enzyme genes, CYP6ER1 and CarE1, in Nilaparvata lugens, a highly destructive rice pest that causes substantial economic losses and has developed insecticide resistance. As microRNAs (miRNAs) are important post-transcriptional regulators of gene expression, whether they are involved in nitenpyram resistance is poorly understood in N. lugens. In this study, knockdown of key genes in the miRNA biogenesis pathway (Dicer1, Drosha, and Argonaute1) changed CYP6ER1 and CarE1 abundance, which confirmed the importance of miRNAs in nitenpyram resistance. Furthermore, global screening of miRNAs associated with nitenpyram resistance in N. lugens was performed, and a total of 42 known and 178 novel miRNAs were identified; of these, 57 were differentially expressed between the susceptible and resistant strains, and two (novel_85 and novel_191) were predicted to target CYP6ER1 and CarE1, respectively. Luciferase reporter assays demonstrated that novel_85 and novel_191 bind to the CYP6ER1 and CarE1 coding regions, respectively, and downregulate their expression. Moreover, modulating novel_85 and novel_191 expression by injection of miRNA inhibitors and mimics significantly altered N. lugens nitenpyram susceptibility. This is the first study to systematically screen and identify miRNAs associated with N. lugens nitenpyram resistance, and provides important information that can be used to develop new miRNA-based targets in insecticide resistance management., (© 2021 Institute of Zoology, Chinese Academy of Sciences.)

Background: Sulfoxaflor has been considered as a new tool for Nilaparvata lugens control in the field. In this study, a laboratory-selected resistant strain and a susceptible strain were used to evaluate the inheritance and fitness costs of sulfoxaflor resistance in N. lugens., Results: The resistant strain (SFX-SEL) showed 123.63-fold resistance compared with the susceptible strain (SS). Progenies of reciprocal crosses (F 1 RS and F 1 SR) showed similar concentration-mortality responses (LC 50 ) to sulfoxaflor and also exhibited a similar degree of dominance; -0.16 for F 1 RS and -0.26 for F 1 SR. Significant differences between the observed and expected mortalities of F 2 individuals suggested that sulfoxaflor resistance is associated with multiple genes. The resistant strain had a relative fitness of 0.75 with substantially decreased female adult period, oviposition days, total fecundity, egg hatchability and female adult survival rate, and prolonged pre-adult period and total pre-oviposition period., Conclusion: Sulfoxaflor resistance in N. lugens was inherited as autosomal, incompletely recessive and multigene. The development of resistance may have a significant fitness cost for the resistant population. Current research provides valuable information for researchers to establish management strategies to delay the development of sulfoxaflor resistance and control N. lugens sustainably in the field. © 2019 Society of Chemical Industry., (© 2019 Society of Chemical Industry.)

In this study, the sensitivity of 20 field populations of Chilo suppressalis (Walker) from five provinces in China to seven insecticides was evaluated during 2016-2018. The results indicated that 20 field populations of C. suppressalis had evolved moderate to high levels of resistance to triazophos (RR 64.5-461.3) and chlorpyrifos (RR 10.1-125.0). Furthermore, C. suppressalis exhibited low to moderate levels of resistance to abamectin (RR 6.5-76.5) and decreased susceptibility to cyantraniliprole (RR 1.0-34.0). The population collected from Nanchang in Jiangxi Province (JXNC) showed high resistance to chlorantraniliprole (RR 148.3-294.3), and other geographical populations remained susceptible to moderate levels of resistance (RR 1.0-37.5). In contrast, C. suppressalis remained susceptible to low levels of resistance to spinetoram (RR 1.0-6.7) and spinosad (RR 1.0-4.6). Significant correlations were found between the Log LC50 values of chlorantraniliprole and cyantraniliprole, chlorpyrifos and triazophos, as well as cyantraniliprole and chlorpyrifos and triazophos. Similarly, significant correlations were found among abamectin, chlorpyrifos, and triazophos. In addition, a significant correlation was also observed between the activity of the detoxification enzymes and the log LC50 values of chlorantraniliprole, cyantraniliprole, abamectin, chlorpyrifos, and triazophos. The findings provide an important reference for implementing effective resistance management strategies and the development of new insecticides in insect pest control., (© The Author(s) 2019. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Buprofezin is a chitin synthesis inhibitor that is very effective against Homopteran pests, such as the white-backed planthopper (WBPH), S. furcifera (Horvath). In the present study, resistance selection, cross-resistance and mechanisms of buprofezin resistance were investigated in this planthopper species. However, the mechanism associated with resistance to growth regulator insecticides (IGRs) remains largely unknown. A resistant strain (Bup-R) with a resistance level (22-fold) to buprofezin was developed through continuous selection for 47 generations from a laboratory susceptible strain (Bup-S). The results showed that the Bup-R exhibited no cross-resistance to other tested insecticides. Synergism tests showed that piperonyl butoxide (PBO) (SR = 3.9-fold) and diethyl maleate (DEM) (SR = 1.8-fold) had synergistic effects on buprofezin toxicity in the resistant strain (F 47 ). Enzyme activity results revealed an approximate 5.7-fold difference in cytochrome P450 monooxygenase and a 2-fold difference in glutathione S-transferase (GST) between the resistant and susceptible strains, suggesting that the increased activity of these two enzymes is likely the main detoxification mechanism involved in resistance to buprofezin in this species. Furthermore, the mRNA expression levels of cytochrome P450 (CYP) and GST genes by quantitative real-time PCR results indicated that sixteen P450 and one GST gene were significantly overexpressed in the Bup-R strain, among which thirteen P450 genes and one GST gene were >2-fold higher than in the Bup-S strain. The present study increases our knowledge of the buprofezin resistance mechanism in S. furcifera and provides a useful reference for integrated pest management (IPM) strategies., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The toxicity of insecticides is associated with a variety of factors including temperature, and global warming is bound to lead to the outbreak of pests; therefore, it is important to study the influence of temperature on insecticide toxicity and pest control. In this study, the influence of temperature on the toxicity of insecticides to Nilaparvata lugens (BPH) was determined. The results showed that the sensitivity of BPH to cycloxaprid (LC 50  = 42.5-0.388 mg/L), nitenpyram (LC 50  = 3.49-0.187 mg/L), triflumezopyrim (LC 50  = 0.354-0.0533 mg/L) and chlorpyrifos (LC 50  = 36.3-7.41 mg/L) increased significantly when the temperature changed from 18 °C to 36 °C. BPH sensitivity to etofenprox (LC 50  = 9.04-54.2 mg/L) was also affected by temperature. Additionally, the feeding amount and the activities of three detoxification enzymes [cytochrome P450 (P450), glutathione S-transferase (GST) and carboxylesterase (CarE)] of BPH at different temperatures were also measured. The feeding amounts were positively correlated with temperature increases while the activities of P450 and GST were significantly inhibited. The correlation analysis showed that changes in P450 activity (but not GST activity) were closely related to the sensitivity of BPH to cycloxaprid, nitenpyram, chlorpyrifos, and etofenprox according to the variation in temperatures. This study provides a theoretical basis for the rational use of chemical pesticides under the global warming trend and provides a reference for the integrated management of BPH in the field., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The brown planthopper, Nilaparvata lugens (Stål), is one of the most economically important rice pests in Asia and has become resistant to various kinds of insecticides, including neonicotinoid insecticides. In this study, an N. lugens clothianidin-resistant (CLR) strain and a susceptible (CLS) strain were established, and the potential resistance mechanisms of N. lugens to clothianidin were elucidated. The cross-resistance studies showed that the clothianidin-resistant strain exhibited cross-resistance to most neonicotinoid insecticides, especially nitenpyram (99.19-fold) and dinotefuran (77.68-fold), while there was no cross-resistance to chlorpyrifos (1.79-fold). The synergism assays and the activities of the detoxification enzymes were performed, and we found that a cytochrome P450 conferred the clothianidin resistance. Two P450 genes (CYP6ER1 and CYP6AY1) were found to be significantly overexpressed in the CLR strain compared with the CLS strain based on qRT-PCR. In addition, the knockdown of CYP6ER1 by RNA interference dramatically increased the toxicity of clothianidin against N. lugens. These data demonstrated that the overexpression of CYP6ER1 could contribute to clothianidin resistance in N. lugens. Our findings will help to improve the design of effective resistance management strategies to control brown planthoppers., (Copyright © 2018 Elsevier Inc. All rights reserved.)

In the present study, the effects of sublethal concentrations of buprofezin on life-table traits of S. furcifera were evaluated for two consecutive generations (F0 and F1). Our results exhibited that the fecundity, life span (longevity) and hatchability of the F0 and F1 generations were significantly decreased at LC 30 compared to the control. However, copulation was not significantly affected for the F0 or F1 generations at sublethal concentrations. The female life span was affected negatively at both treatments in F0 and at LC 30 in F1, compared to the control. Furthermore, significant effects of the sublethal concentrations were found on the developmental rate of all instars except the 3 rd instar of F1. However, the pre-adult period, total pre-oviposition period (TPOP) and adult pre-oviposition period (APOP) significantly increased in F1 individuals at LC 30 and LC 10 compared to the control. Our findings revealed that demographic characters (survival rate, intrinsic rate of increase (ri), finite rate of increase (λ), net reproductive rate (R 0 ), and gross reproductive rate (GRR)) of the F1 generation (from F0 parents) significantly decreased compared to the untreated group; however, the generation time (T) increased at LC 10 . Therefore, the results suggested that buprofezin could adversely affect individuals in the successive generation.

The brown planthopper is a serious rice pest in China. Chemical insecticides have been considered a satisfactory means of controlling the brown planthopper. In the present study, we determined the susceptibility of twenty-one populations of Nilaparvata lugens to eleven insecticides by a rice-stem dipping method from 2012 to 2014 in eight provinces of China. These field-collected populations of N. lugens had developed high levels of resistance to imidacloprid (resistant ratio, RR=233.3-2029-fold) and buprofezin (RR=147.0-1222). Furthermore, N. lugens showed moderate to high levels of resistance to thiamethoxam (RR=25.9-159.2) and low to moderate levels of resistance to dinotefuran (RR=6.4-29.1), clothianidin (RR=6.1-33.6), ethiprole (RR=11.5-71.8), isoprocarb (RR=17.1-70.2), and chlorpyrifos (RR=7.4-30.7). In contrast, the susceptibility of N. lugens to etofenprox (RR=1.1-4.9), thiacloprid (RR=2.9-8.2) and acetamiprid (RR=2.7-26.2) remained susceptible to moderate levels of resistance. Significant correlations were detected between the LC50 values of imidacloprid and thiamethoxam, dinotefuran, buprofezin, and etofenprox, as well as between clothianidin and thiamethoxam, dinotefuran, ethiprole, acetamiprid, and thiacloprid. Similarly, significant correlations were observed between chlorpyrifos and etofenprox, acetamiprid and thiacloprid. Additionally, the activity of the detoxification enzymes of N. lugens showed a significant correlation with the log LC50 values of imidacloprid, dinotefuran and ethiprole. These results will be beneficial for effective insecticide resistance management strategies to prevent or delay the development of insecticide resistance., (Copyright © 2015 Elsevier B.V. All rights reserved.)

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a globally distributed and important economic pest. Chemical control is the primary approach to regulate populations of this pest. However, resistance to insecticides evolves following heavy and frequent use. Therefore, the insecticide resistance in field populations of P. xylostella collected from Central China from 2013 to 2014 was determined with a leaf-dipping method. Based on the results of the monitoring, P. xylostella has developed high levels of resistance to beta-cypermethrin (resistance ratio=69.76-335.76-fold), Bt (WG-001) (RR=35.43-167.36), and chlorfluazuron (RR=13.60-104.95) and medium levels of resistance to chlorantraniliprole (RR=1.19-14.26), chlorfenapyr (RR=4.22-13.44), spinosad (RR=5.89-21.45), indoxacarb (RR=4.01-34.45), and abamectin (RR=23.88-95.15). By contrast, the field populations of P. xylostella remained susceptible to or developed low levels of resistance to diafenthiuron (RR=1.61-8.05), spinetoram (RR=0.88-2.35), and cyantraniliprole (RR=0.4-2.15). Moreover, the LC50 values of field populations of P. xylostella were highly positively correlated between chlorantraniliprole and cyantraniliprole (r=0.88, P=0.045), chlorantraniliprole and spinosad (r=0.66, P=0.039), spinosad and diafenthiuron (r=0.57, P=0.0060), and chlorfenapyr and diafenthiuron (r=0.51, P=0.016). Additionally, the activities of detoxification enzymes in field populations of P. xylostella were significantly positively correlated with the log LC50 values of chlorantraniliprole and spinosad. The results of this study provide an important base for developing effective and successful strategies to manage insecticide resistance in P. xylostella., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Clothianidin is a neonicotinoid insecticide that acts as a full agonist stimulating nAChRs and is widely used to control the brown planthopper, Nilaparvata lugens (Stål). To investigate the adaptation of N. lugens in the process of developing resistance to clothianidin, a clothianidin-resistant N. lugens strain and an unselected strain were used in this study. The F 1 reciprocal crosses between the resistant and the susceptible strains indicated that the observed resistance was autosomal and incompletely dominant. Chi-square analyses of self-bred and backcrossed progenies suggested that the observed resistance was controlled by multiple genes. The resistant strain exhibited a relative fitness of 0.78 with a significantly increased adult preoviposition period and significantly decreased total fecundity. The current study provides valuable information for resistance management strategies to delay the development of clothianidin resistance in N. lugens. Image 1 • The observed clothianidin resistance of N. lugens was autosomal and incompletely dominant. • The observed resistance was controlled by multiple genes. • The resistant strain exhibited a fitness cost apparent in a significantly reduced total fecundity. [ABSTRACT FROM AUTHOR]

The ATP-binding cassette (ABC) transporter superfamily is one of the largest groups of proteins and plays a non-negligible role in phase III of the detoxification process, which is highly involved in the response of insects to environmental stress (plant secondary metabolites and insecticides). In the present study, in Nilaparvata lugens, we identified 32 ABC transporters, which are grouped into eight subfamilies (ABCA–H) based on phylogenetic analysis. The temporal and spatial expression profiles suggested that the nymphal stages (1st–5th) and adult males showed similarity, which was different from eggs and adult females, and NlABCA1, NlABCA2, NlABCB6, NlABCD2, NlABCG4, NlABCG12, NlABCG15, and NlABCH1 were highly expressed in the midgut and Malpighian tubules. In addition, ABCG12, which belongs to the ABC transporter G subfamily, was significantly upregulated after exposure to sulfoxaflor, nitenpyram, clothianidin, etofenprox, chlorpyrifos, and isoprocarb. Moreover, verapamil significantly increased the sensitivity of N. lugens to nitenpyram, clothianidin, etofenprox, chlorpyrifos, and isoprocarb. These results provide a basis for further research on ABC transporters involved in detoxification in N. lugens, and for a more comprehensive understanding of the response of N. lugens to environmental stress. [ABSTRACT FROM AUTHOR]

Sogatella furcifera (Horváth) is a major threat to rice production in China. Insecticides are a key component of typical pest management schemes, but few studies have quantitatively identified insecticide control failures due to insecticide resistance. Therefore, we measured the susceptibility of eight populations to thirteen insecticides by the rice dipping method in 2018 and further evaluated the likelihood of control failure in this study. The results showed that S. furcifera had high levels of S. furcifera resistance to buprofezin (RR = 76.42–160.14-fold), chlorpyrifos (RR = 93.50–219.90-fold), and pymetrozine (RR > 469.30-fold) and low to moderate levels of resistance to nitenpyram (RR = 1.50–10.21-fold), clothianidin (RR = 3.72–20.43-fold), thiamethoxam (RR = 2.88–19.95-fold), imidacloprid (RR = 4.05–31.81-fold), dinotefuran (RR = 4.55–25.98-fold), isoprocarb (RR = 2.55–15.71-fold), and etofenprox (RR = 5.63–17.74-fold). S. furcifera remained susceptible to cycloxaprid (resistance ratio, RR = 0.56–1.82-fold), triflumezopyrim (RR = 0.77–3.23-fold) and sulfoxaflor (RR = 2.28–4.32-fold). Pymetrozine, isoprocarb and etofenprox were determined to be at risk of control failures if the minimum recommended concentration is applied to manage this pest. Furthermore, significant correlations were found among the logarithms of the median lethal concentration (LC 50) values of thirteen insecticides. Additionally, the activities of esterases in field populations of S. furcifera were significantly positively correlated with the logarithm of the LC 50 values of triflumezopyrim, nitenpyram and clothianidin. The results of this survey offer an important basis for producing effective and useful strategies to manage insecticide resistance in S. furcifera. • High resistance to buprofezin, chlorpyrifos, and pymetrozine in field populations of S. furcifera was observed. • A risk of control failures of pymetrozine, isoprocarb and etofenprox to manage S. furcifera was described. • Correlations were analyzed between the values of the logarithm of the LC 50 values of the insecticides. • Significant correlations were found between esterase and the susceptibility to triflumezopyrim, nitenpyram and clothianidin. [ABSTRACT FROM AUTHOR]

• An HMS hybrid employing P(NIPAM-MAA) as the outer shell of HMS with temperature-responsiveness. • THI-loaded HMS hybrid could utilize the relationship between pesticide efficacy and temperature. • HMS hybrid possessed good biocompatibility and UV-shielding properties. • THI-loaded HMS hybrid provided sustained protection in rice plant against N. lugens. Improving pesticide efficacy, which depends on the smart delivery of pesticides in the field, has been the basis for reducing the use of agricultural chemicals to an optimal level. Herein, a temperature-responsive release formulation (THI@HMS@P(NIPAM-MAA)) that can regulate pesticide release based on the relationship between pesticide efficacy and ambient temperature is proposed. The THI@HMS@P(NIPAM-MAA) was prepared by seeded precipitation polymerization, wherein hollow mesoporous silica (HMS) was employed as the core; a commonly used thermoresponsive copolymer, poly(N -isopropylacrylamide- co -methacrylic acid) (P(NIPAM-MAA)), was used as the outer shell; and a type of positive temperature coefficient insecticide, thiamethoxam (THI), was selected as the model pesticide. The prepared THI@HMS@P(NIPAM-MAA) can effectively protect THI against degradation under UV irradiation and showed strong adhesion to rice leaves. The bioactivity results showed that the mortality of THI@HMS@P(NIPAM-MAA) against Nilaparvata lugens (Stål) (Hemiptera: Delphacidae) was positively correlated with temperature and mainly benefitted from the temperature-induced variation in the release rate. Furthermore, the THI@HMS@P(NIPAM-MAA) possessed long-term bioactivity (14 days) and showed negligible effects on rice seedling growth. This temperature-responsive release formulation may be extended to other positive temperature coefficient pesticides in the future, thus greatly advancing smart pesticide formulation development. [ABSTRACT FROM AUTHOR]