Insecticide Resistance Management Research Articles

Recommendations for Management of Whiteflies, Whitefly-Transmitted Viruses, and Insecticide Resistance for Production of Cucurbit Crops in Florida

This publication lists and describes common viruses spread in cucurbit crops by whiteflies. It includes strategies for managing whiteflies, most of them originally from a similar publication on managing whiteflies in tomatoes.

Exposure of Anopheles gambiae larvae to a sub-lethal dose of an agrochemical mixture induces tolerance to adulticides used in vector control management.

The heavy use of pesticides in agricultural areas often leads to the contamination of nearby mosquito larvae breeding sites. Exposure to complex mixtures of agrochemicals can affect the insecticide sensitivity of mosquito larvae. Our study objective was to determine whether agrochemical residues in Anopheline larval breeding sites can affect the tolerance of adults to commonly used adulticides. We focussed on Fludora® Fusion, a vector control insecticide formulation combining two insecticides (deltamethrin and clothianidin) with different modes of action. An. gambiae larvae were exposed to a sub-lethal dose of a mixture of agrochemical pesticides used in a highly active agricultural area on the Ivory Coast. Comparative bioassays with Fludora Fusion mixture and its two insecticide components (deltamethrin and clothianidin) were carried out between adult mosquitoes exposed or not to the agrochemicals at the larval stage. A transcriptomic analysis using RNA sequencing was then performed on larvae and adults to study the molecular mechanisms underlying the phenotypic changes observed. Bioassays revealed a significantly increased tolerance of adult females to clothianidin (2.5-fold) and Fludora Fusion mixture (2.2-fold) following larval exposure to agrochemicals. Significantly increased tolerance to deltamethrin was not observed suggesting that insecticide exposure affects the adult efficacy of the Fludora Fusion mixture mainly through mechanisms acting on clothianidin. Transcriptomic analysis revealed the potential of agrochemicals to induce various resistance mechanisms including cuticle proteins, detoxification action and altered insecticide sequestration. These results suggest that although the Fludora Fusion mixture is effective for adult vector control, its efficacy may be locally affected by the ecological context. The present study also suggests that, although the complex interactions between the use of agrochemicals and vector control insecticides are difficult to decipher in the field, they still must be considered in the context of insecticide resistance management programmes.

Intensity of insecticide resistance in the major malaria vector Anopheles funestus from Chikwawa, rural Southern Malawi

BackgroundMalaria vector control using insecticide-based approaches has proven to be an effective strategy. However, widespread insecticide resistance among malaria vector populations across sub-Saharan Africa threatens to derail control efforts. This study was conducted in Chikwawa district, an area in rural southern Malawi characterised by persistent malaria transmission and reports of insecticide resistance in the local mosquito population. The aim of the was to characterise the intensity of insecticide resistance within a population of Anopheles funestus sensu lato (s.l.), a major vector of malaria in this district.MethodsLive adult females belonging to the An. funestus group were collected from households by indoor aspiration. The CDC bottle assay was used for phenotypic quantification of resistance to deltamethrin, permethrin and alpha-cypermethrin at 1×, 2.5×, 5× and 10× the recommended diagnostic dose for each of these insecticides. WHO tube assays were used to determine susceptibility to bendiocarb, dichlorodiphenyltrichloroethane (DDT) and pirimiphos-methyl insecticides at diagnostic concentrations.ResultsAnopheles funestus s.l. exposed to 10× the recommended diagnostic dose was highly resistant to alpha-cypermethrin (mortality 95.4%); in contrast, mortality was 100% when exposed to both deltamethrin and permethrin at the same dose. Despite showing susceptibility to deltamethrin and permethrin at the 10× concentration, mortality at the 5× concentration was 96.7% and 97.1%, respectively, indicating moderate resistance to these two insecticides. WHO susceptibility assays indicated strong resistance against bendiocarb (mortality 33.8%, n = 93), whereas there was full susceptibility to DDT (mortality 98.9%, n = 103) and pirimiphos-methyl (mortality 100%, n = 103).ConclusionsStrategies for managing resistance to insecticides, particularly against pyrethroids, must be urgently implemented to maintain the effectiveness of insecticide-based vector control interventions in the area. Such strategies include the wide-scale introduction of third-generation synergist insecticide-treated bed nets (ITNs) and next-generation dual active ingredient ITNs. The use of effective non-pyrethroids, such as pirimiphos-methyl, clothianidin and potentially DDT, could provide a window of opportunity for indoor residual spraying across the district. This strategy would support the current Malawi Insecticide Resistance Management Plan which aims at rotating insecticides to minimise selection pressure and slow down the evolution of resistance to approved insecticides. These actions will help to prevent malaria vector control failure and improve progress towards malaria elimination.Graphical

Incremental cost and cost-effectiveness of the addition of indoor residual spraying with pirimiphos-methyl in sub-Saharan Africa versus standard malaria control: results of data collection and analysis in the Next Generation Indoor Residual Sprays (NgenIRS) project, an economic-evaluation

BackgroundMalaria is a major cause of morbidity and mortality globally, especially in sub-Saharan Africa. Widespread resistance to pyrethroids threatens the gains achieved by vector control. To counter resistance to pyrethroids, third-generation indoor residual spraying (3GIRS) products have been developed. This study details the results of a multi-country cost and cost-effectiveness analysis of indoor residual spraying (IRS) programmes using Actellic®300CS, a 3GIRS product with pirimiphos-methyl, in sub-Saharan Africa in 2017 added to standard malaria control interventions including insecticide-treated bed nets versus standard malaria control interventions alone.MethodsAn economic evaluation of 3GIRS using Actellic®300CS in a broad range of sub-Saharan African settings was conducted using a variety of primary data collection and evidence synthesis methods. Four IRS programmes in Ghana, Mali, Uganda, and Zambia were included in the effectiveness analysis. Cost data come from six IRS programmes: one in each of the four countries where effect was measured plus Mozambique and a separate programme conducted by AngloGold Ashanti Malaria Control in Ghana. Financial and economic costs were quantified and valued. The main indicator for the cost was cost per person targeted. Country-specific case incidence rate ratios (IRRs), estimated by comparing IRS study districts to adjacent non-IRS study districts or facilities, were used to calculate cases averted in each study area. A deterministic analysis and sensitivity analysis were conducted in each of the four countries for which effectiveness evaluations were available. Probabilistic sensitivity analysis was used to generate plausibility bounds around the incremental cost-effectiveness ratio estimates for adding IRS to other standard interventions in each study setting as well as jointly utilizing data on effect and cost across all settings.ResultsOverall, IRRs from each country indicated that adding IRS with Actellic®300CS to the local standard intervention package was protective compared to the standard intervention package alone (IRR 0.67, [95% CI 0.50–0.91]). Results indicate that Actellic®300CS is expected to be a cost-effective (> 60% probability of being cost-effective in all settings) or highly cost-effective intervention across a range of transmission settings in sub-Saharan Africa.DiscussionVariations in the incremental costs and cost-effectiveness likely result from several sources including: variation in the sprayed wall surfaces and house size relative to household population, the underlying malaria burden in the communities sprayed, the effectiveness of 3GIRS in different settings, and insecticide price. Programmes should be aware that current recommendations to rotate can mean variation and uncertainty in budgets; programmes should consider this in their insecticide-resistance management strategies.ConclusionsThe optimal combination of 3GIRS delivery with other malaria control interventions will be highly context specific. 3GIRS using Actellic®300CS is expected to deliver acceptable value for money in a broad range of sub-Saharan African malaria transmission settings.

Resistance in Spodoptera litura (F.) to Insecticides and Detoxification Enzymes

Standard leaf dip bioassay experiments were conducted to study the insecticide resistance in Spodoptera litura (F.) in soybean. Chlorantraniliprole was the most toxic while, cypermethrin and organophosphates (profenophos and triazophos) recorded least toxicity against S. litura populations. Field population of S. litura showed the highest resistance to cypermethrin with resistance ratios (RRs) ranging from 244 to 376. The field populations collected from three locations of Southern Rajasthan exhibited low resistance to newer insecticides, chlorantraniliprole and spinetoram with Lab-SS strain. All the enzyme activities were significantly higher in the whole larval extracts and midgut extracts of S. litura larvae when compared to the Lab-SS strain. Analysis of the carboxyl esterase enzyme in the native PAGE assay revealed that the electrophoretic profiles showed presence of different band regions (EST 1 to EST 7) with esterase activity in the field populations along with the laboratory susceptible strain. The susceptibility of three field populations to different group of insecticides along with the profile of detoxification enzymes indicate the need to formulate a region-specific insecticide resistance management (IRM).

Effects of Methoxyfenozide-Loaded Fluorescent Mesoporous Silica Nanoparticles on Plutella xylostella (L.) (Lepidoptera: Plutellidae) Mortality and Detoxification Enzyme Levels Activities.

The diamond back moth, Plutella xylostella, causes severe damage at all crop stages, beside its rising resistance to all insecticides. The objective of this study was to look for a new control strategy such as application of insecticide-loaded carbon dot-embedded fluorescent mesoporous silica nanoparticles (FL-SiO2 NPs). Two different-sized methoxyfenozide-loaded nanoparticles (Me@FL-SiO2 NPs-70 nm, Me@FL-SiO2 NPs-150 nm) were prepared, with loading content 15% and 16%. Methoxyfenozide was released constantly from Me@FL-SiO2 NPs only at specific optimum pH 7.5. The release of methoxyfenozide from Me@FL-SiO2 NPs was not observed other than this optimum pH, and therefore, we checked and controlled a single release condition to look out for the different particle sizes of insecticide-loaded NPs. This pH-responsive release pattern can find potential application in sustainable plant protection. Moreover, the lethal concentration of the LC50 value was 24 mg/L for methoxyfenozide (TC), 14 mg/L for Me@FL-SiO2 NPs-70 nm, and 15 mg/L for Me@FL-SiO2 NPs-150 nm after 72 h exposure, respectively. After calculating the LC50, the results predicted that Me@FL-SiO2 NPs-70 nm and Me@FL-SiO2 NPs-150 nm exhibited better insecticidal activity against P. xylostella than methoxyfenozide under the same concentrations of active ingredient applied. Moreover, the activities of detoxification enzymes of P. xylostella were suppressed by treatment with insecticide-loaded NPs, which showed that NPs could also be involved in reduction of enzymes. Furthermore, the entering of FL-SiO2 NPs into the midgut of P. xylostella was confirmed by confocal laser scanning microscope (CLSM). For comparison, P. xylostella under treatment with water as control was also observed under CLSM. The control exhibited no fluorescent signal, while the larvae treated with FL-SiO2 NPs showed strong fluorescence under a laser excitation wavelength of 448 nm. The reduced enzyme activities as well as higher cuticular penetration in insects indicate that the nano-based delivery system of insecticide could be potentially applied in insecticide resistance management.

CeO2 nanohybrid as a synergist for insecticide resistance management

Agricultural applications of nanomaterials, such as nanofertilizers, nanopreservation technologies, nanopesticides, and plant nanosensors, have recently attracted much attention. Herein, the CeO2-based nanohybrid MON@CeO2 was designed as a reactive oxygen species (ROS) inhibitor to effectively improve the susceptibility of insect pests to insecticides. MON@CeO2 was fabricated by intercalating CeO2 into mesoporous organosilica nanoparticles (MONs). The obtained MON@CeO2 showed a regular spherical shape with an average particle size of 45.4 nm, good monodispersity, and a negative surface charge (-14.6 mV). Bioassay results showed that MON@CeO2 significantly enhanced the toxicity (more than 2-fold) of nitenpyram, sulfoxaflor, and clothianidin against laboratory insecticide-resistant and field strains of Nilaparvata lugens. In particular, MON@CeO2 orchestrated host detoxification metabolism via downregulating ROS-dependent P450 gene expression, thus reducing host detoxification enzyme activities to overcome insecticide resistance. Furthermore, MON@CeO2 restrained host insecticide resistance in the notorious agricultural pests Aphis gossypii, Spodoptera frugiperda, and Sogatella furcifera. Therefore, MON@CeO2 could be used as a broad-spectrum nanosynergist against insecticide resistance, which would be a novel strategy for sustainable pest management.

Spatial heterogeneity of knockdown resistance mutations in the dengue vector Aedesalbopictus in Guangzhou, China

BackgroundThe city of Guangzhou has been the epicenter of dengue fever in China since the 1990s, with Aedesalbopictus being the primary vector. The main method used to control vectors and prevent dengue fever has been the application of chemical insecticides; however, this control strategy has resulted in the development of resistance to these insecticides in mosquitoes. Here we report our investigation of the patterns of knockdown resistance (kdr) mutations in 15 field populations of Ae.albopictus collected from 11 districts in Guangzhou.ResultsFour mutant alleles (V1016G, F1534S, F1534C, F1534L) were detected in domain II and III of the voltage-gated sodium channel (VGSC) gene. Various allele frequencies of kdr mutations were observed (3.1–25.9% for V1016G, 22.6–85.5% for F1534S, 0–29.0% for F1534L, 0.6–54.2% for F1534C). Seven kdr haplotypes (VF, VS, VL, VC, GF, GC, GS) were identified; the highest frequency of haplotypes was found for the single mutant haplotype VS (50.8%), followed by the wild-type VF haplotype (21.7%) and the single mutant haplotype VC (11.9%). Of the three double mutant haplotypes, GF was the most frequent (8.8%), followed by GC (1.2%) and GS (0.8%). Aedesalbopictus showed spatial heterogeneity in deltamethrin resistance in populations collected in Guangzhou. We also observed significant differences in haplotype frequency. The frequency of the VC haplotype was significantly higher in high-risk dengue areas than in low-risk ones.ConclusionsThe kdr allele V1016G was discovered for the first time in Guangzhou. Genetic isolation in mosquito populations and long-term insecticide selection seem to be responsible for the persistent, patchy distribution of kdr mutant alleles. The small-scale spatial heterogeneity in the distribution and frequency of kdr mutations may have important implications for vector control operations and insecticide resistance management strategies.Graphical

Spatio-Temporal Dynamics of a Dieldrin Resistance Gene in Aedes albopictus and Culex quinquefasciatus Populations From Reunion Island.

The control of mosquito populations using insecticides is increasingly threatened by the spread of resistance mechanisms. Dieldrin resistance, conferred by point mutations in the Rdl gene encoding the γ-aminobutyric acid receptor, has been reported at high prevalence in mosquito populations in response to selective pressures. In this study, we monitored spatio-temporal dynamics of the resistance-conferring RdlR allele in Aedes (Stegomyia) albopictus (Skuse, 1895) and Culex (Culex) quinquefasciatus (Say, 1823) populations from Reunion Island. Specimens of both mosquito species were sampled over a 12-month period in three cities and in sites located at lower (<61 m) and higher (between 503 and 564 m) altitudes. Mosquitoes were genotyped using a molecular test detecting the alanine to serine substitution (A302S) in the Rdl gene. Overall, the RdlR frequencies were higher in Cx. quinquefasciatus than Ae. albopictus. For both mosquito species, the RdlR frequencies were significantly influenced by location and altitude with higher RdlR frequencies in the most urbanized areas and at lower altitudes. This study highlights environmental factors that influence the dynamics of insecticide resistance genes, which is critical for the management of insecticide resistance and the implementation of alternative and efficient vector control strategies.

Insecticide Resistance in the Disease Vector Culex pipiens in Morocco: Intensity, Mechanisms, and Contribution in Insecticide Resistance Management

West Nile (WN) virus has been detected in Morocco in 1996, 2003, and 2010. One WN human case and 94 equine cases with 42 deaths were reported in the first outbreak. The second and the last epizootics were in Kénitra and Mohammedia regions, respectively. Culex pipiens mosquitoes were strongly suspected as WN vectors during these epizootics in Morocco. To help propose the first insecticide resistance management strategy in Morocco, we provide baseline data on the resistance status of C. pipiens mosquitoes to insecticides most used in public health in Morocco. We investigated the resistance intensity of C. pipiens and the role of monooxygenases in pyrethroids resistance using the synergist piperonyl butoxide (PBO) in three prefectures of central Morocco: Mohammedia, Benslimane, and Skhirate. Bioassays were carried out using WHO (World Health Organization) diagnostic test kits for adult mosquitoes, with DDT 4%; deltamethrin 0.05%, 0.25%, and 0.5%; bendiocarb 0.1%, 0.5%, and 1%; and malathion 5%. The synergist PBO 4% was used to check for the involvement of detoxification enzymes in pyrethroids resistant populations. Mosquito populations tested displayed high resistance intensity to pyrethroids and carbamates in Mohammedia and moderate resistance intensity in Skhirate. In Benslimane, the resistance intensity of C. pipiens was high to carbamate and moderate to pyrethroids. The pre-exposure to PBO restored full or partial susceptibility to pyrethroids in the different regions. According to our finding, Mohammedia and Benslimane are at risk level 3 of control failure, while Skhirate is at risk level 2 of it. The employment of IRM is therefore imperative in all study sites.

Insecticide Resistance and Control Failure Likelihood Analysis in Plutella xylostella (Lepidoptera: Plutellidae) Populations From Taiwan.

The status of insecticide resistance levels is important for applying suitable pest management approaches. The present study investigated the insecticide resistance of Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) populations from five major cruciferous growing areas in Taiwan. The surveyed locations were distributed from central to southern Taiwan and included Taichung, Changhua, Yunlin, Chiayi, and Kaohsiung. High levels of resistance to spinosad, indoxacarb, metaflumizone, and chlorantraniliprole were recorded among the surveyed populations except in Taichung. The resistance ratios ranged from 2.376 to 1,236-fold for spinosad and 24.63-1,511-fold for indoxacarb. Similarly, those for metaflumizone and chlorantraniliprole, were 2.563-76.21- and 4.457-683.0-fold, respectively. However, Bacillus thuringiensis subsp. aizawai, Bacillus thuringiensis subsp. kurstaki, emamectin benzoate, and diafenthiuron were still relatively effective against most field populations of P. xylostella. After approximately 10 generations of being maintained in the laboratory without exposure to insecticides, the resistance ratios of the Kaohsiung and Changhua populations declined to approximately 1.4-10-fold, and insecticides with control failure likelihood also began to show a negligible risk of control failure. Although spinosad, indoxacarb, metaflumizone, and chlorantraniliprole have lost their effectiveness in most field populations of P. xylostella in Taiwan, their effectiveness may be recovered in the absence of insecticide-selection pressure for approximately 10 generations. Therefore, we suggest that a constant survey of insecticide resistance and well-designed insecticide rotation based on the survey results are necessary for the effective control and insecticide resistance management of P. xylostella.

Baseline susceptibility of Australian Myzus persicae (Hemiptera: Aphididae) to novel insecticides flonicamid and afidopyropen

The green peach aphid, Myzus persicae (Sulzer) is a significant global pest of a broad range of horticultural and grain crops. Control of M. persicae is primarily dependent on insecticides, however, this species has a high propensity to evolve insecticide resistance and has evolved resistance to over 80 insecticides from various chemical groups worldwide. In Australia, widespread resistance to carbamates, organophosphates, pyrethroids and neonicotinoids in M. persicae populations is commonplace. Given the ability of M. persicae to establish resistance to new chemistries quickly, programs are needed to monitor susceptibility to new insecticides before their widespread use. In this study, we used leaf-dip bioassays to generate sensitivity data and investigate potential cross-resistance in multiple field-collected populations of Australian M. persicae to two recently registered insecticides, flonicamid and afidopyropen. After 144 and 168 h exposure, we found little variation in the susceptibility of M. persicae populations to either flonicamid or afidopyropen, and no evidence of sensitivity shifts in the field. Additionally, there was no evidence of cross-resistance between flonicamid or afidopyropen and multiple known resistance mechanisms for carbamate, pyrethroid, organophosphate and neonicotinoid insecticides. The sensitivity data generated in this study prior to the evolution of field resistance provides a useful starting point for future resistance monitoring, and allows for the development and implementation of insecticide resistance management strategies which should prolong the long-term efficacy of flonicamid and afidopyropen against M. persicae.

Detection of insecticide susceptibility and target-site mutations in field populations of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Fall armyworm, Spodoptera frugiperda (J. E. Smith), is an economically important pest throughout the world. At present, the control of S. frugiperda in China largely relies on the application of chemical insecticides. In this study, the susceptibility of nine field populations of S. frugiperda to eight recommended insecticides was evaluated by using the diet-overlay method. The results indicated that spinetoram, lufenuron, and emamectin benzoate exhibited high acute toxicity to S. frugiperda, whereas chlorantraniliprole, indoxacarb, tetrachlorantraniliprole, chlorfenapyr, and lambda-cyhalothrin exhibited relatively low toxicity. Two site mutations (A201S and F290V) of the Ace-1 gene were identified from the field populations, the R allele frequencies of A201S and F290V ranged from 5.0% to 29.6% and 21.2% to 67.3%, respectively. In addition, the resistant homozygote F290V was detected in the field, with the highest genotype frequency of 40.0% in the JZ population. However, no site mutation in VGSC was detected in any tested field population of S. frugiperda. These results provide valuable information for the selection of insecticides and are helpful for insecticide resistance management of S. frugiperda.

Inheritance mode and fitness costs of acetamiprid resistance in brown planthopper, Nilaparvata lugens (Stål)

The brown planthopper, Nilaparvata lugens (Stål), is a major rice pest in Asia. Acetamiprid is a widely used neonicotinoid insecticide for N. lugens control. Because of the frequent and excessive applications of chemical insecticides, moderate levels of resistance against acetamiprid have been found in field populations of N. lugens in China. To study the inheritance mode and fitness costs of acetamiprid resistance in N. lugens, an acetamiprid-resistant strain (AC-R) was selected from a susceptible strain (AC-S) in the laboratory. After 28 generations of selection, AC-R showed 26.15-fold resistance compared to AC-S. The LC50 and degree of dominance (D) values of the F1RS and F1SR (progenies of reciprocal crosses) indicated that the acetamiprid resistance in N. lugens was inherited as autosomal and incompletely dominant. Significant differences between the expected and observed mortalities of the F2 individuals suggested that acetamiprid resistance is controlled by multiple genes. The AC-R strain showed a relative fitness of 0.71 with a significantly decreased male adult longevity, fecundity, net reproductive rate (R0), and finite rate of increase (λ), and a prolonged adult preoviposition period (APOP). However, the durations of the 1st, 2nd, and 4th instar nymphs of AC-R were significantly shorter than those of AC-S. The current study provides valuable information for understanding acetamiprid resistance and optimizing insecticide resistance management strategies of N. lugens in the field.

Evidence of enhanced reproductive performance and lack-of-fitness costs among soybean aphids, Aphis glycines, with varying levels of pyrethroid resistance.

BACKGROUNDFoliar application of insecticides is the main strategy to manage soybean aphid, Aphis glycines (Hemiptera: Aphididae), in the northcentral United States. Subpopulations of A. glycines have multiple nonsynonymous mutations in the voltage‐gated sodium channel (vgsc) genes that are associated with pyrethroid resistance. We explored if fitness costs are associated with phenotypes conferred by vgsc mutations using life table analyses. We predicted that there would be significant differences between pyrethroid susceptibility and field‐collected, parthenogenetic isofemale clones with differing, nonsynonymous mutations in vgsc genes.RESULTSEstimated resistance ratios for the pyrethroid‐resistant clones ranged from 3.1 to 37.58 and 5.6 to 53.91 for lambda‐cyhalothrin and bifenthrin, respectively. Although life table analyses revealed some biological and demographic parameters to be significantly different among the clonal lines, there was no association between levels of pyrethroid resistance and a decline in fitness. By contrast, one of the most resistant clonal lines (SBA‐MN1‐2017) had a significantly higher finite rate of increase, intrinsic rate of increase and greater overall fitness compared to the susceptible control and other pyrethroid‐resistant clonal lines.CONCLUSIONSOur life history analysis suggests that there are no negative pleotropic effects associated with the pyrethroid resistance in the clonal A. glycines lines used in this study. We discuss the potential impact of these results on efficacies of insecticide resistance management (IRM) and integrated pest management (IPM) plans directed at delaying the spread of pyrethroid‐resistant A. glycines.

A new generation of long-lasting insecticidal nets

The scale-up of malaria interventions over the past two decades has resulted in substantial reductions in malaria burden, especially in sub-Saharan Africa, which accounts for 95% of the global malaria burden. 1 Bhatt S Weiss DJ Cameron E et al. The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015. Nature. 2015; 526: 207-211 Crossref PubMed Scopus (1439) Google Scholar , 2 WHOWorld malaria report 2020: 20 years of global progress and challenges. https://www.who.int/publications/i/item/9789240015791Date: Nov 30, 2020 Date accessed: December 5, 2021 Google Scholar Between 2000 and 2019, an estimated 1·5 billion malaria cases and 7·6 million malaria deaths were averted, with many of the early gains attributed to widescale deployment of insecticide-treated nets and availability of effective drugs. 1 Bhatt S Weiss DJ Cameron E et al. The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015. Nature. 2015; 526: 207-211 Crossref PubMed Scopus (1439) Google Scholar However, progress in global malaria control and elimination efforts have stagnated in recent years, the reasons for which are multifactorial and include the development and spread of insecticide resistance in malaria vectors. The massive scale-up of insecticide-treated nets and, later, long-lasting insecticidal nets (LLINs), which have an insecticide incorporated into the net fibre and can last longer under typical use, was accompanied by the emergence of vector resistance to pyrethroids. 3 Hancock PA Hendriks CJM Tangena JA et al. Mapping trends in insecticide resistance phenotypes in African malaria vectors. PLoS Biol. 2020; 18e3000633 Crossref PubMed Scopus (37) Google Scholar This resistance is now present in all primary vectors throughout much of sub-Saharan Africa. 3 Hancock PA Hendriks CJM Tangena JA et al. Mapping trends in insecticide resistance phenotypes in African malaria vectors. PLoS Biol. 2020; 18e3000633 Crossref PubMed Scopus (37) Google Scholar , 4 Knox TB Juma EO Ochomo EO et al. An online tool for mapping insecticide resistance in major Anopheles vectors of human malaria parasites and review of resistance status for the Afrotropical region. Parasit Vectors. 2014; 7: 76 Crossref PubMed Scopus (86) Google Scholar , 5 Moyes CL Athinya DK Seethaler T et al. Evaluating insecticide resistance across African districts to aid malaria control decisions. Proc Natl Acad Sci USA. 2020; 117: 22042-22050 Crossref PubMed Scopus (17) Google Scholar Studies have shown that a new generation of LLINs that include the synergist piperonyl butoxide have improved efficacy compared with pyrethroid-only nets. 6 WHOGlobal plan for insecticide resistance management in malaria vectors. https://apps.who.int/iris/handle/10665/44846Date: 2012 Date accessed: December 5, 2021 Google Scholar , 7 Mosha JF Kulkarni MA Lukole E et al. Effectiveness and cost-effectiveness against malaria of three types of dual-active-ingredient long-lasting insecticidal nets compared with pyrethroid-only long-lasting insecticidal nets in an area with pyrethroid-resistant mosquitoes in Tanzania: a four-arm, cluster-randomised trial. Lancet. 2022; 399: 1227-1241 Summary Full Text Full Text PDF PubMed Scopus (3) Google Scholar However, although piperonyl butoxide can restore susceptibility in pyrethroid-resistant mosquito populations wherein the primary resistance mechanism is metabolic detoxification by oxidase enzymes, it has minimal impact on other mechanisms of pyrethroid resistance. Insecticide-treated nets with novel active ingredients and different modes of action are needed. The WHO Global Plan for Insecticide Resistance Management recommends the use of two or more compounds of different insecticide classes to make a single product or formulation as an approach to combating resistance. 6 WHOGlobal plan for insecticide resistance management in malaria vectors. https://apps.who.int/iris/handle/10665/44846Date: 2012 Date accessed: December 5, 2021 Google Scholar The challenge is developing products that are not only effective against pyrethroid-resistant mosquitoes but are also safe to humans and are amenable to incorporation into the net fibres. Effectiveness and cost-effectiveness against malaria of three types of dual-active-ingredient long-lasting insecticidal nets (LLINs) compared with pyrethroid-only LLINs in Tanzania: a four-arm, cluster-randomised trialAfter 2 years, chlorfenapyr LLINs provided significantly better protection than pyrethroid-only LLINs against malaria in an area with pyrethroid-resistant mosquitoes, and the additional cost of these nets would be considerably below plausible cost-effectiveness thresholds ($292–393 per DALY averted). Before scale-up of chlorfenapyr LLINs, resistance management strategies are needed to preserve their effectiveness. Poor textile and active ingredient durability in the piperonyl butoxide and pyriproxyfen LLINs might have contributed to their relative lack of effectiveness compared with standard LLINs. Full-Text PDF Open Access

Mosquito population structure, pathogen surveillance and insecticide resistance monitoring in urban regions of Crete, Greece.

BackgroundIn Greece vector borne diseases (VBD) and foremost West Nile virus (WNV) pose an important threat to public health and the tourist industry, the primary sector of contribution to the national economy. The island of Crete, is one of Greece’s major tourist destinations receiving annually over 5 million tourists making regional VBD control both a public health and economic priority.MethodologyUnder the auspices of the Region of Crete, a systematic integrative surveillance network targeting mosquitoes and associated pathogens was established in Crete for the years 2018–2020. Using conventional and molecular diagnostic tools we investigated the mosquito species composition and population dynamics, pathogen infection occurrences in vector populations and in sentinel chickens, and the insecticide resistance status of the major vector species.Principal findingsImportant disease vectors were recorded across the island including Culex pipiens, Aedes albopictus, and Anopheles superpictus. Over 75% of the sampled specimens were collected in the western prefectures potentially attributed to the local precipitation patterns, with Cx. pipiens being the most dominant species. Although no pathogens (flaviviruses) were detected in the analysed mosquito specimens, chicken blood serum analyses recorded a 1.7% WNV antibody detection rate in the 2018 samples. Notably detection of the first WNV positive chicken preceded human WNV occurrence in the same region by approximately two weeks. The chitin synthase mutation I1043F (associated with high diflubenzuron resistance) was recorded at an 8% allelic frequency in Lasithi prefecture Cx. pipiens mosquitoes (sampled in 2020) for the first time in Greece. Markedly, Cx. pipiens populations in all four prefectures were found harboring the kdr mutations L1014F/C/S (associated with pyrethroid resistance) at a close to fixation rate, with mutation L1014C being the most commonly found allele (≥74% representation). Voltage gated sodium channel analyses in Ae. albopictus revealed the presence of the kdr mutations F1534C and I1532T (associated with putative mild pyrethroid resistance phenotypes) yet absence of V1016G. Allele F1534C was recorded in all prefectures (at an allelic frequency range of 25–46.6%) while I1532T was detected in populations from Chania, Rethymnon and Heraklion (at frequencies below 7.1%). Finally, no kdr mutations were detected in the Anopheles specimens included in the analyses.Conclusions/SignificanceThe findings of our study are of major concern for VBD control in Crete, highlighting (i) the necessity for establishing seasonal integrated entomological/pathogen surveillance programs, supporting the design of targeted vector control responses and; ii) the need for establishing appropriate insecticide resistance management programs ensuring the efficacy and sustainable use of DFB and pyrethroid based products in vector control.

Spatio-temporal Variation of Spinosad Susceptibility in Drosophila suzukii (Diptera: Drosophilidae), a Three-year Study in California's Monterey Bay Region.

Spinosyn insecticides are widely used in conventional berry production, and spinosad is regarded as the most effective insecticide for managing Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), spotted-wing drosophila, in organic berry crops. Following the 2017 identification of spinosad resistance in caneberry fields in the Watsonville area, Santa Cruz Co., California, we conducted a study to examine the seasonal and annual susceptibility of D. suzukii over a three-year period. Adult flies were collected from two conventional and two organic caneberry fields in the Monterey Bay region, California, at 'early', 'middle', and 'late' time points during the 2018-2020 growing seasons, and their susceptibility to spinosad was assessed. Results demonstrated that spinosad susceptibility in the D. suzukii field populations generally decreased during the fruit production season (from June through November), and over consecutive seasons. LC50 values of adults from the conventional sites were determined to be as high as 228.7 mg l-1 in 2018, 665.6 mg l-1 in 2019, and 2700.8 mg l-1 in 2020. For the organically managed fields, LC50s of adults were as great as 300.0 mg l-1 in 2018, 1291.5 mg l-1 in 2019, and 2547.1 mg l-1 in 2020. Resistance ratios based on the LC50 values were as high as 10.7-, 13.2-, and 16.9-fold in 2018, 2019, and 2020, respectively. These results should serve as a caution for growers in other production areas, facilitate informed choice of insecticides used in D. suzukii management, and emphasize the need to develop effective insecticide resistance management strategies for this insect.

A feasibility trial of genomics-based diagnosis detecting insecticide resistance of the diamondback moth.

Insecticide resistance management has been key for crop protection for over 70 years and is increasingly important because the development of new active ingredients has decreased in recent years. By monitoring the development of resistance in a timely manner, we can effectively prolong insecticide efficacy. Genomic-based diagnosis can reliably predict resistance development if information on resistant mutations against major pesticides is available. Here, we developed a feasibility trial of genomics-based diagnosis of insecticide resistance in diamondback moth (Plutella xylostella) populations in Nagano Prefecture, Japan. Amplicon sequencing analyses using a next-generation sequencer (Illumina MiSeq) for major insecticides, including diamides, pyrethroids, Bacillus thuringiensis (Bt) toxin (Cry1Ac), organophosphates, and spinosyns, were conducted. Mutations related to the resistance of pyrethroids, organophosphates, and diamides (flubendiamide and chlorantraniliprole) prevailed, while those of a diamide (cyantraniliprole), Bt (Cry1Ac), and spinosyns were scanty, suggesting that they are still effective. The results of the genomics-based diagnosis were generally concordant with the results of bioassays. Resistance development tendencies were generally uniform across Nagano. An insecticide-resistance management campaign can be conducted in Nagano Prefecture with a quick genomic-based diagnosis in early spring while bioassay is the only option for monitoring resistances whose mutations are unavailable. Our study is the first step in the future management of insecticide resistance in all significant pests. © 2022 Society of Chemical Industry.

Biodegradation of insecticides by gut bacteria isolated from stored grain beetles and its implication in host insecticide resistance

Stored grain pests have developed widespread resistance to currently available grain protectants. Although symbiotic microbes played an important role in insecticide resistance of insect hosts, it has not been reported in stored grain pests. In this study, five gut bacteria were excised from adult Sitophilus oryzae (L.) (Coleoptera: Curculionidae), Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae), and Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae). These bacteria can degrade malathion, pirimiphos-methyl, and deltamethrin and utilize these insecticides as the carbon source in vitro. When treated with 0.5–10 mg/kg of malathion, pirimiphos-methyl and 0.3–0.75 mg/kg of deltamethrin, gnotobiotic reinoculation of a given bacterial strain significantly enhanced survival rates of its hosts. The significance of gut bacteria in host insecticide tolerance was insecticide dosage-dependent. Furthermore, the in vitro insecticide biodegradability of gut bacteria was not completely consistent with their in vivo performance in host insecticide resistance. This suggests that there may be other physiological processes responsible for host insecticide tolerance mediated by symbiotic bacteria except for direct degradation of insecticides. These results provide insight into insecticide resistance management of stored grain pests and further study of the association between gut bacteria and insecticide resistance.