Insecticide Resistance Management Research Articles

Toxicity and residual activity of insecticides to Grapholita molesta (Lepidoptera: Tortricidae) in apple orchards: implications for insecticide resistance management.

Organophosphate (OP) insecticides have been used to control Grapholita molesta (Busck, 1916) in Brazil since 1990. However, the evolution of pest insecticide resistance and toxicological reassessments has led to the replacement of OPs with other chemical groups. This study evaluated the toxicity of the insecticides abamectin + cyantraniliprole (1.1 + 3.7g a.i./100L-1), acetamiprid + etofenproxi (9.1 + 16.5g a.i./100L-1), emamectin benzoate (0.5g a.i./100L-1), Sophora flavescens (Fabales: Fabaceae) (22.8g a.i./100L-1), phosmet (87.5g a.i./100L-1), and indoxacarb (11.2g a.i./100L-1) to eggs, larvae, and adults of G. molesta. Additionally, the residual activity of these insecticides in apple orchards was assessed, and the diagnostic concentration for resistance monitoring was estimated using LC99 values (Lethal Concentration that causes 99% mortality in a susceptible population). In larval studies, all insecticides resulted in mortality rates of more than 90%. The insecticide acetamiprid + etofenproxi reduced larval hatching by 99%. This insecticide with phosmet and Sophora flavescens caused over 80% adult mortality and had a 14-day residual activity in apple orchards. The estimated LC99 (μg.ml-1) for resistance monitoring were 1.75 (indoxacarb), 6.45 (metaflumizone), 9.10 (acetamiprid + etofenproxi), 9.67 (Sophora flavescens), 36.13 (phosmet), and 45.61 (abamectin + cyantraniliprole). The insecticides evaluated have high toxicity for G. molesta, being new tools for integrated pest management and for insecticide resistance management in apple orchards.

Fitness Costs in Diamondback Moth Plutella xylostella (L.) (Lepidoptera: Plutellidae) Resistant to Lufenuron, A Chitin-Synthesis Inhibitor Insecticide

The diamondback moth (DBM), Plutella xylostella, is the main pest of Brassicas crops worldwide, and its recorded resistance to 101 active ingredients indicates it is difficult to control. The purpose of this study was to investigate the hypothesis that P. xylostella has fitness costs associated with its resistance to lufenuron, a chitin-synthesis inhibitor insecticide. Thus, concentration–mortality bioassays were performed for susceptible (REC-S), resistant (BZR-R) populations, their progenies F1 and F1′, and one established population without selection pressure (BZR-Rns) after four generations. A fertility life table was used to assess the biological performance of the REC-S and BZR-R. BZR-Rns of P. xylostella. The larval stage, longevity, and survival differed between populations. The reproductive rate (R0) was significantly lower in the F1 (♀R × ♂S) (28.19) and F1′ (♀S × ♂R) (34.06) progenies compared with their parents, but not with the relaxed BZR-Rns (39.39). The mean generation time (T), intrinsic rate of population growth (rm), and doubling time (DT) differed between REC-S and progenies, with fitness of 0.52 and 0.64 for F1 and F1′, respectively. Overall, the results suggest that the resistance of P. xylostella to lufenuron is stable and that low fitness costs appear to be associated with resistance to lufenuron, although heterozygotes showed lower fitness than their parents. Strategies such as preserving refuge areas, rotation of modes of action, etc., are essential for resistance management and prolonging the efficacy of control agents; this highlights the importance of integrated insecticide resistance management.

Genome-wide analysis of detoxification genes conferring diamide insecticide resistance in Spodoptera exigua identifies CYP9A40

For over a decade, diamide insecticides have been effective against lepidopteran pests like beet armyworm, Spodoptera exigua (Hübner, 1808). However, the evolution of resistance poses a challenge to their sustainable use. We identified an I4790M mutation in the S. exigua ryanodine receptor (RyR) gene, but its correlation with resistance varied across the field-collected Korean populations of S. exigua. RNA sequencing and differential gene expression analysis were performed to investigate other resistance mechanisms. Diamide-resistant and susceptible strains and F1 hybrids were compared by mapping RNA-seq reads to the S. exigua reference genome. CYP9A40 was identified as a critical gene in diamide resistance due to its high expression in the resistant strains. Synergist bioassays with piperonyl butoxide supported the role of P450s in diamide metabolic resistance in S. exigua. A strong positive correlation between CYP9A40 over-expression levels (up to 80-fold) and diamide LC50 values was obtained for field-collected populations uniformly showing a 100% frequency of the RyR I4790M target-site resistance allele. To validate the function of CYP9A40 in diamide detoxification, we recombinantly expressed the gene and tested its ability to bind and degrade chlorantraniliprole as a substrate. The results confirmed its catalytic role in diamide metabolism. CYP9A40 has been identified and validated to confer metabolic resistance in Korean S. exigua populations. It works alongside the RyR target-site I4790M mutation to enhance diamide resistance. These mechanisms offer insights for resistance monitoring and support insecticide resistance management programs to improve control strategies for S. exigua.

Molecular Diagnostics for Monitoring Insecticide Resistance in Lepidopteran Pests

Chemical control methods to prevent crop damage have long been directly implicated in the selection of lepidoptera insect populations resistant to insecticides. More recently, new products featuring different modes of action (MoA), developed to mitigate the negative effects of control management on both producers and the environment, are rapidly losing efficacy due to the emergence of insect resistance. Among these, certain resistances are associated with molecular changes in the genomes of pest insects that are valuable for developing molecular markers for diagnostic tools, particularly the point mutations. Molecular diagnosis represents an innovative solution for insecticide resistance management (IRM) practices, allowing for the effective monitoring of insecticide resistance. This approach facilitates decision making by enabling the timely alternation between different modes of action (MoAs). In this context, this review focuses on the major lepidopteran pests that affect globally significant crops, discussing the impacts of insecticide resistance. It gathers literature on diagnostic methods; provides a comparative overview of the advantages of different techniques in terms of efficiency, cost, precision, sensitivity, and applicability; and highlights several novel diagnostic tools. Additionally, this review explores the coffee leaf miner, Leucoptera coffeella, as an applied model to illustrate potential approaches for more effective and sustainable control strategies.

Marking Helicoverpa zea (Lepidoptera: Noctuidae) with fluorophores for use in mark-release-recapture research

Abstract Knowledge of insect dispersal and long-distance migratory flight capacity and patterns represent key factors needed for risk assessment of invasive pest species, insecticide resistance management, and more effective pest control. Having operative tools to both mark and track insect pest movement is therefore critical to achieving such goals. Here, we describe a new procedure for marking Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), one of the most economically important crop pests in the United States. Adult H. zea moths were effectively marked using the liquid fluorophore cartax green, a persistent UV-fluorescent pigment, both directly by topical application and indirectly by briefly submerging pupae in the marking solution prior to adult emergence. Regardless of the application method, the cartax mark was retained on the moths throughout their entire adult lifespan. No mortality differences were observed between cartax green-marked and water-marked (control) moths. Additionally, using rotary flight mills, we found no significant differences in several flight parameters, including total number of flights, flight speeds, flight distances, or flight durations between unmarked and cartax-marked moths. Under laboratory conditions, we did observe the lateral transfer of different colored fluorophores between moths, indicating that undesirable marking could potentially occur. Moreover, we found that not all fluorophores were equally retained on H. zea moths, with cartax green remaining intact on moths longer than did a corresponding magenta fluorophore. The results show that cartax green fluorophore could be a practical marker for H. zea and other holometabolous species targeted for large-scale mark-release-recapture research.

The impact of lethal and sub-lethal exposure of emamectin benzoate on populations of Spodoptera litura (Lepidoptera: Noctuidae) under laboratory conditions

Emamectin benzoate is an avermectin bio-insecticide commonly used for managing several insect pests including Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), a major polyphagous pest of many cultivated crops. The current study was conducted to evaluate the effects of emamectin benzoate on the fitness of S. litura populations exhibiting differential susceptibility to insecticide. The selection process and all the bioassays were carried out using 6-day-old 2nd instar larvae of S. litura. A field-collected population of S. litura was divided into two groups: one selected with emamectin benzoate for eight generations (EB-Sel) and the other kept unexposed (Unsel-Lab) to insecticide in the laboratory. An increase in resistance ratio from 1.71-fold in the F1 generation to 22.54-fold in the F8 generation of the EB-Sel population was observed compared to the Unsel-Lab (F8) population. The EB-Sel and Unsel-Lab populations were treated with their respective lethal and sub-lethal concentrations which resulted in an extended development period, decreased larval survival, and adult emergence along with increased morphological abnormalities in adults. Significant reductions were observed in both male and female longevity, fecundity, egg hatching, net reproductive rate (R0), intrinsic rate of increase (rm), and finite rate of increase (λ) in EB-Sel and Unsel-Lab populations. Higher concentrations of the insecticide also reduced the relative fitness (Rf) of S. litura larvae, with maximum effect at LC50 of the EB-Sel population where the Rf value was 0.32 compared to the Unsel-Lab population. Both populations have been affected by emamectin benzoate exposure, however, the impact was more pronounced in the EB-Sel population indicating fitness costs. Our results suggested the fitness cost linked to emamectin benzoate resistance in S. litura which might favor managing insecticide resistance by reducing the frequency of resistant alleles by removing selection pressure. Consequently, our research provides significant insights to devise better pest management strategies for S. litura.

Comparative transcriptional analysis between susceptible and resistant populations of Aedes (Stegomyia) aegypti (Linnaeus, 1762) after malathion exposure.

Aedes aegypti is an important vector of arboviruses, including dengue, chikungunya and Zika. The application of synthetic insecticides is a frequently used strategy to control this insect. Malathion is an organophosphate insecticide that was widely used in Brazil in the 1980s and 1990s to control the adult form of A. aegypti. In situations where resistance to currently used insecticides is detected, the use of malathion may be resumed as a control measure. Many studies have confirmed resistance to malathion, however, comparative studies of differential gene expression of the entire transcriptome of resistant and susceptible insects are scarce. Therefore, understanding the molecular basis of resistance to this insecticide in this species is extremely important. In this paper, we present the first transcriptomic description of susceptible and resistant strains of A. aegypti challenged with malathion. Guided transcriptome assembly resulted in 39,904 transcripts, where 2133 differentially expressed transcripts were detected, and three were validated by RT-qPCR. Enrichment analysis for these identified transcripts resulted in 13 significant pathways (padj < 0.05), 8 associated with down-regulated and 5 with up-regulated transcripts in treated resistant insects. It was possible to divide the transcripts according to the mechanism of action into three main groups: (i) genes involved in detoxification metabolic pathways; (ii) genes of proteins located in the membrane/extracellular region; and (iii) genes related to DNA integration/function. These results are important in advancing knowledge of genes related to resistance mechanisms in this insect, enabling the development of effective technologies and strategies for managing insecticide resistance.

Characterization of ATP-binding cassette transporters associated with emamectin benzoate tolerance: from the model insect Drosophila melanogaster to the agricultural pest Spodoptera frugiperda.

Multiple families of detoxification genes, including the increasingly recognized family of ATP-binding cassette (ABC) transporters, work together to influence the toxicity of synthetic insecticides and thus their resistance. Effective management of insecticide resistance requires identification of all toxicity-affecting members from each family of toxicity-related genes. Here, we used emamectin benzoate (EB), ABC transporters and Spodoptera frugiperda as a working case to test whether the strategy of 'from the model insect Drosophila melanogaster to agricultural pests' can identify all or most ABC transporter members related to EB tolerance in S. frugiperda. After confirming the involvement of ABC transporters in the toxicity of EB against fruit fly with the ABC inhibitor verapamil, four ABC transporter genes (DmCG3327, DmCG11147, DmCG4822, and DmCG7627) were found to be involved in EB tolerance using RNA interference-based family-wide functional screening. A combination of phylogenic analysis and a reciprocal TBLASTN search identified five S. frugiperda ABC transporter members as homologs (SfABCC4, SfABCG1, and SfABCG23) or one-way best hits (SfABCG4 and SfABCG20) of the four fly ABC genes. Real-time quantitative polymerase chain reaction (qPCR) analysis found that all five S. frugiperda ABC transporter genes were inducible by EB, and expressed in all the developmental stages and larval tissues, but with significant quantitative differences among stages and tissues. A cytotoxicity assay of ABC-overexpressing Sf9 cell lines showed that all the five S. frugiperda ABC transporter genes made Sf9 cells tolerant to EB. This study not only identifies nine ABC transporter genes related to EB tolerance from D. melanogaster (four genes) and S. frugiperda (five genes), but also demonstrates the utility and effectiveness of the 'model to pests' strategy to identify most toxicity-affecting members from a given family of toxicity-related genes. © 2024 Society of Chemical Industry.

Chlorantraniliprole resistance associated with diamondback moth (Lepidoptera: Plutellidae) outbreaks in Arizona Brassica crops.

The diamondback moth, Plutella xylostella (Linnaeus), isone of the most important insect pests of Brassica crops worldwide. In October 2016, outbreaks of an invasive P. xylostella population and unexpected control failures occurred on broccoli and cauliflower crops throughout all vegetable-growing regions in Arizona. Nineteen populations of Plutella xylostella were collected from 2016 to 2021 from various commercial cauliflower fields in Yuma and Scottsdale, Arizona, and from experimental broccoli plots at the University of Arizona, Yuma Agricultural Center (UAYAC), Yuma, Arizona. Populations collected from the commercial cauliflower fields had been transplanted with seedlings produced in a local Yuma nursery in 2016 and Salinas, CA in 2017 to 2018, whereas experimental broccoli plots were direct seeded. These populations were evaluated for their susceptibility to chlorantraniliprole, spinetoram, emamectin benzoate, and cyantraniliprole. In this study, field rate laboratory bioassays, serial dilution laboratory bioassays, and field efficacy spray experiments were performed. The field rate laboratory bioassay results showed that spinetoram, emamectin benzoate, and cyantraniliprole remained effective at controlling P. xylostella, but chlorantraniliprole did not control P. xylostella at the field rate. Additionally, serial dilution bioassays confirmed significant levels of cyantraniliprole and chlorantraniliprole resistance in the P. xylostella populations collected from transplanted cauliflower fields. However, the results of the multiyear/growing-seasons study monitoring the susceptibility of P. xylostella populations collected from direct-seeded broccoli and field efficacy trials conducted at the UAYAC indicated that the resistance to diamide insecticides was neither uniform nor persistent following the 2016 outbreak. Nevertheless, the risk for P. xylostella resistance in Arizona vegetable-growing regions exists, particularly in Brassica transplants. Therefore, we recommend that Arizona Brassica growers remain vigilant and practice rigorous insecticide resistance management to offset the development of resistance.

The I4790K mutation of the ryanodine receptor is responsible for anthranilic diamide resistance in field populations of Plutella xylostella (Lepidoptera: Plutellidae).

Insecticide resistance in Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) is a major constraint on the global production of cruciferous crops. For effective management of insecticide resistance, it is necessary to develop a molecular detection tool for predicting insecticide resistance levels based on the mutation frequency of target sites. In this study, a susceptible strain (SHggt) of P. xylostella was subjected to chlorantraniliprole and tetraniliprole selection under laboratory conditions to obtain the CHLSel and TETSel strains, respectively, to determine their resistance development, cross-resistance and mutation frequencies of the P. xylostella ryanodine receptor (PxRyR). In addition, the tetraniliprole resistance and the mutation frequencies of the PxRyR from 7 field populations were evaluated. Continuous selection over 30 generations resulted in resistance ratios (RRs) of 7,073.2-fold and 6,971.0-fold for the CHLSel and TETSel strains, respectively, and thousandfold increases in cross-resistance to unexposed diamides, e.g., cyantraniliprole and flubendiamide, were observed. For the field populations, three out of seven populations have developed more than thousandfold resistance to tetraniliprole. Among the three investigated target site mutations in PxRyR, only I4790K was detected in both laboratory-selected strains. However, 2 mutations, I4790K and G4946E, were detected in field populations. A positive correlation between RRs and K allele frequencies was observed in the laboratory-selected/relaxed strains and field populations of P. xylostella. These results suggest a possible link between the development of anthranilic diamide resistance and the frequency of the PxRyR I4790K mutation, which can be used to develop effective strategies for diamide resistance management in P. xylostella.

Insecticide Resistance Management: A Detailed Review

Insecticide Resistance Management: A Detailed Review

Baseline susceptibility of an A1 quarantine pest - the South American tomato pinworm Tuta absoluta (Lepidoptera: Gelechiidae) to insecticides: past incidents and future probabilities in line to implementing successful pest management.

Tomato is a widely cultivated crop significant for its economic and nutritional benefits. The South American tomato pinworm, Tuta absoluta, originated in Peru South America and has invaded many nations, causing up to 100% yield loss in tomatoes. The pest was classified as a quarantine pest by the European Plant Protection Organization, before invading the Spain region. Later, this quarantine pest also invaded other regions of Europe, Africa and Asian countries. Invasive insect pests cause global economic losses of 70 billion dollars annually. Among the several management measures suggested against pests, insecticides are the primary method in practice among growers due to significant results, easier operations, and other crucial advantages. Anyhow, repeated application of insecticides has caused the pest to evolve resistance against most of the insecticides in vogue, resulting in a chain of events like management failures, using increased doses of insecticides, intensified chemical residues in the food chain, and irreparable environmental contamination. Major insecticides globally used to control T. absoluta belong to organophosphates, synthetic pyrethroids, neonicotinoids, diamides, avermectins, spinosyns, and oxadizines. Understanding the baseline susceptibility of pests to insecticides helps for better pest management options and is the same for T. absoluta populations to insecticides. The current review paper discusses the T. absoluta distribution, biology, spread, host range, baseline insecticide susceptibility, global insecticide resistance status, and possible management inputs based on our understanding of insecticide susceptibility. The pest can be managed with integrated insecticide resistance management including molecular approaches.

Overexpression of SmUGGT1 Confers Imidacloprid Resistance to Sitobion miscanthi (Takahashi).

Sitobion miscanthi, the main species of wheat aphids, is one kind of harmful pest. Chemical insecticides are the important agrochemical products to effectively control wheat aphids. However, the broad application has led to serious resistance of pests to several insecticides, and understanding insecticide resistance mechanisms is critical for integrated pest management. In this study, SmUGGT1, a new uridine diphosphate (UDP)-glycosyltransferase (UGT) gene, was cloned and more strongly expressed in the SM-R (the resistant strain to imidacloprid) than in the SM-S (the susceptible strain to imidacloprid). The increased susceptibility to imidacloprid was observed after silencing SmUGGT1, indicating that it can be related to the resistance to imidacloprid. Subsequently, SmUGGT1 regulated post-transcriptionally in the coding sequences (CDs) by miR-81 was verified and involved in the resistance to imidacloprid in S. miscanthi. This finding is crucial in the roles of UGT involved in insecticide resistance management in pests.

Realized heritability and fitness costs of flupyradifurone resistance in the cowpea aphid, Aphis craccivora Koch

The cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae) is a serious insect pest that infests legume crops. Flupyradifurone (FPF) is a butenolide insecticide that selectively targets sucking insects including aphids and whiteflies. However, the realized heritability (h2) and fitness costs associated with resistance to FPF have not yet been assessed with A. craccivora. In this study, A. craccivora showed the potential to develop resistance to FPF under continuous selection, with an overall mean estimated h2 of resistance of 0.21. Results of fitness costs showed no differences in the developmental time (except for N2 and N3), longevity, fecundity, adult pre-reproductive period (APRP), total pre-reproductive period (TPRP), and oviposition days (Od) of the FPF-R strain compared to the S-strain. In contrast, all population growth parameters, including the growth reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), mean generation time (T), and doubling time (DT), were significantly lower in the FPF-R strain than in the S-strain. Fitness cost studies revealed that resistance to FPF decreased the relative fitness of the FPF-R strain to 0.76 compared with that of the S-strain. The estimation of realized heritable h2 and identification of resistance fitness costs provide a basis for designing insecticide resistance management (IRM) programs to sustain susceptibility in insect populations.

Evaluating foliar insecticides and economic thresholds for Tychius picirostris (Coleoptera: Curculionidae) management in Oregon white clover seed production.

The clover seed weevil, Tychius picirostris Fabricius (Coleoptera: Curculionidae), is a major pest in Oregon white clover seed crops. Reliance on synthetic pyrethroid insecticides and limited availability of diverse modes of action (MoAs) has increased insecticide resistance selection in regional T. picirostris populations, emphasizing the need to evaluate novel chemistries and rotational strategies for effective insecticide resistance management (IRM). The efficacy of 8 foliar insecticide formulations for managing T. picirostris adult and larval life stages was determined in small and large-plot field trials across 2 crop years. In both years, bifenthrin (Brigade 2EC), the grower's standard, showed negligible adult and larval suppression. Insecticide formulations with isocycloseram and cyantraniliprole active ingredients reduced adult and larval populations when applied at BBCH 59-60 (prebloom) and BBCH 65-66 (full bloom) growth stages, respectively. While differences in T. picirostris abundance were observed among insecticide treatments, seed yield differences were not detected in large-plot trials. Larval abundance was correlated with reduced seed yield, and an economic threshold of ≥3 larvae per 30 inflorescences was determined as a conservative larval threshold to justify foliar applications of diamide insecticides. Additional commercial white clover seed fields were surveyed to compare larval scouting techniques, including a standard Berlese funnel and a grower's do-it-yourself funnel. Both larval extraction techniques were correlated and provided similar estimates of larval abundance. These findings demonstrate new MoAs, optimal insecticide application timing, and larval monitoring methods that can be incorporated into an effective T. picirostris IRM program in white clover seed crops.

Decoding defenses: Biochemical insights into insecticide resistance in tea mosquito bug, Helopeltis theivora Waterhouse (Hemiptera: Miridae) from tea plantations of Eastern India

Helopeltis theivora is one of the major tea pests in India and the strategies of management largely depend on application of different insecticides. Resistance in ten field populations of H. theivora collected from different tea growing regions of Eastern India to three insecticides was evaluated by leaf dip method in the laboratory. The results showed varied levels of susceptibility in nine populations to thiamethoxam and deltamethrin with a resistance coefficient (RC) ranging from 2.04 to 30.95 and 1.56–59.81-fold, respectively. Upper Assam and Central Dooars populations showed high resistance to thiamethoxam and deltamethrin. A high resistance to deltamethrin was also recorded in the Eastern Dooars (RC = 52.74) and Western Dooars (RC = 53.07) populations. There was no resistance to quinalphos in any of the populations (RC = 0.11–0.60). The Darjeeling population was relatively susceptible to the insecticides. Biochemical enzyme assays suggested that glutathione S-transferases (GST), general esterase (GE) and cytochrome P450 (CYP) activities were high in most of the field populations as compared to the susceptible population. However, the expression of CYP was statistically at par between the Cachar, Tripura, Darjeeling and susceptible population. GST and GE activity displayed a strong significant correlation with LC50 values of thiamethoxam and deltamethrin while a moderate to strong linear relationship was recorded between CYP and the LC50s of thiamethoxam and deltamethrin, respectively. A weak positive correlation was established between LC50 of quinalphos and the enzymes. Synergistic assays reveal that the addition of synergists’ piperonyl butoxide and diethyl maleate with thiamethoxam and deltamethrin enhanced the toxicity of these insecticides. The results of this study will contribute to the insecticide resistance management and integrated management of H. theivora.

Lethal, Sublethal, and Offspring Effects of Fluralaner and Dinotefuran on Three Species of Bactrocera Fruit Flies.

Fruit flies cause substantial economic damage, and their management relies primarily on chemical insecticides. However, pesticide resistance has been reported in several fruit fly species, the mitigation of which is crucial to enhancing fruit fly control. Here, we assess the toxicity of a novel insecticide (fluralaner) and a common insecticide (dinotefuran) against three fruit fly species, Bactrocera dorsalis (Hendel), Bactrocera cucurbitae (Coquillett), and Bactrocera tau (Walker). Both pesticides exhibit robust lethal and sublethal effects against all three fruit fly species, with fluralaner being more potent. Fluralaner and dinotefuran suppress the reproductive capacities and survival rates of fruit flies. However, at the 50% lethal concentration, fluralaner stimulates the reproductive capacity of B. dorsalis and the survival rate of B. tau. Fluralaner also causes significant transgenerational effects, impacting the offspring hatching rate of B. cucurbitae and B. tau and reducing the proportion of female offspring. Thus, both pesticides exhibit high potential for controlling fruit flies. However, their application should be tailored according to species variations and the diverse effects they may induce. Collectively, the findings of this study outline the sublethal effects of two insecticides against fruit flies, helping to optimize their application to ensure the effective management of insecticide resistance.

Evaluation of Biopesticides for Management of Bemisia tabaci Middle East-Asia Minor 1 (Hemiptera: Aleyrodidae) in Florida.

The sweetpotato whitefly, Bemisia tabaci MEAM1, is a pest known to significantly impact tomato development and yields through direct damage and virus transmission. To manage this pest, the current study compared the effectiveness of various insecticide rotations. Field trials included rotations involving synthetic insecticides, biochemicals, and microbial agents, applied according to their highest labeled concentrations. The results indicated that while standard synthetic insecticides consistently reduced whitefly egg and nymph counts significantly, microbial biopesticide rotations also achieved reductions, although less consistently. This study demonstrated that while traditional chemical treatments remain highly effective, microbial biopesticides containing Beauveria bassiana and Cordyceps javanica present a viable alternative to manage MEAM1 in tomato fields. The data generated in this study provided baseline information for further investigations to determine the potential for optimizing integrated pest management (IPM) and insecticide resistance management (IRM) strategies by incorporating microbial biopesticides in rotations with a variety of modes of action to sustainably manage B. tabaci MEAM1 populations in agricultural settings.

Biological threats to global malaria elimination Ⅲ Vector insecticide resistance

The insecticide resistance is becoming increasingly severe in malaria vectors and has become one of the most important threats to global malaria elimination. Currently, malaria vectors not only have developed high resistance to conventional insecticides, including organochlorine, organophosphates, carbamates, and pyrethroids, but also have been resistant to recently used neonicotinoids and pyrrole insecticides. This article describes the current status of global insecticide resistance in malaria vectors and global insecticide resistance management strategies, analyzes the possible major challenges in the insecticide resistance management, and proposes the response actions, so as to provide insights into global insecticide resistance management and contributions to global malaria elimination.

Can neonicotinoid and pyrrole insecticides manage malaria vector resistance in high pyrethroid resistance areas in Côte d'Ivoire?

BackgroundAnopheles mosquito resistance to insecticide remains a serious threat to malaria vector control affecting several sub-Sahara African countries, including Côte d’Ivoire, where high pyrethroid, carbamate and organophosphate resistance have been reported. Since 2017, new insecticides, namely neonicotinoids (e.g.; clothianidin) and pyrroles (e.g.; chlorfenapyr) have been pre-qualified by the World Health Organization (WHO) for use in public health to manage insecticide resistance for disease vector control.MethodsClothianidin and chlorfenapyr were tested against the field-collected Anopheles gambiae populations from Gagnoa, Daloa and Abengourou using the WHO standard insecticide susceptibility biossays. Anopheles gambiae larvae were collected from several larval habitats, pooled and reared to adulthood in each site in July 2020. Non-blood-fed adult female mosquitoes aged 2 to 5 days were exposed to diagnostic concentration deltamethrin, permethrin, alpha-cypermethrin, bendiocarb, and pirimiphos-methyl. Clothianidin 2% treated papers were locally made and tested using WHO tube bioassay while chlorfenapyr (100 µg/bottle) was evaluated using WHO bottle assays. Furthermore, subsamples of exposed mosquitoes were identified to species and genotyped for insecticide resistance markers including the knock-down resistance (kdr) west and east, and acetylcholinesterase (Ace-1) using molecular techniques.ResultsHigh pyrethroid resistance was recorded with diagnostic dose in Abengourou (1.1 to 3.4% mortality), in Daloa (15.5 to 33.8%) and in Gagnoa (10.3 to 41.6%). With bendiocarb, mortality rates ranged from 49.5 to 62.3%. Complete mortality (100% mortality) was recorded with clothianidin in Gagnoa, 94.9% in Daloa and 96.6% in Abengourou, while susceptibility (mortality > 98%) to chlorfenapyr 100 µg/bottle was recorded at all sites and to pirimiphos-methyl in Gagnoa and Abengourou. Kdr-west mutation was present at high frequency (0.58 to 0.73) in the three sites and Kdr-east mutation frequency was recorded at a very low frequency of 0.02 in both Abengourou and Daloa samples and absent in Gagnoa. The Ace-1 mutation was present at frequencies between 0.19 and 0.29 in these areas. Anopheles coluzzii represented 100% of mosquitoes collected in Daloa and Gagnoa, and 72% in Abengourou.ConclusionsThis study showed that clothianidin and chlorfenapyr insecticides induce high mortality in the natural and pyrethroid-resistant An. gambiae populations in Côte d’Ivoire. These results could support a resistance management plan by proposing an insecticide rotation strategy for vector control interventions.