The evolutionary origins of pesticide resistance

The molecular mechanisms of insecticide resistance in aphid crop pests

Aphids are a group of hemipteran insects that include some of the world's most economically important agricultural pests. The control of pest aphids has relied heavily on the use of chemical insecticides, however, the evolution of resistance poses a serious threat to their sustainable control. Over 1000 cases of resistance have now been documented for aphids involving a remarkable diversity of mechanisms that, individually or in combination, allow the toxic effect of insecticides to be avoided or overcome. In addition to its applied importance as a growing threat to human food security, insecticide resistance in aphids also offers an exceptional opportunity to study evolution under strong selection and gain insight into the genetic variation fuelling rapid adaptation. In this review we summarise the biochemical and molecular mechanisms underlying resistance in the most economically important aphid pests worldwide and the insights study of this topic has provided on the genomic architecture of adaptive traits.

A major 6 Mb superlocus is involved in pyrethroid resistance in the common bed bug Cimex lectularius

In the last few years, the bed bug Cimex lectularius has been an increasing problem worldwide, mainly due to the development of insecticide resistance to pyrethroids. The characterization of resistance alleles is a prerequisite to improve surveillance and resistance management. To identify genomic variants associated with pyrethroid resistance in Cimex lectularius, we compared the genetic composition of two recent and resistant populations with that of two ancient-susceptible strains using a genome-wide pool-seq design. We identified a large 6 Mb "superlocus" showing particularly high genetic differentiation and association with the resistance phenotype. This superlocus contained several clustered resistance genes and was also characterized by a high density of structural variants (inversions, duplications). The possibility that this superlocus constitutes a resistance "supergene" that evolved after the clustering of alleles adapted to insecticide and after reduction in recombination is discussed.

A high-throughput KASP assay provides insights into the evolution of multiple resistant mutations in populations of the two-spotted spider mite Tetranychus urticae across China

BACKGROUND

The two-spotted spider mite (TSSM), Tetranychus urticae (Acari: Tetranychidae), is a cosmopolitan phytophagous pest in agriculture and horticulture. It has developed resistance to many acaricides by target-site mutations. Understanding the status and evolution of resistant mutations in the field is essential for resistance management. Here, we applied a high-throughput Kompetitive allele-specific polymerase chain reaction (KASP) method for detecting six mutations conferring resistance to four acaricides of the TSSM. We genotyped 3274 female adults of TSSM from 43 populations collected across China in 2017, 2020, and 2021.

RESULTS

The KASP genotyping of 24 testing individuals showed 99% agreement with Sanger sequencing results. KASP assays showed that most populations had a high frequency of mutations conferring avermectin (G314D and G326E) and pyridaben (H92R) resistance. The frequency of mutation conferring bifenazate (A269V and G126S) and etoxazole (I1017F) resistance was relatively low. Multiple mutations were common in the TSSM, with 70.2% and 24.6% of individuals having 2-6 and 7-10 of 10 possible resistant alleles, respectively. No loci were linked in most populations among the six mutations, indicating the development of multiple resistance is mainly by independent selection. However, G314D and I1017F on the nuclear genome deviated from Hardy-Weinberg equilibrium in most populations, indicating significant selective pressure on TSSM populations by acaricides or fitness cost of the mutations in the absence of acaricide selection.

CONCLUSION

Our study revealed that the high frequency of TSSMs evolved multiple resistant mutations in population and individual levels by independent selection across China, alarming for managing multiple-acaricides resistance. © 2023 Society of Chemical Industry.

Interchromosomal linkage disequilibrium and linked fitness cost loci associated with selection for herbicide resistance

The adaptation of weeds to herbicide is both a significant problem in agriculture and a model of rapid adaptation. However, significant gaps remain in our knowledge of resistance controlled by many loci and the evolutionary factors that influence the maintenance of resistance. Here, using herbicide-resistant populations of the common morning glory (Ipomoea purpurea), we perform a multilevel analysis of the genome and transcriptome to uncover putative loci involved in nontarget-site herbicide resistance (NTSR) and to examine evolutionary forces underlying the maintenance of resistance in natural populations. We found loci involved in herbicide detoxification and stress sensing to be under selection and confirmed that detoxification is responsible for glyphosate (RoundUp) resistance using a functional assay. We identified interchromosomal linkage disequilibrium (ILD) among loci under selection reflecting either historical processes or additive effects leading to the resistance phenotype. We further identified potential fitness cost loci that were strongly linked to resistance alleles, indicating the role of genetic hitchhiking in maintaining the cost. Overall, our work suggests that NTSR glyphosate resistance in I. purpurea is conferred by multiple genes which are potentially maintained through generations via ILD, and that the fitness cost associated with resistance in this species is likely a by-product of genetic hitchhiking.

Use of whey protein as a natural polymer for the encapsulation of plant biocontrol bacteria: A review

Climate changes, drought, the salinity of water and soil, the emergence of new breeds of pests and pathogens, the industrialization of countries, and environmental contamination are among the factors limiting the production of agricultural products. The use of chemicals (in the form of fertilizers, pesticides and fungicides) to enhance products against biotic and abiotic stresses has limitations. To eliminate the effects of agricultural chemicals, synthetic agrochemicals should be replaced with natural substances and useful microorganisms. To be more effective and efficient, plant biocontrol bacteria need a coating layer around themselves to protect them from adverse conditions. Whey protein, a valuable by-product of the cheese industry, is one of the important natural polymers. Due to its high protein content, safety, and biodegradability, whey can have many applications in agriculture and encapsulation of bacteria to resist pests and plant diseases. This compound is a rich source of amino acids that can activate plant defense systems and defense enzymes. Considering the amazing potentialities of formulation whey protein, this review attends to the efficiency of whey protein as coating layers on fruit and vegetables and in the packaging system to increase the shelf life of agricultural products against phytopathogens.

Intraspecific diversity in the mechanisms underlying abamectin resistance in a cosmopolitan pest

Pesticide resistance relies on a myriad of mechanisms, ranging from single mutations to a complex and polygenic architecture, and it involves mechanisms such as target-site insensitivity, metabolic detoxification, or a combination of these, with either additive or synergistic effects. Several resistance mechanisms against abamectin, a macrocyclic lactone widely used in crop protection, have been reported in the cosmopolitan pest Tetranychus urticae. However, it has been shown that a single mechanism cannot account for the high levels of abamectin resistance found across different mite populations. Here, we used experimental evolution combined with bulked segregant analyses to map quantitative trait loci (QTL) associated with abamectin resistance in two genetically unrelated populations of T. urticae. In these two independent QTL mapping experiments, three and four QTLs were identified, of which three were shared between experiments. Shared QTLs contained genes encoding subunits of the glutamate-gated chloride channel (GluCl) and harboured previously reported mutations, including G314D in GluCl1 and G326E in GluCl3, but also novel resistance candidate loci, including DNA helicases and chemosensory receptors. Surprisingly, the fourth QTL, present only in only one of the experiments and thus unique for one resistant parental line, revealed a non-functional variant of GluCl2, suggesting gene knock-out as resistance mechanism. Our study uncovers the complex basis of abamectin resistance, and it highlights the intraspecific diversity of genetic mechanisms underlying resistance in a cosmopolitan pest.

The complete genome assemblies of 19 insect pests of worldwide importance to agriculture

There are many insect pests worldwide that damage agricultural crop and reduce yield either by direct feeding or by the transmission of plant diseases. To date, control of pest insects has been achieved largely by applying synthetic insecticides. However, insecticide use can be seriously impacted by legislation that limits their use or by the evolution of resistance in the target pest. Thus, there is a move towards less use of insecticides and increased adoption of integrated pest management strategies using a wide range of non-chemical and chemical control methods. For good pest control there is a need to understand the mode of action and selectivity of insecticides, the life cycles of the pests and their biology and behaviours, all of which can benefit from good quality genome data. Here we present the complete assembled (chromosome level) genomes (incl. mtDNA) of 19 insect pests, Agriotes lineatus (click beetle/wireworm), Aphis gossypii (melon/cotton aphid), Bemisia tabaci (cotton whitefly), Brassicogethes aeneus (pollen beetle), Ceutorhynchus obstrictus (seedpod weevil), Chilo suppressalis (striped rice stem borer), Chrysodeixis includens (soybean looper), Diabrotica balteata (cucumber beetle), Diatraea saccharalis (sugar cane borer), Nezara viridula (green stink bug), Nilaparvata lugens (brown plant hopper), Phaedon cochleariae (mustard beetle), Phyllotreta striolata (striped flea beetle), Psylliodes chrysocephala (cabbage stem flea beetle), Spodoptera exigua (beet army worm), Spodoptera littoralis (cotton leaf worm), Diabrotica virgifera (western corn root worm), Euschistus heros (brown stink bug) and Phyllotreta cruciferae (crucifer flea beetle). For the first 15 of these we also present the annotation of genes encoding potential xenobiotic detoxification enzymes. This public resource will aid in the elucidation and monitoring of resistance mechanisms, the development of highly selective chemistry and potential techniques to disrupt behaviour in a way that limits the effect of the pests.

Fine-grained weed recognition using Swin Transformer and two-stage transfer learning

Weeding is very critical for agriculture due to its importance for reducing crop yield loss. Accurate recognition of weed species is one of the major challenges for achieving automatic and precise weeding. To improve the recognition performance of weeds and crops with similar visual characteristics, a fine-grained weed recognition method based on Swin Transformer and two-stage transfer learning is proposed in this study. First, the Swin Transformer network is introduced to learn the discriminative features that can distinguish subtle differences between visually similar weeds and crops. Second, a contrastive loss is applied to further enlarge the feature differences between different categories of weeds and crops. Finally, a two-stage transfer learning strategy is proposed to address the problem of insufficient training data and improve the accuracy of weed recognition. To evaluate the effectiveness of the proposed method, we constructed a private weed dataset (MWFI) with maize seedling and seven species of associated weeds that are collected in the farmland environment. The experimental results on this dataset show that the proposed method achieved the recognition accuracy, precision, recall, and F1 score of 99.18%, 99.33%, 99.11%, and 99.22%, respectively, which are superior to the performance of the state-of-the-art convolutional neural network (CNN)-based architectures including VGG-16, ResNet-50, DenseNet-121, SE-ResNet-50, and EfficientNetV2. Additionally, evaluation results on the public DeepWeeds dataset further demonstrate the effectiveness of the proposed method. This study can provide a reference for the design of automatic weed recognition systems.

Weed genomics: yielding insights into the genetics of weedy traits for crop improvement

Weeds cause tremendous economic and ecological damage worldwide. The number of genomes established for weed species has sharply increased during the recent decade, with some 26 weed species having been sequenced and de novo genomes assembled. These genomes range from 270 Mb (Barbarea vulgaris) to almost 4.4 Gb (Aegilops tauschii). Importantly, chromosome-level assemblies are now available for 17 of these 26 species, and genomic investigations on weed populations have been conducted in at least 12 species. The resulting genomic data have greatly facilitated studies of weed management and biology, especially origin and evolution. Available weed genomes have indeed revealed valuable weed-derived genetic materials for crop improvement. In this review, we summarize the recent progress made in weed genomics and provide a perspective for further exploitation in this emerging field.

The role of structural variants in pest adaptation and genome evolution of the Colorado potato beetle, Leptinotarsa decemlineata (Say)

Structural variation has been associated with genetic diversity and adaptation. Despite these observations, it is not clear what their relative importance is for evolution, especially in rapidly adapting species. Here, we examine the significance of structural polymorphisms in pesticide resistance evolution of the agricultural super-pest, the Colorado potato beetle, Leptinotarsa decemlineata. By employing a parent offspring trio sequencing procedure, we develop highly contiguous reference genomes to characterize structural variation. These updated assemblies represent >100-fold improvement of contiguity and include derived pest and ancestral nonpest individuals. We identify >200,000 structural variations, which appear to be nonrandomly distributed across the genome as they co-occur with transposable elements and genes. Structural variations intersect with exons in a large proportion of gene annotations (~20%) that are associated with insecticide resistance (including cytochrome P450s), development, and transcription. To understand the role structural variations play in adaptation, we measure their allele frequencies among an additional 57 individuals using whole genome resequencing data, which represents pest and nonpest populations of North America. Incorporating multiple independent tests to detect the signature of natural selection using SNP data, we identify 14 genes that are probably under positive selection, include structural variations, and SNPs of elevated frequency within the pest lineages. Among these, three are associated with insecticide resistance based on previous research. One of these genes, CYP4g15, is coinduced during insecticide exposure with glycosyltransferase-13, which is a duplicated gene enclosed within a structural variant adjacent to the CYP4g15 genic region. These results demonstrate the significance of structural variations as a genomic feature to describe species history, genetic diversity, and adaptation.

Engineered silica nanomaterials in pesticide delivery: Challenges and perspectives

Over the past decade, nanopesticide has been developed rapidly for exploring effective and safe alternatives to conventional pesticides with significant drawbacks and risks. Many nanotechnologies, including pesticide nanoemulsions, polymer-based nanopesticides, and metal/metal oxide nanoparticle-based pesticides have emerged and are extensively reviewed. Engineered silica nanomaterials (ESNs) have also shown promising potential as carriers in nanopesticides for modern agriculture. However, there are limited reviews specifically on ESN-based nanopesticides. Herein, we provide a comprehensive review on the recent progress of ESN-based nanopesticide technologies. An introduction of synthetic technology, formation mechanism, and surface engineering technology is firstly presented. Then, the advantages of ESN-based pesticide formulation and their structure-function-relationship are illustrated in detail. Finally, our perspectives on challenges and future research in ESN-based nanopesticide development are discussed.

The blackgrass genome reveals patterns of non-parallel evolution of polygenic herbicide resistance

Globally, weedy plants are a major constraint to sustainable crop production. Much of the success of weeds rests with their ability to rapidly adapt in the face of human-mediated management of agroecosystems. Alopecurus myosuroides (blackgrass) is a widespread and impactful weed affecting agriculture in Europe. Here we report a chromosome-scale genome assembly of blackgrass and use this reference genome to explore the genomic/genetic basis of non-target site herbicide resistance (NTSR). Based on our analysis of F2 seed families derived from two distinct blackgrass populations with the same NTSR phenotype, we demonstrate that the trait is polygenic and evolves from standing genetic variation. We present evidence that selection for NTSR has signatures of both parallel and non-parallel evolution. There are parallel and non-parallel changes at the transcriptional level of several stress- and defence-responsive gene families. At the genomic level, however, the genetic loci underpinning NTSR are different (non-parallel) between seed families. We speculate that variation in the number, regulation and function of stress- and defence-related gene families enable weedy species to rapidly evolve NTSR via exaptation of genes within large multi-functional gene families. These results provide novel insights into the potential for, and nature of plant adaptation in rapidly changing environments.

Do genotypes ameliorate herbivory stress through silicon amendments differently? A case study of wheat

Agricultural productivity relies on plant resistance to insect pests, with silicon (Si) being increasingly recognized as an important anti-herbivore defense. However, the processes by which Si works to counteract the effects of insect injury are not completely understood. The role of Si in mitigating the adverse effects of herbivory has been mostly studied at the species level in various crops, ignoring the sensitivity and variability at the genotypic level. Understanding such variation across genotypes is important because Si-derived benefits are associated with the amount of Si accumulated in the plant. Therefore, the present investigation was pursued to study the effect of different Si concentrations (0, 125, and 250 mg L⁻¹) on Si accumulation and plant growth using two wheat genotypes (WW-101 and SW-2) under grasshopper herbivory for 48 h. The higher Si absorption increased the concentration of leaf chlorophyll, carotenoids, soluble sugars, and proteins. Silicon application at higher concentrations increased the dry weight, antioxidant enzyme activity, total phenolics, flavonoids and shoot Si concentration, whereas it decreased the electrolyte leakage, hydrogen peroxide (H₂O₂) and malonaldehyde (MDA) levels, thereby preventing leaf damage. We infer that the higher Si concentration alleviates the adverse effects of herbivory in wheat by improving the accumulation of secondary metabolites and enhancing the antioxidant defense system. The effects were pronounced in the genotype 'WW-101' compared to 'SW-2' for most of the studied traits, indicating overall stress response to be genotype-dependent. Thus, Si acquisition efficiency of genotypes should be considered while developing efficient crop management strategies.

Increasing ecological heterogeneity can constrain biopesticide resistance evolution

Microbial biopesticides containing living parasites are valuable emerging crop protection technologies against insect pests, but they are vulnerable to resistance evolution. Fortunately, the fitness of alleles that provide resistance, including to parasites used in biopesticides, frequently depends on parasite identity and environmental conditions. This context-specificity suggests a sustainable approach to biopesticide resistance management through landscape diversification. To mitigate resistance risks, we advocate increasing the range of biopesticides available to farmers, whilst simultaneously encouraging other aspects of landscape-wide crop heterogeneity that can generate variable selection on resistance alleles. This approach requires agricultural stakeholders to prioritize diversity as well as efficiency, both within agricultural landscapes and the biocontrol marketplace.

Novel fungicide quinofumelin shows selectivity for fungal dihydroorotate dehydrogenase over the corresponding human enzyme

The species selectivity of class 2 dihydroorotate dehydrogenase (DHODH), a target enzyme for quinofumelin, was examined. The Homo sapiens DHODH (HsDHODH) assay system was developed to compare the selectivity of quinofumelin for fungi with that for mammals. The IC₅₀ values of quinofumelin for Pyricularia oryzae DHODH (PoDHODH) and HsDHODH were 2.8 nM and >100 µM, respectively. Quinofumelin was highly selective for fungal over human DHODH. Additionally, we constructed recombinant P. oryzae mutants where PoDHODH (PoPYR4) or HsDHODH was inserted into the PoPYR4 disruption mutant. At quinofumelin concentration of 0.01-1 ppm, the PoPYR4 insertion mutants could not grow, but the HsDHODH gene-insertion mutants thrived. This indicates that HsDHODH is a substitute for PoDHODH, and quinofumelin could not inhibit HsDHODH as in the HsDHODH enzyme assay. Comparing the amino acid sequences of human and fungal DHODHs indicates that the significant difference at the ubiquinone-binding site contributes to the species selectivity of quinofumelin.

Antifungal alternation can be beneficial for durability but at the cost of generalist resistance

The evolution of resistance to pesticides is a major burden in agriculture. Resistance management involves maximizing selection pressure heterogeneity, particularly by combining active ingredients with different modes of action. We tested the hypothesis that alternation may delay the build-up of resistance not only by spreading selection pressure over longer periods, but also by decreasing the rate of evolution of resistance to alternated fungicides, by applying an experimental evolution approach to the economically important crop pathogen Zymoseptoria tritici. Our results show that alternation is either neutral or slows the overall resistance evolution rate, relative to continuous fungicide use, but results in higher levels of generalism in evolved lines. We demonstrate that the nature of the fungicides, and therefore their relative intrinsic risk of resistance may underly this trade-off, more so than the number of fungicides and the rhythm of alternation. This trade-off is also dynamic over the course of resistance evolution. These findings open up new possibilities for tailoring resistance management effectively while optimizing interplay between alternation components.

Bionanotechnology in Agriculture: A One Health Approach

Healthy eating habits are one of the requirements for the health of society. In particular, in natura foods are increasingly encouraged, since they have a high concentration of nutrients. However, these foods are often grown in the presence of agrochemicals, such as fertilizers and pesticides. To increase crop productivity and achieve high vigor standards in less time, farmers make excessive use of agrochemicals that generate various economic, environmental, and clinical problems. In this way, bionanotechnology appears as an ally in developing technologies to improve planting conditions, ranging from the health of farmers and consumers to the production of new foods and functional foods. All these improvements are based on the better use of land use in synergy with the lowest generation of environmental impacts and the health of living beings, with a view to the study and production of technologies that take into account the concept of One Health in its processes and products. In this review article, we will address how caring for agriculture can directly influence the quality of the most desired foods in contemporary society, and how new alternatives based on nanotechnology can point to efficient and safe solutions for living beings on our planet.

"Ectomosphere": Insects and Microorganism Interactions

This study focuses on interacting with insects and their ectosymbiont (lato sensu) microorganisms for environmentally safe plant production and protection. Some cases help compare ectosymbiont microorganisms that are insect-borne, -driven, or -spread relevant to endosymbionts' behaviour. Ectosymbiotic bacteria can interact with insects by allowing them to improve the value of their pabula. In addition, some bacteria are essential for creating ecological niches that can host the development of pests. Insect-borne plant pathogens include bacteria, viruses, and fungi. These pathogens interact with their vectors to enhance reciprocal fitness. Knowing vector-phoront interaction could considerably increase chances for outbreak management, notably when sustained by quarantine vector ectosymbiont pathogens, such as the actual Xylella fastidiosa Mediterranean invasion episode. Insect pathogenic viruses have a close evolutionary relationship with their hosts, also being highly specific and obligate parasites. Sixteen virus families have been reported to infect insects and may be involved in the biological control of specific pests, including some economic weevils. Insects and fungi are among the most widespread organisms in nature and interact with each other, establishing symbiotic relationships ranging from mutualism to antagonism. The associations can influence the extent to which interacting organisms can exert their effects on plants and the proper management practices. Sustainable pest management also relies on entomopathogenic fungi; research on these species starts from their isolation from insect carcasses, followed by identification using conventional light or electron microscopy techniques. Thanks to the development of omics sciences, it is possible to identify entomopathogenic fungi with evolutionary histories that are less-shared with the target insect and can be proposed as pest antagonists. Many interesting omics can help detect the presence of entomopathogens in different natural matrices, such as soil or plants. The same techniques will help localize ectosymbionts, localization of recesses, or specialized morphological adaptation, greatly supporting the robust interpretation of the symbiont role. The manipulation and modulation of ectosymbionts could be a more promising way to counteract pests and borne pathogens, mitigating the impact of formulates and reducing food insecurity due to the lesser impact of direct damage and diseases. The promise has a preventive intent for more manageable and broader implications for pests, comparing what we can obtain using simpler, less-specific techniques and a less comprehensive approach to Integrated Pest Management (IPM).

Rapid adaptation in a fast-changing world: Emerging insights from insect genomics

Many researchers have questioned the ability of biota to adapt to rapid anthropogenic environmental shifts. Here, we synthesize emerging genomic evidence for rapid insect evolution in response to human pressure. These new data reveal diverse genomic mechanisms (single locus, polygenic, structural shifts; introgression) underpinning rapid adaptive responses to a variety of anthropogenic selective pressures. While the effects of some human impacts (e.g. pollution; pesticides) have been previously documented, here we highlight startling new evidence for rapid evolutionary responses to additional anthropogenic processes such as deforestation. These recent findings indicate that diverse insect assemblages can indeed respond dynamically to major anthropogenic evolutionary challenges. Our synthesis also emphasizes the critical roles of genomic architecture, standing variation and gene flow in maintaining future adaptive potential. Broadly, it is clear that genomic approaches are essential for predicting, monitoring and responding to ongoing anthropogenic biodiversity shifts in a fast-changing world.

A comprehensive assessment of insecticide resistance mutations in source and immigrant populations of the diamondback moth Plutella xylostella (L.)

BACKGROUND

The diamondback moth (DBM) Plutella xylostella has developed resistance to almost all insecticides used to control it. Populations of DBM in temperate regions mainly migrate from annual breeding areas. However, the distribution pattern of insecticide resistance of DBM within the context of long-distance migration remains unclear.

RESULTS

In this study, we examined the frequency of 14 resistance mutations for 52 populations of DBM collected in 2010, 2011, 2017 and 2018 across China using a high-throughput KASP genotyping method. Mutations L1041F and T929I conferring pyrethroid resistance, and mutations G4946E and E1338D conferring chlorantraniliprole resistance were near fixation in most populations, whereas resistant alleles of F1020S, M918I, A309V and F1845Y were uncommon or absent in most populations. Resistance allele frequencies were relatively stable among different years, although the frequency of two mutations decreased. Principal component analysis based on resistant allele frequencies separated a southern population as an outlier, whereas the immigrants clustered with other populations, congruent with the migration pattern of northern immigrants coming from the Sichuan area of southwestern China. Most resistant mutations deviated from Hardy-Weinberg equilibrium due to a lower than expected frequency of heterozygotes. The deviation index of heterozygosity for resistant alleles was significantly higher than the index obtained from single nucleotide polymorphisms across the genome. These findings suggest heterogeneous selection pressures on resistant mutations.

CONCLUSION

Our results provide a picture of resistant mutation patterns in DBM shaped by insecticide usage and migration of this pest, and highlight the widespread distribution of resistance alleles in DBM. © 2022 Society of Chemical Industry.

Reduced Sensitivity to Fluopyram in Meloidogyne graminis following Long-Term Exposure in Golf Turf

In recent years, some golf course superintendents in Florida have reported that the turf health is no longer as great, and nematode responses to fluopyram have decreased. The objective of this research was to determine if the mechanism of the reported reduced efficacy was attributable to either: i) enhanced degradation accelerating its breakdown in the soil, or ii) reduced sensitivity to the nematicide in the nematode populations. In a field experiment, soil and nematodes were collected from small plots that had been treated multiple times over four years, for only one year, or never treated. Soil and nematodes were additionally collected from commercial turf sites where either multiple applications of fluopyram had been made for numerous years, or it had never been used. Bioassay experiments found no evidence of enhanced degradation. However, M. graminis collected from small field plots and commercial sites with long-term use of fluopyram were less sensitive to fluopyram in-vitro than those from small plots and commercial sites where fluopyram had not been used. These results indicate that nematicide resistance is a likely cause of reduced fluopyram efficacy on golf-course turf in Florida.

Trichoderma Species: Our Best Fungal Allies in the Biocontrol of Plant Diseases-A Review

Biocontrol agents (BCA) have been an important tool in agriculture to prevent crop losses due to plant pathogens infections and to increase plant food production globally, diminishing the necessity for chemical pesticides and fertilizers and offering a more sustainable and environmentally friendly option. Fungi from the genus Trichoderma are among the most used and studied microorganisms as BCA due to the variety of biocontrol traits, such as parasitism, antibiosis, secondary metabolites (SM) production, and plant defense system induction. Several Trichoderma species are well-known mycoparasites. However, some of those species can antagonize other organisms such as nematodes and plant pests, making this fungus a very versatile BCA. Trichoderma has been used in agriculture as part of innovative bioformulations, either just Trichoderma species or in combination with other plant-beneficial microbes, such as plant growth-promoting bacteria (PGPB). Here, we review the most recent literature regarding the biocontrol studies about six of the most used Trichoderma species, T. atroviride, T. harzianum, T. asperellum, T. virens, T. longibrachiatum, and T. viride, highlighting their biocontrol traits and the use of these fungal genera in Trichoderma-based formulations to control or prevent plant diseases, and their importance as a substitute for chemical pesticides and fertilizers.

Epigenetic regulations as drivers of insecticide resistance and resilience to climate change in arthropod pests

Arthropod pests are remarkably capable of rapidly adapting to novel forms of environmental stress, including insecticides and climate change. The dynamic interplay between epigenetics and genetics explains the largely unexplored reality underlying rapid climatic adaptation and the development of insecticide resistance in insects. Epigenetic regulation modulates gene expression by methylating DNA and acetylating histones that play an essential role in governing insecticide resistance and adaptation to climate change. This review summarises and discusses the significance of recent advances in epigenetic regulation that facilitate phenotypic plasticity in insects and their symbiotic microbes to cope with selection pressure implied by extensive insecticide applications and climate change. We also discuss how epigenetic changes are passed on to multiple generations through sexual recombination, which remains enigmatic. Finally, we explain how these epigenetic signatures can be utilized to manage insecticide resistance and pest resilience to climate change in Anthropocene.

Population genomic insights into invasion success in a polyphagous agricultural pest, Halyomorpha halys

Invasive species are increasingly threatening ecosystems and agriculture by rapidly expanding their range and adapting to environmental and human-imposed selective pressures. The genomic mechanisms that underlie such rapid changes remain unclear, especially for agriculturally important pests. Here, we used genome-wide polymorphisms derived from native, invasive, and intercepted samples and populations of the brown marmorated stink bug (BMSB), Halyomorpha halys, to gain insights into population genomics processes that have promoted the successful global invasion of this polyphagous pest. Our analysis demonstrated that BMSB exhibits spatial structure but admixture rates are high among introduced populations, resulting in similar levels of genomic diversity across native and introduced populations. These spatial genomic patterns suggest a complex invasion scenario, potentially with multiple bridgehead events, posing a challenge for accurately assigning BMSB incursions to their source using reduced-representation genomic data. By associating allele frequencies with the invasion status of BMSB populations, we found significantly differentiated single nucleotide polymorphisms (SNPs) located in close proximity to genes for insecticide resistance and olfaction. Comparing variations in allele frequencies among populations for outlier SNPs suggests that BMSB invasion success has probably evolved from standing genetic variation. In addition to being a major nuisance of households, BMSB has caused significant economic losses to agriculture in recent years and continues to expand its range. Despite no record of BMSB insecticide resistance to date, our results show high capacity for potential evolution of such traits, highlighting the need for future sustainable and targeted management strategies.

Three perspectives on the prediction of chemical effects in ecosystems

The increasing production, use and emission of synthetic chemicals into the environment represents a major driver of global change. The large number of synthetic chemicals, limited knowledge on exposure patterns and effects in organisms and their interaction with other global change drivers hamper the prediction of effects in ecosystems. However, recent advances in biomolecular and computational methods are promising to improve our capacity for prediction. We delineate three idealised perspectives for the prediction of chemical effects: the suborganismal, organismal and ecological perspective, which are currently largely separated. Each of the outlined perspectives includes essential and complementary theories and tools for prediction but captures only part of the phenomenon of chemical effects. Links between the perspectives may foster predictive modelling of chemical effects in ecosystems and extrapolation between species. A major challenge for the linkage is the lack of data sets simultaneously covering different levels of biological organisation (here referred to as biological levels) as well as varying temporal and spatial scales. Synthesising the three perspectives, some central aspects and associated types of data seem particularly necessary to improve prediction. First, suborganism- and organism-level responses to chemicals need to be recorded and tested for relationships with chemical groups and organism traits. Second, metrics that are measurable at many biological levels, such as energy, need to be scrutinised for their potential to integrate across levels. Third, experimental data on the simultaneous response over multiple biological levels and spatiotemporal scales are required. These could be collected in nested and interconnected micro- and mesocosm experiments. Lastly, prioritisation of processes involved in the prediction framework needs to find a balance between simplification and capturing the essential complexity of a system. For example, in some cases, eco-evolutionary dynamics and interactions may need stronger consideration. Prediction needs to move from a static to a real-world eco-evolutionary view.

Pesticide contamination in agro-ecosystems: toxicity, impacts, and bio-based management strategies

Continuous rise in application of pesticides in the agro-ecosystems in order to ensure food supply to the ever-growing population is of greater concern to the human health and the environment. Once entered into the agro-ecosystem, the fate and transport of pesticides is determined largely by the nature of pesticides and the soil attributes, in addition to the soil-inhabiting microbes, fauna, and flora. Changes in the soil microbiological actions, soil properties, and enzymatic activities resulting from pesticide applications are the important factors substantially affecting the soil productivity. Disturbances in the microbial community composition may lead to the considerable perturbations in cycling of major nutrients, metals, and subsequent uptake by plants. Indiscriminate applications are linked with the accumulation of pesticides in plant-based foods, feeds, and animal products. Furthermore, rapid increase in the application of pesticides having long half-life has also been reported to contaminate the nearby aquatic environments and accumulation in the plants, animals, and microbes surviving there. To circumvent the negative consequences of pesticide application, multitude of techniques falling in physical, chemical, and biological categories are presented by different investigators. In the present study, important findings pertaining to the pesticide contamination in cultivated agricultural soils; toxicity on soil microbes, plants, invertebrates, and vertebrates; effects on soil characteristics; and alleviation of toxicity by bio-based management approaches have been thoroughly reviewed. With the help of bibliometric analysis, thematic evolution and research trends on the bioremediation of pesticides in the agro-ecosystems have also been highlighted.

Global Pattern of kdr-Type Alleles in Musca domestica (L.)

Purpose of Review

Houseflies, Musca domestica L., are an important sanitary pest that affects human and domesticated animals. They are mechanical carriers of more than 100 human and animal diseases including protozoan, bacterial, helminthic, and viral infections. Recently, it was demonstrated that houseflies acquired, harbored, and transmitted SARS-CoV-2 (COVID-19) for up to 1 day post-exposure. The most widely used control strategy relays on the application of pyrethroid insecticides due to their effectiveness, low mammalian toxicity, low cost, and environmental safety. The main mechanism of action of pyrethroids is to exert their toxic effects through affecting the voltage-sensitive sodium channel (VSSC) modifying the transmission of the nerve impulse and leading to the death of the insects. Target site insensitivity of the VSSC is due to the presence of single nuclear polymorphisms (SNPs) named knockdown mutations (kdr). In this review, we synthetize recent data on the type and distribution of these mutations globally.

Recent Findings

Housefly resistance is reported in several countries. Increased applications of pyrethroids to control housefly populations led to the emergence of multiple evolutionary origins of resistance determined by five amino acid substitutions or specific mutations in the VSSC: kdr (L1014F), kdr-his (L1014H), super-kdr (M918T + L1014F), type N (D600N + M918T + L1014F), and 1B (T929I + L1014F). According to the global map obtained, high levels of resistance to pyrethroids are associated with the L1014F mutation found mostly in North America, Europe, and Asia, while the super-kdr mutation was mostly found in the American continent. The level of protection conferred by these alleles against pyrethroids was generally kdr-his < kdr < Type N ≤ super-kdr ≤ 1B. The relative fitness of the alleles under laboratory conditions was susceptible ≅ kdr-his > kdr > super-kdr suggesting that the fitness cost of an allele was relative to the presence of other alleles in a population and that the reversion of resistance in a free insecticide environment might be quite variable from one region to another.

Summary

An adequate integrated pest management program should consider monitoring susceptibility to pyrethroids to detect early levels of resistance and predict the spread and evolution of resistant phenotypes and genotypes. From this review, the pyrethroid resistance status of housefly population was determined in very few countries and has evolved independently in different areas of the world affecting chemical control programs.

Rapid weed adaptation and range expansion in response to agriculture over the past two centuries

North America has experienced a massive increase in cropland use since 1800, accompanied more recently by the intensification of agricultural practices. Through genome analysis of present-day and historical samples spanning environments over the past two centuries, we studied the effect of these changes in farming on the extent and tempo of evolution across the native range of the common waterhemp (Amaranthus tuberculatus), a now pervasive agricultural weed. Modern agriculture has imposed strengths of selection rarely observed in the wild, with notable shifts in allele frequency trajectories since agricultural intensification in the 1960s. An evolutionary response to this extreme selection was facilitated by a concurrent human-mediated range shift. By reshaping genome-wide diversity across the landscape, agriculture has driven the success of this weed in the 21st century.

Evolution of Benzimidazole Resistance Caused by Multiple Double Mutations of β-Tubulin in Corynespora cassiicola

Cucumber target leaf spot caused by Corynespora cassiicola has devastated greenhouse cucumber production. In our previous study, the resistance monitoring of C. cassiicola to carbendazim was carried out, and a large number of resistant populations carrying various mutations (M163I&E198A, F167Y&E198A, F200S&E198A, or E198A) in β-tubulin were detected. However, the single-point mutations M163I, F167Y, and F200S have remained undetected. To investigate the evolutionary mechanism of double mutations in β-tubulin of C. cassiicola resistance to benzimidazoles, site-directed mutagenesis was used to construct alleles with corresponding mutation genotypes in β-tubulin. Through PEG-mediated protoplast transformation, all the mutants except for the M163I mutation were obtained and conferred resistance to benzimidazoles. It was found that the mutants conferring the E198A or double-point mutations showed high resistance to carbendazim and benomyl, but the mutants conferring the F167Y or F200S mutations showed moderate resistance. Except, the F200S mutants showed low resistance, the resistance level of the other mutants to thiabendazole seemed no difference. In addition, compared to the other mutants, the F167Y and F200S mutants suffered a more severe fitness penalty in mycelial growth, sporulation, and virulence. Thus, combined with the resistance level, fitness, and molecular docking results, we concluded that the field double mutations (F167Y&E198A and F200S&E198A) evolved from the single mutations F167Y and F200S, respectively.

Population-level variation in pesticide tolerance predicts survival under field conditions in mayflies

An increasing number of studies have found tolerance variation in populations consistently exposed to contaminants, but few studies have examined whether these laboratory-derived estimates of tolerance have survival implications in field conditions. We examined four populations of the mayfly Stenacron interpunctatum for variation in tolerance to the common agricultural insecticide clothianidin. Using laboratory bioassays, we found a 2.3× range in 96 h EC50 tolerance values to clothianidin between our four populations. We then conducted a common-garden experiment with nymphs from each population placed into the collection stream most heavily impacted by upstream agricultural activities to assess whether our laboratory tolerance estimates predict survival under field conditions. We monitored survival and growth in situ for three weeks during the spring planting season, when clothianidin is applied to croplands upstream of our study site. While growth was similar across all groups, the most tolerant population, which was native to the impacted stream, had higher survival than the more sensitive populations. This suggests that population-level variation in contaminant tolerance as measured in laboratory bioassays could have real-world survival implications for sensitive aquatic macroinvertebrates in contaminated streams.

Discovery of malathion resistance QTL in Drosophila melanogaster using a bulked phenotyping approach

Drosophila melanogaster has proved an effective system with which to understand the evolutionary genetics and molecular mechanisms of insecticide resistance. Insecticide use has left signatures of selection in the fly genome, and both functional and quantitative genetic studies in the system have identified genes and variants associated with resistance. Here, we use D. melanogaster and leverage a bulk phenotyping and pooled sequencing "extreme quantitative trait loci" approach to genetically dissect variation in resistance to malathion, an organophosphate insecticide. We resolve 2 quantitative trait loci, one of which implicates allelic variation at the cytochrome P450 gene Cyp6g1, a strong candidate based on previous work. The second shows no overlap with hits from a previous genome-wide association study for malathion resistance, recapitulating other studies showing that different strategies for complex trait dissection in flies can yield apparently different architectures. Notably, we see no genetic signal at the Ace gene. Ace encodes the target of organophosphate insecticide inhibition, and genome-wide association studies have identified strong Ace-linked associations with resistance in flies. The absence of quantitative trait locus implicating Ace here is most likely because our mapping population does not segregate for several of the known functional polymorphisms impacting resistance at Ace, perhaps because our population is derived from flies collected prior to the widespread use of organophosphate insecticides. Our fundamental approach can be an efficient, powerful strategy to dissect genetic variation in resistance traits. Nonetheless, studies seeking to interrogate contemporary insecticide resistance variation may benefit from deriving mapping populations from more recently collected strains.

Characterization of Indoxacarb Resistance in the Fall Armyworm: Selection, Inheritance, Cross-Resistance, Possible Biochemical Mechanisms, and Fitness Costs

The fall armyworm, Spodoptera frugiperda (J.E. Smith), is a voracious insect pest that is difficult to control due to resistance to insecticides and Bt proteins. We assessed cross-resistance, resistance mechanism, and fitness costs based on the life history traits of S. frugiperda. We established an S. frugiperda strain selected for resistance to indoxacarb (Ind-SEL) from a field-collected population and an unselected strain, Ind-UNSEL. Results indicated that after 24 generations of selection, the resistance to indoxacarb was increased by 472.67-fold as compared to the Ind-UNSEL. There was high cross-resistance to deltamethrin (31.23-fold) with very low or negligible cross-resistance to chlorantraniliprole, emamectin benzoate, and/or methoxyfenozide in the Ind-SEL population. Butoxide synergist increased susceptibility to indoxacarb, indicating that P450 enzymes may be involved in indoxacarb resistance. Significantly longer developmental time of larvae extended pupal duration, shorter adult longevity, and lower fecundity were observed in Ind-SEL as compared with the Ind-UNSEL population. The Net reproductive rate (R₀) was the only growth parameter that differs between crosses of Ind-SEL♂ × Ind-UNSEL♀ (176 ± 46) and Ind-SEL♀ × Ind-UNSEL♂ (328 ± 57). On the other hand, all population growth parameters differ between Ind-SEL and Ind-UNSEL strains. Our work contributes to the growing body of research that demonstrates the importance of strain genetics in fitness cost experiments and helps resistance management programs make decisions.

The target site of the novel fungicide quinofumelin, Pyricularia oryzae class II dihydroorotate dehydrogenase

The target site of the novel fungicide quinofumelin was investigated in the rice blast fungus Pyricularia oryzae. Quinofumelin-induced mycelial growth inhibition was reversed by orotate but not by dihydroorotate. Recovery tests suggested that the target site of quinofumelin was dihydroorotate dehydrogenase (DHODH), which catalyzes the oxidation of dihydroorotate to orotate. Quinofumelin strongly inhibited P. oryzae class 2 DHODH (DHODH II) (IC₅₀: 2.8 nM). The inhibitory activities of mycelial growth and DHODH II were strongly positively correlated, indicating that DHODH II inhibition by quinofumelin lead to antifungal activity. A P. oryzae DHODH II gene (PoPYR4) disruption mutant (ΔPopyr4), showing the same tendency as the quinofumelin-treated wild strain in recovery tests, was constructed, and disease symptoms were not observed in rice plants infected by ΔPopyr4. Thus, DHODH II, which plays an important role in pathogenicity and mycelial growth, is found to be the target site of quinofumelin.

Trans-driven variation in expression is common among detoxification genes in the extreme generalist herbivore Tetranychus urticae

The extreme adaptation potential of the generalist herbivore Tetranychus urticae (the two-spotted spider mite) to pesticides as well as diverse host plants has been associated with clade-specific gene expansions in known detoxifying enzyme families, and with extensive and rapid transcriptional responses. However, how this broad transcriptional potential is regulated remains largely unknown. Using a parental/F1 design in which four inbred strains were crossed to a common inbred strain, we assessed the genetic basis and inheritance of gene expression variation in T. urticae. Mirroring known phenotypic variation in the progenitor strains of the inbreds, we confirmed that the inbred strains we created were genetically distinct, varied markedly in pesticide resistance, and also captured variation in host plant fitness as is commonly observed in this species. By examining differences in gene expression between parents and allele-specific expression in F1s, we found that variation in RNA abundance was more often explained in trans as compared to cis, with the former associated with dominance in inheritance. Strikingly, in a gene ontology analysis, detoxification genes of the cytochrome P450 monooxygenase (CYP) family, as well as dioxygenases (DOGs) acquired from horizontal gene transfer from fungi, were specifically enriched at the extremes of trans-driven up- and downregulation. In particular, multiple CYPs and DOGs with broad substrate-specificities for pesticides or plant specialized compounds were exceptionally highly upregulated as a result of trans-regulatory variation, or in some cases synergism of cis and trans, in the most multi-pesticide resistant strains. Collectively, our findings highlight the potential importance of trans-driven expression variation in genes associated with xenobiotic metabolism and host plant use for rapid adaptation in T. urticae, and also suggests modular control of these genes, a regulatory architecture that might ameliorate negative pleiotropic effects.

Environmental effects of harvesting some Mexican wild edible insects: An overview

Most traditional edible insects are collected from the forest and agricultural fields, where they are considered pests. However, their importance goes beyond this. They also have an ecological role and potential to be an emerging alternative source of high-quality nutrients that can help satisfy the growing food demand for the human population. Agricultural insect pests are a healthy food source during the harvesting season in many tropical countries. In Mexico, wild insects such as chicatana (queen of flying leaf-cutter ant, Atta mexicana Smith, 1,858; Hymenoptera: Formicidae), chapulín (grasshopper, Pyrgomorphidae), chinicuil (agave red worm, Comadia redtenbacheri Hammerschmidt, 1,848: Lepidoptera, Cossidae), and meocuil (agave white worm, Aegiale hesperiaris Walker 1,856, Lepidoptera, Hesperiidae) are seasonally collected from the agricultural land and forest for food and medicine. Thus, their consumption might be regarded as support for biological plague control. However, in most countries (Mexico included), there is a lack of legislation about edible insects from harvesting to sacrifice and even their main safety aspects. So then, this research aims to provide an updated assessment of the potential use of agricultural pest insects as a sustainable alternative for food, considering current international legislative and ethical concerns about harvesting and consuming wild edible insects, focusing on some of the wild edible pest insects in Mexico.

High-Resolution Genetic Mapping Combined with Transcriptome Profiling Reveals That Both Target-Site Resistance and Increased Detoxification Confer Resistance to the Pyrethroid Bifenthrin in the Spider Mite Tetranychus urticae

Pyrethroids are widely applied insecticides in agriculture, but their frequent use has provoked many cases of resistance, in which mutations in the voltage-gated sodium channel (VGSC), the pyrethroid target-site, were shown to play a major role. However, for the spider mite Tetranychus urticae, it has also been shown that increased detoxification contributes to resistance against the pyrethroid bifenthrin. Here, we performed QTL-mapping to identify the genomic loci underlying bifenthrin resistance in T. urticae. Two loci on chromosome 1 were identified, with the VGSC gene being located near the second QTL and harboring the well-known L1024V mutation. In addition, the presence of an L925M mutation in the VGSC of a highly bifenthrin-resistant strain and its loss in its derived, susceptible, inbred line indicated the importance of target-site mutations in bifenthrin resistance. Further, RNAseq experiments revealed that genes encoding detoxification enzymes, including carboxyl/choline esterases (CCEs), cytochrome P450 monooxygenases and UDP-glycosyl transferases (UGTs), were overexpressed in resistant strains. Toxicity bioassays with bifenthrin (ester pyrethroid) and etofenprox (non-ester pyrethroid) also indicated a possible role for CCEs in bifenthrin resistance. A selection of CCEs and UGTs were therefore functionally expressed, and CCEinc18 was shown to metabolize bifenthrin, while teturUGT10 could glycosylate bifenthrin-alcohol. To conclude, our findings suggest that both target-site and metabolic mechanisms underlie bifenthrin resistance in T. urticae, and these might synergize high levels of resistance.

Open access databases available for the pesticide lead discovery

Pesticide research is a multi-disciplinary collaborative study, and big data analysis based on integrating information from databases benefits decision-making in pesticide research. In the last 40 years, dozens of pesticide-related databases have been built up to describe their biological activities, toxicity, modes of action, and environmental risks, etc. However, these data are scattered and overlapping in different databases in multiple inconsistent formats, which is not convenient for information analysis and comparison. In this study, the content of 26 open access databases related to pesticide research was illustrated according to the information provided for the ligand-based drug design (LBDD) and receptor-based (or structure-based drug design, SBDD), and was summarized into three categories:1) the correspondence between the chemical structures and functional properties (biological activity, resistance, toxicity, environmental adaptation); 2) action mode study (target identification, target structures, and biological pathways); 3) computational servers for pesticide design. To our knowledge, this is the first review about the open access databases for pesticide research. The data classification could facilitate the information accessibility for pesticide research, and speed up the decision-making process in pesticide discovery.

Detection of L1014F knockdown resistance mutation in Culex tritaeniorhynchus populations

Culex tritaeniorhynchus is a major Japanese encephalitis virus vector distributed in Southeast Asia and surrounding countries. The aim of the present study is to investigate insecticide resistance status among 10 Cx. tritaeniorhynchus populations of the Mediterranean region of Turkey. Bioassay results indicated that all of the populations were resistant or at least possibly resistant to 1,1'-(2,2,2-Trichloroethane-1,1-diyl) bis (4-chlorobenzene) (DDT) (4%), [(dimethoxyphosphorothioyl) sulfanyl] butanedioate, Diethyl (malathion) (5%), and 2-[(Propan-2-yl) oxy] phenyl methylcarbamate (propoxur) (0,1%). Whereas, some of the populations were still susceptible to 3-Phenoxybenzyl (1RS)-cis, trans-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropane carboxylate (permethrin) (0,75%) and (S)-Cyano (3-phenoxy phenyl) methyl (1R,3R)-3-(2,2-dibromoethen-1-yl)-2,2-dimethylcyclopropane-1-carboxylate (deltamethrin) (0,05%). Biochemical analysis results showed altered alpha esterase, beta esterase, para-nitrophenyl acetate (PNPA), and glutathione-s-transferase (GST) levels in some populations while all of the populations had increased oxidase levels except for the Yumurtalık population. Additionally, all of the populations had sensitive acetylcholinesterase (AChE) levels similar to the control group except for the Erzin population. Correlation analysis showed a significant correlation between mortality rates for deltamethrin and alpha esterase, beta esterase, PNPA, and GST levels while mortality rates for permethrin were significantly correlated with GST levels. An allele-specific polymerase chain reaction (AS-PCR) detected high L1014F allele frequency in the populations. Overall results indicate the urgent need for monitoring and mapping of insecticide resistance in Cx. tritaeniorhynchus populations of the study area for effective vector control management.

Widespread resistance to anticoagulant rodenticides in Mus musculus domesticus in the city of Barcelona

Control of rodent populations is a big challenge because of the rapid evolution of resistance to commonly used rodenticides and the collateral negative impacts that these products may have on biodiversity. Second-generation anticoagulants are very efficient but different single nucleotide polymorphisms (SNPs) in the Vkorc1 gene may confer resistance in rodents. We sequenced exons 1, 2 and 3 of the Vkorc1 gene from 111 mice (Mus musculus domesticus) captured across the city of Barcelona and found SNPs associated with resistance to first- and second-generation anticoagulants in all of them. Although most of the SNPs were associated with resistance to bromadiolone, we also found SNPs associated with resistance to brodifacoum. Out of all the individuals analyzed, 94.59 % carried mutations associated to introgression events with Mus spretus, a sympatric rodent species. Currently most of the chemical products for rodent control commercialized in the area are based on bromadiolone, although recent public control campaigns have already shifted to other products. Thus, the widespread occurrence of resistant mice to bromadiolone represents a challenge for rodent control in Barcelona and may increase the risk of secondary poisoning of animals preying on this species. Public health managers, pest control companies and citizens should be aware that the use of bromadiolone based products is ineffective and represents a risk for the environment, including human and animal health.

Effect of thyme essential oil and its two components on toxicity and some physiological parameters in mulberry pyralid Glyphodes pyloalis Walker

Extensive usage of synthetic pesticides has proved to be destructive to all living being and the resurgence of pest resistance. Compounds derived from certain plants are usually safer compared to chemical control of pest. The present study thus intended to use Thymus vulgaris essential oil (EO) and two of its derivatives including thymol and carvacrol in order to see their deleterious effects on Glyphodes pyloalis (Walker). We also studied the oil components. This pest has recently become a serious concern for the silk industry. Our results showed that the thyme EO contain several components including thymol (26.9%), ρ-Cymene (14.54%), linalool (13.39%) and carvacrol (5.7%). Our toxicity tests revealed an estimated LD₅₀ values for thyme EO, thymol and carvacrol 2.82, 32.18 and 56.54 μg/larva, respectively. However, the thyme EO was more toxic than its two tested compounds. The activity of certain detoxifying enzymes such as α- and β-esterase, glutathione S-transferase and cytochrome P450 were significantly inhibited by thymol-treated larvae compared to the control group. Similarly, the activity of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase and alkaline phosphatases enzymes in thymol-treated larvae decreased while the activity of acid phosphatases increased. Our results suggest that thyme EO and its components have potential for the control of G. pyloalis larvae in mulberry orchards, where no synthetic chemicals are allowed.

Host plants and insecticides shape the evolution of genetic and clonal diversity in a major aphid crop pest

Understanding the spatiotemporal dynamics of pesticide resistance at the landscape scale is essential to anticipate the evolution and spread of new resistance phenotypes. In crop mosaics, host plant specialization in pest populations is likely to dampen the spread of pesticide resistance between different crops even in mobile pests such as aphids. Here, we assessed the contribution of host-based genetic differentiation to the dynamics of resistance alleles in Myzus persicae, a major aphid pest which displays several insecticide resistance mechanisms. We obtained a representative sample of aphids from a crop mosaic through a suction trap for 7 years and from various crops as a reference collection. We genotyped these aphids at 14 microsatellite markers and four insecticide-resistant loci, analyzed the genetic structure, and assigned host-based genetic groups from field-collected aphids. Four well-defined genetic clusters were found in aerial samples, three of which with strong association with host-plants. The fourth group was exclusive to aerial samples and highly divergent from the others, suggesting mixture with a closely related taxon of M. persicae associated with unsampled plants. We found a sharp differentiation between individuals from peach and herbaceous plants. Individuals from herbaceous hosts were separated into two genetic clusters, one more strongly associated with tobacco. The 4-loci resistance genotypes showed a strong association with the four genetic clusters, indicative of barriers to the spread of resistance. However, we found a small number of clones with resistant alleles on multiple host-plant species, which may spread insecticide resistance between crops. The 7-year survey revealed a rapid turn-over of aphid genotypes as well as the emergence, frequency increase and persistence of clones with resistance to several families of insecticides. This study highlights the importance of considering landscape-scale population structure to identify the risk of emergence and spread of insecticide resistance for a particular crop.

Evidence of hard-selective sweeps suggests independent adaptation to insecticides in Colorado potato beetle (Coleoptera: Chrysomelidae) populations

Pesticide resistance provides one of the best examples of rapid evolution to environmental change. The Colorado potato beetle (CPB) has a long and noteworthy history as a super-pest due to its ability to repeatedly develop resistance to novel insecticides and rapidly expand its geographic and host plant range. Here, we investigate regional differences in demography, recombination, and selection using whole-genome resequencing data from two highly resistant CPB populations in the United States (Hancock, Wisconsin and Long Island, New York). Demographic reconstruction corroborates historical records for a single pest origin during the colonization of the Midwestern and Eastern United States in the mid- to late-19th century and suggests that the effective population size might be higher in Long Island, NY than Hancock, WI despite contemporary potato acreage of Wisconsin being far greater. Population-based recombination maps show similar background recombination rates between these populations, as well as overlapping regions of low recombination that intersect with important metabolic detoxification genes. In both populations, we find compelling evidence for hard selective sweeps linked to insecticide resistance with multiple sweeps involving genes associated with xenobiotic metabolism, stress response, and defensive chemistry. Notably, only two candidate insecticide resistance genes are shared among both populations, but both appear to be independent hard selective sweep events. This suggests that repeated, rapid, and independent evolution of genes may underlie CPB's pest status among geographically distinct populations.

Migratory behaviour of Brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), in India as inferred from genetic diversity and reverse trajectory analysis

The brown planthopper, Nilaparvata lugens (Stål) is a major sucking insect pest of rice. This insect has long been considered as migratory; however, its route in India is still unknown. Hence, to find out its migration route genetic diversity, genetic structure and gene flow of 16 N. lugens populations from major rice growing regions of India was studied based on mitochondrial cytochrome oxidase I (COI). The results revealed a high genetic homogeneity among the populations on the basis of genetic diversity statistics and neutrality tests. There was a prevalence of a single major haplotype across the country. No spatial relevance was found with the genetic structure of the populations indicating presence of excessive gene flow among them. Extensive gene flow among populations was also confirmed with the presence of higher number of immigrants in North, Central, and East India. To further clarify the migration sources, 48 h air-mass reverse trajectory was performed for Varanasi just aftermath of cyclones Amphan and Yaas, which disclosed Eastern/Northeastern states along with Bangladesh and Myanmar as the possible source areas. Overall, the results revealed a single panmictic homogeneous population of N. lugens in India with extensive gene flow as a consequence of their migration. These findings will help in better forecasting enabling efficient regional management of this important rice pest.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03337-6.

Contribution of insect gut microbiota and their associated enzymes in insect physiology and biodegradation of pesticides

Synthetic pesticides are extensively and injudiciously applied to control agriculture and household pests worldwide. Due to their high use, their toxic residues have enormously increased in the agroecosystem in the past several years. They have caused many severe threats to non-target organisms, including humans. Therefore, the complete removal of toxic compounds is gaining wide attention to protect the ecosystem and the diversity of living organisms. Several methods, such as physical, chemical and biological, are applied to degrade compounds, but as compared to other methods, biological methods are considered more efficient, fast, eco-friendly and less expensive. In particular, employing microbial species and their purified enzymes makes the degradation of toxic pollutants more accessible and converts them into non-toxic products by several metabolic pathways. The digestive tract of insects is usually known as a superior organ that provides a nutrient-rich environment to hundreds of microbial species that perform a pivotal role in various physiological and ecological functions. There is a direct relationship between pesticides and insect pests: pesticides reduce the growth of insect species and alter the phyla located in the gut microbiome. In comparison, the insect gut microbiota tries to degrade toxic compounds by changing their toxicity, increasing the production and regulation of a diverse range of enzymes. These enzymes breakdown into their derivatives, and microbial species utilize them as a sole source of carbon, sulfur and energy. The resistance of pesticides (carbamates, pyrethroids, organophosphates, organochlorines, and neonicotinoids) in insect species is developed by metabolic mechanisms, regulation of enzymes and the expression of various microbial detoxifying genes in insect guts. This review summarizes the toxic effects of agrochemicals on humans, animals, birds and beneficial arthropods. It explores the preferential role of insect gut microbial species in the degradation process and the resistance mechanism of several pesticides in insect species. Additionally, various metabolic pathways have been systematically discussed to better understand the degradation of xenobiotics by insect gut microbial species.

Baseline Susceptibility and Cross-Resistance of HearNPV in Helicoverpa armigera (Lepidoptera: Noctuidae) in Brazil

The marked adoption of bioinsecticides in Brazilian agriculture in recent years is, at least partially, explained by the increasingly higher levels of insect pest resistance to synthetic insecticides. In particular, several baculovirus-based products have been registered in the last 5 years, including Helicoverpa armigera nucleopolyhedrovirus (HearNPV: Baculoviridae: Alphabaculovirus (Armigen^®)). Understanding the susceptibility of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) to HearNPV is an important step toward development of robust Integrated Pest Management (IPM) and Insect Resistance Management programs (IRM) aimed at managing this serious insect pest. In this study, droplet feeding bioassays were used to characterize the baseline susceptibility to HearNPV (Armigen^®) in H. armigera populations collected from major soybean and cotton-growing regions in Brazil. We defined and validated a diagnostic concentration for susceptibility monitoring of H. armigera populations to HearNPV. Additionally, cross-resistance between HearNPV and the insecticides flubendiamide and indoxacarb was evaluated by testing HearNPV in a susceptible strain and in resistant strains of H. armigera to these insecticides. A low interpopulation variation of H. armigera to HearNPV was detected. The LC₅₀ values ranged from 1.5 × 10⁵ to 1.1 × 10⁶ occlusion bodies (OBs) per mL (7.3-fold variation). The mortality rate at the identified diagnostic concentration of 6.3 × 10⁸ OBs/mL, based on the calculated LC₉₉, ranged from 98.6 to 100% in populations of H. armigera collected from 2018 to 2020. No cross-resistance was detected between HearNPV and flubendiamide or indoxacarb. These results suggest that HearNPV (Armigen^®) can be an effective tool in IPM and IRM programs to control H. armigera in Brazil.

Antibacterial Activity of Aureonuclemycin Produced by Streptomyces aureus Strain SPRI-371

Actinomycetes play a vital role as one of the most important natural resources for both pharmaceutical and agricultural applications. The actinomycete strain SPRI-371, isolated from soil collected in Jiangsu province, China, was classified as Streptomyces aureus based on its morphological, physiological, biochemical and molecular biological characteristics. Its bacterial activity metabolites were identified as aureonuclemycin (ANM), belonging to adenosine derivatives with the molecular formula C16H19N5O9 for ANM A and C10H13N5O3 for ANM B. Simultaneously, the industrial fermentation process of a mutated S. aureus strain SPRI-371 was optimized in a 20 m3 fermentation tank, featuring a rotation speed of 170 rpm, a pressure of 0.05 MPa, an inoculum age of 36−40 h and a dissolved oxygen level maintained at 1−30% within 40−80 h and at >60% in the later period, resulting in an ANM yield of >3700 mg/L. In the industrial separation of fermentation broth, the sulfuric acid solution was selected to adjust pH and 4# resin was used for adsorption. Then, it was resolved with 20% ethanol solution and concentrated in a vacuum (60−65 °C), with excellent results. Antibacterial experiments showed that ANM was less active or inactive against Xanthomonas oryzae pv. oryzae, Xanthomonas citri subsp. citri and Xanthomonas oryzae pv. oryzicola and most bacteria, yeast and fungi in vitro. However, in vivo experiments showed that ANM exhibited extremely significant protective and therapeutic activity against diseases caused by X. oryzae pv. oryzae and X. oryzae pv. oryzicola in rice and X. citri in oranges and lemons. In field trials, ANM A 150 gai/ha + ANM B 75 gai/ha exhibited excellent therapeutic activity against rice bacterial leaf blight, citrus canker and rice bacterial leaf streak. Furthermore, as the dosage and production cost of ANM are lower than those of commercial drugs, it has good application prospects.

A gene-based capture assay for surveying patterns of genetic diversity and insecticide resistance in a worldwide group of invasive mosquitoes

Understanding patterns of diversification, genetic exchange, and pesticide resistance in arthropod disease vectors is necessary for effective population management. With the availability of next-generation sequencing technologies, one of the best approaches for surveying such patterns involves the simultaneous genotyping of many samples for a large number of genetic markers. To this end, the targeting of gene sequences of known function can be a cost-effective strategy. One insect group of substantial health concern are the mosquito taxa that make up the Culex pipiens complex. Members of this complex transmit damaging arboviruses and filariae worms to humans, as well as other pathogens such as avian malaria parasites that are detrimental to birds. Here we describe the development of a targeted, gene-based assay for surveying genetic diversity and population structure in this mosquito complex. To test the utility of this assay, we sequenced samples from several members of the complex, as well as from distinct populations of the relatively under-studied Culex quinquefasciatus. The data generated was then used to examine taxonomic divergence and population clustering between and within these mosquitoes. We also used this data to investigate genetic variants present in our samples that had previously been shown to correlate with insecticide-resistance. Broadly, our gene capture approach successfully enriched the genomic regions of interest, and proved effective for facilitating examinations of taxonomic divergence and geographic clustering within the Cx. pipiens complex. It also allowed us to successfully survey genetic variation associated with insecticide resistance in Culex mosquitoes. This enrichment protocol will be useful for future studies that aim to understand the genetic mechanisms underlying the evolution of these ubiquitous and increasingly damaging disease vectors.

The mosquito taxa that make up the Culex pipiens complex are important vectors of the agents of several human diseases such as West Nile and St. Louis encephalitides, and lymphatic filariasis. They are also important vectors of avian malaria, which impacts livestock and wildlife. The development of effective strategies for the control of these mosquitoes requires knowledge of their origins, distribution, dispersal patterns, and the extent to which discreet taxonomic entities within the complex interbreed. To achieve these objectives, it is necessary to compare patterns of genetic diversity across many mosquito samples, which can be cost-prohibitive. To address this limitation, we developed a targeted, gene-based assay that allowed us to cost-effectively genotype a large number of genetic variants from a representative global sampling of individual Cx. pipiens complex mosquitoes. We show that this assay is a powerful tool for examining genetic structure and hybridization among populations. We also explore its utility for surveying alleles previously shown to be associated with insecticide resistance. Future use of this enrichment assay and the bioinformatics methods described here will allow researchers to study evolutionary patterns across the Cx. pipiens complex as well as monitor the presence of genetic variation that could affect control efforts.