Insecticide Resistance Research Articles

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

Abstract 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 + 3.7 g a.i./100 L−1), acetamiprid + etofenproxi (9.1 + 16.5 g a.i./100 L−1), emamectin benzoate (0.5 g a.i./100 L−1), Sophora flavescens (Fabales: Fabaceae) (22.8 g a.i./100 L−1), phosmet (87.5 g a.i./100 L−1), and indoxacarb (11.2 g a.i./100 L−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.

Tolerance pattern against the heavy metals and pesticides in Escherichia coli isolated from water samples.

In this study water samples were investigated for the presence of heavy metals and pesticide resistance in Escherichia coli (E. coli) collected from district Jhal Magsi. Identification of E. coli was carried out via Polymerase Chain Reaction (PCR) assays. Heavy metals and pesticide resistance were conducted by the Kirby-Bauer disk diffusion method. E. coli was confirmed by using uidA (623bp) and usp (515bp) genes primer. A relatively high resistance rate was observed for Cd and DDT (2, 4 D) with 100% at the concentration of 1600µl/mL. Samples showed the resistance pattern for Cr with 55% and sensitivity was 45% at 800µl/mL. Resistance and sensitive percentage of Pb, Co were observed 61, 63, and 39, 37% at 400µl/mL. Cyanazine resistance and the sensitive percentage were 51 and 49% at 800µg/mL. For Chlorpyrifos and Carbofuran, 54 and 65% resistance and sensitivity 46 and 35% were measured at a lower range of 400µl/mL. Excessive use of heavy metals and pesticide pollution in standing water near agriculture fields contributed to accelerating the abundance of multi-pollutant-resistant E. coli in water that could be useful in the bioremediation of pesticides and heavy metals.

Detection of the 1016Gly and 989Pro Knockdown Resistance Mutations in Florida, USA Aedes aegypti

Aedes aegypti is a major arboviral disease vector and is therefore a critical target for control by public health programs. Early eradication efforts have shown that Ae. aegypti can rapidly build insecticide resistance, and, now, resistance to pyrethroids, the major class of adulticides used for operational control, is common in many populations. A major contributor to this resistance is a group of knockdown resistance (kdr) SNPs that normally exist in distinct ensembles in the Western Hemisphere and the Indopacific with little known mixing. In this study, we detected, and confirmed, using multiple methods, the Indopacific kdr SNPs, both V1016G and S989P, in three recent collections from Osceola County, Florida. This represents a large expansion of the geographic range of the Indopacific kdr SNPs. We consider the implications of this finding on future insecticide resistance surveillance studies, including assessing the ability of our current screening tools to detect these SNPs. We find that the presence of the Indopacific SNPs requires the modification of existing resistance screening protocols and requires further work to understand the operational implications for mosquito control.

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.

The effect of next-generation, dual-active-ingredient, long-lasting insecticidal net deployment on insecticide resistance in malaria vectors in Benin: results of a 3-year, three-arm, cluster-randomised, controlled trial

The effect of next-generation, dual-active-ingredient, long-lasting insecticidal net deployment on insecticide resistance in malaria vectors in Benin: results of a 3-year, three-arm, cluster-randomised, controlled trial

Decoding the genomic terrain: functional insights into 14 chemosensory proteins in whitefly Bemisia tabaci Asia II-1

Genome-wide analysis of Bemisia tabaci Asia II-1 unravelled for the first-time full-length sequences of 14 chemosensory proteins (CSPs), their exon-intron boundaries, insertion sites of retrotransposons, and clustering patterns on chromosomes. All the CSPs sans CSP6 have an N-terminal signal peptide. The presence of OS-D superfamily and PhBP domains in different CSPs suggests their roles in chemosensory signal transduction and pheromone binding. Motif analysis reveals the conservation and cohesiveness of CSPs in hemiptera. The phylogenetic analysis uncovers the evolutionary lineages of Hemipteran CSPs. RT-qPCR analysis showed spatial expression of CSPs in different body tissues of B. tabaci adults. In-silico docking analysis showed high-affinity binding of CSP 1 and 5 with two insecticides, imidacloprid and fipronil, with energy values ranging from − 5.8 to -9.3 kcal/mol, along with the details of interacting aminoacidic residues in the hydrophobic binding pockets of these two CSPs. Further functional validation was done through insecticide bioassays and RNAi. This study provides novel insights into the genomic architecture of CSPs in B. tabaci Asia II-1, and functional characterisation suggests that CSP1 and 5 genes may have indirect roles in insecticide resistance. It lays the foundation for further research on developing new control strategies for B. tabaci.

Characterization of insecticide resistance and their mechanisms in field populations of the German cockroach (Blattodea: Ectobiidae) in Taiwan under different treatment regimes.

This study investigated how management strategies influence resistance profiles in German cockroach (Blattella germanica (L.)) populations and their impact on the performance of commercial gel baits containing fipronil, imidacloprid, and indoxacarb. Field populations from premises managed under 3 different strategies: Baiting, random insecticide (RI) used, and insecticide rotation (IR) were tested. Almost all populations under RI and IR were resistant to deltamethrin, but low to moderate resistance was observed under the Baiting approach. Cytochrome P450 monooxygenases (P450) were involved in deltamethrin resistance in these resistant populations. All individuals under Baiting and RI were homozygous for the L993F mutation, but the populations under IR lacked homozygous-resistant individuals. Eighty-three percent of field populations with complete homozygosity for the Rdl mutation displayed low mortality upon exposure to 3× LD95 fipronil. The effect of P450 and the Rdl mutation conferred high fipronil resistance in populations under the Baiting approach, recording moderate performance indices (PI) of 44-67 in fipronil bait. By contrast, those populations under RI and IR, in which involve glutathione S-transferases in fipronil resistance, had high PIs of 78-93. Almost 80% of populations exhibited over 90% mortality at 3× LD95 indoxacarb treatment, accompanied by high PIs of 90-100 in indoxacarb bait. Partial mortality from 1× LD95 imidacloprid occurred across all field populations due to the involvement of P450. PIs of imidacloprid bait ranged 5-57 and 20-94 in populations under RI and IR, respectively. Field populations demonstrate different resistance profiles depending on the treatment regimes, and the resistance mechanisms involved influenced gel bait's effectiveness.

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.

Bio Nanoparticles as Antimicrobial Agents

One such novel technology is nanotechnology, which has been revolutionized in health care, textile, materials, information and communication technology, and energy sectors too. There are many ways depicted in various literatures to synthesize silver nanoparticles. These include physical, chemical, and biological methods. The physical and chemical methods are numerous in number, and many of these methods are expensive or use toxic substances which are major factors that make them “not so favored” methods of synthesis. An alternate, feasible method to synthesize silver nanoparticles is to employ biological methods of using microbes and plants. Biotechnology has considered a safe agricultural tool to enhance crop protection, subsequently to produce more agricultural products, improve food process, nutritional value, and better flavor. Side by side it has detrimental ecological consequences such as spreading genetically engineered genes to indigenous plants, elevated toxicity, which may transmit through food chain, disrupting nature’s system of pest control, developing new weeds or virus strains, biodiversity loss, and insecticidal resistance (Goswami et al., 2010). Hence, it is necessary to bring forth new innovative technology/methods to overcome the above mentioned problems. The potential application of biogenic nanoparticles as antimicrobial agents will be also reviewed. The mechanism of action of nanoparticles as bactericidal and antifungal agents will be highlighted in this chapter.

Advances in Soybean Genetic Improvement

The soybean (Glycine max) is a globally important crop due to its high protein and oil content, which serves as a key resource for human and animal nutrition, as well as bioenergy production. This review assesses recent advancements in soybean genetic improvement by conducting an extensive literature analysis focusing on enhancing resistance to biotic and abiotic stresses, improving nutritional profiles, and optimizing yield. We also describe the progress in breeding techniques, including traditional approaches, marker-assisted selection, and biotechnological innovations such as genetic engineering and genome editing. The development of transgenic soybean cultivars through Agrobacterium-mediated transformation and biolistic methods aims to introduce traits such as herbicide resistance, pest tolerance, and improved oil composition. However, challenges remain, particularly with respect to genotype recalcitrance to transformation, plant regeneration, and regulatory hurdles. In addition, we examined how wild soybean germplasm and polyploidy contribute to expanding genetic diversity as well as the influence of epigenetic processes and microbiome on stress tolerance. These genetic innovations are crucial for addressing the increasing global demand for soybeans, while mitigating the effects of climate change and environmental stressors. The integration of molecular breeding strategies with sustainable agricultural practices offers a pathway for developing more resilient and productive soybean varieties, thereby contributing to global food security and agricultural sustainability.

Structured, Inbred and Plastic: the Genome and Population Genetics of the weed False cleavers (Galium spurium)

Abstract False cleavers (Galium spurium L.) is an aggressive weed from the Rubiaceae. Here we assemble a chromosome scale draft of its genome, laying the foundations for determining the genetic basis of auxinic herbicide resistance and for systematic research into its polyphyletic genus. We use the genome to examine the population genetics in material from the Canadian Prairies and, in concert with a common greenhouse experiment, to examine whether the phenotypic variation observed in the field results primarily from genetic or environmental factors. The genome assembly covers approximately 85% of G. spurium’s expected 360Mbp genome size with 94% of BUSCO genes complete and most single copy (89%). Approximately 37% of the genome is repetitive elements and 35,540 genes were annotated using RNA-Seq data, including 100 homologs for genes involved or, potentially involved in, herbicide resistance. The genome shows strong synteny with other members of the Rubiaceae including smooth bedstraw (Cruciata laevipes Opiz) and robusta coffee [Coffea canephora (Pierre ex Froehner]. Double digested RADseq data for the 19 populations from the Canadian Prairies indicated that G. spurium has high levels of population structure (FST = 0.54) and inbreeding (FIS =0.86) with low levels of hetrozygosity (HO = 0.02) and nucleotide diversity (π = 0.0003). Variation in flowering time and seed weight largely overlapped among populations grown in the greenhouse. A redundancy analysis investigating genotype-phenotype associations showed few associations between SNP variation and these characteristics. In contrast, the majority of SNPs under selection were associated with mericarp hook density. This suggests that for most traits, environmental variation rather than genetic variation likely underlies phenotypic differences observed in the field. Several genes of interest including several homologs involved in the assembly of the Skp1-Culliun-F-Box IR1/AFB E3 ubiquitin ligase complex (e.g. CAND1, ECR1) are located in areas of the genome with evidence of selection and are targets for further investigation.

Resistance of Anopheles gambiae s.s. against commonly used insecticides and implication of cytochrome P450 monooxygenase in resistance to pyrethroids in Lambaréné (Gabon)

BackgroundInsecticides are a crucial component of vector control. However, resistance constitute a threat on their efficacy and the gains obtained over the years through malaria vector control. In Gabon, little data on phenotypic insecticide resistance in Anopheles vectors are published, compromising the rational implementation of resistance management strategies. We assessed the susceptibility to pyrethroids, carbamates and organophosphates of Anopheles gambiae sensu lato (s.l.) and discuss the mechanisms involved in the pyrethroid resistance-phenotype.MethodsA. gambiae s.l. larvae were collected from breeding sites in Lambaréné. Emerging adults were used in WHO tube assays at an insecticide concentration that defines resistance (diagnostic concentration). Subsequently, deltamethrin and permethrin were used at 5x and 10x diagnostic concentrations and after preexposure with the cytochrome p450 (and glutathione S-transferase) inhibitor piperonyl butoxide (PBO). A subset of mosquitoes was typed by molecular methods and screened using Taqman assays for mutations conferring target site resistance at the Voltage-gated sodium channel 1014 (Vgsc-1014) locus and the acetylcholinesterase (Ace-1) gene.ResultsAll mosquitoes were A. gambiae sensu stricto (s.s.) and resistant to permethrin, deltamethrin and alphacypermethrin (mortality less than 98%). However, mosquitoes were susceptible to malathion but resistant to bendiocarb. The level of resistance was high for permethrin and at least moderate for deltamethrin. Pre-exposure to PBO significantly increased the mortality of resistant mosquitoes (P < 0.0001). They became fully susceptible to deltamethrin and permethrin-induced mortality increased 4-fold. The G119S Ace-1 resistance allele, which confers resistance to both organophosphates and carbamates, was not present. All sampled mosquitoes were either homozygous for the Vgsc-L1014F or heterozygous for Vgsc-L1014F/L1014S, a marker for resistance to pyrethroids and organochlorides.ConclusionThese findings demonstrate a role of cytochrome P450 monooxygenases in the pyrethroid-resistance of A. gambiae s.s. from Lambaréné. Combining PBO with pyrethroids, as done in second generation bednets, may be used to revert resistance. In addition, malathion could also be used in combination with pyrethroids-based methods for resistance management.

Toxicity and Sublethal Effect of Chlorantraniliprole on Multiple Generations of Aedes aegypti L. (Diptera: Culicidae)

Due to the quick development of insecticide resistance, it is crucial to optimize management programs by understanding the sublethal effects of effective insecticides like chlorantraniliprole on Aedes aegypti L. populations. Using age-stage and two-sex life tables, we investigated the sublethal impacts of chlorantraniliprole on Ae. aegypti. Larval duration in the progeny of exposed parents was reduced by 0.33–0.42 days, whereas, the longevity of male and female adults was decreased by 1.43–3.05 days. Similarly, the egg-laying capacity of F1 and F2 progeny of the exposed parents was significantly reduced from 27.3% to 41.2%. The mean generation time (T) increased up to 11.8% in exposed populations, and the net reproduction rate (Ro) decreased by 51.50–55.60%. After 24 h of chlorantraniliprole treatment, there was a significant increase in cytochrome P450 activity. Contrarily, the activity of glutathione S-transferase (GST) initially declined but started increasing after 48 h of treatment. This research highlights the importance of chlorantraniliprole in mosquito management, as well as the importance of considering sublethal effects when developing strategies to handle them. Having a thorough understanding of the harmful effects of insecticides on mosquito populations can greatly enhance the effectiveness of insecticide-based interventions, while also minimizing the risk of pest resurgence.

Oxyfluorfen use in Combination with Clomazone or Quinclorac

Abstract Oxyfluorfen, a Herbicide Resistance Action Committee (HRAC)/Weed Science Society of America (WSSA) Group 14 herbicide that inhibits protoporphyrinogen IX oxidase, has shown significant potential in controlling barnyardgrass. Despite its current lack of labeling for use in midsouthern U.S. rice due to the potential for crop injury, the introduction of a trait in rice that confers resistance to oxyfluorfen could provide producers with an effective alternative site of action for weed control. Field experiments were conducted during the 2021 and 2022 growing seasons near Stuttgart, AR, and near Lonoke, AR, to determine the optimum rates of clomazone (280 or 336 g ha-1) and oxyfluorfen (673 or 840 g ha-1) to use in sequential preemergence (PRE) and postemergence (POST) applications on a silt loam soil and to assess the efficacy of oxyfluorfen when combined with clomazone and quinclorac PRE, followed by oxyfluorfen POST. No differences in barnyardgrass control were observed among treatments 14 days after emergence (DAE) in three site years, as all control was ≥90%. By 35 days after the postemergence application (DAPOST), all barnyardgrass control was ≥94% for herbicide treatments in all site years. All herbicide treatments resulted in lower barnyardgrass seed production than the nontreated in 2021. Contrasts revealed that oxyfluorfen applied PRE on a silt loam soil resulting in barnyardgrass control similar to clomazone or quinclorac alone at 14 DAE. Although oxyfluorfen combined with clomazone or quinclorac did not increase barnyardgrass control, an additional site of action for control of this weed could help reduce the evolution of resistance. Mixing oxyfluorfen with clomazone in a dry-seeded rice production system in the midsouthern U.S. would effectively control barnyardgrass and reduce the risk for resistance to both herbicides, further highlighting the potential of oxyfluorfen in rice production.

Novel programming pipeline for herbicide resistance prediction

Novel programming pipeline for herbicide resistance prediction

Anopheles gambiae Re-Emergence and Resurgent Malaria Transmission in Eastern Rwanda, 2010-2020.

Rwanda achieved unprecedented malaria control gains from 2000 to 2010, but cases increased 20-fold between 2011 and 2017. Vector control challenges and environmental changes were noted as potential explanations, but no studies have investigated causes of the resurgence or identified which vector species drove transmission. We conducted a retrospective study in four sites in eastern Rwanda that conducted monthly entomological surveillance and outpatient malaria care. We compared sporozoite rates, human blood index (HBI), and relative abundance of the primary vectors, Anopheles gambiae and Anopheles arabiensis, from 2017 to 2020. We then modeled the effects of vector control interventions, insecticide resistance, and temperature changes on species composition and reported malaria incidence. Sporozoite rates were 28 times higher and HBI was four times higher in An. gambiae compared with An. arabiensis. Insecticide-treated bed nets, first distributed nationally in 2010, were associated with decreased An. gambiae relative abundance. However, increased pyrethroid resistance was associated with increased An. gambiae relative abundance and malaria incidence. Epidemic malaria peaks corresponded to periods of model-predicted An. gambiae re-emergence, and increased regional air temperatures during the period were further associated with increased malaria incidence. Indoor residual spraying (IRS), implemented with non-pyrethroid insecticides later in the period, was associated with 86% reductions in An. gambiae relative abundance and 75% reductions in malaria incidence. These findings suggest that increased pyrethroid resistance and the re-emergence of An. gambiae were closely linked to the malaria resurgence in eastern Rwanda. Non-pyrethroid IRS or other control measures that effectively target An. gambiae may help prevent future resurgences.

Yeast encapsulation of photosensitive insecticides increases toxicity against mosquito larvae while protecting microorganisms

An important defense against the deadly diseases that mosquitoes transmit is the application of insecticides that reduce mosquito populations. Unfortunately, the evolution and subsequent spread of insecticide resistance has decreased their efficacy. Therefore, new mosquito control strategies are needed. One class of larvicides, known as photosensitive insecticides, or PSIs, kills larvae via light-activated oxidative damage. PSIs are promising larvicides because of their high larvicidal efficacy, rapid photodegradation, inexpensive cost, and mechanism that is dissimilar to other insecticide classes. We explored a novel delivery strategy for increasing both the larvicidal efficiency and environmental biocompatibility of PSIs, known as yeast encapsulation. Using the PSIs, curcumin and methylene blue, we measured the survival of Anopheles gambiae larvae and Escherichia coli following exposure to either non-encapsulated or yeast-encapsulated PSIs and a photoperiod. Yeast encapsulation increased the phototoxicity of both curcumin and methylene blue against mosquito larvae, likely by increasing ingestion. Furthermore, yeast encapsulation protected E. coli from the phototoxicity of yeast-encapsulated curcumin, but not yeast-encapsulated methylene blue. Yeast encapsulation increases the larvicidal efficacy of a PSI while also increasing biocompatibility. Therefore, yeast encapsulation of PSIs is a promising insecticide delivery strategy for mosquito control.

The V410L kdr allele in the VGSC confers higher levels of field resistance to permethrin in urban mosquito populations of Aedes aegypti (L.).

Females of Aedes aegypti transmit emerging arboviruses including Zika, dengue, yellow fever, and chikungunya. Control of these adult mosquitoes heavily relies on synthetic insecticides, including pyrethroids. However, insecticide resistance development in populations poses a significant challenge to vector control, particularly from knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC), the target of pyrethroids. This study investigated the field efficacy of Permanone, a pyrethroid-based insecticide, against Ae. aegypti by assessing the impact of three common kdr mutations (V410L, V1016I, F1534C) on mosquito survival under a real operational mosquito control scenario, by quantifying the pesticide delivered in the field. Field cage tests (FCTs) were conducted while conducting a realistic mosquito control application. Female mosquitoes from six operational areas from Harris County, TX, USA were exposed to Permanone delivered with a handheld sprayer. Permanone deposited near the cages was estimated from aluminum boats placed in the field during FCTs using gas chromatography-mass spectrometry (GC-MS). Mortality rates were recorded, and individual mosquitoes were genotyped for kdr mutations. A probit regression model was used to analyze the factors influencing mosquito survivorship. As the distance from the application source route increased, the amount of Permanone deposited decreased, resulting in higher survivorship frequency of Ae. aegypti females with the triple-resistant kdr genotype (LL/II/CC). The L allele at the 410-site significantly contributed to an increased resistance level when co-occurring with other kdr mutations. This study linked the survival probabilities of mosquitoes with different kdr genotypes, and the amount of pesticide they received in the field. Pesticide quantification, control efficacy results and genotyping allowed us to empirically determine the impact of genotypic resistance on vector control in the field. © 2024 Society of Chemical Industry.

Electric inter-row control of lupin plants does not adversely affect the neighbouring non-target lupin plants

Abstract Inter-row weed control is used in a wide range of crops, traditionally applied via physical cultivation or banded herbicide application. However, these methods may result in crop damage, herbicide resistance development, or off-target environmental impacts. Electric inter-row weed control presents an alternative, though its potential impact on crop yield requires further investigation. One of the modes of action of electric weed control is the continuous electrode-plant contact method, which passes a current through the weed and into the roots. As the current passes into the roots, it can potentially disperse through the soil to neighbouring root systems. Such off-target current dispersion, particularly in moist topsoil with low resistance, poses potential concern for neighbouring crops when electric inter-row weed control is applied. This research evaluated the continuous electrode-plant contact method, using a ZassoTM XPower machine, in comparison with mowing, across three trials conducted in 2022 and 2023. Both treatments were used to remove target lupin plants adjacent to a row of non-target lupin. Electric weed control was applied to plants in dry soil or following a simulated rainfall event. The trials demonstrated that electric weed control and mowing did not reduce density and biomass of neighbouring non-target lupin plants compared to the untreated control. Likewise, pod and seed production, grain size and protein, as well as grain germinability and vigour of the resulting seedlings was not reduced by these weed control tactics. This research used technology that was not fit for purpose in broad scale grain crops but concludes that electric weed control via the continuous electrode-plant contact method or mowing did not result in crop damage. Therefore, it is unlikely that damage will occur using commercial-grade electric weed control or mowing technology designed for large acreage inter-row weed control, thus offering non-chemical weed management options.