Insecticide Resistance Research Articles

Quantifying farm sustainability through the lens of ecological theory.

The achievements of the Green Revolution in meeting the nutritional needs of a growing global population have been won at the expense of unintended consequences for the environment. Some of these negative impacts are now threatening the sustainability of food production through the loss of pollinators and natural enemies of crop pests, the evolution of pesticide resistance, declining soil health and vulnerability to climate change. In the search for farming systems that are sustainable both agronomically and environmentally, alternative approaches have been proposed variously called 'agroecological', 'conservation agriculture', 'regenerative' and 'sustainable intensification'. While the widespread recognition of the need for more sustainable farming is to be welcomed, this has created etymological confusion that has the potential to become a barrier to transformation. There is a need, therefore, for objective criteria to evaluate alternative farming systems and to quantify farm sustainability against multiple outcomes. To help meet this challenge, we reviewed the ecological theories that explain variance in regulating and supporting ecosystem services delivered by biological communities in farmland to identify guiding principles for management change. For each theory, we identified associated system metrics that could be used as proxies for agroecosystem function. We identified five principles derived from ecological theory: (i) provide key habitats for ecosystem service providers; (ii) increase crop and non-crop habitat diversity; (iii) increase edge density: (iv) increase nutrient-use efficiency; and (v) avoid extremes of disturbance. By making published knowledge the foundation of the choice of associated metrics, our aim was to establish a broad consensus for their use in sustainability assessment frameworks. Further analysis of their association with farm-scale data on biological communities and/or ecosystem service delivery would provide additional validation for their selection and support for the underpinning theories.

Marching towards bioeconomy: Larvicidal effect of three indigenous plant extracts from Sri Lanka—Garcinia quaesita, Garcinia zeylanica, and Coleus hadiensis on dengue vector Aedes aegypti

AbstractBioeconomy would be a beneficial solution for funding through the rational use of finances and human resources in order to achieve better productivity and fruitfulness of mosquito control programs. Synthetic insecticides are widely used to repress mosquitoes. However, it instigates problems such as insecticide resistance among mosquitoes such as developing resistance, bio‐accumulation, and ecosystem destabilization. Natural plant‐based products are a healthy alternative to use as mosquito larvicides. The country has to spend a considerable cost for buying synthetic insecticides too. Therefore, the present study was undertaken to evaluate larvicidal efficacy of Garcinia zeylanica, Garcinia quaesita, and Coleus hadiensis against Aedes aegypti mosquito larvae. Fresh leaves of plants were collected, and the aqueous crude extract was prepared. Phytochemicals were extracted using refluxing technique. A concentration series of crude extract of leaves were prepared separately from 20 to 100 mg/L. Batches of each containing 100 third instar larvae of Ae. aegypti were used for larval bioassays. Ae. aegypti mosquito larvae were evaluated in accordance with the guidelines of World Health Organization. The experimental setup was repeated four times at each concentration. Probit analysis was used to evaluate the relationship of mortality with the concentration of aqueous crude extract. The G. zeylanica and G. quaesita leaf extracts showed a dose‐dependent effect against Ae. aegypti larvae after the 24 and 48 h exposure period. Interestingly, C. hadiensis did not show any dose‐dependent effect against A. aegypti mosquito larvae. The percentage mortality rates have shown a significant variance among different concentrations (P = 0.000). The recorded LC50 and LC90 for aqueous crude extract of G. zeylanica were 27.167 and 52.861 g/L, respectively, and LC50 and LC90 for aqueous crude extract of G. quaesita were 36.841 and 76.036 g/L, respectively, after 24 h of exposure period. The G. zeylanica and G. quaesita plant's high larvicidal activity is supported by the presence of phytochemicals such as saponins, steroids, flavonoids, and phenol, which showed combination effects in terms of larvicidal action to mosquito larvae. Hence, there is a potential of G. zeylanica and G. quaesita aqueous leaf extracts as a key source for the development of an environment‐friendly plant‐based larvicide against Ae. aegypti. Hence, this warrants vector control entities to re‐think “biological wealth for economic prosperity” with environmentally friendly country‐wide control approaches for medically important disease vectors.

Identification and characterization of uridine diphosphate glycosyltransferases in Dioryctria abietella, with an emphasis on putative roles in olfaction and reproduction

AbstractMultiple physiological processes are involved in the interactions between the herbivore Dioryctria abietella and Pinaceae plants, with a key adaptation being the metabolic detoxification of host plant defensive substances. Moreover, the synthetic insecticides applied to control this coneworm are also shaping genes related to detoxification, such as the uridine diphosphate (UDP) glycosyltransferase (UGT) genes. Yet, the molecular mechanisms underpinning the resistance of D. abietella to toxic compounds remain unknown. In this study, we present an important UGT gene family involved in the detoxification mechanisms of D. abietella. Combining bioinformatic and transcriptomic approaches, a total of 37 UGT‐coding genes were identified from the transcriptome of D. abietella, with 20 full‐length sequences that shared high homology with UGTs found in other pyralid moths. These DabiUGTs were phylogenetically clustered into 12 subfamilies, with the three small clusters in the UGT33 and UGT40 clades mainly contributing to the size of the UGT gene repertoire in D. abietella. Expression profiles obtained from RNA sequencing (RNA‐Seq), reverse transcription PCR (RT‐PCR) and quantitative real‐time PCR (qPCR) revealed that over half of DabiUGTs had a broad tissue expression profile, with 28, 28, 31 and 35 genes detected separately in antennae, legs, abdomens and reproductive tissues. Notably, DabiUGT20, DabiUGT25, DabiUGT28 and DabiUGT34 were all significantly enriched in the antennae. Several DabiUGTs had significant expression levels in reproductive tissues, including DabiUGT6, DabiUGT9, DabiUGT24, DabiUGT26 and DabiUGT32 in female accessory glands, DabiUGT15 in male accessory glands and DabiUGT25 in male testes. Altogether, our results identify candidate DabiUGTs for mediating olfaction and reproduction in D. abietella, warranting further investigation into the roles of DabiUGTs in pesticide resistance, odorant detection and reproduction.

Bed Bug Infestation: An Updated Review.

In the past decade, there has been a global resurgence of bed bug infestations, especially in developed countries. Proper awareness and identification of bed bug infestations are essential to guide treatment and eradication. The purpose of this article is to familiarize physicians with bed bug bites so that they can effectively diagnose, treat, and address questions about bed bug bites and infestations. Bed bug bites are often painless. Typical reactions include pruritic, erythematous maculopapules occurring in clusters or in a linear or curvilinear distribution in exposed areas of the body. A small red punctum may be visualized at the center of the bite mark. Lesions that appear three in a row and papules on the upper eyelid associated with erythema and edema are highly suggestive of bites from bed bugs. Exaggerated local reactions such as vesicles, urticarial wheals, urticarial perilesional plaques, diffuse urticaria, bullae, and nodules may occur in previously sensitized individuals. Reactions to bed bug bites are self-limited. As such, treatment is mainly symptomatic. Topical pramoxine and oral antihistamines can be used to alleviate pruritus. Topical corticosteroids can be used for significant eruptions to control inflammation and pruritus, and to hasten resolution of the lesions. Integrated pest management, an approach for the eradication of bed bugs, includes monitoring devices (active monitors include the use of heat or carbon dioxide attractants and passive monitors include the use of sticky pads for trapping), and judicious use of nonchemical and chemical treatments known to be effective. Nonchemical interventions include keeping affected areas clean and free of clutter, vacuuming, washing linens with hot water, caulking wall holes and cracks where bugs can hide, proper disposal of highly infested items, and placement of bed bug traps/interceptors at the base of beds and furniture. Chemical interventions involve the use of insecticides such as synthetic pyrethroids, silicates, insect growth disruptors, carbamates, organophosphates, neonicotinoids, diethyl-meta-toluamide, chlorfenapyr, fipronil and plant essential oils. Insecticides should be used with caution to prevent over-exposure and toxicity (in particular, cardiovascular and neurologic toxicity), especially if there are young children around. It is important to note that multiple mechanisms of insecticide resistance exist and as such, chemical treatment should only be undertaken by trained professionals who understand the current literature on resistance. Both nonchemical and chemical technologies should be combined for optimal results. Bed bug infestations may cause diverse dermal reactions, stigmatization, poor self-esteem, emotional stress, anxiety, significant adverse effect on quality of life, and substantial socioeconomic burden to society. As such, their rapid detection and eradication are of paramount importance. Consultation with a professional exterminator is recommended to fully eradicate an infestation.

Palmer Amaranth in the Pacific Northwest

AbstractPalmer amaranth is one of the most troublesome pigweeds in crop production systems in the United States. It only recently started to appear in the Pacific Northwest (PNW). A coordinated extension and outreach effort among land grant universities (University of Idaho, Oregon State University, and Washington State University), Amalgamated Sugar, other commodity commissions, and industry was launched to track Palmer amaranth in the PNW. In 2023, tissue samples were collected from pigweeds suspected to be Palmer amaranth with tests providing confirmation. Palmer amaranth was detected in several crops as well as right‐of‐way and private property. Most of the Palmer amaranth populations were confirmed to be resistant to glyphosate. Additional surveys and resistance screening efforts are underway to map the distribution of Palmer amaranth and assess the level of herbicide resistance across the region. Earn 0.5 CEUs in Integrated Pest Management by reading this article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Histological validation of in-vivo larvicidal efficacy of marine Streptomyces sp. RD06 secondary metabolites against filariasis causing Culex quinquefasciatus and statistical media optimization for larvicidal derivatives production

Mosquito-borne disease pandemics, such as the Zika virus and chikungunya, have escalated cognizance of how critical it is to implement proficient mosquito vector control measures. The prevention of Culicidae is becoming more difficult these days because of the expeditious imminence of synthetic pesticide resistance and the universal expansion of tremendously invasive mosquito vectors. The present study highlights the insecticidal and larvicidal efficacy of the prospective novel actinobacterium derived from the marine Streptomyces sp. RD06 secondary metabolites against Culex quinquefasciatus mosquito. The pupicidal activity of Streptomyces sp. RD06 showed LC50=199.22 ± 11.54 and LC90= 591.84 ± 55.41 against the pupa. The purified bioactive metabolites 1, 2-Benzenedicarboxylic acid, diheptyl ester from Streptomyces sp. RD06 exhibited an LC50 value of 154.13 ± 10.50 and an LC90 value of 642.84 ± 74.61 tested against Cx. quinquefasciatus larvae. The Streptomyces sp. RD06 secondary metabolites exhibited 100 % non-hatchability at 62.5 ppm, and 82 % of hatchability was observed at 250 ppm. In addition, media optimization showed that the highest biomass production was attained at a temperature of 41.44 °C, pH 9.23, nitrogen source 11.43 mg/ml, and carbon source 150 mg/ml. Compared to control larvae, the histology and confocal microscopy results showed destruction to the anal gill, lumen content, and epithelial layer residues in the treated larvae. Utilizing an eco-friendly method, these alternative inventive insecticidal derivatives from Streptomyces sp. RD06 eradicates Culex quinquefasciatus. This study highlights the promising potential of these Streptomyces sp. RD06 secondary metabolites to develop affordable and efficacious mosquito larvicides to replace synthetic insecticides in the future.

Understanding the Spread of Insecticide Resistance through Population Genetic Approach: A Review

This review discusses the application of the population genetic approach in elucidating the deployment of insecticide resistance to mosquito vectors. Although there have been a lot of scientific work describing population genetic research and insecticide resistance, a study focusing on the spread of insecticide resistance using the population genetic approach needs to be done. Population genetics explains how a population is diverse in response to fitness and the cost of environmental factors. Thus, readers can relate this process to how insecticides spread in the population. Additionally, some fundamental mechanisms of insecticide resistance are also covered. As successive reproduction of advantageous phenotypic traits, such as resistance depends on many factors including continuous pressure, recombination rate, migration rate, genetic drift, and so on. Currently, genome-wide association studies involve chromosome-wide SNPs in which recombination hotspots occur or microsatellite flanking region of resistance gene target in which the fixation process can potentially serve as a suitable marker for elucidating the deployment. The information provided in this review to facilitate how the susceptible individual still exists despite the predominance of resistant individuals and how the resistance reverts to the vulnerable state.

Field evaluation of the residual efficacy of new generation insecticides for potential use in indoor residual spray programmes in South Africa

BackgroundThe decreasing residual efficacy of insecticides is an important factor when making decisions on insecticide choice for national malaria control programmes. The major challenge to using chemicals for vector control is the selection for the development of insecticide resistance. Since insecticide resistance has been recorded for most of the existing insecticides used for indoor residual spraying, namely, DDT, pyrethroids, organophosphates and carbamates, and new chemicals are necessary for the continued success of indoor residual spraying. The aim of this study was to assess the residual efficacy of Actellic 300CS, SumiShield™ 50WG and Fludora®Fusion by spraying on different wall surfaces.MethodsOne hundred and sixty-eight houses with different wall surface types (mud, cement, painted cement, and tin) which represented the rural house wall surface types in KwaZulu-Natal, South Africa were used to evaluate the residual efficacy of Actellic 300CS, SumiShield 50WG and Fludora®Fusion with DDT as the positive control. All houses were sprayed by experienced spray operators from the Malaria Control Programme. Efficacy of these insecticides were evaluated by contact bioassays against Anopheles arabiensis, a vector species. The residual efficacy of the insecticide formulations was evaluated against a susceptible insectary-reared population of An. arabiensis using WHO cone bioassays.ResultsEffectiveness of the three insecticides was observed up to 12 months post-spray. When assessing the achievement of 100% mortality over time, SumiShield performed significantly better than DDT on mud (OR 2.28, 95% CI 1.72–3.04) and painted cement wall types (OR 3.52, 95% CI 2.36–5.26). On cement wall types, Actellic was found to be less effective than DDT (OR 0.55, 95% CI 0.37–0.82) while Fludora®Fusion was less effective on tin wall types (OR 0.67, 95% CI 0.47–0.95). When compared to the combined efficacy of DDT on mud surfaces, SumiShield applied to each of the mud, cement and painted cement wall types and DDT applied to the cement wall types was found to be significantly more effective. These insecticides usually resulted in 100% mortality for up to 12 months with a delayed mortality period of 96–144 h, depending on the insecticide evaluated and the surface type sprayed.ConclusionField evaluation of these insecticides have shown that Actellic, SumiShield and Fludora®Fusion are suitable replacements for DDT. Each of these insecticides can be used for malaria vector control, requiring just one spray round. These insecticides can be used in rotation or as mosaic spraying.

A mathematical model for mapping the insecticide resistance trend in the Anopheles gambiae mosquito population under climate variability in Africa

The control of arthropod disease vectors using chemical insecticides is vital in combating malaria, however the increasing insecticide resistance (IR) poses a challenge. Furthermore, climate variability affects mosquito population dynamics and subsequently IR propagation. We present a mathematical model to decipher the relationship between IR in Anopheles gambiae populations and climate variability. By adapting the susceptible-infected-resistant (SIR) framework and integrating temperature and rainfall data, our model examines the connection between mosquito dynamics, IR, and climate. Model validation using field data achieved 92% accuracy, and the sensitivity of model parameters on the transmission potential of IR was elucidated (e.g. μPRCC = 0.85958, p-value < 0.001). In this study, the integration of high-resolution covariates with the SIR model had a significant impact on the spatial and temporal variation of IR among mosquito populations across Africa. Importantly, we demonstrated a clear association between climatic variability and increased IR (width = [0–3.78], α = 0.05). Regions with high IR variability, such as western Africa, also had high malaria incidences thereby corroborating the World Health Organization Malaria Report 2021. More importantly, this study seeks to bolster global malaria combat strategies by highlighting potential IR ‘hotspots’ for targeted intervention by National malria control programmes.

Pyrethroid resistance and gene expression profile of a new resistant An. gambiae colony from Uganda reveals multiple resistance mechanisms and overexpression of Glutathione-S-Transferases linked to survival of PBO-pyrethroid combination.

The effectiveness of long-lasting insecticidal nets (LLINs) are being threatened by growing resistance to pyrethroids. To restore their efficacy, a synergist, piperonyl butoxide (PBO) which inhibits cytochrome P450s has been incorporated into pyrethroid treated nets. A trial of PBO-LLINs was conducted in Uganda from 2017 and we attempted to characterize mechanisms of resistance that could impact intervention efficacy. We established an Anopheles gambiae s.s colony in 2018 using female mosquitoes collected from Busia district in eastern Uganda. We first assessed the phenotypic resistance profile of this colony using WHO tube and net assays using a deltamethrin dose-response approach. The Busia colony was screened for known resistance markers and RT-qPCR targeting 15 genes previously associated with insecticide resistance was performed. The Busia colony had very high resistance to deltamethrin, permethrin and DDT. In addition, the colony had moderate resistance to alpha-cypermethrin and lambda-cyhalothrin but were fully susceptible to bendiocarb and fenitrothion. Exposure to PBO in combination with permethrin and deltamethrin resulted in higher mortality rates in both net and tube assays, with a higher mortality observed in net assays than tube assays. The kdr marker, Vgsc-995S was at very high frequency (91.7-98.9%) whilst the metabolic markers Coeae1d and Cyp4j5-L43F were at very low (1.3% - 11.5%) and moderate (39.5% - 44.7%) frequencies respectively. Our analysis showed that gene expression pattern in mosquitoes exposed to deltamethrin, permethrin or DDT only were similar in comparison to the susceptible strain and there was significant overexpression of cytochrome P450s, glutathione-s-transferases (GSTs) and carboxyl esterases (COEs). However, mosquitoes exposed to both PBO and pyrethroid strikingly and significantly only overexpressed closely related GSTs compared to unexposed mosquitoes while major cytochrome P450s were underexpressed. The high levels of pyrethroid resistance observed in Busia appears associated with a wide range of metabolic gene families.

While the priest climbs a post, the devil climbs ten: major biological threats from parasite and vector to malaria control and elimination

Malaria is one of the most serious mosquito-borne infectious diseases in the world. The global malaria control progress has stalled in recent years, which is largely due to the biological threats from the malaria pathogen Plasmodium and the vector Anopheles mosquitoes. This article provides an overview of biological threats to global malaria elimination, including antimalarial drug resistance, deletions in the malaria rapid diagnostic test target P. falciparum histidine-rich protein 2/3 (Pfhrp2/3) genes, vector insecticide resistance and emergence of invasive vector species, so as to provide insights into malaria and vector research and the formulation and adjustment of the malaria control and elimination strategy.

IMPACT OF SOIL STERILIZATION FROM DIFFERENT LOCATIONS, WHEAT SEEDS CLEANING AND THEIR INTERACTIONS ON WEED CONTROL, AND YIELD AND YIELD COMPONENTS

IMPACT OF SOIL STERILIZATION FROM DIFFERENT LOCATIONS, WHEAT SEEDS CLEANING AND THEIR INTERACTIONS ON WEED CONTROL, AND YIELD AND YIELD COMPONENTS

Reflexivity and certified crop advisors’ knowledge paradigms as related to pesticide resistance management

A major unintended risk of modern US agricultural use of pesticides has been pesticide resistance—a situation in which overuse of simplified pesticide-reliant pest management practices results in the loss of pesticide efficacy and results in yield declines, labor and time costs, environmental hazards, and other negative consequences. It has been posited that addressing pesticide resistance will necessitate a transformation in how agriculture is done, including major structural diversification of management practices and the involvement of a broad community of diverse stakeholders co-producing knowledge. Crop advisors—those agronomists providing paid-for agronomic advice to farmers independently or as part of a larger corporation—are one group has a high potential impact on what pesticide resistance management strategies and farmers' information networks. However, there is minimal research on how crop advisors approach the topic of pesticide resistance with their customers, including the reductionist or reflexive approaches they may draw on in their information provisioning. We explore this topic through a series of regional focus groups intended to uncover crop advisors’ perspectives on structural barriers to resistance management and use of reflexivity in their application of reductionist or iterative knowledge provisioning paradigms. We find that crop advisors recognize complex structural barriers to effective pesticide resistance management; while modern reductionist approaches were evident in attempts to overcome these barriers, crop advisors also engaged in reflexivity and drew on iterative forms of knowledge provisioning, particularly when unaffiliated with an agrichemical company and when working with fewer customers and higher value specialty crops. Additionally, those crop advisors applying a reductionist advising approach did not necessarily adhere to a modernist ideology; rather, we found that most crop advisors were reflexively critical of this approach and preferred a more iterative format but were constrained from taking action on this preference due to structures based in the capitalist industrialized US agricultural system. We propose that reflexivity is present but insufficient to alter patterns of pesticide resistance information and management without significant structural alterations.

Introgression from local cultivars is a driver of agricultural adaptation in Argentinian weedy rice.

Weedy rice, a pervasive and troublesome weed found across the globe, has often evolved through fertilization of rice cultivars with little importance of crop-weed gene flow. In Argentina, weedy rice has been reported as an important constraint since the early 1970s, and, in the last few years, strains with herbicide-resistance are suspected to evolve. Despite their importance, the origin and genetic composition of Argentinian weedy rice as well its adaptation to agricultural environments has not been explored so far. To study this, we conducted genotyping-by-sequencing on samples of Argentinian weedy and cultivated rice and compared them with published data from weedy, cultivated and wild rice accessions distributed worldwide. In addition, we conducted a phenotypic characterization for weedy-related traits, a herbicide resistance screening and genotyped accessions for known mutations in the acetolactate synthase (ALS) gene, which confers herbicide resistance. Our results revealed large phenotypic variability in Argentinian weedy rice. Most strains were resistant to ALS-inhibiting herbicides with a high frequency of the ALS mutation (A122T) present in Argentinian rice cultivars. Argentinian cultivars belonged to the three major genetic groups of rice: japonica, indica and aus while weeds were mostly aus or aus-indica admixed, resembling weedy rice strains from the Southern Cone region. Phylogenetic analysis supports a single origin for aus-like South American weeds, likely as seed contaminants from the United States, and then admixture with local indica cultivars. Our findings demonstrate that crop to weed introgression can facilitate rapid adaptation to agriculture environments.

The Anopheles coluzzii range extends into Kenya: detection, insecticide resistance profiles and population genetic structure in relation to conspecific populations in West and Central Africa

BackgroundAnopheles coluzzii is a primary vector of malaria found in West and Central Africa, but its presence has hitherto never been documented in Kenya. A thorough understanding of vector bionomics is important as it enables the implementation of targeted and effective vector control interventions. Malaria vector surveillance efforts in the country have tended to focus on historically known primary vectors. The current study sought to determine the taxonomic status of samples collected from five different malaria epidemiological zones in Kenya as well as describe the population genetic structure and insecticide resistance profiles in relation to other An. coluzzii populations.MethodsMosquitoes were sampled as larvae from Busia, Kwale, Turkana, Kirinyaga and Kiambu counties, representing the range of malaria endemicities in Kenya, in 2019 and 2021 and emergent adults analysed using Whole Genome Sequencing (WGS) data processed in accordance with the Anopheles gambiae 1000 Genomes Project phase 3. Where available, historical samples from the same sites were included for WGS. Comparisons were made with An. coluzzii cohorts from West and Central Africa.ResultsThis study reports the detection of An. coluzzii for the first time in Kenya. The species was detected in Turkana County across all three time points from which samples were analyzed and its presence confirmed through taxonomic analysis. Additionally, there was a lack of strong population genetic differentiation between An. coluzzii from Kenya and those from the more northerly regions of West and Central Africa, suggesting they represent a connected extension to the known species range. Mutations associated with target-site resistance to DDT and pyrethroids and metabolic resistance to DDT were found at high frequencies up to 64%. The profile and frequencies of the variants observed were similar to An. coluzzii from West and Central Africa but the ace-1 mutation linked to organophosphate and carbamate resistance present in An. coluzzii from coastal West Africa was absent in Kenya.ConclusionsThese findings emphasize the need for the incorporation of genomics in comprehensive and routine vector surveillance to inform on the range of malaria vector species, and their insecticide resistance status to inform the choice of effective vector control approaches.

Could bacteriophages be used as a novel pest management tool to control gut endosymbionts in Western Flower Thrips?

Several species of Thysanoptera are considered agricultural pests, especially Frankliniella occidentalis (Western Flower Thrips, WFT). The damage WFT causes to plants can either be direct by feeding and oviposition activity or indirect by WFT serving as vectors for several plant viruses, bacteria, and fungi. Properties of WFT like polyphagy, cryptic lifestyle, fast reproduction and the ability to quickly develop insecticide resistance make them difficult to control. Alternative pest management tactics are thus in high demand. Potential targets are the facultative or obligate endosymbionts that affect the life history parameters of WFT. The known endosymbionts of WFT: BFo1/BFo2 (B = bacteria, Fo = Frankliniella occidentalis, number indicate different types) positively influence their fertility and development. Elimination of these endosymbionts could result in a decreased individual reproduction level and decreased population growth. Bacteriophages specific against BFo1/BFo2 were isolated and characterized and were applied in a no-choice feeding assay to female WFT. Antibiotic and sugar solutions served as controls. Phage-treated thrips showed no significant difference in survival, fecundity, oviposition rate or developmental time of the progeny compared to the control, whereas antibiotic treatment caused a decline in survival, fecundity, and oviposition rate, but not in the developmental time of offspring. The results showed a rapid decline of the bacteriophage concentration in the feed solution, which the WFT salivary gland products might cause. The complex relationship between thrips, endosymbionts and bacteriophages, needs further attention before bacteriophages could be used as potential management tools.

Survey of target site mutations linked with insecticide resistance in Italian populations of Aphis gossypii.

Aphis gossypii is a worldwide agricultural pest that causes high levels of economic losses by feeding and transmitting virus diseases. It is usually controlled by chemical insecticides, but this could lead to the selection of resistant populations. Several single nucleotide polymorphisms (SNPs) have been identified associated with insecticide resistance. Monitoring activities to detect the presence of such mutations in field populations can have an important role in insect pest management but, currently, no information on Italian strains is available. The presence of target site mutations conferring resistance to different insecticides was analysed in Italian field collected populations of A. gossypii with an allele specific approach (QSGG, Qualitative Sybr-Green Genotyping). Primers were designed to detect mutations in genes coding acetylcholinesterase (S431F), nicotinic acetylcholine receptor (R81T) and voltage-gated sodium channel (M918L and L1014F). S431F was widespread but with high variability across populations. R81T was detected for the first time in Italy but only in two populations. The L1014F mutation (kdr) was not found, while in the samples showing the M918L two different nucleotidic substitutions were detected. Mutant allele frequencies were, respectively, 0.70 (S431), 0.31 (M918) and 0.02 (R81). Further analysis on the voltage-gated sodium channel gene showed the presence of eight haplotypes and one non-synonymous mutation in the gene coding region. Multiple target-site mutations were detected within Italian populations. The combinations of genotypes observed in certain locations could affect negatively the control of this pest. Preliminary insights on the genetic structure in the Italian populations of A. gossypii were acquired. © 2024 Society of Chemical Industry.

Determination of insecticide resistance in cotton whitefly in north India

The whitefly, Bemisia tabaci (Gennadius) considered as most destructive pest, poses a significant threat to various crop species globally has developed resistance due to the indiscriminate use of synthetic chemicals. A study was carried out in 2018 at ICAR-Indian Agricultural Research Institute, New Delhi to determine insecticide resistance, in five Asia II 1 populations of B. tabaci from different cotton (Gossypium hirsutum L.) growing regions of north India. The susceptibility of the populations to different insecticide classes, viz. synthetic pyrethroid (cypermethrin); neonicotinoids (imidacloprid and thiamethoxam); thiourea (diafenthiuron) and diamide (cyantraniliprole) were assessed. Results revealed substantial heterogeneity in the responses of these populations to the insecticides. Sriganganagar and Bathinda populations exhibited moderate resistance to cypermethrin, imidacloprid, and thiamethoxam. Low level of resistance was observed in Bathinda and Sriganganagar populations against diafenthiuron. All populations were highly susceptible to cyantraniliprole. No cross-resistance was observed between cyantraniliprole and other insecticides, suggesting its potential as an alternative for managing insecticide resistance. High levels of detoxification enzymes (esterase, cytochrome P450 monooxygenase, and glutathione-S-transferase) in Sriganganagar and Bathinda populations indicated a positive correlation between insecticide resistance and detoxifying enzymes. These findings offer valuable insight for implementing insecticide rotation strategies to combat B. tabaci resistance in India.

Developing an Effective Push–Pull System for Managing Outbreaks of the Invasive Pest Bactrocera dorsalis (Diptera: Tephritidae) in Nephelium lappaceum Orchards

Outbreaks of the oriental fruit fly, Bactrocera dorsalis (Hendel), present significant challenges to global fruit production, necessitating effective control measures that minimize environmental risks and pesticide resistance. This study aimed to develop and evaluate the effectiveness of four distinct push–pull control strategies for managing B. dorsalis outbreaks in a Nephelium lappaceum orchard. These strategies involved the inclusion of low-concentration abamectin, spraying repellent with a drone or manually, using methyl eugenol (ME) or food bait and employing either two types of attractants and repellents or a single type. The findings indicated that incorporating the low-concentration abamectin into the push–pull system, utilizing ME as an attractant instead of food lures and manually applying abamectin and attractants were all effective in reducing the B. dorsalis population size and minimizing fruit damage. While increasing the diversity of repellents and attractants enhanced the long-term effectiveness of the system, it did not result in a significant decrease in B. dorsalis population size or fruit damage rate compared to using a single repellent or attractant. In conclusion, the push–pull strategy emerged as a viable method for managing B. dorsalis outbreaks, offering potential benefits in reducing environmental risks and pesticide resistance. However, the study underscored the importance of the context-specific construction of push–pull strategies to optimize their effectiveness in orchard settings.

Effect of aluminum on growth and herbicide resistance in Commelina communis and Tradescantia fluminensis, two invasive weed species in tea gardens

Effect of aluminum on growth and herbicide resistance in Commelina communis and Tradescantia fluminensis, two invasive weed species in tea gardens