Imidacloprid Treatment Research Articles

Imidacloprid unique and repeated treatment produces cholinergic transmission disruption and apoptotic cell death in SN56 cells.

Imidacloprid (IMI), the most widely used worldwide neonicotinoid biocide, produces cognitive disorders after repeated and single treatment. However, little was studied about the possible mechanisms that produce this effect. Cholinergic neurotransmission regulates cognitive function. Most cholinergic neuronal bodies are present in the basal forebrain (BF), regulating memory and learning process, and their dysfunction or loss produces cognition decline. BF SN56 cholinergic wild-type or acetylcholinesterase (AChE), β-amyloid-precursor-protein (βAPP), Tau, glycogen-synthase-kinase-3-beta (GSK3β), beta-site-amyloid-precursor-protein-cleaving enzyme 1 (BACE1), and/or nuclear-factor-erythroid-2-related-factor-2 (NRF2) silenced cells were treated for 1 and 14 days with IMI (1 μM to 800 μM) with or without recombinant heat-shock-protein-70 (rHSP70), recombinant proteasome 20S (rP20S) and with or without N-acetyl-cysteine (NAC) to determine the possible mechanisms that mediate this effect. IMI treatment for 1 and 14 days altered cholinergic transmission through AChE inhibition, and triggered cell death partially through oxidative stress generation, AChE-S overexpression, HSP70 downregulation, P20S inhibition, and Aβ and Tau peptides accumulation. IMI produced oxidative stress through reactive oxygen species production and antioxidant NRF2 pathway downregulation, and induced Aβ and Tau accumulation through BACE1, GSK3β, HSP70, and P20S dysfunction. These results may assist in determining the mechanisms that produce cognitive dysfunction observed following IMI exposure and provide new therapeutic tools.

Investigating the spatial associations between thatch and white grub populations in imidacloprid‐treated turfgrass

AbstractField surveys were conducted on golf courses reporting the inability of imidacloprid to control white grubs (Coleoptera: Scarabaeidae) when applied preventively. Surveys of five sites with significant past imidacloprid use (>10 years) revealed significantly greater white grub populations in rough‐mown turf following imidacloprid treatment than that of adjacent short‐mown fairways. Additionally, spatial analysis by distance indicEs (SADIE) analyses demonstrated a positive correlation between white grub and thatch spatial patterns. To investigate the impact of thatch on imidacloprid efficacy and translocation throughout the turfgrass plant, greenhouse experiments were conducted using turf with differing thatch levels. Imidacloprid concentrations in soil and plant tissues were measured with high‐performance liquid chromatography (HPLC) and compared to values obtained through an enzyme‐linked immunosorbent assay (ELISA) kit to determine if the latter could be a cost‐effective alternative in future studies. ELISA provided reliable estimates of concentrations of imidacloprid compared to HPLC, with only minor discrepancies noted across different types of treatments and assessment timings. Despite finding higher imidacloprid levels in leaf tissues compared to roots and some differences in concentration across thatch treatments, there was no clear pattern showing that thatch thickness significantly affects imidacloprid penetration or accumulation in plant tissues or soil over time. These findings suggest that factors other than thatch thickness may contribute to the observed field failures of imidacloprid in controlling white grubs. Further research is necessary to identify these factors and optimize the use of imidacloprid in turfgrass pest management strategies.

Improving Sphenophorus levis Adult Mortality Through Solid Insecticide Applications and Increased Insecticide Dose.

The sugarcane weevil (Sphenophorus levis Vaurie, 1978) is currently considered the most important sugarcane pest in Brazil, causing significant yield losses. Application methods of insecticides for S. levis control have not been effective, mostly due to the insect's cryptic behavior below the soil surface which suppresses the correct placement of insecticide active ingredients on target. Two experiments were conducted using an innovative bioassay methodology that simulates sugarcane field conditions to effectively evaluate S. levis adult mortality and insecticide residues in the soil under different treatments. The first experiment aimed to assess the efficacy of two liquid- and solid-applied insecticides, while the second aimed to examine the effect of increasing the dose of lambda-cyhalothrin + thiamethoxam on S. levis adult control. The novel bioassays simulated liquid and solid insecticide applications on sugarcane by exposing S. levis adults to chemical residuals on rhizomes and in soil after insecticide application. In the first experiment, low S. levis adult control was detected (< 53% mortality) across all treatments, where both solid and liquid applications of lambda-cyhalothrin + thiamethoxam provided greater efficacy levels than imidacloprid and control treatments, respectively. Solid applications maintained higher insecticide concentrations in the soil for longer periods than liquid insecticide applications, providing maximum insect control levels 7days after application. The second experiment revealed that solid applications at higher insecticide doses significantly improved control of S. levis adult (76.7% mortality) and resulted in greater insecticide concentrations in the soil compared to the recommended label rate (58.8% mortality).

Physiological and gene expression responses of Protohermes xanthodes (Megaloptera: Corydalidae) larvae to imidacloprid.

Megaloptera larvae are important bioindicator species and potential resource insects. To further cultivate their economic role, their living environment must be examined in more detail. In this study, we analyzed the physiological and biochemical effects of a sublethal dose of imidacloprid, a widely used neonicotinoid insecticide, on the larvae of Protohermes xanthodes. After treatment with imidacloprid, P. xanthodes larvae exhibited clear symptoms of poisoning, including the head curling up toward the ventral surface. Additionally, the activity of acetylcholinesterase was significantly inhibited following exposure. The activities of glutathione S-transferases initially continuously increased but showed a slight decrease after 8days. Catalase activity initially increased and then decreased following imidacloprid treatment; superoxide dismutase activity fluctuated over time, and peroxidase activity continuously increased. The expression levels of HSP70s genes were evaluated using qRT-PCR. These results indicate that P. xanthodes larvae exhibit a toxic response to imidacloprid exposure, manifested as oxidative stress, as observed through behavioral and physiological indicators.

Heterologous expression and characterization of two delta glutathione S-transferases genes involved in imidacloprid metabolism in Grapholita molesta

Glutathione S-transferases (GSTs) are multifunctional enzymes, and insect GSTs play a pivotal role in the metabolism of insecticides. Grapholita molesta is a worldwide pest that causes substantial economic losses to the fruit industry. However, it remains unclear how imidacloprid, a commonly used insecticide in orchards, is metabolized by G. molesta. In the present study, the synergist diethyl maleate (DEM), which inhibits the GST activity, exhibited a 22-fold synergistic ratio against imidacloprid. Two new GST genes, GmGSTD2 (OR096251) and GmGSTD3 (OR096252), were identified and successfully cloned, showing the highest expression in the Malpighian tubes. Knockdown of GmGSTD2 and GmGSTD3 by RNA interference, increased the mortality of G. molesta from 28% to 47% following imidacloprid treatment. Both recombinant GmGSTD2 and GmGSTD3 proteins exhibited 1-chloro-2,4-dinitrobenzene (CDNB) activity and could be inhibited by imidacloprid in vitro, with maximum inhibition was 60% for GmGSTD2 and 80% for GmGSTD3. These results suggested that GSTs participate in the metabolism of imidacloprid with GmGSTD2 and GmGSTD3 playing key roles in this process.

Effects of the insecticide imidacloprid on aquatic invertebrate communities of the Ecuadorian Amazon

Imidacloprid is a neonicotinoid insecticide that has received particular attention due to its widespread use and potential adverse effects for aquatic and terrestrial ecosystems. Its toxicity to aquatic organisms has been evaluated in central and southern Europe as well as in (sub-)tropical regions of Africa and Asia, showing high toxic potential for some aquatic insects and zooplankton taxa. However, its toxicity to aquatic organisms representative of tropical regions of Latin America has never been evaluated. To fill this knowledge gap, we carried out a mesocosm experiment to assess the short- and long-term effects of imidacloprid on freshwater invertebrate communities representative of the Ecuadorian Amazon. A mesocosm experiment was conducted with five weekly applications of imidacloprid at four nominal concentrations (0.01 μg/L, 0.1 μg/L, 1 μg/L and 10 μg/L). Toxic effects were evaluated on zooplankton and macroinvertebrate populations and communities, as well as on water quality parameters for 70 days. Given the climatic conditions prevailing in the study area, characterized by a high solar radiation and abundant rainfall that resulted in mesocosm overflow, there was a rapid dissipation of the test compound from the water column (half-life: 4 days). The macroinvertebrate taxa Callibaetis pictus (Ephemeroptera), Chironomus sp. (Diptera), and the zooplankton taxon Macrocyclops sp., showed population declines caused by the imidacloprid treatment, with a 21-d Time Weighted Average No Observed Effect Concentrations (21-d TWA NOEC) of 0.46 μg/L, except for C. pictus which presented a 21-d TWA NOEC of 0.05 μg/L. In general terms, the sensitivity of these taxa to imidacloprid was greater than that reported for surrogate taxa in temperate zones and similar to that reported in other (sub-)tropical regions. These results confirm the high sensitivity of tropical aquatic invertebrates to this compound and suggest the need to establish regulations for the control of imidacloprid contamination in Amazonian freshwater ecosystems.

Pharmacotherapeutic potential of malvidin to cure imidacloprid induced hepatotoxicity via regulating PI3K/AKT, Nrf-2/Keap-1 and NF-κB pathway

Imidacloprid (IMI) is one of the top-notch insecticides that adversely affects the body organs including the liver. Malvidin (MAL) is a natural flavonoid which exhibits a wide range of pharmacological properties. This research was designed to evaluate the protective ability of MAL to counteract IMI instigated liver toxicity in rats. Thirty-two rats were divided into four groups including control, IMI (5mg/kg), IMI (5mg/kg) + MAL (10mg/kg) and MAL (10mg/kg) alone treated group. The recommended dosages were administrated through oral gavage for 4 weeks. It was revealed that IMI intoxication disrupted the PI3K/AKT and Nrf-2/Keap-1 pathway. Furthermore, the activities of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), heme-oxygenase-1 (OH-1) and glutathione reductase (GSR) were reduced while upregulating reactive oxygen species (ROS) and malondialdehyde (MDA) levels after IMI treatment. Moreover, IMI poisoning increased the levels of ALT (Alanine aminotransferase), AST (Aspartate transaminase), and ALP (Alkaline phosphatase) while reducing the levels of total proteins and albumin in hepatic tissues of rats. Besides, IMI administration escalated the expressions of Bcl-2-associated protein x (Bax) and cysteine–aspartic acid protease-3 (Caspase-3) while downregulating the expressions of B-cell lymphoma 2 (Bcl-2). Similarly, IMI intoxication, increased the levels of Interleukin-6 (IL-6), Nuclear factor kappa-B (NF-κB), Interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and the activity of cyclooxygenase-2 (COX-2). Furthermore, IMI disrupted the normal architecture of hepatic tissues. However, MAL treatment remarkably protected the liver tissues via regulating abovementioned disruptions.

Impact of imidacloprid exposure on gestational hyperglycemia: A multi-omics analysis

Imidacloprid (IMI), a commonly utilized neonicotinoid insecticide, has been identified to adversely impact glucose homeostasis. Pregnant women are believed to be more sensitive to toxins than non-pregnant women, and the impact of IMI exposure on gestational hyperglycemia remain unclear. To explore the impact, pregnant mice fed a high-fat diet were exposed to different doses (0.06, 0.6, 6 mg/kg bw/day) of IMI by gavage. Glucose homeostasis-related parameters were measured. The glucose homeostasis influenced by IMI treatment was explored through integrating gut microbiota, metabolomic and transcriptomic analysis. Results showed that IMI-H (6 mg/kg bw/day) exposure notably restricted gestational weight gain and perturbed glucose homeostasis characterized by reduced glucose tolerance and insulin sensitivity, alongside elevated levels of fasting blood glucose and insulin. Multi-omics analysis revealed that IMI-H exposure induced significant changes in the richness and composition of the gut microbiome. The metabolite profiles of serum samples and cecal contents, and transcriptome of liver and ileum were all affected by IMI-H treatment. The altered gut microbiota, metabolites and genes exhibited significant correlations with glucose homeostasis-related parameters. These differential metabolites and genes were implicated in various metabolic pathways including bile secretion, glucagon signaling pathway, lipid metabolism, fatty acid metabolism. Significant correlations were observed between the altered gut microbiota and caecum metabolome as well as liver transcriptome. For example, the abundance of Oscillibacter was strongly correlated with gut microflora-related metabolites (Icosenoic acid, Lysosulfatide, and fluticasone) and liver differential genes (Grin3b, Lifr, and Spta1). Together, IMI exposure resulted in significant changes in microbial composition, along with alterations in certain metabolites and genes associated with metabolic process, which may promote gestational hyperglycemia.

Assessing the application of a biochar-supported iron oxide catalyst to the treatment of imidacloprid by photo-Fenton technologies

Emerging contaminants entail a great challenge to conventional treatment systems because they are not able to remove most of these bio-recalcitrant compounds. In particular, the presence of pesticides, such as imidacloprid, in the environment is a great hazard to soil microbiota, pollinating insects, and the aquatic environment. This research aims to enhance the treatment efficiency of advanced oxidation processes applied to the removal of bio-recalcitrant pollutants that are present in stormwater by assessing the application of a newly designed, economical, and efficient treatment alternative. Specifically, solar and LED (365 and 420 nm) heterogeneous photo-Fenton processes were carried out to remove a concentration of 5 mg·L−1 of imidacloprid, which was selected as the model pollutant that has been identified present in stormwater, using a magnetic iron oxides catalyst supported on pinewood waste biochar. The removal kinetics and mineralization of this contaminant were determined under the effect of the natural pH value of the solution and under a circumneutral pH environment, and heterogeneous and homogeneous catalytic contributions to the process were assessed. All these treatments achieved the successful efficient removal of the contaminant whether applying LED (UVA or visible blue) or solar radiation. The heterogeneous photo-Fenton treatment using a magnetic iron oxide catalyst supported on pinewood waste biochar totally removed imidacloprid after 10 minutes of oxidation at the initial natural pH value of the solution using 365 nm UVA LED radiation. Moreover, a 70% TOC removal was addressed after 60 minutes of treatment. The solar version of this heterogeneous photo-Fenton process removed the contaminant after 60 minutes of reaction, together to a TOC removal of the 60–65% after 120 minutes of treatment, including certain photolytic contribution; as well as it showed very efficient results under the effect of a circumneutral pH value. The assessed biochar-supported iron oxide catalyst was displayed as very stable under all the tested reaction conditions and its heterogeneous contribution to the process was confirmed superior to an exclusive homogeneous process.

Improving the quality and toxicity of rice husk liquid smoke to control edamame soybean pests

Purpose of the research to improve the quality and toxicity of husk charcoal liquid smoke which is effective and selective in controlling edamame soybean plant pests, safe for predatory and pollinators arthropods, and does not contain the dangerous compound Benzo(a)pyrene. The resulting product can be used as a substitute for synthetic insecticides which are non-selective and unsafe for predators, pollinators and human health. The technique used was to set the temperature of the pyrolysis process between 200-300°C to produce grade 3 and distillation of grade 3 to grade 2 with a temperature of 80-100°C. Research was carried out at Jember State Polytechnic, from August to September 2023. The observation parameters were content of grade 3 and grade 2 compounds using GCMS, Bioassay tests against S. litura 3rd instar using concentrations of 0%, 1%. 2%, 3%, 4% and 5% each for 10 test insects, with 3 repetitions, using the feed immersion method. LC50 and LC95 test used PoloPlus 1.0. Field tests compared arthropod diversity, grade 3, grade 2 and Imidacloprid treatments, using the Kruskal-Wallis test. The diversity index uses the Shannon-Wiener (H’) and Sympson Dominance Index (C’) formulas. Conclusion LC95 grade 3 was 3%, Grade 2 was 4%. Both were not found Benzo(a)pyrene. The grade 3 pest population was not significantly different compared to Imidacloprid. Grade 3 and grade 2 predators and pollinators were higher than Imidacloprid, the diversity of Grade 3, grade 2 and Imidacloprid treatments were moderate diversity, balanced ecosystem and no species dominance found.

RNA Interference Reveals the Impacts of CYP6CY7 on Imidacloprid Resistance in Aphis glycines.

Cytochrome P450 (CYP) is a group of important detoxification enzymes found in insects related to their resistance to insecticides. To elucidate the CYP6 family genes of P450, which are potentially related to imidacloprid resistance in Aphis glycines, the CYP6 cDNA sequences of A. glycines were studied. The transcriptome of A. glycines was constructed, and the CYP6 cDNA sequences of A. glycines were screened. Their relative expression levels in response to imidacloprid induction were examined through qRT-PCR, and the CYP6s with higher expression levels were used to study the detoxification of imidacloprid through RNA interference and a bioassay. Twelve CYP6s were obtained from the A. glycines transcriptome. These samples were named by the International P450 Nomenclature Committee and registered in GenBank. After 3, 6, 12, 24 and 48 h of induction with LC50 concentrations of imidacloprid, the relative expression levels of these CYP6s increased; the expression level of CYP6CY7 experienced the highest increase, being more than 3-fold higher than that of those of the non-imidacloprid-induced CYP6s. After RNA interference for CYP6CY7, the relative expression level of CYP6CY7 significantly decreased after 3, 6 and 12 h, while the corresponding P450 enzyme activity decreased after 12 and 24 h. The mortality of A. glycines due to imidacloprid treatment increased by 14.71% at 24 h. CYP6CY7 might detoxify imidacloprid in A. glycines. This study provides a theoretical basis for the further study of the mechanism of action of CYP6s and potential new methods for improving insecticidal efficacy.

Utilizing Remote Sensing to Quantify the Performance of Soybean Insecticide Seed Treatments

Soybean (Glycine max) is one of the most important oilseed crops grown in North America and a key contributor to the global protein supply. Insect feeding by a major soybean pest, the bean leaf beetle (BLB; Cerotoma trifurcata), can result in economic yield loss if not controlled. The objective of this research was to use unmanned aerial vehicle (UAV) image analysis to compare the agronomic and efficacy traits of two soybean insecticide seed treatments (IST) in locations with BLB feeding. Across the 2018–2023 field trial locations, 29 had low BLB feeding pressure (less than 25% feeding damage to no IST plots) and 31 had high BLB feeding pressure (greater than 25% feeding damage to no IST plots). In low BLB pressure locations, cyantraniliprole and imidacloprid seed treatments had significantly higher BLB efficacy, significantly higher UAV greenness, and significantly higher final yield as compared to no IST. In high BLB pressure locations, cyantraniliprole and imidacloprid seed treatments were significantly better compared to no IST for BLB efficacy, UAV emergence, UAV vigor, UAV greenness, and final yield. In high BLB pressure locations, cyantraniliprole had significantly higher BLB efficacy, significantly better UAV emergence, and significantly higher yield compared to imidacloprid. The cyantraniliprole treatment had a +254.5 kg/ha increase compared to no IST in low BLB pressure locations and a +213.7 kg/ha increase in high BLB pressure locations. The imidacloprid treatment had a +163.4 kg/ha yield increase compared to no IST in low BLB pressure locations and a +121.4 kg/ha yield increase in high BLB pressure locations. The use of UAV image analysis enabled quantification of the effect of BLB feeding on early-season agronomic traits and, when combined with efficacy and final yield data, successfully differentiated the performance of two soybean ISTs in environments with low or high insect pressure.

The inappropriate application of imidacloprid destroys the ability of predatory natural enemies to control pests in the food chain: A case study of the feeding behavior of Orius similis on Frankliniella occidentalis

Insecticides are an indispensable and important tool for agricultural production. However, the inappropriate application of insecticides can cause damage to the food chain and ecosystem. Orius similis is an important predatory and natural enemy of Frankliniella occidentalis. Imidacloprid is widely used to control pests, but will inevitably exert adverse effects on O. similis. In order to determine the effect of different imidacloprid treatments on the ability of O. similis to prey on the 2nd-instar nymphs of F. occidentalis, we determined the toxicity and predation of imidacloprid on different stages of O. similis under contact and ingestion treatments. In addition, we used the Holling disc equation to evaluate the ability of O. similis to search and exhibit predatory activity following contact and ingestion treatments. Analysis showed that the highest LC10 and LC20 values for imidacloprid contact and ingestion toxicity treatment were 17.06 mg/L and 23.74 mg/L, respectively. Both imidacloprid treatments led toa reduction in the predatory of O. similis on prey. The functional responses of the 3rd to 5th instar nymphs, along with female and male O. similis adults to the 2nd-instar nymphs of F. occidentalis were consistent with the Holling type II response following contact and ingestion with imidacloprid. However, following imidacloprid treatment, the handing time (Th) of O. similis with single F. occidentalis was prolonged and the instantaneous attack rate (a) was reduced after imidacloprid treatment. The predatory capacity (a/Th) of female O. similis adults when treated with the LC10 concentration of imidacloprid by ingestion was 52.85; this was lower than that of the LC10 concentration of imidacloprid in the contact treatment (57.67). The extent of predation of O. similis on the 2nd-instar nymphs of F. occidentalis was positively correlated with prey density, although the search effect was negatively correlated with prey density. The most extensive search effect was exhibited by adult O. similis females. Simulations with the Hessell-Varley interference model showed that an increase in the number of O. similis would reduce search efficiency regardless of whether they were treated with imidacloprid or not. Thus, O. similis, especially female adults, exhibited strong potential for controlling the 2nd-instar nymphs of F. occidentalis. The toxicity of ingestion following treatment with the same concentration of imidacloprid in O. similis was greater than that of contact treatment. When using O. similis to control F. occidentalis in the field, we should increase the number of female adults released, and prolong the interval between imidacloprid treatment and O. similis exposure. This strategy will improve the control ability of O. similis, coordinate both chemical and biological control, reduce the impact of pesticides on the environment, and improve the efficiency of agricultural production.

Imidacloprid triggered changes in strawberry fruits on edible quality and phenolic profiles by applied at two growth stages

Increasing evidence showed that imidacloprid affects plants’ abiotic or biotic stress tolerance. However, the effects of imidacloprid on the quality of fruits remain elusive. This work aimed to study the effects of imidacloprid applied at different growth stages on the edible quality and phenolic profile of strawberry fruit in the field experiment. For the first time, lower fruit quality was observed in the mature strawberry fruits after imidacloprid treatment at the fruit-bearing completion stage (five days after pollination). Compared to the control group, the mature strawberry fruit wights and the SCC/TA ratio declined about 18.2–30.0 % and 10.3–16.8 %, respectively. However, those attributes did not occur in the mature strawberry fruits by imidacloprid treatment at the fruit maturation stage (30 days after pollination). Among the 30 phenolic compounds, nine presented significant up-regulation or down-regulation after imidacloprid application at two different growth stages, suggesting that the application period played an essential role in evaluating the effects of imidacloprid on the quality of fruits. A significant effect on fruit quality was presented at the strawberry early growth stage treated by imidacloprid. This study provided a new insight into how and when imidacloprid affects the quality of strawberry fruits, contributing to the future’s more scientific application of imidacloprid on strawberries.

Resveratrol alleviates imidacloprid-induced mitochondrial apoptosis, necroptosis, and immune dysfunction in chicken lymphocyte lines by inhibiting the ROS/MAPK signaling pathway.

Imidacloprid (IMI) is a neonicotinoid insecticide with the highest global market share, and IMI exposure in the environment can negatively affect many nontarget organisms (a general term for organisms affected by drugs other than target organisms). Resveratrol (RSV), a non-flavonoid polyphenolic organic compound derived from peanuts, grapes, and other plants, has anti-inflammatory and antioxidant effects. It is currently unclear how RSV protects against cell damage caused by IMI. Therefore, we established an experimental model of chicken lymphocyte lines exposed to 110 μg/mL IMI and/or 0.5 μM RSV for 24 h. According to the experimental results, IMI markedly raised intracellular reactive oxygen species levels and diminished the activity of the cellular antioxidant enzymes (CAT, SOD, and GPx), leading to MDA accumulation and decreased T-AOC. JNK, ERK, and P38, the essential components of the mitogen-activated protein kinase (MAPK) signaling pathway, were also expressed more when IMI was present. Additionally, IMI resulted in upregulation of mitochondrial apoptosis (Caspase 3, Caspase 9, Bax, and Cyt-c) and necroptosis (Caspase 8, RIPK1, RIPK3, and MLKL) related factors expression, downregulation of Bcl-2 expression, induction of upregulation of cytokine IL-6 and TNF-α expression, and downregulation of IFN-γ expression. The combined treatment of RSV and IMI significantly reduced cellular oxidative stress levels, inhibited the MAPK signaling pathway, and alleviated IMI-induced mitochondrial apoptosis, necroptosis, and immune dysfunction. To summarize, RSV antagonized IMI-induced mitochondrial apoptosis, necroptosis, and immune dysfunction in chicken lymphocyte lines by inhibiting the ROS/MAPK signaling pathway.

Basal Bark Treatment of Imidacloprid for Hemlock Woolly Adelgids (Adelges tsugae)

Hemlock wooly adelgid (Adelgis tsugae Annand) (HWA) has invaded much of eastern hemlock’s (Tsugae canadensis L. Carrière) native range. Arborists and forest managers have successfully handled this pest using either contact or systemic pesticides. One of these pesticides, imidacloprid, has often been applied using a soil or trunk injection. Although imidacloprid has been labeled as a basal bark spray to control HWA, minimal information regarding its efficacy is available. This study compared bark treatments to soil treatment of imidacloprid at high and low application rates, as well as the use of a bark adjuvant. The results showed that basal bark treatments were as effective as soil treatments. Hence, basal bark treatments of imidacloprid can be an effective method for control of HWAs in eastern hemlock trees. A bark adjuvant may not be necessary, as it was not found to influence the amount of imidacloprid in the tissues.

Metal-Organic Framework-Based Insecticide and dsRNA Codelivery System for Insecticide Resistance Management.

Targeted silencing of resistance-associated genes by specific double-stranded RNA (dsRNA) is an attractive strategy for overcoming insecticide resistance in insect pests. However, silencing target genes of insect pests by feeding on dsRNA transported via plants remains challenging. Herein, a codelivery system of insecticide and dsRNA is designed by encapsulating imidacloprid and dsNlCYP6ER1 within zeolitic imidazolate framework-8 (ZIF-8) nanoparticles to improve the susceptibility of Nilaparvata lugens (Stål) to imidacloprid. With an average particle size of 195 nm and a positive surface charge, the derived imidacloprid/dsNlCYP6ER1@ZIF-8 demonstrates good monodispersity. Survival curve results showed that the survival rates of N. lugens treated with imidacloprid and imidacloprid@ZIF-8 were 82 and 62%, respectively, whereas, in the imidacloprid/dsNlCYP6ER1@ZIF-8 treatment group, the survival rate of N. lugens is only 8%. Pot experiments demonstrate that the survival rate in the imidacloprid/dsNlCYP6ER1@ZIF-8 treatment group was much lower than that in the imidacloprid treatment group, decreasing from 54 to 24%. The identification of NlCYP6ER1 expression and the fluorescence tracking of ZIF-8 demonstrate that ZIF-8 can codeliver dsRNA and insecticide to insects via rice. Safety evaluation results showed that the dsNlCYP6ER1@ZIF-8 nanoparticle had desirable biocompatibility and biosafety to silkworm. This dsRNA and insecticide codelivery system may be extended to additional insecticides with potential resistance problems in the future, greatly enhancing the development of pest resistance management.

Exploring the toxicity of biodegradable microplastics and imidacloprid to earthworms (Eisenia fetida) from morphological and gut microbial perspectives

Biodegradable microplastics (BMPs) pose serious environmental problems to soil organisms, and their adsorption capacity might make pesticides more dangerous for soil organisms. Therefore, in this study, polylactic acid (PLA) BMPs and imidacloprid (IMI) were used as a representative of BMPs and pesticides, respectively. Eisenia fetida was used as a test animal to investigate the effects of environmentally relevant concentrations of single and compound contaminated PLA BMPs and IMI on mortality, growth, number of offspring, tissue damage, and gut microorganisms of E.fetida. Exposure to PLA BMPs treatment and PLA BMPs + IMI treatment resulted in a sustained increase in E.fetida mortality, reaching 16.7% and 26.7%, respectively. The growth inhibition rate of single treatments was significantly increased. The compound contamination had the greatest effect on E.fetida offspring compared to the control. PLA BMPs and IMI cause histological damage to E.fetida, with the compound treatment causing the most severe damage. Based on the results of 16S sequencing, the bacterial communities in E.fetida gut and soil treated to PLA BMPs and IMI were significantly different. PLA BMPs + IMI treatment suppresses the abundance and diversity of E.fetida gut microorganisms, disrupting the homeostasis of bacterial communities and causing immune and metabolic dysfunction. These findings highlight the more severe damage of combined PLA BMPs and IMI pollution to E.fetida, and help to assess the risk of earthworm exposure to environmentally relevant concentrations of PLA BMPs and IMI.

The interaction of nicotinic acetylcholine receptor subunits Ldα3, Ldα8 and Ldβ1 with neonicotinoids in Colorado potato beetle, Leptinotarsa decemlineata

The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), is an extremely destructive notifiable quarantine pest. Over the last two decades, neonicotinoid insecticides, particularly thiamethoxam and imidacloprid, have been used to control it in Xinjiang, and local field populations have developed different levels of resistance in consequence. However, the contributions of nicotinic acetylcholine receptors (nAChRs) to neonicotinoid resistance are currently poorly understood in CPB. Previous studies have shown that nAChRα1, α3, α8 and β1 are major target subunits for neonicotinoids in some model and important agricultural insects including nAChRα1 subunit of L. decemlineata (Ldα1). In this study, the expression levels of Ldα3, Ldα8 and Ldβ1 following 72 h of treatments with median lethal doses of thiamethoxam and imidacloprid were compared using real-time quantitative PCR. These genes were then individually and simultaneously knocked down with Ldα1 by RNA interference (RNAi) using a double-stranded RNA (dsRNA) feeding method for six days to explore their roles in CPB susceptibility to imidacloprid and thiamethoxam. The results showed that the expressions of Ldα3, Ldα8 and Ldβ1 were significantly decreased by 36.99–74.89% after thiamethoxam and imidacloprid treatments, compared with the control. The significant downregulation of the target genes resulting from RNAi significantly reduced the mortality of adults exposed to thiamethoxam and imidacloprid by 34.53% –56.44% and 28.78%–43.93%, respectively. Furthermore, the adult survival rates were not affected by every dsRNA-feeding treatment, while the body weight of the test adults significantly deceased after four and six days of individual gene RNAi. This study showed that Ldα3, Ldα8 and Ldβ1 are down-regulated by thiamethoxam and imidacloprid and play important roles in the tolerance of CPB to neonicotinoids.

Imidacloprid-induced stress affects the growth of pepper plants by disrupting rhizosphere-plant microbial and metabolite composition

Overusing imidacloprid (IMI) has been found to impede secondary metabolism and hinder plant growth. The impact of IMI stress on the interaction between metabolites, rhizosphere, and plant-microbe dispersion through various pathways in pepper plants has not been extensively studied. This study investigated the effects of IMI on plant signaling components, secondary metabolic pathways, and microbial communities in the rhizosphere and phyllosphere. Here, the distribution of IMI and its metabolites (6-chloronicotinic acid, IMI-desnitro, 5-hydroxy-IMI, IMI-urea, and IMI-olefin) was primarily observed in the pepper plant leaves. A rise in IMI concentration had a more significant inhibitive effect on the metabolism of pepper leaves than on pepper roots. The findings of non-target metabolomics indicated that IMI exposure primarily suppresses secondary metabolism in pepper plants, encompassing flavones, phenolic acids, and phytohormones. Notably, the IMI treatment disrupted the equilibrium between plants and microbes by decreasing the population of microorganisms such as Vicinamibacteria, Verrucomicrobiae, Gemmatimonadetes, and Gammaproteobacteria in the phyllosphere, as well as Vicinamibacteria, Gemmatimonadetes, Gammaproteobacteria, and Alphaproteobacteria in the rhizosphere of pepper plants. The study demonstrates that overexposure to IMI harms microbial composition and metabolite distribution in the rhizosphere soil and pepper seedlings, inhibiting plant growth.