Search Results (11)

Fluorinated pyrethroids, such as cyfluthrin and cyhalothrin, are more effective insecticides due to their enhanced stability and lipophilicity. However, they pose greater risks to non-target organisms. Their persistence in the environment and accumulation in tissues can lead to increased toxicity and ecological concerns. This study investigates the biodegradation of the fluorinated pyrethroids β-cyfluthrin (BCF) and λ-cyhalothrin (LCH) using a newly isolated Bacillus sp. MFK14 from a garden soil microbial consortium. Initial screening using ¹⁹F NMR analysis showed that the microbial consortium degraded both pyrethroids, leading to the isolation of Bacillus sp. MFK14. Subsequent GC-MS analysis revealed various degradation intermediates in both pyrethroids after incubation with Bacillus sp. MFK14. Notably, Bacillus sp. MFK14 completely degraded β-cyfluthrin and λ-cyhalothrin within 48 h at 30 °C. Fluoride ions from β-cyfluthrin and trifluoroacetic acid (TFA) from λ-cyhalothrin were detected as the end-products by ¹⁹F NMR analysis of the aqueous fraction. The pathway of the degradation was proposed for both the pyrethroids indicating shared biodegradation pathways despite different fluorinations. Inhibition studies with 1-ABT suggested the involvement of bacterial cytochrome P450 (CYP) enzymes in their biodegradation. The CYPome of Bacillus sp. MFK14 includes 23 CYP variants that showed significant sequence similarity to known bacterial CYPs, suggesting potential roles in pyrethroid biodegradation and environmental persistence. These findings highlight the potential for bioremediation of fluorinated pesticides, offering an environmentally sustainable approach to mitigate their ecological impact. Full article

Pepper is one of the most widely consumed foods around the world. China is the leading producer, while Mexico is the primary exporter. To support these roles, the responsible use of agrochemicals is essential. Additionally, investigating the factors influencing pesticide dissipation is critical to ensure that residue levels do not exceed established Maximum Residue Limits (MRLs) and to achieve the required pre-harvest interval (PHI). This is essential to prevent trade-related issues and mitigate potential health risks to consumers. Consequently, this study aims to evaluate the dissipation dynamics of acetamiprid, azoxystrobin, and β-cyfluthrin residues in jalapeño peppers cultivated under both greenhouse and open-field conditions. Three applications of a manufacturer’s suggested dosage were evaluated, with 7-day intervals between each. The residual content was quantified after 1 h and 1, 3, 7, 14, and 21 days following each application. A QuEChERS method utilizing ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) and gas chromatography equipped with a micro electron capture detector (GC-µECD) to determine the pesticide residues was optimized and validated, obtaining suitable performance, with satisfactory linearity, detection and quantification limits, recovery rates, and accuracy. The dissipation curves were constructed from the residues and dissipation percentages of the pesticides over time, elucidating the initial residuality, accumulation, half-life, residence time, and total persistence of the active ingredient. In addition, an analysis was carried out, relating climatic conditions to the cumulative dissipation of pesticides. The results show an increase in the initial residues, half-life, and residence time of pesticides in the greenhouse. Otherwise, in the open field, the residues of the pesticides acetamiprid and azoxystrobin increased over the initial applications. Climatic conditions, mainly evapotranspiration during crop growing, involve the dissipation of pesticides in jalapeño pepper. The validation method demonstrated satisfactory parameters, aligning with the guidelines provided by the US EPA and SENASICA. All concentrations quantified in real samples were found to be below the MRLs, ensuring compliance with regulatory standards. Additionally, the dissipation kinetics played a critical role in elucidating key aspects such as residence times, latency periods, and marketing timelines for ensuring food safety. This kinetics provided essential insights into the behavior and persistence of the residues, contributing to a more comprehensive understanding of their dynamics in agricultural and commercial contexts. We believe these findings underscore the reliability and applicability of the method for monitoring pesticide residues in real-world scenarios. Full article

Pyrethroids are one of the most commonly used insecticides worldwide in agriculture, public health, and household products. To monitor the presence of pyrethroids in the environment and in food, a broad-spectrum monoclonal antibody (mAb), CL/CN-1D2, was prepared. This mAb demonstrates a 50% inhibitory concentration (IC50) for different pyrethroids: cypermethrin (129.1 µg/L), β-cypermethrin (199.6 µg/L), cyfluthrin (215.5 µg/L), fenpropathrin (220.3 µg/L), λ-cyhalothrin (226.9 µg/L), β-cyfluthrin (241.7 µg/L), deltamethrin (591.2 µg/L), and fenvalerate (763.1 µg/L). Using the mAb CL/CN-1D2, a highly sensitive heterologous indirect competitive ELISA (ic-ELISA) was developed for the rapid detection of these pyrethroids. The limit of detection (LOD) for the eight pyrethroids in water, milk, celery, and leek matrices ranged from 24.4 to 152.2 μg/kg. The recoveries ranged from 65.1% to 112.4%, with a coefficient of variation (CV) below 15%. A robust correlation (R² = 0.9945) between the ic-ELISA and GC indicated that the ic-ELISA is a reliable tool for the rapid and cost-effective screening of pyrethroids residues. Full article

Isocycloseram is a novel insecticide belonging to the class of isoxazoline (IRAC MoA Group 30) that exhibits excellent efficacy and selectivity against invertebrate pests. We evaluated the efficacy of two 0.1% isocycloseram formulations against a laboratory and four insecticide-resistant field strains of common bed bugs (Cimex lectularius L.) (Hemiptera: Cimicidae) by direct spray and forced exposure on three surfaces (fabric, vinyl tiles, and unpainted pinewood). Their efficacy was compared with that of five commercial insecticides including Demand CS (0.03% λ-cyhalothrin), Temprid FX (0.05% imidacloprid and 0.025% β-cyfluthrin), Crossfire (0.4% clothianidin, 0.01% metofluthrin, and 1.0% piperonyl butoxide), Bedlam Plus (0.4% d-phenothrin, 1.0% MGK 264, and 0.05% imidacloprid), and PT Phantom II (0.5% chlorfenapyr). Both isocycloseram 45 SC and 400 SC formulations were the most effective among the tested insecticides. The isocycloseram 45 SC formulation caused faster mortality than the 400 SC formulation. Four hours of exposure to 0.025, 0.05, and 0.1% isocycloseram 45 SC residue on porous and non-porous surfaces caused 100% bed bug mortality after 3–4 days. Exposure to 30-day-aged 0.1% isocycloseram 45 SC residue for 4 h still caused 100% mortality, compared to 0–73% mortality by the five commercial insecticides. Isocycloseram is a highly effective compound for controlling resistant C. lectularius populations. Full article

Insecticide resistance is one of the factors contributing to the resurgence of the common bed bug, Cimex lectularius L. This study aimed to profile the resistance levels of field-collected C. lectularius populations to two neonicotinoids and one pyrethroid insecticide and the performance of selected insecticide sprays and an inorganic dust. The susceptibility of 13 field-collected C. lectularius populations from the United States to acetamiprid, imidacloprid, and deltamethrin was assessed by topical application using a discriminating dose (10 × LD₉₀ of the respective chemical against a laboratory strain). The RR₅₀ based on KT₅₀ values for acetamiprid and imidacloprid ranged from 1.0–4.7 except for the Linden 2019 population which had RR₅₀ of ≥ 76.9. Seven populations had RR₅₀ values of > 160 for deltamethrin. The performance of three insecticide mixture sprays and an inorganic dust were evaluated against three C. lectularius field populations. The performance ratio of Transport GHP (acetamiprid + bifenthrin), Temprid SC (imidacloprid + β-cyfluthrin), and Tandem (thiamethoxam + λ-cyhalothrin) based on LC₉₀ were 900–2017, 55–129, and 100–196, respectively. Five minute exposure to CimeXa (92.1% amorphous silica) caused > 95% mortality to all populations at 72 h post-treatment. Full article

The active forms of contact insecticides used for combatting mosquito-borne infectious diseases are typically crystalline solids. Numerous molecular crystals are polymorphic, crystallizing in several solid forms characterized by different physicochemical properties, including bioavailability. Our laboratory recently found that the activity of crystalline contact insecticides is inversely dependent on the thermodynamic stability of their polymorphs, suggesting that efficacy can be enhanced by the manipulation of the solid-state structure. This paper argues that crystallography should be central to the development of contact insecticides, particularly because their efficacy continues to be compromised by insecticide resistance, especially among Anopheles mosquito populations that spread malaria. Although insecticidal compounds with new modes of action have been introduced to overcome resistance, new insecticides are expensive to develop and implement. The repurposing of existing chemical agents in metastable, more active crystalline forms provides an inexpensive and efficient method for ‘evergreening’ compounds whose risks are already well-established. We report herein seven new single-crystal structures of insecticides used for controlling infectious disease vectors. The structures reported herein include pyrethroid insecticides recommended by the WHO for indoor residual spraying (IRS)-bifenthrin, β-cyfluthrin, etofenprox, α-cypermethrin, and λ-cyhalothrin as well as the neonicotinoid insecticide thiacloprid. Full article

Phytophagous insects, including Asian citrus psyllids (Diaphorina citri Kuwayama), use multiple sensory modalities (vision, olfaction, and gustation,) to locate and accept host plants. We explored incorporation of several sensory cues into a multi-modal attract-and-kill device (AK device) using a three-dimensional shape to increase visibility, as well as elements of color, attractant, phagostimulant, UV reflectant, and toxicant. Attraction of adult D. citri to the device was mediated by a combination of a highly reflective yellow cylinder, a UV reflectant compound (magnesium oxide), and an odorant blend as a short-range attractant. The device surface was coated with a slow-release wax matrix (SPLAT™) augmented with a phagostimulant consisting of a 3-component blend (formic acid, acetic acid, and para-cymene) and an insecticide (β-cyfluthrin). Psyllids landing on the device attempted to feed from the wax matrix, became intoxicated, died, and fell from the device. The device remained fully active over a period of 12 weeks partly because dead psyllids or nontargets did not adhere to the surface as occurs on adhesive yellow sticky cards, the industry standard. Laboratory and field assays showed that the device attracted and killed significantly more adult D. citri than ordinary yellow sticky cards. This device or a future iteration based on the design elements of this device is expected to contribute to sustainable and environmentally appropriate management of D. citri by exploiting the psyllid’s innate behavioral responses to visual, olfactory, and gustatory stimuli. Full article

In 2017 and 2018, a field survey was initiated on Greek olive orchards to investigate the attractiveness of bait spray applications and the impact of cover and bait sprays applied against the olive fruit fly Bactrocera oleae (Diptera: Tephritidae), on the honeybee, Apis mellifera L. and bumblebees Bombus terrestris, by investigating the pesticides’ residual prevalence. Bee colonies were evenly distributed in three sites located on coastal areas of Western Crete and visited almost weekly between July and October. Samples collected, were analyzed using existing or developed-optimized liquid and gas chromatographic methods. In bee samples, concentrations varied from 0.0013 to 2.3 mg/kg for dimethoate, from 0.0013–0.059 mg/kg for its metabolite omethoate, and from 0.0035 to 0.63 mg/kg regarding the pyrethroids, β-cyfluthrin and λ-cyhalothrin. In one bee sample dimethoate concentration exceeded both acute oral and contact median lethal dose (LD₅₀). Residue findings in bees, along with verified olive oil residues corroborated that those insecticides had been applied in the olive orchards and transferred to bees. The possibility of non-target effects of the bait sprays to the bees, as well as the impact of the contaminated olive to the bees are discussed. Full article

Horn flies, Haematobia irritans, a major cattle pest in the USA, cause substantial economic losses and current control methods rely heavily on insecticides. Three horn fly populations were evaluated for insecticide susceptibility to permethrin, β-cyfluthrin, and diazinon. Susceptibility was variable by population, with the greatest resistance exhibited by a 66-fold resistance ratio (RR) to permethrin and >14-fold RR to diazinon. Mechanisms of resistance were determined using molecular techniques and enzymatic assays. The knockdown resistance (kdr) genotype (L150F) associated with pyrethroid resistance, and a G262A mutation in acetylcholinesterase, previously associated with organophosphate resistance, were found in all field populations evaluated. Insensitivity of diazoxon at the acetylcholinesterase (AChE) target site was significantly different in horn flies from one of the field sites. For metabolic detoxifying enzymes, cytochrome P450 nor general esterases showed a significant difference between field strains and a laboratory susceptible strain. Pyrethroid resistance was likely due to the presence of the L150F mutation in the population. In vitro studies targeting the AChE enzyme did not support the notion that the G262A mutation was the sole cause of resistance to organophosphates, and, therefore, the exact resistance mechanism to diazinon was not able to be confirmed. Full article

Because certain flavonols and phenolic acids are found in pollen and nectar of most angiosperms, they are routinely ingested by Apis mellifera, the western honey bee. The flavonol quercetin and the phenolic acid p-coumaric acid are known to upregulate detoxification enzymes in adult bees; their presence or absence in the diet may thus affect the toxicity of ingested pesticides. We conducted a series of longevity assays with one-day-old adult workers to test if dietary phytochemicals enhance longevity and pesticide tolerance. One-day-old bees were maintained on sugar syrup with or without casein (a phytochemical-free protein source) in the presence or absence of quercetin and p-coumaric acid as well as in the presence or absence of two pyrethroid insecticides, bifenthrin and β-cyfluthrin. Dietary quercetin (hazard ratio, HR = 0.82), p-coumaric acid (HR = 0.91) and casein (HR = 0.74) were associated with extended lifespan and the two pyrethroid insecticides, 4 ppm bifenthrin (HR = 9.17) and 0.5 ppm β-cyfluthrin (HR = 1.34), reduced lifespan. Dietary quercetin enhanced tolerance of both pyrethroids; p-coumaric acid had a similar effect trend, although of reduced magnitude. Casein in the diet appears to eliminate the life-prolonging effect of p-coumaric acid in the absence of quercetin. Collectively, these assays demonstrate that dietary phytochemicals influence honey bee longevity and pesticide stress; substituting sugar syrups for honey or yeast/soy flour patties may thus have hitherto unrecognized impacts on adult bee health. Full article

Two strains of the common bed bug, Cimex lectularius L., eggs and first instars collected from pyrethroid-resistant adults were evaluated for insecticide resistance and compared to a susceptible strain. Dose-response bioassays were conducted using two insecticide formulations (Temprid: imidacloprid/β-cyfluthrin, and Transport: acetamiprid/ bifenthrin). The lethal concentration (LC₅₀) for the two resistant egg strains exposed to imidacloprid/β-cyfluthrin ranged from 3 to 5-fold higher than susceptible strain eggs. Resistant strain eggs dipped into formulations of acetamiprid/bifenthrin had LC₅₀ values which were significantly greater (39 to 1,080-fold) than susceptible strain eggs. Similar to eggs, resistant strain first instars exposed to residual applications of imidacloprid/β-cyfluthrin had LC₅₀ values ranging from 121 to 493-fold greater than susceptible strain first instars. When resistant strain first instars were treated with acetamiprid/bifenthrin, they had LC₅₀ values that were 99 to >1,900-fold greater than susceptible strain first instars. To determine differences between egg and first instar resistance, stage resistance ratios (SRR) were compared between the two stages. There was little difference between the egg and first instar stages, indicated by small SRR values ranging from 1.1 to 10.0. This study suggests that insecticide resistance is expressed early during bed bug development. Full article