Application Of Pyrethroids Research Articles

Pre-Conception And First Trimester Exposure To Pesticides And Associations With Stillbirth.

Associations of pesticide exposures during pre-conception with stillbirth have not been well explored. We linked Arizona pesticide use records with birth certificates from 2006-2020 and estimated associations of living within 500meters of any pyrethroid, organophosphate (OP), or carbamate pesticide applications during a 90 day pre-conception window or the first trimester, with stillbirth. We considered a binary measure of exposure (any exposure), as well as log-pounds and log-acres applied within 500m, in a negative control exposure framework with log-binomial regression. We included 1,237,750 births, 2,290 stillbirths, and 27 pesticides. During pre-conception, any exposure to pesticides were associated with stillbirth, including cyfluthrin (RR=1.97, 95% CI 1.17,3.32), zeta-cypermethrin (RR=1.81, 95%CI 1.20, 2.74), organophosphates as a class (RR=1.60, 95%CI 1.16, 2.19), malathion (RR=2.02, 95%CI 1.26, 3.24), carbaryl (RR=6.39, 95%CI 2.07, 19.74), and propamocarb hydrochloride (RR=7.72, 95%CI 1.10, 54.20) . During the first trimester, fenpropathrin (RR=4.36, 95%CI 1.09, 17.50), permethrin (RR=1.57, 95%CI 1.02, 2.42), organophosphates as a class (RR=1.50, 95%CI 1.11, 2.01), acephate (RR=2.31, 95%CI 1.22, 4.40), and formetanate hydrochloride (RR=7.22, 95%CI 1.03, 50.58) were associated with stillbirth. Interpretations were consistent when using continuous measures of pounds or acres of exposure. Pesticide exposures during pre-conception and first trimester may be associated with stillbirth.

Challenges in bermudagrass production in the southeastern USA

AbstractBermudagrass (Cynodon dactylon (L.) Pers.) is one of the primary perennial forages in the southeastern USA. Newer hybrid cultivars have superior production and nutritive value compared to common ecotypes. However, there are many challenges facing bermudagrass production in the region. First, the bermudagrass stem maggot (BSM; Atherigona reversura Villeneuve) has severely damaged bermudagrass throughout the region. Strategically timed pyrethroid applications significantly reduce adult BSM populations, but efforts are needed to develop integrated pest management plans. Second, an increasing number of producers are noting challenges with green‐up following winter dormancy. This may be attributed to disease, unbalanced soil fertility, and weed pressure. Perhaps one of the most limiting factors for continued production is the deficit of sprigs and trained personnel to sprig hybrid bermudagrasses. This research is critically important as the need for cold‐tolerant bermudagrass is increasing as tall fescue (Lolium arundinaceum (Schreb.) S. J. Darbyshire) is declining due to changes in temperature and precipitation throughout the northern parts of the region. Plant breeders are investigating hybrid bermudagrass at latitudes >35° with respect to freeze or cold tolerance. Despite the many challenges facing hybrid bermudagrass in the southeastern USA, researchers are working to ensure its persistence, productivity, and availability for the future.

Improved management of the bermudagrass stem maggot

AbstractThe bermudagrass stem maggot (BSM; Atherigona reversura Villeneuve) continues to damage bermudagrass [Cynodon dactlyon (L.) Pers.] pastures and hayfields throughout the southeastern United States each season. This management guide describes how to identify the damage to the forage and the bermudagrass stem maggot as a larva, pupa, and fly. Strategically timed pyrethroid applications reduce adult BSM populations and yield loss, but ongoing efforts are focused on developing integrated pest management plans that include cultural, physical, and biological suppression efforts. Research is ongoing to improve the effectiveness of insecticide applications and screen new modes of action to prevent resistance to the pyrethroids. However, long‐term solutions will require development and release of tolerant bermudagrass cultivars to reduce the reliance on pesticides. Fine‐stem bermudagrass lines are more susceptible to bermudagrass stem maggot damage than lines with thicker stem diameters. While ‘Tifton 85’ is still considered the standard to which we compare all other bermudagrass lines for BSM tolerance, there is still room for improvement. Genotypes currently under evaluation maintain the positive attributes of Tifton 85 while overcoming these challenges.

Pesticides, cancer, and oxidative stress: an application of machine learning to NHANES data

BackgroundThe large-scale application of pyrethroids and organophosphorus pesticides has great benefits for pest control. However, the increase of cancer incidence rate in recent years has also caused public concern about the health risks of pesticides. Hence, we utilized data from the National Health and Nutrition Examination Survey (NHANES) to assess the association and risk between pesticide exposure and several cancers, along with the comprehensive impact of oxidative stress. In this study, six cancers and six common pesticides were included to analyze their correlation and risk. And the levels of eight oxidative stress marks and two inflammatory markers were used for stratified analysis. Multiple logistic regression analysis was applied to estimate the odds ratio and 95% confidence intervals. Machine learning prediction models were established to evaluate the importance of different exposure factors.ResultsAccording to the data analyzed, each pesticide increased the risk of three to four out of six cancers on average. Iron, aspartate aminotransferase (AST), and gamma glutamyl transferase levels positively correlated with cancer risk in most cases of pesticide exposure. Except for demographic factors, factors such as AST, iron, and 3-phenoxybenzoic acid showed high contributions to the random forest model, which was consistent with our expectations. The receiver operating characteristic curve showed that the prediction model had sufficient accuracy (74.2%).ConclusionOur results indicated that specific pesticide exposure increased the risk of cancer, which may be mediated by various oxidative stress mechanisms. Additionally, some biochemical indicators have the potential to be screened for cancer prevention.

Impact of Cypermethrin (Arpon G) on Soil Health and Zea mays Growth: A Microbiological and Enzymatic Study

In defining the research objective, consideration was given to the expanding range of applications of third-generation pyrethroids, including cypermethrin—the active substance in Arpon G preparation. The interest in cypermethrin is due to its high thermostability and photostability. This study verified the effect of Arpon G on both the soil condition and the growth and development of Zea mays. To this end, the alpha and beta diversity of bacterial and fungal communities were characterized using the NGS (Next Generation Sequencing) method, as was the response of soil enzymes. The positive response of Z. mays to the soil application of cypermethrin corresponded to higher soil microbial and biochemical activity. Sowing the soil with Z. mays moderated changes in the biodiversity of alpha- and beta-bacterial communities to a greater extent than cypermethrin. The influence of both parameters was less significant for fungi. Although bacteria belonging to the Actinobacteria phylum and fungi from the Ascomycota phylum dominated in the soil, the use of Arpon G reduced the abundance of unique nucleotide sequences in the mycobiome to a greater extent than in the bacteriobiome. The inhibitory potential of Arpon G was only evident for acid phosphatase (by 81.49%) and arylsulfatase (by 16.66%) in the soil sown with Z. mays. The activity of catalase, dehydrogenases, β-glucosidase, arylsulfatase, and alkaline phosphatase was most strongly associated with the abundance of bacteria, while dehydrogenases were correlated with the abundance of fungi at the genus level. Arpon G can, thus, be considered a safe insecticide for soil conditions and, consequently, for its productive function.

Pyrethrins and Pyrethroids: A Comprehensive Review of Natural Occurring Compounds and Their Synthetic Derivatives

This comprehensive scientific review provides an in-depth analysis of both the natural compounds, pyrethrins, and their synthetic derivatives, pyrethroids, focusing on their classification, biosynthesis, mechanism of action, general and pharmaceutical uses, as well as their toxicity and environmental impact. Pyrethrins, derived from certain plant species, have long been recognized for their potent insecticidal properties. The review begins by examining the classification of pyrethrins and pyrethroids, elucidating their structural characteristics and unique features within the field of natural and synthetic compounds. The biosynthetic pathways responsible for producing pyrethrins in plants are discussed, highlighting the enzymatic reactions and genetic regulation involved. In addition, the synthesis of pyrethroid derivatives is explored, including both natural and synthetic sources and potential optimization strategies. Understanding the mechanisms of action by which pyrethrins and pyrethroids exert their insecticidal effects is a crucial aspect of this review. Complex interactions with the nervous systems of target organisms are examined, providing insights into their selective toxicity and modes of action. In addition, the various applications of these compounds are explored, from their use in agriculture for pest control to their incorporation into household insecticides and potential pharmaceutical applications. The review also critically evaluates the potential toxicity of pyrethrins and pyrethroids to human health. By consolidating current knowledge and research findings, this review provides a comprehensive understanding of the properties and applications of pyrethrins and pyrethroids, highlighting their benefits and risks, and the importance of responsible and sustainable use in various areas.

Profiling Insecticide Susceptibility of Aedes Albopictus From Hot Springs in Selangor, Malaysia.

The present study establishes insecticide susceptibility profiles of Aedes albopictus adult populations from 4 hot springs in Selangor, Malaysia, against 7 pyrethroids through an adult mosquito susceptibility bioassay. All Ae. albopictus populations were subjected to a 1-h exposure to each pyrethroid following the World Health Organization. The mortalities were recorded at 60 min of exposure to bifenthrin, 30 min for other pyrethroids, and 24 h posttreatment for all pyrethroids. Complete mortalities were observed upon exposures to the pyrethroids under 60 min and at 24 h posttreatment, excluding permethrin 0.25%, alpha-cypermethrin 0.05%, and bifenthrin 0.2%. These findings indicated that permethrin, deltamethrin, lambda-cyhalothrin, cyfluthrin, and etofenprox possess the recommended pyrethroid adulticide active ingredients that could be applied in vector control programs at these hot springs in the future. Nevertheless, the application of pyrethroids should be carefully monitored in rotation with other insecticide classes, including organophosphates and carbamates to avoid the development of insecticide resistance among mosquito vectors towards all insecticides. Although there were no reported cases of Aedes-borne pathogens at these hot springs to date, the current study results could still assist the Malaysian health authorities in determining approaches to control Aedes populations in these hot springs, if required in the future.

Growth, tolerance, and enzyme activities of Trichoderma strains in culture media added with a pyrethroids-based insecticide

The application of pyrethroids and carbamates represents an environmental risk and may exert adverse effects on beneficial microorganisms such as Trichoderma, which contribute to the biocontrol of several fungal phytopathogens. This research evaluated the tolerance of several strains of Trichoderma to a selected culture medium contaminated with a commercial insecticide (H24®) composed of pyrethroids, permethrin and prallethrin, and carbamate propoxur, and determined the influence of this insecticide on the release of enzymes such as chitinases, peroxidases, and endoglucanases by a consortium of selected Trichoderma strains grown in liquid culture medium. Four out of 10 Trichoderma strains showed tolerance to 200ppm (∼48.3% of growth) of the commercial insecticide after 96h of exposure to a contaminated solid medium. After eight days of growth in liquid culture, the insecticide enhanced extracellular protein content and peroxidase activities in the Trichoderma consortium but decreased both chitinase and glucanase activities. These fungal responses should be considered when implementing strategies that combine alternative pesticides and fungal biocontrollers for managing fungal phytopathogens.

A novel strategy for screening mutations in the voltage-gated sodium channel gene of Aedes albopictus based on multiplex PCR-mass spectrometry minisequencing technology

BackgroundThe current prevention and control strategy for Aedes albopictus heavily relies on comprehensive management, such as environmental management and chemical control. However, the wide application of pyrethroids has facilitated the development of insecticide resistance, primarily via mutations in the voltage-gated sodium channel (VGSC) gene. This study aims to develop a novel strategy for detecting mutations in the VGSC gene in Ae. albopictus using multiplex PCR-mass spectrometry (MPCR-MS) minisequencing technology.MethodsWe established a new strategy for detecting mutations in the VGSC gene in Ae. albopictus using MPCR-MS minisequencing technology. MPCR amplification and mass probe extension (MPE) were first used, followed by single nucleotide polymorphism (SNP) typing mass spectrometry, which allows the simultaneous detection of multiple mutation sites of the VGSC gene in 96 samples of Ae. albopictus. A total of 70 wild-collected Ae. albopictus were used to evaluate the performance of the method by comparing it with other methods.ResultsThree target sites (1016, 1532, 1534) in the VGSC gene can be detected simultaneously by double PCR amplification combined with matrix-assisted laser desorption ionization–time-of-flight mass spectrometry, achieving a detection limit of 20 fg/μl. We applied this method to 70 wild-collected Ae. albopictus, and the obtained genotypes were consistent with the routine sequencing results, suggesting the accuracy of our method.ConclusionsMPCR-MS minisequencing technology provides a sensitive and high-throughput approach to Ae. albopictus VGSC gene mutation screening. Compared with conventional sequencing, this method is economical and time-saving. It is of great value for insecticide resistance surveillance in areas with a high risk of vector-borne disease.Graphical

Inhalation and dermal exposure to biocidal products during foam and spray applications.

Foaming and spraying are common application techniques for biocidal products. In the past, inhalation and dermal exposure during spraying have been investigated extensively. Currently, however, no exposure data are available for foaming, hindering a reliable risk assessment for foam applications of biocidal products. The focus of this project was the quantification of inhalation and potential dermal exposure to non-volatile active substances during the foam application of biocidal products in occupational settings. In some settings, exposure during spray application was measured for comparative purposes. The inhalation and dermal exposure of operators were investigated during the application of benzalkonium chlorides and pyrethroids by foaming and spraying, considering both small- and large-scale application devices. Inhalation exposure was measured by personal air sampling; potential dermal exposure was measured using coveralls and gloves. Potential dermal exposure was substantially higher than inhalation exposure. Changing from spraying to foaming reduced inhalation exposure to airborne non-volatile active substances, but had no relevant effect on potential dermal exposure. However, for potential dermal exposure, considerable differences were observed between the application device categories. To our knowledge, this study presents the first comparative exposure data for the foam and spray application of biocidal products in occupational settings with detailed contextual information. The results indicate a reduction of inhalation exposure with foam application compared to spray application. However, special attention is necessary for dermal exposure, which is not reduced by this intervention.

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

Houseflies, Musca domestica L., are an important sanitary pest that affects human and domesticated animals. They are mechanical carriers of more than 100 human and animal diseases including protozoan, bacterial, helminthic, and viral infections. Recently, it was demonstrated that houseflies acquired, harbored, and transmitted SARS-CoV-2 (COVID-19) for up to 1day post-exposure. The most widely used control strategy relays on the application of pyrethroid insecticides due to their effectiveness, low mammalian toxicity, low cost, and environmental safety. The main mechanism of action of pyrethroids is to exert their toxic effects through affecting the voltage-sensitive sodium channel (VSSC) modifying the transmission of the nerve impulse and leading to the death of the insects. Target site insensitivity of the VSSC is due to the presence of single nuclear polymorphisms (SNPs) named knockdown mutations (kdr). In this review, we synthetize recent data on the type and distribution of these mutations globally. Housefly resistance is reported in several countries. Increased applications of pyrethroids to control housefly populations led to the emergence of multiple evolutionary origins of resistance determined by five amino acid substitutions or specific mutations in the VSSC: kdr (L1014F), kdr-his (L1014H), super-kdr (M918T + L1014F), type N (D600N + M918T + L1014F), and 1B (T929I + L1014F). According to the global map obtained, high levels of resistance to pyrethroids are associated with the L1014F mutation found mostly in North America, Europe, and Asia, while the super-kdr mutation was mostly found in the American continent. The level of protection conferred by these alleles against pyrethroids was generally kdr-his < kdr < Type N ≤ super-kdr ≤ 1B. The relative fitness of the alleles under laboratory conditions was susceptible ≅ kdr-his > kdr > super-kdr suggesting that the fitness cost of an allele was relative to the presence of other alleles in a population and that the reversion of resistance in a free insecticide environment might be quite variable from one region to another. An adequate integrated pest management program should consider monitoring susceptibility to pyrethroids to detect early levels of resistance and predict the spread and evolution of resistant phenotypes and genotypes. From this review, the pyrethroid resistance status of housefly population was determined in very few countries and has evolved independently in different areas of the world affecting chemical control programs.

Field applications of granular and liquid pyrethroids, carbaryl, and IGRs to control the asian longhorned tick (Haemaphysalis longicornis) and impacts on nontarget invertebrates

Few documented control strategies exist for the invasive tick, Haemaphysalis longicornis, despite its potential to reach extremely high numbers and vector human and animal pathogens. In 2020, we evaluated the effects of single applications of five granular and liquid acaricides on H. longicornis in a public park in northern New Jersey. Acaricides tested included pyrethroids (lambda-cyhalothrin, bifenthrin), a carbamate (carbaryl), and the insect growth regulators (IGRs) pyriproxyfen and novaluron. We also monitored the impact of each treatment on non-target soil and above-ground invertebrate species using pitfall and sticky traps, respectively. We recorded over 70,000 H. longicornis ticks in the study area from July to October 2020. An average of 99% control was achieved with lambda-cyhalothrin spray and 95% with granular bifenthrin. In contrast, granular carbaryl did not significantly reduce any life stages of H. longicornis. The IGR (pyriproxyfen/novaluron) resulted in a significant 45% reduction of the larval stage following treatments in July. No other stages were significantly impacted by pyriproxyfen alone or in combination with novaluron. Analysis of non-target species revealed that the community composition of soil-dwelling arthropods was strongly impacted by pyrethroid treatments and, to a lesser extent, by the carbamate treatment. The granular pyrethroid bifenthrin had more pronounced effects and impacted a broader range of non-target groups in the pitfall traps than the liquid pyrethroid lambda-cyhalothrin. Arthropod groups that were negatively impacted included Isopoda, Formicidae, Coleoptera, Araneae, Acari, and Grylloidea. Collembola numbers, however, were elevated in both pyrethroid treatments. The community composition of arthropods collected on the above-ground sticky traps was strongly impacted only in the liquid lambda-cyhalothrin treatment. The primary groups impacted in the sticky trap analysis were Collembola and Hemiptera. Community composition in traps remained distinct in the pyrethroid treatments through the entire survey period up to 62 days post-treatment. The results of this study indicate that pyrethroid acaricides were highly effective at controlling H. longicornis, while other compounds, including carbaryl and IGRs, did not achieve consistent levels of control. Further research is needed to find effective and environmentally sustainable alternatives. Integrated management programs can include the judicious use of pyrethroids to control H. longicornis.

Pyrethroid Susceptibility in Field Populations of Picture-Winged Flies (Diptera: Ulidiidae) Infesting Fresh Market Sweet Corn in Florida

Picture-winged flies (Diptera: Ulidiidae) are the most damaging insect pests of sweet corn (Zea mays L.) produced in Florida for the fresh market. Management of these pests, referred to as corn silk flies, relies on frequent pyrethroid applications targeting adults. In response to the need for an insecticide resistance management (IRM) program for corn silk flies in this highly intensive crop system, glass vial bioassays were conducted to determine the susceptibility of 12 corn silk fly populations to the pyrethroid beta-cyfluthrin. Two Euxesta eluta Loew and nine Euxesta stigmatias Loew populations were obtained by collecting infested ears in commercial and experimental fields in 2020 and 2021. One E. eluta laboratory colony was used as a susceptible reference population. The E. eluta reference colony was the most susceptible population, with an LC50 value of 0.01 µg/vial. The E. stigmatias field populations were generally less susceptible to beta-cyfluthrin than the E. eluta field populations, with the highest LC50 values attaining 3.51 µg/vial and 0.19 µg/vial, respectively. In addition, the five E. stigmatias populations from commercial sweet corn fields were as much as 17.6 times less susceptible than the four E. stigmatias populations from nontreated fields. Results suggest that E. stigmatias is less susceptible to pyrethroids than E. eluta. Results also suggest that corn silk flies in commercial sweet corn fields are selected for reduced pyrethroid susceptibility throughout the growing season. This study successfully used the glass vial bioassay method for corn silk flies, providing a new tool to initiate an IRM program.

A systematic review of human biomonitoring studies of 3-phenoxybenzoic acid, a urinary biomarker pyrethroid insecticide exposure, 1997 to 2019

Pyrethroid insecticides are used, for example, in agriculture, indoor environments, and mosquito control programs, resulting in human exposure. Urinary 3-phenoxybenzoic acid (3-PBA) is a nonspecific biomarker for exposure to many pyrethroids. This systematic review identified human biomonitoring studies with 3-PBA that characterize environmental pyrethroid exposures in children and adolescents, pregnant women, and adults or occupational pyrethroid exposures relative to the National Health and Nutrition Examination Survey (NHANES) populations in the United States (US). PubMed, Embase, and SciFinder were searched for "3-phenoxybenzoic acid”, CAS No. 3739–38–6, and urine or urinary or urine level. Duplicate studies and studies meeting the exclusion criteria were removed from the search results based on predetermined exclusion criteria. This screening process identified 57 papers. Twenty-one, thirteen, twenty-two, and eleven manuscripts reported urinary 3-PBA levels in children, pregnant women, environmentally exposed adults, and occupationally exposed adults, respectively. Median 3-PBA levels ranged from 0.2 to 4.7 µg/g creatinine in children (1999–2016), 0.23–1.55 µg/g creatinine in pregnant women (1997–2014), and 0.11–3.34 µg/g creatinine in environmentally exposed adults (1999–2017). 3-PBA levels in occupationally exposed adults were significantly higher than in environmentally exposed populations, ranging from 0.43 to 14 µg/g creatinine (2004–2017). 3-PBA levels in children and adults from the general North American population increased significantly with the sampling year. A decrease in 3-PBA levels was noted in the adult cohorts from PR China and Japan. 3-PBA levels in most studies appeared to be comparable to levels in the NHANES populations; however, some smaller studies had high pyrethroid exposures. Factors contributing to higher 3-PBA levels in the general population included primarily dietary exposures and residential and agricultural pyrethroid applications. These findings demonstrate that pyrethroid exposures are near-ubiquitous worldwide and, in some regions, appear to increase over time. Thus, exposures to pyrethroid insecticides represent a continuing public health concern.

Insecticide Induced Resurgence of Brown Planthopper, Nilaparvata lugens (Stål) on Rice

The research was undertaken in the entomological field of Bangladesh Agricultural University (BAU), Mymensingh during the Boro crop of 2015-16 and 2016-17. Fourteen generic of single-molecule insecticide along with control were used separately in this experiment. Among the 14 single-molecule insecticides, four generics were synthetic pyrethroid group insecticide. Causes of resurgence were determined in the form of a resurgence ratio. More resurgence of brown planthopper, Nilaparvata lugens (Stål) on rice was induced by the application of all synthetic pyrethroids i.e., Cypermethrin, Deltamethrin, Fenvalerate, and Lambda cyhalothrin along with Acetamiprid, Chlorpyrifos, Phenthoate, and Thiamethoxam (resurgence ration 1.0 or above) compared to Pymetrozine 50WG (0.26), Dinotefuran 20SG (0.29), Isoprocarb/MIPC 75WP (0.43), Cartap 50SP (0.76) and Imidacloprid 20SL (0.91). Commonly used recommended insecticides i.e., Imidacloprid 20SL, Cartap 50SP, Isoprocarb/MIPC 75WP, Pymetrozine 50WG, and Thiamethoxam 25WG were used in 3 different doses (i.e., low, recommended, and high) and found that all recommended insecticides were induced higher resurgence ratio (≥1.0) except Pymetrozine 50WG when applied at sub-lethal dose. A positive correlation was found between resurgence ratio and yield loss.

Towards understanding transfluthrin efficacy in a pyrethroid-resistant strain of the malaria vector Anopheles funestus with special reference to cytochrome P450-mediated detoxification

Malaria vector control interventions rely heavily on the application of insecticides against anopheline mosquitoes, in particular the fast-acting pyrethroids that target insect voltage-gated sodium channels (VGSC). Frequent applications of pyrethroids have resulted in resistance development in the major malaria vectors including Anopheles funestus, where resistance is primarily metabolic and driven by the overexpression of microsomal cytochrome P450 monooxygenases (P450s). Here we examined the pattern of cross-resistance of the pyrethroid-resistant An. funestus strain FUMOZ-R towards transfluthrin and multi-halogenated benzyl derivatives, permethrin, cypermethrin and deltamethrin in comparison to the susceptible reference strain FANG. Transfluthrin and two multi-fluorinated derivatives exhibited micromolar potency - comparable to permethrin - to functionally expressed dipteran VGSC in a cell-based cation influx assay. The activity of transfluthrin and its derivatives on VGSC was strongly correlated with their contact efficacy against strain FUMOZ-R, although no such correlation was obtained for the other pyrethroids due to their rapid detoxification by the resistant strain. The low resistance levels for transfluthrin and derivatives in strain FUMOZ-R were only weakly synergized by known P450 inhibitors such as piperonyl butoxide (PBO), triflumizole and 1-aminobenzotriazole (1-ABT). In contrast, deltamethrin toxicity in FUMOZ-R was synergized > 100-fold by all three P450 inhibitors. The biochemical profiling of a range of fluorescent resorufin and coumarin compounds against FANG and FUMOZ-R microsomes identified 7-benzyloxymethoxy-4-trifluoromethylcoumarin (BOMFC) as a highly sensitive probe substrate for P450 activity. BOMFC was used to develop a fluorescence-based high-throughput screening assay to measure the P450 inhibitory action of potential synergists. Azole fungicides prochloraz and triflumizole were identified as extremely potent nanomolar inhibitors of microsomal P450s, strongly synergizing deltamethrin toxicity in An. funestus. Overall, the present study contributed to the understanding of transfluthrin efficacy at the molecular and organismal level and identified azole compounds with potential to synergize pyrethroid efficacy in malaria vectors.

Ambient Pyrethroid Pesticide Exposures in Adult Life and Depression in Older Residents of California's Central Valley.

Pyrethroid pesticide exposures may be associated with the onset of depression in later life via disruption of dopaminergic, serotonergic, and neurological functioning. We sought to investigate the association between living near agricultural pyrethroid pesticide applications and depression measures in central California, using two waves (PEG 1&2, total N = 1,654) of a case control study of Parkinson’s disease (PD). At enrollment, participants self-reported history of use of depression medications and dates of MD-diagnosed depression and anxiety. Participants also completed a Geriatric Depression Scale-Short Form upon enrollment. We used the California Pesticide Use Registry to assign estimated ambient pyrethroid pesticide exposures at participant’s home addresses over the 5 years before the index date (date of outcome, or an age-matched year for participants without the outcome). We used logistic and linear regression to evaluate associations between living near any pyrethroid applications over the 5-year index period and measures of depression and anxiety. We also evaluated modification by study wave and PD status. We observed associations of pyrethroids with depression, depression medications, and anxiety (adjusted odds ratio [aOR] depression = 1.54, 95% confidence interval [CI] 1.14, 2.07; aOR depression medications = 1.68, 95% CI 1.25, 2.25; aOR anxiety = 1.60, 95% CI 1.17, 2.18). However, we observed no associations with mild/moderate depressive symptoms according to the GDS score at enrollment (aOR = 1.04, 95% CI 0.77, 1.42). We did not observe a consistent modification of the pyrethroid-depression associations by study wave and PD status. Ambient pyrethroid pesticide exposures may be associated with measures of depression in later life.

Synthetic Pyrethroid, Natural Product, and Entomopathogenic Fungal Acaricide Product Formulations for Sustained Early Season Suppression of Host-Seeking Ixodes scapularis (Acari: Ixodidae) and Amblyomma americanum Nymphs.

We compared the ability of product formulations representing a synthetic pyrethroid acaricide (Talstar P Professional Insecticide), a natural product-based acaricide (Essentria IC3), and an entomopathogenic fungal acaricide (Met52 EC Bioinsecticide) to suppress Ixodes scapularis Say and Amblyomma americanum (L.) nymphs when applied following USEPA approved manufacturers' label recommendations for tick control using hand-pumped knapsack sprayers before the beginning of their seasonal activity period in the spring. We applied Met52 EC Bioinsecticide (11% Metarhizium anisopliae Strain F52) to five 100 m2 plots (10.6 ml AI/plot) in mid-April 2020. Two weeks later at the end of April 2020, we treated an additional five 100 m2 plots each with either Talstar P Professional Insecticide (7.9% bifenthrin @ 2.5 ml AI/plot) or Essentria IC3 (10% rosemary oil, 5% geraniol, and 2% peppermint oil @ 86.6 ml AI/plot). Weekly sampling of all plots through the end of June 2020 showed that both Met52 EC Bioinsecticide and Essentria IC3 failed to maintain a 90% suppression threshold for I. scapularis, compared to control plots, and required two additional applications over the course of the trial. In contrast, Talstar P Professional Insecticide suppressed 100% of I. scapularis nymphs and ≥96 and 100% of A. americanum nymphs and adults, respectively. Such pre-season applications of synthetic pyrethroids significantly reduce the early season acarological risk for exposure to host-seeking ticks as well as the frequency of acaricide applications.

A life stage-targeted acaricide application approach for the control of Haemaphysalis longicornis

Haemaphysalis longicornis Neumann is an invasive tick species that has recently been detected in the eastern United States. We designed field studies to monitor the population dynamics of H. longicornis over a year (2019) in New Jersey, and to assess the efficacy of a pyrethroid acaricide (lambda-cyhalothrin) in controlling this tick using a stage-treatment approach. Nymphs were the most abundant life stage found host-seeking from May through early July, followed by a brief period of high adult activity in mid-July, and a very high larval peak extending from late July through October. Overall, 542 adults, 1910 nymphs, and 69,238 larvae were recorded during the sampling. In the present study, the efficacy of acaricide treatments to suppress host-seeking ticks was assessed by applying lambda-cyhalothrin once during each of the three periods of activity for nymphs (June), adults (July), and larvae (August), or sequentially during all three months. Control plots were left untreated and used for phenology studies. Applications in June and July provided 100 % control of all life stages, including the dominant nymphal and adult stages for 42 and 35 d, respectively. Ticks re-established at normal or reduced levels following applications in June or July, respectively, compared to untreated controls. The application in August provided 100 % control for 49 d, and a high level of suppression (>99 % control) remained through the end of the tick season in October. This study therefore supports that single pyrethroid applications can provide 100 % control of H. longicornis for up to 7 wk, and a single late-summer application towards the end of host-seeking adult activity can provide near complete control of the larval population. An evaluation of single applications over the course of the season revealed that treatments in July or August did not lead to significant reductions in the nymphal population. However, multiple sequential treatments targeting all life stages provided 66 %, 97 %, and >99 % control of adults, nymphs, and larvae, respectively through the season of H. longicornis activity.

Preventive insecticide use affects arthropod decomposers and decomposition in field crops

Insecticides use in field crops has grown increasingly prophylactic, which poses a potentially unnecessary risk to arthropod decomposers. These decomposers — including millipedes (Diplopoda), soil mites (Acari, mostly Oribatida), and Collembola — act as alternative prey for generalist predators, facilitate crop-residue breakdown, and can influence nutrient cycling. However, the abundance and activity of arthropod decomposers may be reduced by extensive prophylactic pesticide use. We conducted a three-year field experiment in no-till corn and soybean fields to assess how neonicotinoid seed coatings or broadcast applications of a pyrethroid insecticide affect arthropod decomposers and litter decomposition. Both insecticides reduced densities of arthropod decomposers and reduced decomposition of plant litter by over 10%. Neonicotinoid seed coatings reduced collembolan densities by 34% and millipede densities by 52%, while the pyrethroid significantly reduced oribatid mite densities by 24% and millipede densities by 82%. Lower mite and millipede densities correlated with slower litter loss, and decomposition was slower under neonicotinoid seed coatings and broadcast pyrethroid applications. These results indicate that perennial, widespread use of prophylactic insecticides is likely to have concerning negative effects on the availability of alternative prey, plant residue breakdown, and nutrient cycling in field crops.