Occurrence, distribution, and driving factors of current-use pesticides in commonly cultivated crops and their potential risks to non-target organisms: A case study in Hainan, China

Environmental exposure patterns to 94 current-use pesticides in women of reproductive age who are preparing for pregnancy

Current-use pesticides (CUPs), including insecticides, fungicides, and herbicides, are extensively employed in agriculture to manage pests, diseases, and weeds. Nonetheless, their widespread application raises significant concerns regarding potential impacts on human health, particularly with reproductive health. This study focuses on exploring the landscape of CUP exposure among pre-pregnancy women. Based on a cohort study comprising 354 pre-pregnancy women of reproductive age in Beijing, China, we measured the concentrations of 94 CUPs in serum and conducted an in-depth analysis of exposure profiles, health risks, and contributing factors. The results revealed that the serum of pre-pregnancy women was contaminated with CUPs, of which the median concentrations ranged from 0.114 (fenamiphos-sulfone) to 61.2 ng/L (mefenacet). Among the 94 CUPs, 54 exhibited detection rates higher than 50 %, including 26 insecticides, 14 fungicides, and 14 herbicides. The exposure concentration profile highlighted that the insecticides contributed 56 % to the total CUP concentration percentages, with organophosphate insecticides being the primary contributors within this category (63.0 %). The average daily intake (ADI) of CUPs ranged from 2.23 to 16,432.28 ng/kg, while diflubenzuron had the highest ADI. Health risk assessments showed that exposure to a combination of total insecticides or herbicides poses a moderate risk for 15.8 % and 30.2 % of women, with mefenacet being the most significant, which showed moderate hazard in 29.4 % of participants. The overlap analysis showed that methiocarb-sulfone, diflubenzuron, and mefenacet were the dominant pesticides. In addition, maternal age, annual income level, smoking, and vitamin B12 supplementation were associated with serum CUP concentrations. Our study contributes a novel and comprehensive exposure profile of CUPs in pre-pregnancy women in northern China, providing valuable insights for evaluating the potential consequences of pre-pregnancy exposure on reproductive health. SYNOPSIS: We provided a comprehensive exposure landscape, health effects, and influential factors of 94 current-use pesticides among pre-pregnancy women in China.

Host-parasitoid trophic webs in complex agricultural systems

The composition and dynamics of ecological communities are complex because of the presence of large numbers of organisms, belonging to many different species, each with their own evolutionary history, and their numerous interactions. The construction and analysis of trophic webs summarizes interactions across trophic levels and links community structure to properties such as ecosystem services. We focus on agro-ecological communities, which may be simpler than natural communities but nonetheless present considerable challenges to describe and understand. We review the characteristics and study of communities comprised of plants, phytophagous insects and insect parasitoids with particular regard to the maintenance of sustainable agro-ecological communities and ecosystem services, especially biological pest control. We are constrained to largely overlook other members of these communities, such as hyper-parasitoids, predators, parasites and microbes. We draw chiefly on recent literature while acknowledging the importance of many advances made during the immediately preceding decades. Trophic web construction and analysis can greatly improve the understanding of the role and impact of herbivores and natural enemies in agro-ecological communities and the various species interactions, such as apparent competition, which assists biocontrol strategies. The study of trophic webs also helps in predicting community ecology consequences of externally-driven changes to agro-ecosystems.

Effects of solid and aqueous dietary diflubenzuron ingestion on some biological parameters in synthetic pyrethroid-resistant German cockroach, Blattella germanica L. (Blattodea: Ectobiidae)

Cockroaches, widespread pests found in metropolitan areas, are known as vectors of various disease agents, including viruses, fungi and antibiotic-resistant bacteria, as well as causing allergies in humans. Insect growth regulators have been used in pest management for several decades. These insecticides disrupt insect development and reproduction. Chitin synthesis inhibitors interfere with chitin biosynthesis in insects, causing abortive moulting and mortality, as well as inhibiting egg fertility, and larval hatching in insects. In this research, we evaluated the various effects of diflubenzuron, a chitin synthesis inhibitor, on synthetic pyrethroid-resistant German cockroach (Blattella germanica L. Blattodea: Ectobiidae), including ootheca production, oothecal viability, ootheca incubation time, the number of nymphs emerging from the ootheca and survivorship of nymphs. The cockroaches were fed diets that contained diflubenzuron, which was added to solid bait (impregnated fish food) and ingestible aqueous bait (impregnated cotton). Three concentrations (0.5%, 1% and 2%) were used in the experiments. As a result, diflubenzuron treatment led to ootheca production ranging from 60% to 100%; statistically, no difference was found between the treatment and the control groups. The number of nymphs emerging from the first and second ootheca was reduced by 40%-100% in the diflubenzuron-treated groups compared with the control. Nymphs exposed to diflubenzuron-impregnated solid bait and ingestible aqueous bait experienced mortality exceeding 92.1% and 66.27% within 15 days, respectively. In conclusion, diflubenzuron is a potential insecticide for use in cockroach baits to control B. germanica, as it caused high nymphal and embryonic mortality in the synthetic pyrethroid-resistant population and decreased the number of nymphs emerging from the ootheca.

Residue levels, processing factors and risk assessment of pesticides in ginger from market to table

Ginger is consumed as a spice and medicine globally. However, pesticide residues in ginger and their residue changes during processing remain poorly understood. Our results demonstrate that clothianidin, carbendazim and imidacloprid were the top detected pesticides in 152 ginger samples with detection rates of 17.11-27.63%, and these pesticides had higher average residues of 44.07-97.63 μg/kg. Although most samples contained low levels of pesticides, 66.45% of the samples were detected with pesticides, and 38.82% were contaminated with 2-5 pesticides. Peeling, washing, boiling and pickling removed different amounts of pesticides from ginger (processing factor range: 0.06-1.56, most <1). By contrast, pesticide residues were concentrated by stir-frying and drying (0.50-6.45, most >1). Pesticide residues were influenced by pesticide physico-chemical parameters involving molecular weight, melting point, degradation point and octanol-water partition coefficient by different ginger processing methods. Chronic and acute dietary risk assessments suggest that dietary exposure to pesticides from ginger consumption was within acceptable levels for the general population. This study sheds light on pesticide residues in ginger from market to processing and is of theoretical and practical value for ensuring ginger quality and safety.

Occurrence, multiphase partitioning, drivers, and ecological risks of current-use herbicides in a river basin dominated by rice-vegetable rotations in tropical China

Rice-vegetable rotation practices prevail in subtropical and tropical agriculture worldwide, with applications of current-use herbicides (CUHs) vital for nontarget plant control. After application, CUHs migrate to environmental compartments, where the occurrence, fate, and ecological risks have not been well characterized. To further understand the occurrence and multiphase partitioning, as well as to evaluate potential drivers and mixture risks in environmental compartments, we analyzed 11 CUHs in 576 samples from 36 rice-vegetable rotations in Nandu River basin, Hainan, China. Samples included soil, water, suspended particulate matter, and sediment collected during both rice and vegetable planting periods. The CUH concentrations varied across environmental compartments, but with high levels of glyphosate and aminomethylphosphonic acid organophosphorus herbicides (OPHs) frequently detected, accounting for 82.3 % to 99.0 % in environmental compartments. Phenoxy acid (PAA) and chloroacetanilide (ANH) herbicides were detected at lower frequencies. Spatiotemporal variation was significantly different among OPHs, ANHs, and PAAs, with geographic and crop-related patterns most evident for CUHs rather than OPHs. Structural equation model, redundancy, and boosted regression tree analyses indicated environmental compartment properties (pH, organic matter, and Fe/Al oxides), crop type, and wet/dry climate were important drivers of spatiotemporal patterns. Fugacity ratios indicated multiphase partitioning and transport of CUHs differed in rice and vegetable planting periods. A new assessment framework based on species-sensitive distributions and environmental compartment weight index indicated unacceptable risks of CUHs (risk quotient >1 in >50 % of sites), with most risks from OPHs (10.5 % to 98.0 %) and butachlor, acetochlor, and 2,4-dichlorophenoxyacetic acid. Risk hot spots were identified as the soil, the central region, and the vegetable planting period, potentially threatening nontarget organisms (e.g., Lemna minor, Glomus intraradices, and Apis mellifera). This study provides a new risk assessment framework and demonstrates the domination of OPHs in CUH contamination and risks in the tropics, thus helping guide policymakers and stakeholders on herbicide management.

Multi-residue monitoring and dietary risk assessment of 17 pesticides and 3 related metabolites in rice and rice flour from markets in China

Pesticide residues in rice have attracted widespread public attention in recent years. This research aimed to monitor the residues of 17 pesticides and their 3 metabolites in 120 samples of rice and rice flour collected from markets in China using the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, Safe) pretreatment method combined with high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The monitoring results showed that isoprothiolane, tricyclazole, fenoxanil, and tebuconazole were detected in the rice samples, with detection frequencies of 33.3%, 17.5%, 8.3%, and 2.5%, and concentrations ranging from 0.02 to 0.1 mg/kg (median = 0.04), 0.01 to 0.17 mg/kg (median = 0.14), 0.04 to 0.06 mg/kg (median = 0.05), and 0.01 to 0.02 mg/kg (median = 0.01), respectively. The residues of these four pesticides were all below their corresponding maximum residue levels (MRLs) set by China. Additionally, isoprothiolane, tricyclazole, fenoxanil, and tebuconazole were detected in rice flour samples, with detection frequencies of 74.2%, 55.0%, 5.0%, and 2.5%, and concentrations ranging from 0.01 to 0.1 mg/kg (median = 0.04), 0.01 to 0.04 mg/kg (median = 0.02), 0.01 to 0.06 mg/kg (median = 0.03), and 0.02 to 0.04 mg/kg (median = 0.03), respectively. Furthermore, the chronic dietary intake risk (HQc), the acute dietary intake risk (HQa), and cumulative dietary risk (HI) for all the detected pesticides were evaluated and found well below 100%, indicating that the dietary intake risks would not pose potential health risks.

Occurrence and ecological risks of flonicamid and its metabolites in multiple substrates from intensive rice-vegetable rotations in tropical China

Rice-vegetable rotations are dominant in (sub)-tropical agriculture worldwide. However, fate and risks of the insecticide flonicamid (FLO) and its main degradates (collectively called FLOMs) in multiple substrates from those cropping systems remain largely unknown. In this study, we characterized residual concentrations, driving factors, transport, and potential ecological risks of FLOMs in different substrates in 28 tropical rice-vegetable rotations. Concentrations (median) of FLOMs were 0.013-3.03 (0.42) ng g-1 in plants, 0.012-1.92 (0.23) ng g-1 in soil, 0.029-0.63 (0.126) μg L-1 in water, and 0.002-0.398 (0.055) ng g-1 in sediments. Flonicamid and its metabolite N-(4-trifluoromethylnicotinoyl) glycine were the dominant species in the four substrates (84.1 % to 88.5 %). Plants had the highest levels of FLOMs, with the highest bioconcentration factor in peppers. According to boosted regression trees coupled with a partial least squares structural equation model, levels and composition of FLOMs showed high spatiotemporal and crop-related patterns in different substrates, with patterns highly codetermined by agricultural practices (e.g., crop type and FLO/neonicotinoid/pyrethroid applications), substrate parameters (e.g., pH, organic matter or total organic carbon), and climate features (e.g., wet/dry seasons). Moreover, a fugacity method indicated differences in transport and partitioning patterns in different substrates during rice and vegetable planting periods. Integrated substrate risk assessment of FLOMs contamination was conducted based on species-sensitive distributions and substrate weight index. Although overall risks of FLOM contamination in tropical rice-vegetable rotations were negligible to low, the highest risks were in soils, vegetable planting periods, and a central intensively planted area.

Neonicotinoids in draining micro-watersheds dominated by rice-vegetable rotations in tropical China: Multimedia occurrence, influencing factors, transport, and associated ecological risks

Multimedia contamination by neonicotinoid (NEO) residues has attracted global attention. However, data regarding the multimedia polluted status under certain typical cropping scenarios and the associated risks are scarce. Here, the multimedia occurrence, spatiotemporal distribution, driving factors, transport, and ecological risks of NEOs from tropical rice-vegetable rotation fields were characterized. The heavy NEOs resided in multiple media, and imidacloprid and acetamiprid were the prevailing NEOs, with concentration contributions of 65-80%. The pollution levels of the NEOs, rather than their compositions, exhibited significant spatiotemporal heterogeneity and were highly correlated with the collective (agricultural practices and climate conditions) and differential (e.g., media properties) factors identified using an auto linear regression model. Furthermore, the multimedia transport of NEOs was largely similar but non-negligibly different during the rainy and dry seasons. A new multimedia ecological risk assessment revealed that 50.6% sites were at high risk, and the risk hotspots occurred in the central areas and the winter planting period. The risks were largely contributed by imidacloprid and thiamethoxam, indicating that there were non-ignorable ecological risks. Our results highlight the differential pollution patterns (distribution, transport, and driving factors) of the prevailing NEOs under tropical agricultural scenarios, and the fact that special attention should be paid to the risks posed by NEOs.

Distribution of Emamectin Benzoate Granules in Maize Plants by Broadcasting into Maize Leaf Whorls

Good control effects on fall armyworm (FAW) can be obtained by broadcasting emamectin benzoate (EB) granules into maize leaf whorls. However, the distribution of EB in maize plants is not clear. In this study, EB granules were prepared by the rotating granulation method, and the granules were characterized using a Fourier transform infrared spectrometer. The behavior of EB granules in water was observed using a microscope, and in vitro release of EB from granules was also studied. A method for the determination of EB in maize plants, old leaves, grains, and cobs was established by using ultra-performance liquid chromatography-tandem mass spectrometry. The results showed that EB was loaded in granules successfully, and the granules disintegrated slowly in water, so the release of granules could be regulated using various water contents. The prepared EB granules were qualified and stable. The field experiment showed that the concentration of EB in maize leaf whorls could be maintained above 0.23 mg·kg^-1 within 3 days after broadcasting EB granules. This ensured that FAW could be killed in a short time. Then, EB gradually transferred to the old leaves. After 21 days of application, the content of EB in the old leaves was 0.07 mg·kg^-1, which has long-time control effects on FAW. The control effects of the three doses of granules against Spodoptera frugiperda were higher than 78% after 14 days of application. At the tested dosage, no phytotoxicity to crops was observed. At harvest, neither the maize grain nor the cobs had EB content. New controlled formulations to S. frugiperda were developed and will be suitable for application in mountainous areas where the lack of water resources is a factor.

Exploring Contact Toxicity of Essential Oils against Sitophilus zeamais through a Meta-Analysis Approach

Sitophilus zeamais is a primary pest of maize. Our aim was to perform a qualitative review and meta-analyses with 56 scientific articles published from 1 January 2000 to 1 October 2022 dealing with direct (topical application) and indirect (impregnation of essential oils, EOs, onto filter paper or maize grains) contact toxicity of EOs against S. zeamais. Three independent meta-analyses of single means of LD50 (direct contact) and LC50 (indirect contact) were conducted using a random effect model. Essential oils more frequently evaluated were those belonging to Asteraceae, Apiaceae, Lamiaceae, Myrtaceae, Piperaceae, and Rutaceae. The LC50 global mean values were 33.19 µg/insect (CI95 29.81-36.95) for topical application; 0.40 µL/cm2 (CI95 0.25-0.65) for filter paper indirect contact; and 0.50 µL/g maize (CI95 0.27-0.90) for maize grains indirect contact. The species Carum carvi, Salvia umbratica, Ilicium difengpi, Periploca sepium, Cephalotaxus sinensis, Murraya exotica, Rhododendron anthopogonoides, Ruta graveolens, Eucalyptus viminalis, Ocotea odorifera, Eucalyptus globulus, Eucalyptus dunnii, Anethum graveolens, Ilicium verum, Cryptocarya alba, Azadirachta indica, Chenopodium ambrosioides, Cupressus semperivens, Schinus molle, Piper hispidinervum, Mentha longifolia, and Croton pulegiodorus showed LC50 or LD50 values lower than the global means, indicating good insecticidal properties. Our results showed that EOs have great potential to be used as bioinsecticides against S. zeamais.