A review of the factors that influence pesticide residues in pollen and nectar: Future research requirements for optimising the estimation of pollinator exposure

Discovery and biological characterization of a novel mesoionic insecticide fenmezoditiaz

BACKGROUND

Many piercing-sucking insects have developed resistance or cross-resistance to many insecticides targeting insect neural nicotinic acetylcholine receptor (nAChR). Here we are aiming to present the discovery of a novel mesoionic insecticide, fenmezoditiaz, by BASF through structure-based drug design (SBDD) approaches. It has recently been added to the Insecticide Resistance Action Committee mode of classification (IRAC 4E). It is being developed for plant protection against piercing-sucking pests, especially rice hopper complex.

RESULTS

The soluble acetylcholine binding protein (AChBP) from the sea slug Aplysia californica was modified using site-directed mutagenesis and based on putative aphid nAChR subunit sequences to create soluble insect-like AChBPs. Among them, insect-like β1 AChBP and native aphid membrane preparation showed the highest correlated biochemical affinity toward structurally diverse ligands. This mutant AChBP was used to understand how insect nAChRs structurally interact with mesoionics, which was then utilized to design novel mesoionics including fenmezoditiaz. It is an excellent systemic insecticide with diverse application methods and has a broad insecticidal spectrum, especially against piercing/sucking insects. It lacks cross-resistance for neonicotinoid resistant plant hoppers. Field-collected brown plant hopper populations from Asian countries showed high susceptibility.

CONCLUSIONS

Fenmezoditiaz is a systemic insecticide with a broad spectrum, lack of cross-resistance and it could be an additional tool for integrated pest management and insecticide resistance management, especially for the rice hopper complex. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Assessing the ecological impact of pesticides/herbicides on algal communities: A comprehensive review

The escalating use of pesticides in agriculture for enhanced crop productivity threatens aquatic ecosystems, jeopardizing environmental integrity and human well-being. Pesticides infiltrate water bodies through runoff, chemical spills, and leachate, adversely affecting algae, vital primary producers in marine ecosystems. The repercussions cascade through higher trophic levels, underscoring the need for a comprehensive understanding of the interplay between pesticides, algae, and the broader ecosystem. Algae, susceptible to pesticides via spillage, runoff, and drift, experience disruptions in community structure and function, with certain species metabolizing and bioaccumulating these contaminants. The toxicological mechanisms vary based on the specific pesticide and algal species involved, particularly evident in herbicides' interference with photosynthetic activity in algae. Despite advancements, gaps persist in comprehending the precise toxic effects and mechanisms affecting algae and non-target species. This review consolidates information on the exposure and toxicity of diverse pesticides and herbicides to aquatic algae, elucidating underlying mechanisms. An emphasis is placed on the complex interactions between pesticides/herbicides, nutrient content, and their toxic effects on algae and microbial species. The variability in the harmful impact of a single pesticide across different algae species underscores the necessity for further research. A holistic approach considering these interactions is imperative to enhance predictions of pesticide effects in marine ecosystems. Continued research in this realm is crucial for a nuanced understanding of the repercussions of pesticides and herbicides on aquatic ecosystems, mainly algae.

Greenhouse cultivation enhances pesticide bioaccumulation in cowpeas following repeated spraying

Understanding pesticide residue patterns in crops is important for ensuring human health. However, data on residue accumulation and distribution in cowpeas grown in the greenhouse and open field are lacking. Our results suggest that acetamiprid, chlorantraniliprole, cyromazine, and thiamethoxam residues in greenhouse cowpeas were 1.03-15.32 times higher than those in open field cowpeas. Moreover, repeated spraying contributed to the accumulation of pesticide residues in cowpeas. Clothianidin, a thiamethoxam metabolite, was detected at 1.04-86.00 μg/kg in cowpeas. Pesticide residues in old cowpeas were higher than those in tender cowpeas, and the lower half of the plants had higher pesticide residues than did the upper half. Moreover, pesticide residues differed between the upper and lower halves of the same cowpea pod. Chronic and acute dietary risk assessments indicated that the human health risk was within acceptable levels of cowpea consumption. Given their high residue levels and potential accumulation, pesticides in cowpeas should be continuously assessed.

Exposure to a fungicide for a field-realistic duration does not alter bumble bee fecal microbiota structure

Social bees are frequently exposed to pesticides when foraging on nectar and pollen. Recent research has shown that pesticide exposure not only impacts social bee host health but can also alter the community structure of social bee gut microbiotas. However, most research on pesticide-bee gut microbiota interactions has been conducted in honey bees; bumble bees, native North American pollinators, have received less attention and, due to differences in their ecology, may be exposed to certain pesticides for shorter durations than honey bees. Here, we examine how exposure to the fungicide chlorothalonil for a short, field-realistic duration alters bumble bee fecal microbiotas (used as a proxy for gut microbiotas) and host performance. We expose small groups of Bombus impatiens workers (microcolonies) to field-realistic chlorothalonil concentrations for 5 days, track changes in fecal microbiotas during the exposure period and a recovery period, and compare microcolony offspring production between treatments at the end of the experiment. We also assess the use of fecal microbiotas as a gut microbiota proxy by comparing community structures of fecal and gut microbiotas. We find that chlorothalonil exposure for a short duration does not alter bumble bee fecal microbiota structure or affect microcolony production at any concentration but that fecal and gut microbiotas differ significantly in community structure. Our results show that, at least when exposure durations are brief and unaccompanied by other stressors, bumble bee microbiotas are resilient to fungicide exposure. Additionally, our work highlights the importance of sampling gut microbiotas directly, when possible.IMPORTANCEWith global pesticide use expected to increase in the coming decades, studies on how pesticides affect the health and performance of animals, including and perhaps especially pollinators, will be crucial to minimize negative environmental impacts of pesticides in agriculture. Here, we find no effect of exposure to chlorothalonil for a short, field-realistic period on bumble bee fecal microbiota community structure or microcolony production regardless of pesticide concentration. Our results can help inform pesticide use practices to minimize negative environmental impacts on the health and fitness of bumble bees, which are key native, commercial pollinators in North America. We also find that concurrently sampled bumble bee fecal and gut microbiotas contain similar microbes but differ from one another in community structure and consequently suggest that using fecal microbiotas as a proxy for gut microbiotas be done cautiously; this result contributes to our understanding of proxy use in gut microbiota research.

Residue dynamics of a contact and a systemic fungicide in pollen, nectar, and other plant matrices of courgette (Cucurbita pepo L.)

Pollen and nectar can be contaminated with a range of pesticides, including insecticides, fungicides, and herbicides. Since these matrices are important food sources for pollinators and other beneficial insects, their contamination can represent a key route of exposure. However, limited knowledge exists with respect to pesticide residue levels and their dynamics in these matrices for many crops and active ingredients (AIs). We used controlled glasshouse studies to investigate the residue dynamics of a systemic (cyprodinil) and a contact (fludioxonil) fungicide in the floral matrices and other plant parts of courgette/zucchini (Cucurbita pepo L.). We aimed to better understand the processes behind residue accumulation and decline in pollen and nectar. Each AI was applied to plants, either by spraying whole plants or by targeted spraying onto leaves only. Samples of pollen, nectar, anthers, flowers, and leaves were taken on the day of application and each subsequent morning for up to 13 days and analysed for residues using LC-MS/MS. Significant differences in residue levels and dynamics were found between AIs and floral matrices. The present study allowed for the identification of potential routes by which residues translocate between tissues and to link those to the physicochemical properties of each AI, which may facilitate the prediction of residue levels in pollen and nectar. Residues of the contact AI declined more quickly than those of the systemic AI in pollen and nectar. Our results further suggest that the risk of oral exposure for pollinators may be considerably reduced by using contact AIs during the green bud stage of plants, but application of systemic compounds could still result in a low, but continuous long-term exposure for pollinators with limited decline.

Present status of insecticide impacts and eco-friendly approaches for remediation-a review

Insecticides are indispensable for modern agriculture to ensuring crop protection and optimal yields. However, their excessive use raises concerns regarding their adverse effects on agriculture and the environment. This study examines the impacts of insecticides on agriculture and proposes remediation strategies. Excessive insecticide application can lead to the development of resistance in target insects, necessitating higher concentrations or stronger chemicals, resulting in increased production costs and disruption of natural pest control mechanisms. In addition, non-target organisms, such as beneficial insects and aquatic life, suffer from the unintended consequences of insecticide use, leading to ecosystem imbalances and potential food chain contamination. To address these issues, integrated pest management (IPM) techniques that combine judicious insecticide use with biological control and cultural practices can reduce reliance on chemicals. Developing and implementing selective insecticides with reduced environmental persistence is crucial. Promoting farmer awareness of responsible insecticide use, offering training and resources, and adopting precision farming technologies can minimize overall insecticide usage.

Interaction of chlorothalonil and Varroa destructor on immature honey bees rearing in vitro

Under realistic environmental conditions, bees are often exposed to multiple stressors, especially Varroa destructor and pesticides. In this study, the effects of exposure to NOAEC of chlorothalonil during the larval stage, in the presence or absence of V. destructor, was examined in terms of survival, morphological and transcriptional changes. The interaction between chlorothalonil and V. destructor on the survival of honey bee was additive. V. destructor are the dominant factor in the interaction for survival and transcriptome alternation. The downregulation of the genes related to tissue growth and caste differentiation may directly link to the mortality of honey bees. Either chlorothalonil or V. destructor induces the irregular morphology of trophocytes and oenocytes in the fat body. In addition to irregular shapes, oenocytes in V. destructor alone and double-stressor treatment group showed altered nuclei and vacuoles in the cytoplasm. The interaction of V. destructor and chlorothalonil at the larval stage have potential adverse effects on the subsequent adult bees, with up-regulation of genes involved in lipid metabolism and detoxification/defense in fat body tissue. Our findings provide a comprehensive understanding of combinatorial effects between biotic and abiotic stressors on one of the most important pollinators, honey bees.

A critical review on the accumulation of neonicotinoid insecticides in pollen and nectar: Influencing factors and implications for pollinator exposure

Neonicotinoids are a class of neuro-active insecticides widely used to protect major crops, primarily because of their broad-spectrum insecticidal activity and low vertebrate toxicity. Owing to their systemic nature, plants readily take up neonicotinoids and translocate them through roots, leaves, and other tissues to flowers (pollen and nectar) that serve as a critical point of exposure to pollinators foraging on treated plants. The growing evidence for potential adverse effects on non-target species, especially pollinators, and persistence has raised serious concerns, as these pesticides are increasingly prevalent in terrestrial and aquatic systems. Despite increasing research efforts, our understanding of the potential toxicity of neonicotinoids and the risks they pose to non-target species remains limited. Therefore, this critical review provides a succinct evaluation of the uptake, translocation, and accumulation processes of neonicotinoids in plants and the factors that may affect the eventual build-up of neonicotinoids in pollen and nectar. The role of plant species, as well as the physicochemical properties and application methods of neonicotinoids is discussed. Potential knowledge gaps are identified, and questions meriting future research are suggested for improving our understanding of the relationship between neonicotinoid residues in plants and exposure to pollinators.

Global assessment of honeybee exposure to pesticides through guttation consumption: An indicator approach

Guttation consumption is a potential pathway of pesticide residue exposure in honeybees. However, modeling tools for assessing honeybee exposure to pesticide residues in guttation drops are lacking. In this study, we propose an indicator-based approach for qualitatively or quantitatively analyzing the guttation-based exposure pathway, allowing us to conduct region-specific pesticide residue exposure assessments for honeybees. Exposure scores (the product of guttation production and residue level scores) were established to compare or rank honeybee exposure to pesticide residues via guttation intake across locations using three specified indicators (i.e., air temperature, relative humidity, and precipitation intensity). Warm, dry regions had high residue level scores (indicating high residue levels in guttation), whereas cold, wet regions had high guttation production scores (indicating high possibilities of guttation formation on leaf surfaces); their exposure scores were a combination of these two values. We evaluated and ranked honeybee exposure to imidacloprid residue across regions in Brazil, China, the United States, and selected European Union member states, revealing that pesticide application in many Brazilian federative units may raise honeybee risks due to high exposure scores. We also compared the guttation pathway to other common exposure pathways (nectar and pollen), suggesting that for some moderately lipophilic compounds, the guttation exposure pathway may not be ignored and should be further evaluated.

Honey bees and bumble bees may be exposed to pesticides differently when foraging on agricultural areas

In an agricultural environment, where crops are treated with pesticides, bees are likely to be exposed to a range of chemical compounds in a variety of ways. The extent to which different bee species are affected by these chemicals, largely depends on the concentrations and type of exposure. We quantified the presence of selected pesticide compounds in the pollen of two different entomophilous crops; oilseed rape (Brassica napus) and broad bean (Vicia faba). Sampling was performed in 12 sites in Ireland and our results were compared with the pollen loads of honey bees and bumble bees actively foraging on those crops in those same sites. Detections were compound specific, and the timing of pesticide application in relation to sampling likely influenced the final residue contamination levels. Most detections originated from compounds that were not recently applied on the fields, and samples from B. napus fields were more contaminated compared to those from V. faba fields. Crop pollen was contaminated only with fungicides, honey bee pollen loads contained mainly fungicides, while more insecticides were detected in bumble bee pollen loads. The highest number of compounds and most detections were observed in bumble bee pollen loads, where notably, all five neonicotinoids assessed (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam) were detected despite the no recent application of these compounds on the fields where samples were collected. The concentrations of neonicotinoid insecticides were positively correlated with the number of wild plant species present in the bumble bee-collected pollen samples, but this relationship could not be verified for honey bees. The compounds azoxystrobin, boscalid and thiamethoxam formed the most common pesticide combination in pollen. Our results raise concerns about potential long-term bee exposure to multiple residues and question whether honey bees are suitable surrogates for pesticide risk assessments for all bee species.

Predicting pesticide residues in pod fruits with a modified peel-like uptake model: A green pea demonstration

Peas are among the most popular leguminous plants, consumed by both humans and animals in large quantities. Pesticides are widely used globally to increase pea yield, and as a result, pesticide residues can be taken up by pea plants and bioaccumulate in their fruits, including peas and pods. However, there is a lack of modeling approaches available to predict residue concentrations in peas. To address this issue, a pod fruit model (specifically designed for neutral organic compounds) was proposed to simulate the bioaccumulation process of pesticide residues in pea plants, which was developed by modifying a peel-like uptake model. The simulation results, based on green pea as the modeling demonstration, reveal that moderately-lipophilic pesticides (i.e., log KOW around 3) have higher simulated concentrations in peas at harvest compared to hydrophilic (i.e., log KOW less than 0) or highly-lipophilic (i.e., log KOW over 5) pesticides, which is due to the enhanced uptake process of moderately-lipophilic compounds in the pod-pea system, such as their ability to penetrate the pod cuticle and be transported via phloem sap. The sensitivity test and variability analysis conducted in this study revealed that the degradation kinetics, including metabolism, hydrolysis, and photolysis, had a significant impact on moderately-lipophilic pesticides due to their high simulated concentrations in the pea plant. This can result in substantial loss of residue mass via degradation. The validation of the model demonstrated that the simulation results, specifically residue concentrations in the fruit, were consistent with the harvested data. However, some inconsistency was observed immediately after pesticide application, which could be attributed to plant growth dynamics and initial surface mass distributions. The proposed pod fruit model provides new insights into the bioaccumulation process of pesticide residues in pea plants and enables high-throughput simulations of residue concentrations at harvest. To enhance the performance of the pod fruit model, future research should consider plant growth dynamics, plant uptake of ionizable compounds, and initial mass distribution functions.

Pesticide residues in honey bee (Apis mellifera) pollen collected in two ornamental plant nurseries in Connecticut: Implications for bee health and risk assessment

Honey bees (Apis mellifera L.) are one of the most important managed pollinators of agricultural crops. While potential effects of agricultural pesticides on honey bee health have been investigated in some settings, risks to honey bees associated with exposures occurring in the plant nursery setting have received little attention. We sought to identify and quantify pesticide levels present in honey bee-collected pollen harvested in two ornamental plant nurseries (i.e., Nursery A and Nursery B) in Connecticut. From June to September 2018, pollen was collected weekly from 8 colonies using bottom-mounted pollen traps. Fifty-five unique pesticides (including related metabolites) were detected: 24 insecticides, 20 fungicides, and 11 herbicides. Some of the pesticide contaminants detected in the pollen had not been applied by the nurseries, indicating that the honey bee colonies did not exclusively forage on pollen at their respective nursery. The average number of pesticides per sample was similar at both nurseries (i.e., 12.9 at Nursery A and 14.2 at Nursery B). To estimate the potential risk posed to honey bees from these samples, we utilized the USEPA's BeeREX tool to calculate risk quotients (RQs) for each pesticide within each sample. The median aggregate RQ for nurse bees was 0.003 at both nurseries, well below the acute risk level of concern (LOC) of ≥0.4. We also calculated RQs for larvae due to their increased sensitivity to certain pesticides. In total, 6 samples had larval RQs above the LOC (0.45-2.51), resulting from the organophosphate insecticide diazinon. Since 2015, the frequency and amount of diazinon detected in pollen increased at one of our study locations, potentially due to pressure to reduce the use of neonicotinoid insecticides. Overall, these data highlight the importance of considering all life stages when estimating potential risk to honey bee colonies from pesticide exposure.

Pesticide mixtures detected in crop and non-target wild plant pollen and nectar

Cultivation of mass flowering entomophilous crops benefits from the presence of managed and wild pollinators, who visit flowers to forage on pollen and nectar. However, management of these crops typically includes application of pesticides, the presence of which may pose a hazard for pollinators foraging in an agricultural environment. To determine the levels of potential exposure to pesticides, their presence and concentration in pollen and nectar need assessing, both within and beyond the target crop plants. We selected ten pesticide compounds and one metabolite and analysed their occurrence in a crop (Brassica napus) and a wild plant (Rubus fruticosus agg.), which was flowering in field edges. Nectar and pollen from both plants were collected from five spring and five winter sown B. napus fields in Ireland, and were tested for pesticide residues, using QuEChERS and Liquid Chromatography tandem mass spectrometry (LC-MS/MS). Pesticide residues were detected in plant pollen and nectar of both plants. Most detections were from fields with no recorded application of the respective compounds in that year, but higher concentrations were observed in recently treated fields. Overall, more residues were detected in B. napus pollen and nectar than in the wild plant, and B. napus pollen had the highest mean concentration of residues. All matrices were contaminated with at least three compounds, and the most frequently detected compounds were fungicides. The most common compound mixture was comprised of the fungicides azoxystrobin, boscalid, and the neonicotinoid insecticide clothianidin, which was not recently applied on the fields. Our results indicate that persistent compounds like the neonicotinoids, should be continuously monitored for their presence and fate in the field environment. The toxicological evaluation of the compound mixtures identified in the present study should be performed, to determine their impacts on foraging insects that may be exposed to them.

Honey bee foraging ability suppressed by imidacloprid can be ameliorated by adding adenosine

Honey bees are important pollinators in most ecosystem, but they are currently facing many threats, which have led to a reduction in their population. Previous studies have indicated that neonicotinoid pesticide can impair the memory and learning ability of honey bees, which can eventually lead to a decline in their foraging and homing abilities. In this study, we investigated the homing ability barrier from the perspective of energy supply. We believe that when worker bees experience stress, their energy supply may shift from pro-movement to pro-resistance; this will lead to inadequate energy provision to the flight muscles, causing a reduction in wingbeat frequency and impairing the flight ability of the worker bees. To test this, the worker bees were treated with imidacloprid, and wing beats between the treatment groups were compared. Their glucose, glycogen, trehalose, and ATP contents were also measured, and their genes for energy metabolism and resistance were analyzed. The addition of adenosine improved the ATP content and helped recover the wingbeat frequency of the worker bees. The preliminary results obtained showed that wingbeat frequency and glucose content in the worker bees treated with imidacloprid were significantly lower than those in the control group. This result is consistent with our hypothesis and demonstrates that energy supply imbalances can prevent worker bees from returning to their hives.

A Modeling Approach for Assessing Ecological Risks of Neonicotinoid Insecticides from Emission to Nontarget Organisms: A Case Study of Cotton Plant

The use of neonicotinoid insecticides in agriculture has posed threats to ecological systems, and there is a need to assess the ecological risks of neonicotinoids from emission to nontarget organisms. We introduced a modeling approach to assess the ecological risks of neonicotinoids using honeybee and earthworm as model organisms, and the simulation was flexible under different environmental conditions. Using the cotton plant as an example, the simulation results demonstrated that under current recommended application rates, the use of common neonicotinoid insecticides posed no threat to earthworms, with the simulated risk quotients (RQs) much lower than 1. However, the simulation for some neonicotinoid insecticides (e.g., acetamiprid) indicated that using these insecticides on cotton plants could threaten honeybees, with simulated RQs higher than 1. The variability analysis showed that in high-latitude regions, the unacceptable risk to honeybees posed by insecticide application can be further elevated due to cold, wet weather that results in relatively high insecticide levels in pollen and nectar. The model evaluation showed large overlaps of simulated risk intervals between the proposed and existing (BeeREX) models. Because the proposed and existing models have different simulation mechanisms, we recommend that these two models be used together to complement each other in future studies. Environ Toxicol Chem 2023;42:928-938. © 2023 SETAC.

Modeling banana uptake of pesticides by incorporating a peel-pulp interaction system into a multicompartment fruit tree model

According to field research, banana peels have a significant impact on the uptake of pesticide residues by banana pulps. To predict pesticide residue concentrations in harvested bananas, however, current modeling approaches did not take into consideration the banana peel as a single simulating compartment. To address the problem, we incorporated a peel-pulp interaction system into a modified multicompartment fruit tree model in order to simulate pesticide residue concentrations in banana plants. The simulation results revealed that lipophilicity played a crucial role in regulating pesticide bioaccumulation in banana plants, showing that moderately- or highly-lipophilic compounds had a high potential for bioaccumulation in banana pulps and peels. Some model inputs, such as peel thickness, degradation rates in plant tissues, and dissipation rates in the soil, had a substantial impact on the bioaccumulation of pesticides in banana pulps and peels. Even if more aspects (such as dynamically morphological properties of banana plants and ionizable chemical compounds) must be considered for in future research, the proposed modeling approach can aid in the comprehension of the pesticide bioaccumulation mechanism in banana plants.

Field recommended concentrations of pyraclostrobin exposure disturb the development and immune response of worker bees (Apis mellifera L.) larvae and pupae

The strobilurin fungicide pyraclostrobin is widely used to prevent and control the fungal diseases of various nectar and pollen plants. Honeybees also directly or indirectly contact this fungicide with a long-term exposure period. However, the effects of pyraclostrobin on the development and physiology of Apis mellifera larvae and pupae during continuous exposure have been rarely known. To investigate the effects of field-realistic concentrations of pyraclostrobin on honeybee survival and development, the 2-day-old larvae were continuously fed with different pyraclostrobin solutions (100 mg/L and 83.3 mg/L), and the expression of development-, nutrient-, and immune-related genes in larvae and pupae were examined. The results showed that two field-realistic concentrations of pyraclostrobin (100 and 83.3 mg/L) significantly decreased the survival and capped rate of larvae, the weight of pupae and newly emerged adults, and such decrease was a positive correlation to the treatment concentrations. qPCR results showed that pyraclostrobin could induce the expression of Usp, ILP2, Vg, Defensin1, and Hymenoptaecin, decrease the expression of Hex100, Apidaecin, and Abaecin in larvae, could increase the expression of Ecr, Usp, Hex70b, Vg, Apidaecin, and Hymenoptaecin, and decreased the expression of ILP1, Hex100 and Defensin1in pupae. These results reflect pyraclostrobin could decrease nutrient metabolism, immune competence and seriously affect the development of honeybees. It should be used cautiously in agricultural practices, especially in the process of bee pollination.

Wild Bee Exposure to Pesticides in Conservation Grasslands Increases along an Agricultural Gradient: A Tale of Two Sample Types

Conservation efforts have been implemented in agroecosystems to enhance pollinator diversity by creating grassland habitat, but little is known about the exposure of bees to pesticides while foraging in these grassland fields. Pesticide exposure was assessed in 24 conservation grassland fields along an agricultural gradient at two time points (July and August) using silicone band passive samplers (nonlethal) and bee tissues (lethal). Overall, 46 pesticides were detected including 9 herbicides, 19 insecticides, 17 fungicides, and a plant growth regulator. For the bands, there were more frequent/higher concentrations of herbicides in July (maximum: 1600 ng/band in July; 570 ng/band in August), while insecticides and fungicides had more frequent/higher concentrations in August (maximum: 110 and 65 ng/band in July; 1500 and 1700 ng/band in August). Pesticide concentrations in bands increased 16% with every 10% increase in cultivated crops. The bee tissues showed no difference in detection frequency, and concentrations were similar among months; maximum concentrations of herbicides, insecticides, and fungicides in July and August were 17, 27, and 180 and 19, 120, and 170 ng/g, respectively. Pesticide residues in bands and bee tissues did not always show the same patterns; of the 20 compounds observed in both media, six (primarily fungicides) showed a detection-concentration relationship between the two media. Together, the band and bee residue data can provide a more complete understanding of pesticide exposure and accumulation in conserved grasslands.

Effects of spinetoram and glyphosate on physiological biomarkers and gut microbes in Bombus terrestris

The sublethal effects of pesticide poisoning will have significant negative impacts on the foraging and learning of bees and bumblebees, so it has received widespread attention. However, little is known about the physiological effects of sublethal spinetoram and glyphosate exposure on bumblebees. We continuously exposed Bombus terrestris to sublethal (2.5 mg/L) spinetoram or glyphosate under controlled conditions for 10 days. The superoxide dismutase, glutathione-S-transferase, carboxylesterase, prophenoloxidase, α-amylase and protease activities, and changes in gut microbes were measured to understand the effects of sublethal pesticide exposure on the physiology and gut microbes of bumblebees. Sublethal pesticide exposure to significantly increased superoxide dismutase activity and significantly decreased gut α-amylase activity in bumblebees but had no significant effect on glutathione-S-transferase, carboxylesterase or gut protease activities. In addition, glyphosate increased the activity of prophenoloxidase. Interestingly, we observed that neither of the two pesticides had a significant effect on dominant gut bacteria, but glyphosate significantly altered the structure of the dominant gut fungal community, and reduced the relative abundance of Zygosaccharomyces associated with fat accumulation. These results suggest that sublethal spinetoram and glyphosate do not significantly affect the detoxification system of bumblebees, but may affect bumblebee health by inhibiting energy acquisition. Our results provide information on the sublethal effects of exposure to low concentrations of glyphosate and spinetoram on bumblebees in terms of physiology and gut microbes.

Modeling pesticide residue uptake by leguminous plants: a geocarpic fruit model for peanuts

BACKGROUND

Pesticide residues are frequently found in leguminous plants; however, no modeling approaches predict residue concentrations in edible legume seeds. In this study, a geocarpic fruit model, simplified for neutral organic compounds, was proposed for high-throughput simulations (over 700 pesticides) of the residue uptake by peanut plants, which characterized three scenarios, namely (i) pesticide foliar application during the pre-seed development stage, (ii) foliar application during the seed development stage, and (iii) soil contamination before plant germination.

RESULTS

In the foliar application scenario, in general, lipophilic pesticides have high simulated residue unit doses (RUDs, residue concentrations in plants per 1.0 kg ha^-1 of pesticide application) in peanut leaves owing to intensified uptake via surface deposition, whereas hydrophilic pesticides have high simulated RUDs in peanuts because the uptake of residues via diffusion is enhanced. For the soil-contamination scenario, organic compounds with moderate lipophilicity have a high bioconcentration potential (i.e. the soil-plant system) in leaves and peanuts, due to large transpiration stream concentration factors (TSCFs) that boost the uptake via transpiration.

CONCLUSIONS

The simulation results have some degrees of agreement with field measurements, indicating that the proposed model can be used as a screening tool for dietary risk assessment of pesticides in peanuts. In future research, pH-dependent physicochemical properties (e.g. soil-water partition coefficient and TSCF) and degradation rate constants of chemicals need to be refined to improve the simulation analysis. © 2022 Society of Chemical Industry.

The BEEHAVEecotox Model-Integrating a Mechanistic Effect Module into the Honeybee Colony Model

Mechanistic effect models are powerful tools for extrapolating from laboratory studies to field conditions. For bees, several good models are available that can simulate colony dynamics. Controlled and reliable experimental systems are also available to estimate the inherent toxicity of pesticides to individuals. However, there is currently no systematic and mechanistic way of linking the output of experimental ecotoxicological testing to bee models for bee risk assessment. We introduce an ecotoxicological module that mechanistically links exposure with the hazard profile of a pesticide for individual honeybees so that colony effects emerge. This mechanistic link allows the translation of results from standard laboratory studies to relevant parameters and processes for simulating bee colony dynamics. The module was integrated into the state-of-the-art honeybee model BEEHAVE. For the integration, BEEHAVE was adapted to mechanistically link the exposure and effects on different cohorts to colony dynamics. The BEEHAVEecotox model was tested against semifield (tunnel) studies, which were deemed the best study type to test whether BEEHAVEecotox predicted realistic effect sizes under controlled conditions. Two pesticides used as toxic standards were chosen for this validation to represent two different modes of action: acute mortality of foragers and chronic brood effects. The ecotoxicological module was able to predict effect sizes in the tunnel studies based on information from standard laboratory tests. In conclusion, the BEEHAVEecotox model is an excellent tool to be used for honeybee risk assessment, interpretation of field and semifield studies, and exploring the efficiency of different mitigation measures. The principles for exposure and effect modules are portable and could be used for any well-constructed honeybee model. Environ Toxicol Chem 2022;41:2870-2882. © 2022 Bayer AG & Sygenta, et al. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Pesticide usage practices and the exposure risk to pollinators: A case study in the North China Plain

Due to the frequent pesticide applications, bees are suffered from pesticide exposure risks via consumption and direct contact with sprayed drifts. However, if pesticides are misused and the potential exposure risk to bees based on realistic pesticide application data are still little reported. In this study, pesticide application patterns in wheat-maize rotation system, vegetable and apple producing areas, was studied by interviewing farmers in Quzhou County, the North China Plain. The pesticide use status was evaluated by the recommended and actual applied dose and risk quotient (RQ) based Bee-REX model was used to assess the exposure risks of pesticide to bees based on the collected pesticide application data. The results showed that over half (52 %) of farmers in selected sites misused pesticides and orchard owners were frequently misused pesticides. Positive correlations were found between pesticide usage performance and farmers' specialized training experience. Pesticides applied in orchards have caused higher exposure risks to bees with the mean of RQs exceed 120 and 1880 via acute contact and dietary routes, respectively. Pesticide misuse significantly elevates the exposure risk to bees that the mean RQ under misuse scenarios was 5.8 times than that of correct use. Abamectin, fipronil and neonicotinoids contributed most to the pesticide exposure risk to bees. The main findings of this study imply that more sustainable pest and pollinator management strategies, including the moratorium high-risk insecticides and providing diverse flower resources and habitats, are highly needed. Additionally, measures such as implementing farmer educating and training programs should also be put on the agenda.

Fungicides and bees: a review of exposure and risk

Fungicides account for more than 35% of the global pesticide market and their use is predicted to increase in the future. While fungicides are commonly applied during bloom when bees are likely foraging on crops, whether real-world exposure to these chemicals - alone or in combination with other stressors - constitutes a threat to the health of bees is still the subject of great uncertainty. The first step in estimating the risks of exposure to fungicides for bees is to understand how and to what extent bees are exposed to these active ingredients. Here we review the current knowledge that exists about exposure to fungicides that bees experience in the field, and link quantitative data on exposure to acute and chronic risk of lethal endpoints for honey bees (Apis mellifera). From the 702 publications we screened, 76 studies contained quantitative data on residue detections in honey bee matrices, and a further 47 provided qualitative information about exposure for a range of bee taxa through various routes. We compiled data for 90 fungicides and metabolites that have been detected in honey, beebread, pollen, beeswax, and the bodies of honey bees. The risks posed to honey bees by fungicide residues was estimated through the EPA Risk Quotient (RQ) approach. Based on residue concentrations detected in honey and pollen/beebread, none of the reported fungicides exceeded the levels of concern (LOC) set by regulatory agencies for acute risk, while 3 and 12 fungicides exceeded the European Food Safety Authority (EFSA) chronic LOC for honey bees and wild bees, respectively. When considering exposure to all bees, fungicides of most concern include many broad-spectrum systemic fungicides, as well as the widely used broad-spectrum contact fungicide chlorothalonil. In addition to providing a detailed overview of the frequency and extent of fungicide residue detections in the bee environment, we identified important research gaps and suggest future directions to move towards a more comprehensive understanding and mitigation of the risks of exposure to fungicides for bees, including synergistic risks of co-exposure to fungicides and other pesticides or pathogens.

Modeling pesticide residues in nectar and pollen in support of pesticide exposure assessment for honeybees: A generic modeling approach

Pesticide residues in nectar and pollen of plants can damage honeybees; however, few modeling approaches have simulated residue levels in nectar and pollen in support of exposure assessment for honeybees. This study introduced a generic modeling approach based on plant uptake models and simple partitioning rules that specifies soil incorporation and foliar spray application scenarios of pesticides and is flexible for conducting variability analysis for various environmental conditions, pesticide application patterns, chemical individuals, and plant varieties. The results indicated that, in general, systemic or moderate lipophilicity (log K_OW of ~2.5) pesticides have relatively high simulated residue levels in nectar and pollen because of the enhanced residue uptake process from soil. For non-systemic or highly lipophilic pesticides, the residue uptake via leaf surface deposition pathway can be enhanced, and more residues will be bioaccumulated in pollen than nectar due to a relatively high lipid content of pollen (as compared to nectar), but the overall residue levels in nectar and pollen are lower than systemic or moderately lipophilic pesticides. The variability analysis showed that environmental conditions, pesticide application patterns, chemical properties, and plant varieties cause considerable variations in simulated residue levels in nectar and pollen, indicating that spatiotemporal, chemical, and plant-related factors must be considered in pesticide exposure assessment for honeybees. Moreover, the comparison between the simulated and measured data showed a high degree of consistency, indicating that the proposed model could be used to conduct a screening-level pesticide exposure assessment for honeybees.

Physiological and Biochemical Variations in Celery by Imidacloprid and Fenpyroximate

Pesticides are one of the abiotic stresses that have had an impact on the quality of agricultural products, especially in China. This study was the first to explore the soluble protein (SP) accumulation, peroxidase (POD) activity, and superoxide dismutase (SOD) activity variations in the stem and leaf of celery plants in the field after 2 h, 1, 3, 5, 8, 10, 14, 21, 28-day of spraying imidacloprid (IMI) and fenpyroximate (FEN) at various doses. The findings demonstrated that there was no notable difference in ultimate residues between 1 F and 10 F, and even with the 10 F treatment, the residues were not a concern. The SP accumulation alterations were mainly provoked by residues, which dramatically boosted in stem and eventually declined in leaf. The POD activity in celery was a dynamic process with a marked shift (enhanced and declined) when compared with non-pesticide treatment after 28 days. The field trial exhibited that the SOD was principally positioned in leaf whether pesticides were applied or not, which might be due to the distinctive structure of the celery leaf compared with the stem. No obvious linear relation between application dose and SOD activity was observed.

Translocation and metabolism of the chiral neonicotinoid cycloxaprid in oilseed rape (Brassica napus L.)

Neonicotinoids have been banned in some countries because of increased nontarget resistance and ecological toxicity. Cycloxaprid is a potentially promising substitute, but its metabolism in plants is still poorly understood. The study aims to clarify the translocation of cycloxaprid, identify its metabolites, propose possible metabolic pathways and compare differences between enantiomers in oilseed rape via ¹⁴C tracing technology and HPLC-QTOF-MS. The results showed that most cycloxaprid remained in the treated leaves, and only a small amount translocated to the anthers. Seven metabolites were identified, and the possible metabolic pathway was divided into two phases. Phase Ⅰ metabolism included two metabolites obtained via cleavage of the oxa-bridged seven-membered ring. Phase II metabolism was responsible for glucose conjugate formation. The possible metabolic pathways revealed that the proportion of phase I metabolites gradually decreased over time, and the phase II metabolites transformed from monosaccharide and disaccharide conjugates to trisaccharide and tetrasaccharide conjugates. The levels of metabolites were significantly different between the enantiomers. In particular, the main metabolite was M4, which has confirmed biological toxicity. M2 was the only metabolite detected in rapeseed. The results will promote the scientific application of cycloxaprid in agriculture and could have implications for assessing environmental risk.

Simultaneous detection of ten kinds of insecticide residues in honey and pollen using UPLC-MS/MS with graphene and carbon nanotubes as adsorption and purification materials

An analytical method of simultaneous detection of ten insecticide residues in honey and pollen was established. The samples were purified with QuEChERS approach using new adsorbents and analyzed with UPLC-MS/MS. The results showed that both of graphene and carbon nanotubes were highly efficient adsorbents for the dSPE clean up to eliminate coextractives in the samples, and graphene was superior to carbon nanotubes for the detection of pesticide residues in honey and pollen samples. The proposed method was used to detect pesticide residues in 25 honey samples and 30 pollen samples which were randomly collected from more than ten provinces in China. All honey samples contain 1-27 μg/kg of chlorpyrifos residues. Only 4% of the honey samples were detected containing acetamiprid and imidacloprid, while the other seven pesticides were not detected. Chlorpyrifos residues were found in all pollen samples (5-66 μg/kg), among which twenty percent exceeded the maximum residue limits (MRLs, 50 μg/kg, European Commission Regulation). Most of the pollen samples containing pesticide concentrations higher than MRLs were collected from rape, followed by lotus, camellia, and rose. Besides, 36.7% and 33.3% of the pollen samples had imidacloprid and flupyradifurone higher than 5 μg/kg. A total of 26.7% pollen samples were detected containing bifenthrin, while none of the other six pesticides were detected in pollen samples.

Effects of Provision Type and Pesticide Exposure on the Larval Development of Osmia lignaria (Hymenoptera: Megachilidae)

Wild and managed bee populations are in decline, and one of many environmental causes is the impact of pesticides on developing bees. For solitary bees, delayed larval development could lead to asynchronous adult emergence, unhealthy and inefficient adult pollinators, and decreased brood production and survival. We examined a methodology for testing Osmia lignaria Say (Hymenoptera: Megachilidae) larval responses to pesticide exposure using a laboratory bioassay. We created two provision types: a homogenized blend of O. lignaria provisions from an apple orchard and homogenized almond pollen pellets collected by honey bees plus sugar water. Pesticides were administered to the provisions to compare toxic effects. We recorded larval developmental durations for second-fifth instar and for fifth instar to cocoon initiation for larvae fed provisions treated with water (control) or doses of three pesticides and a representative spray-tank mixture (acetamiprid, boscalid/pyraclostrobin, dimethoate, and acetamiprid plus boscalid/pyraclostrobin). All larvae survived to cocoon initiation when only water was added to provisions. Impacts of pesticide treatments significantly differed between the apple and almond homogenates. The greatest treatment effects occurred when the homogenized almond provision was mixed with acetamiprid alone and when combined with boscalid/pyraclostrobin. Optimizing bioassays through the use of appropriate larval food for exposing solitary bee larvae to agrochemicals is crucial for assessing risks for pollinators.

Analysis of honey bee exposure to multiple pesticide residues in the hive environment

Since the loss of honeybees in hives could have a greater impact on colony health than those of their foraging bees, it is imperative to know beehives' pesticide exposure via oral ingestion of contaminated in-hive matrices. Here, a 4-year monitoring survey of 64 pesticide residues in pollen, nectar and related beehive matrices (beebread and honey) from China's main honey producing areas was carried out using a modified version of the QuEChERS multi-residue method. The results showed that 93.6% of pollen, 81.5% of nectar, 96.6% of beebread, and 49.3% of honey containing at least one target pesticide were detected either at or above the method detection limits (MDLs), respectively, with up to 19 pesticides found per sample. Carbendazim was the most frequently detected pesticide (present in >85% of the samples), and pyrethroids were also abundant (median concentration = 134.3-279.0 μg/kg). The transfer of pesticides from the environment into the beehive was shown, but the pesticide transference ratio may be affected by complex factors. Although the overall risk to colony health from pesticides appears to be at an acceptable level, the hazard quotient/hazard index (HQ/HI) value revealed that pyrethroids were clearly the most influential contributor, accounting for up to 45% of HI. Collectively, these empirical findings provide further insights into the extent of contamination caused by agricultural pesticide use on honeybee colonies.

Structural Biology-Guided Design, Synthesis, and Biological Evaluation of Novel Insect Nicotinic Acetylcholine Receptor Orthosteric Modulators

The development of novel and safe insecticides remains an important need for a growing world population to protect crops and animal and human health. New chemotypes modulating the insect nicotinic acetylcholine receptors have been recently brought to the agricultural market, yet with limited understanding of their molecular interactions at their target receptor. Herein, we disclose the first crystal structures of these insecticides, namely, sulfoxaflor, flupyradifurone, triflumezopyrim, flupyrimin, and the experimental compound, dicloromezotiaz, in a double-mutated acetylcholine-binding protein which mimics the insect-ion-channel orthosteric site. Enabled by these findings, we discovered novel pharmacophores with a related mode of action, and we describe herein their design, synthesis, and biological evaluation.

Dissipation and transformation of the diamide insecticide cyantraniliprole in ornamental snapdragon (Antirrhinum majus)

Dissipation and transformation of cyantraniliprole, a new diamide class of insecticides, were investigated under greenhouse conditions, using snapdragon (Antirrhinum majus) as the model plant. Dissipation of cyantraniliprole in treated leaves was found to be dependent upon application methods (foliar spray versus soil drench) and doses (high versus low dose), with the parent insecticide being the major residue at various sampling points. A high-dose foliar application resulted in pesticide residue of 6.7-23.8 μg/g foliar fresh weight over 8 weeks of treatments, while in soil drench treatment the residue varied from 0.8 to 1.4 μg/g. However, the residue contents were similar between the two application methods at a low application dose. The transformation pathways of cyantraniliprole were primarily intramolecular rearrangements, with IN-J9Z38 being the major metabolite across treatments. Several other metabolites were also identified, some of which were unique to the application methods. Out of total 26 metabolites tentatively identified in this study, 10 metabolites were unique to foliar application, while six metabolites were unique to soil drench. In addition to plant-mediated biotransformation, photodegradation of the parent compound was identified as a potential mechanism in foliar application.

The use of the Hazard Quotient approach to assess the potential risk to honeybees (Apis mellifera) posed by pesticide residues detected in bee-relevant matrices is not appropriate

BACKGROUND

Pesticide residue data for pollen and nectar are valuable for characterizing realistic exposure of pollinators, e.g. from agricultural crops, flowering margins. Interpretation of residues relies on comparing exposure with toxicity and the Hazard Quotient (HQ) is widely utilized. However, the HQ (threshold of concern 50) was only validated for foliar sprays, based on application rate as a proxy for exposure, not measured residues in bee-relevant matrices.

RESULTS

A review of the literature showed a range of HQ approaches and thresholds of concern used to assess non-foliar applications and residues detected in bee-relevant matrices, mostly pollen. The use of the HQ thresholds to assess risks associated with residue data or non-foliar spray application methods is not validated, does not reflect realistic exposure and the conclusions reached differ substantially from current risk assessment approaches. Re-evaluation of residue data from the first published use of the concentration-based HQ (2013) and a recent paper (2021) reduced the proportion of pesticides where a conclusion of potential risk was reached from 30 to 7% and 28% to 3-6%, respectively.

CONCLUSIONS

An understanding of the applicability of the selected risk assessment approach to the available residue data is needed to enable robust conclusions to be drawn on the potential risk to bees. Use of the HQ approach to assess the risk posed by application methods other than foliar sprays or residues in nectar and pollen is likely to result in unreliable conclusions. An alternative approach should be used to assess the significance of measured residues.

Humans Share More Preferences for Floral Phenotypes With Pollinators Than With Pests

Studies on the selection of floral traits usually consider pollinators and sometimes herbivores. However, humans also exert selection on floral traits of ornamental plants. We compared the preferences of bumblebees (Bombus terrestris), thrips (Frankliniella occidentalis), and humans for flowers of snapdragon. From a cross of two species, Antirrhinum majus and Antirrhinum linkianum, we selected four Recombinant Inbred Lines (RILs). We characterised scent emission from whole flowers and stamens, pollen content and viability, trichome density, floral shape, size and colour of floral parts. We tested the preferences of bumblebees, thrips, and humans for whole flowers, floral scent bouquets, stamen scent, and individual scent compounds. Humans and bumblebees showed preferences for parental species, whereas thrips preferred RILs. Colour and floral scent, in combination with other floral traits, seem relevant phenotypes for all organisms. Remarkably, visual traits override scent cues for bumblebees, although, scent is an important trait when bumblebees cannot see the flowers, and methyl benzoate was identified as a key attractant for them. The evolutionary trajectory of flowers is the result of multiple floral traits interacting with different organisms with different habits and modes of interaction.

Pollinators and plant nurseries: how irrigation and pesticide treatment of native ornamental plants impact solitary bees

A key conservation goal in agroecosystems is to understand how management practices may affect beneficial species, such as pollinators. Currently, broad gaps exist in our knowledge as to how horticultural management practices, such as irrigation level, might influence bee reproduction, particularly for solitary bees. Despite the extensive use of ornamental plants by bees, especially little is known about how irrigation level may interact with insecticides, like water-soluble neonicotinoids, to influence floral rewards and bee reproduction. We designed a two-factor field cage experiment in which we reared Megachile rotundata (Fabricius) (Hymenoptera: Megachilidae) on containerized ornamental plants grown under two different irrigation levels and imidacloprid treatments (30% label rate dosage of a nursery formulation or an untreated control). Lower irrigation was associated with modest decreases in nectar volume and floral abundance in untreated plants, whereas irrigation did not affect plants treated with imidacloprid. Furthermore, higher irrigation decreased the amount of imidacloprid entering nectar. Imidacloprid application strongly reduced bee foraging activity and reproduction, and higher irrigation did not offset any negative effects on bees. Our study emphasizes the impact of a nursery neonicotinoid formulation on solitary bee foraging and reproduction, while highlighting interactions between irrigation level and neonicotinoid application in containerized plants themselves.

Organochlorine pesticide residues in Uganda's honey as a bioindicator of environmental contamination and reproductive health implications to consumers

Honey has multifaceted nutritional and medicinal values; however, its quality is hinged on the floral origin of the nectar. Taking advantage of the large areas that they cover; honeybees are often used as bioindicators of environmental contamination. The focus of the present paper was to examine the quality of honey from within the vicinity of an abandoned pesticide store in Masindi District in western Uganda. Surficial soils (<20 cm depths) and honey samples were collected from within the vicinity of the abandoned pesticide store and analysed for organochlorine pesticide (OCP) residues using gas chromatograph coupled to an electron capture detector (GC-ECD). The mean level of ∑DDTs in all the soil samples was 503.6 µg/kg dry weight (d.w). ∑DDTs contributed 92.2% to the ∑OCPs contamination loads in the soil samples, and others (lindane, aldrin, dieldrin, and endosulfans) contributed only 7.8%. Ratio (p, p'-DDE+p, p'-DDD)/p, p'-DDT of 1.54 suggested historical DDT input in the area. In all the honey samples, the mean level of ∑DDTs was 20.9 µg/kg. ∑DDTs contributed 43.3% to ∑OCPs contamination loads in the honey samples, followed by lindane (29.8%), endosulfans (23.6%) and dieldrin (3.2%), with corresponding mean levels of 14.4, 11.4 and 1.55 µg/kg, respectively. Reproductive risk assessment was done based on the hazard quotient (HQ) and hazard index (HI) procedure. In our study, the calculated HIs for adults (102.38), and children (90.33) suggested high potential health risks to the honey consumers. Lindane, endosulfan and p, p'-DDD detected in the honey samples at levels exceeding the acute reference dose (ARfD) are known risk factors for spontaneous abortion, reduced implantation, menstrual cycle shortening, impaired semen quality, and prostate cancer in exposed individuals and experimental animal models.

Emulsions containing essential oils, their components or volatile semiochemicals as promising tools for insect pest and pathogen management

Most of the traditional strategies used for facing the management of insect pest and diseases have started to fail due to different toxicological issues such as the resistance of target organism and the impact on environment and human health. This has made mandatory to seek new effective strategies, which minimize the risks and hazards without compromising the effectiveness of the products. The use of essential oils, their components and semiochemicals (pheromones and allelochemicals) has become a promising safe and eco-sustainable alternative for controlling insect pest and pathogens. However, the practical applications of this type of molecules remain rather limited because their high volatility, poor solubility in water and low chemical stability. Therefore, it is required to design strategies enabling their use without any alteration of their biological and chemical properties. Oil-in-water nano/microemulsions are currently considered as promising tools for taking advantage of the bioactivity of essential oils and their components against insects and other pathogens. Furthermore, these colloidal systems also allows the encapsulation and controlled release of semiochemicals, which enables their use in traps for monitoring, trapping or mating disruption of insects, and in push-pull strategies for their behavioral manipulation. This has been possible because the use of nano/microemulsions allows combining the protection provided by the hydrophobic environment created within the droplets with the enhanced dispersion of the molecules in an aqueous environment, which favors the handling of the bioactive molecules, and limits their degradation, without any detrimental effect over their biological activity. This review analyzes some of the most recent advances on the use of emulsion-like dispersions as a tool for controlling insect pest and pathogens. It is worth noting that even though the current physico-chemical knowledge about these systems is relatively poor, a deeper study of the physico-chemical aspects of nanoemulsions/microemulsions containing essential oils, their components or semiochemicals, may help for developing most effective formulations, enabling the generalization of their use.

The investigation of honey bee pesticide poisoning incidents in Czechia

Honey bees are major pollinators of crops with high economic value. Thus, bees are considered to be the most important nontarget organisms exposed to adverse effects of plant protection product use. The side effects of pesticides are one of the major factors often linked to colony losses. Fewer studies have researched acute poisoning incidents in comparison to the study of the sublethal effects of pesticides. Here, we compared pesticides in dead/dying bees from suspected poisoning incidents and the suspected crop source according to government protocols. Additionally, we analyzed live bees and bee bread collected from the brood comb to determine recent in-hive contamination. We used sites with no reports of poisoning for reference. Our analysis confirmed that not all of the suspected poisonings correlated with the suspected crop. The most important pesticides related to the poisoning incidents were highly toxic chlorpyrifos, deltamethrin, cypermethrin and imidacloprid and slightly toxic prochloraz and thiacloprid. Importantly, poisoning was associated with pesticide cocktail application. Almost all poisoning incidents were investigated in relation to rapeseed. Some sites were found to be heavily contaminated with several pesticides, including a reference site. However, other sites were moderately contaminated despite agricultural use, including rapeseed cultivation sites, which can influence the extent of pesticide use, including tank mixes and other factors. We suggest that the analysis of pesticides in bee bread and in bees from the brood comb is a useful addition to dead bee and suspected crop analysis in poisoning incidents to inform the extent of recent in-hive contamination.

A Review on Prediction Models for Pesticide Use, Transmission, and Its Impacts

The lure of increased productivity and crop yield has caused the imprudent use of pesticides in great quantity that has unfavorably affected environmental health. Pesticides are chemicals intended for avoiding, eliminating, and mitigating any pests that affect the crop. Lack of awareness, improper management, and negligent disposal of pesticide containers have led to the permeation of pesticide residues into the food chain and other environmental pathways, leading to environmental degradation. Sufficient steps must be undertaken at various levels to monitor and ensure judicious use of pesticides. Development of prediction models for optimum use of pesticides, pesticide management, and their impact would be of great help in monitoring and controlling the ill effects of excessive use of pesticides. This paper aims to present an exhaustive review of the prediction models developed and modeling strategies used to optimize the use of pesticides.

Lethal and Sublethal Effects of Pyriproxyfen on Apis and Non-Apis Bees

Pyriproxyfen is a juvenile hormone mimic used extensively worldwide to fight pests in agriculture and horticulture. It also has numerous applications as larvicide in vector control. The molecule disrupts metamorphosis and adult emergence in the target insects. The same types of adverse effects are expected on non-target insects. In this context, the objective of this study was to evaluate the existing information on the toxicity of pyriproxyfen on the honey bee (Apis mellifera) and non-Apis bees (bumble bees, solitary bees, and stingless bees). The goal was also to identify the gaps necessary to fill. Thus, whereas the acute and sublethal toxicity of pyriproxyfen against A. mellifera is well-documented, the information is almost lacking for the non-Apis bees. The direct and indirect routes of exposure of the non-Apis bees to pyriproxyfen also need to be identified and quantified. More generally, the impacts of pyriproxyfen on the reproductive success of the different bee species have to be evaluated as well as the potential adverse effects of its metabolites.

Seek and you shall find: An assessment of the influence of the analytical methodologies on pesticide occurrences in honey bee-collected pollen with a systematic review

Honey bee mortality and colony losses have been reported worldwide. Although this phenomenon is caused by a combination of factors, agrochemicals have received special attention due to their potential effects on bees. In agricultural and urban environments bees are exposed to several compounds that may interact in unexpected ways, but information on the extent of pesticide exposure remains unclear. Several monitoring studies have been conducted to evaluate the field-realistic exposure of bees to pesticides after their release on the market. However, their outputs are difficult to compare and harmonize due to differences in the analytical methodologies and the sampling protocols (e.g. number of screened compounds and analysed samples, and detection limits (LODs)). Here, we hypothesize that the analytical methodologies used in the monitoring studies may strongly affect the pesticide occurrences in pollen underestimating the real pesticide exposure. By mean of a systematic literature review, we have collected relevant information on pesticide contaminations in the honey bee-collected pollen. Our findings showed that the pesticide occurrences were associated with the analytical methodologies and the real pesticide exposure has likely been underestimated in some monitoring studies. For four highly toxic compounds, the LOD used in these monitoring studies exceeded the doses that cause toxic effects on honey bees. We recommend that, especially for the highly toxic compounds, the LODs used in the monitoring studies should be low enough to exclude lethal or sublethal effects on bees and avoid "false negative" samples.

Pollinator exposure to systemic insecticides and fungicides applied in the previous fall and pre-bloom period in apple orchards

Pollinators provide a crucial ecosystem service by pollinating commercially cultivated crops, but they are frequently exposed to various agricultural chemicals used for pest management. In this study, we assessed the potential exposure of pollinators to various systemic insecticides and a fungicide used in apple orchards. Residue levels were determined for the whole flower as well as pollen and nectar separately for pre-bloom applications of acetamiprid, imidacloprid, sulfoxaflor, thiacloprid, thiamethoxam, and myclobutanil. Very low pesticide residue levels (2-70 parts per billion, ppb) were found in the whole flower, pollen and nectar samples compared with pesticide concentrations of 60-200 parts per million (ppm) in applied foliarly only 5 days earlier. Insecticide residues from nectar and pollen samples were below the USA EPA classification of No Observable Effect Limit (NOEL) for acute toxicity to honey bees, suggesting that a single foraging visit to flowers may not cause toxicity to bees. However, cumulative acute exposure from multiple flower visits could potentially be harmful to bees, and needs to be studied further. We also examined apple flowers for residues of several systemic insecticides that were applied for brown marmorated stink bug control late in the fall of the previous season. None of the fall sprays that contained premixed insecticide active ingredients (viz., thiamethoxam + lambda-cyhalothrin, and imidacloprid + beta-cyfluthrin), including multiple applications of individual active ingredients (viz., dinotefuran, clothianidin, and sulfoxaflor), persisted until the following spring. Based on these findings, fall applications of insecticides used for controlling invasive pests such as the brown marmorated stink bug (Halyomorpha halys) and the spotted lanternfly (Lycorma delicatula) could be considered safe to pollinator species foraging in apple orchards during the spring bloom the following season.

Plant protection product residues in plant pollen and nectar: A review of current knowledge

Exposure to Plant Protection Products, PPPs, (fungicides, herbicides and insecticides) is a significant stressor for bees and other pollinators, and has recently been the focus of intensive debate and research. Specifically, exposure through contaminated pollen and nectar is considered pivotal, as it presents the highest risk of PPP exposure across all bee species. However, the actual risk that multiple PPP residues might pose to non-target species is difficult to assess due to the lack of clear evidence of their actual concentrations. To consolidate the existing knowledge of field-realistic residues detected in pollen and nectar directly collected from plants, we performed a systematic literature review of studies over the past 50 years (1968-2018). We found that pollen was the matrix most frequently evaluated and, of the compounds investigated, the majority were detected in pollen samples. Although the overall most studied category of PPPs were the neonicotinoid insecticides, the compounds with the highest median concentrations of residues in pollen were: the broad spectrum carbamate carbofuran (1400 ng/g), the fungicide and nematicide iprodione (524 ng/g), and the organophosphate insecticide dimethoate (500 ng/g). In nectar, the highest median concentration of PPP residues detected were dimethoate (1595 ng/g), chlorothalonil (76 ng/g), and the insecticide phorate (53.5 ng/g). Strong positive correlation was observed between neonicotinoid residues in pollen and nectar of cultivated plant species. The maximum concentrations of several compounds detected in nectar and pollen were estimated to exceed the LD_50s for honey bees, bumble bees and four solitary bee species, by several orders of magnitude. However, there is a paucity of information for the biggest part of the world and there is an urgent need to expand the range of compounds evaluated in PPP studies.

Characterizing honey bee exposure and effects from pesticides for chemical prioritization and life cycle assessment

Agricultural pesticides are key contributors to pollinator decline worldwide. However, methods for quantifying impacts associated with pollinator exposure to pesticides are currently missing in comparative risk screening, chemical substitution and prioritization, and life cycle impact assessment methods. To address this gap, we developed a method for quantifying pesticide field exposure and ecotoxicity effects of honey bees as most economically important pollinator species worldwide. We defined bee intake and dermal contact fractions representing respectively oral and dermal exposure per unit mass applied, and tested our model on two pesticides applied to oilseed rape. Our results show that exposure varies between types of forager bees, with highest dermal contact fraction of 59 ppm in nectar foragers for lambda-cyhalothrin (insecticide), and highest oral intake fractions of 32 and 190 ppm in nectar foragers for boscalid (fungicide) and lambda-cyhalothrin, respectively. Hive oral exposure is up to 115 times higher than forager oral exposure. Combining exposure with effect estimates yields impacts, which are three orders of magnitude higher for the insecticide. Overall, nectar foragers are the most affected forager type for both pesticides, dominated by oral exposure. Our framework constitutes an important step toward integrating pollinator impacts in chemical substitution and life cycle impact assessment, and should be expanded to cover all relevant pesticide-crop combinations.

The Impact of Pesticides on Flower-Visiting Insects: A Review with Regard to European Risk Assessment

Flower-visiting insects (FVIs) are an ecologically diverse group of mobile, flying species that should be protected from pesticide effects according to European policy. However, there is an ongoing decline of FVI species, partly caused by agricultural pesticide applications. Therefore, the risk assessment framework needs to be improved. We synthesized the peer-reviewed literature on FVI groups and their ecology, habitat, exposure to pesticides, and subsequent effects. The results show that FVIs are far more diverse than previously thought. Their habitat, the entire agricultural landscape, is potentially contaminated with pesticides through multiple pathways. Pesticide exposure of FVIs at environmentally realistic levels can cause population-relevant adverse effects. This knowledge was used to critically evaluate the European regulatory framework of exposure and effect assessment. The current risk assessment should be amended to incorporate specific ecological properties of FVIs, that is, traits. We present data-driven tools to improve future risk assessments by making use of trait information. There are major knowledge gaps concerning the general investigation of groups other than bees, the collection of comprehensive data on FVI groups and their ecology, linking habitat to FVI exposure, and study of previously neglected complex population effects. This is necessary to improve our understanding of FVIs and facilitate the development of a more protective FVI risk assessment. Environ Toxicol Chem 2019;38:2355-2370. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.