Different mulch films, consistent results: soil fauna responses to microplastic.

Agricultural activities contribute to plastic pollution, with unintentional introduction and intentional use of plastic mulch films leading to the accumulation of microplastic particles in soils. The lack of removal techniques and scarce information on the effects on soil organisms, especially for biodegradable mulch films, necessitate an assessment of potential effects. This study aimed to elucidate the effects of mulch film microplastic on soil fauna by investigating reproduction output and subcellular responses before and after recovery from exposure. Two common soil organisms, Folsomia candida and Eisenia fetida, were exposed to petroleum-based polyethylene (PE) and biodegradable polylactic acid/polybutylene adipate terephthalate (PLA/PBAT) microplastic for 28 days, according to OECD guidelines 232 and 222, respectively. Juvenile numbers revealed no polymer- or concentration-dependent effects on E. fetida and F. candida reproduction after exposure to up to 5 and 10 g/kgdw soil, respectively. To provide a more sensitive and early indication of sublethal effects, subcellular responses in E. fetida were analyzed. Glutathione S-transferase (GST) activity increased with rising microplastic concentration; however, catalase (CAT), acetylcholine esterase (AChE) activity, and reactive oxygen species (ROS) did not differ from control levels. Further, the more environmentally relevant PE polymer was chosen for in-depth assessment of subcellular response after 28-day microplastic exposure and subsequent 28 days in uncontaminated soil with E. fetida. No significant differences in biomarker activity and stress levels were observed. We conclude that mulch film-derived microplastic did not adversely affect earthworm and collembolan species in this scenario, except for a slight induction in the detoxification enzyme glutathione S-transferase.

Does copper contamination change thermotaxis of the soil arthropod Folsomia candida (Collembola)?

Behavioural thermoregulation (thermotaxis) is essential for soil invertebrates to evade thermal extremes in terrestrial environments. Extensive and continuous use of copper (Cu) based products has led to elevated Cu concentration in soils across the globe and in some areas reaching concentrations that are hazardous to soil invertebrates. We hypothesised that environmental stressors, for example, exposure to heavy metals may compromise the adaptive behavioural thermoregulation of organisms, but very little is known of such interactions. In this study, we chose Cu as a model toxicant and investigated the potential effect of Cu-contaminated soils on the behavioural thermoregulation of springtails (Folsomia candida). We measured the distribution of springtails when placed on a temperature gradient ranging from 6 to 46 °C and estimated their thermal preference as an indicator of behavioural thermoregulation. Results showed that within 60 min of being introduced to the thermal gradient, the distribution of springtails was unimodal with slight skewness towards high temperature. Springtails exhibited a consistent preferred temperature range of approximately 21-23 °C across all Cu exposure levels and time points. However, Cu contamination increased the frequency of springtails recorded along the gradient where temperature was above 30 °C. We interpreted this observation as Cu-exposed animals having an elevated risk of entering heat coma and not being able to evade noxious temperatures. We conclude that Cu contamination does not alter the thermal preference of F. candida but compromises their ability to tolerate extreme high temperature. Incorporating behavioural responses into ecotoxicological assessments provides ecologically relevant insights into the impacts of chemical pollution on soil ecosystems.

Assessing the multi-dimensional impact of lead-induced toxicity on collembola found in maize fields: From oxidative stress to genetic disruptions.

The prolonged exposure of agricultural soils to heavy metals from wastewater, particularly in areas near industrial facilities, poses a significant threat to the well-being of living organisms. The World Health Organization (WHO) has established standard permissible limits for heavy metals in agricultural soils to mitigate potential health hazards. Nevertheless, some agricultural fields continue to be irrigated with wastewater containing industrial effluents. This study aimed to assess the concentration of lead in soil samples collected from agricultural fields near industrial areas. Subsequently, we determined the lethal concentration (LC50) of lead (Pb) and other heavy metals for two Collembola species, namely Folsomia candida, a standard organism for soil ecotoxicity tests, and comparing it with Proisotoma minuta. The research further examined the toxic effects of lead exposure on these two species, revealing depletion in the energy reservoirs and alterations in the tissue histology of both organisms. The study revealed that lead can induce genotoxic damage as it evidently has moderate binding affinity with the ct-DNA and hence can cause DNA fragmentation and the formation of micronuclei. Elevated lipid peroxidation (LPO) levels and protein carbonylation levels were observed, alongside a reduction in antioxidant enzymes (CAT, SOD & GPx). These findings suggest that lead disrupts the balance between oxidants and the antioxidant enzyme system, impairing defense mechanisms and consequential derogatory damage within microarthropods. The investigation elucidates a complex network of various signaling pathways compromised as a result of lead toxicity. Hence, it presents a novel perspective that underscores the pressing necessity for implementing an integrated risk assessment framework at the investigated site.

Multigenerational toxicity of microplastics derived from two types of agricultural mulching films to Folsomia candida.

Degradation and fragmentation of mulching films represents an increasing source of microplastics (MPs, plastic particles 1 µm to 5 mm in size) to agricultural soils. MPs have been shown to affect many soil invertebrates, including springtails. However, these studies typically use test materials representing less environmentally relevant particle types, such as pristine uniform MPs, which do not represent the large range of particle sizes and morphologies found in the field. This study aimed at providing insight into the adverse effects of MPs originating from agricultural mulching films, by using artificially aged MPs derived from both biodegradable (starch-polybutadiene adipate terephthalate (PBAT)) blend, as well as conventional (linear low-density polyethylene (LLDPE)) plastic polymers. The soil dwelling springtail Folsomia candida was exposed to these MPs for five generations in order to elucidate population effects due to possible reproduction toxicity, endocrine disruption, mutagenesis or developmental toxicity. F. candida were exposed to 0, 0.0016, 0.008, 0.04, 0.2, 1, 2, 3, 4 and 5 % (w/w dry soil) MPs in Lufa 2.2 soil, which includes concentrations within the range of environmental relevance. Juveniles produced at each concentration were transferred to the next generation, with the parental, F2 and F4 generations being exposed for four weeks and F1 and F3 generations for five weeks. No concentration-dependent effects on F. candida survival or reproduction were observed in exposures to either of the MPs, in any of the generations. These results suggest that the particular MPs used in this study, derived from mulching films used on agricultural soils, may not be potent toxicants to F. candida, even after long-term exposure and at elevated concentrations.

Field-realistic doses of the neonicotinoid acetamiprid impact natural soil arthropod community diversity and structure.

The neonicotinoid acetamiprid is used as a foliar insecticide spray, which results in direct exposure of a wide variety of soil organisms. Laboratory testing indicated that acetamiprid is toxic to the Collembola (springtails) species Folsomia candida, while Acari (mites) seem relatively insensitive to neonicotinoids. Since such opposing effects on different soil arthropods might imbalance natural arthropod communities, this study determined: (i) if field-realistic doses of acetamiprid affect the abundance and diversity in soil arthropod communities, and (ii) whether these potential effects are short-term or persist after degradation of acetamiprid. Intact soil cores collected from an untreated grassland field were placed in the mesocosm set up 'CLIMECS', and the naturally sourced communities were exposed to a control and increasing field-realistic doses of acetamiprid (i.e. 0, 0.05, 0.2, 0.8 mg a.s./kg dry soil). Before and 7 and 54 days after spraying the insecticide, the abundance of mites and springtails and springtail diversity were assessed. Springtail and mite abundances were similar at the start of the experiment, but springtail abundance was significantly lowered while mite abundance increased shortly after exposure to increasing doses of acetamiprid. At the highest dose, springtail numbers decreased by 53% on average while the number of mites increased by 26%. This effect was no longer visible after 54 days, suggesting recovery of the community as a whole reflected by observed changes in community dissimilarity: shortly after application springtail communities clearly diverged from the control in terms of species composition, while communities converged again in the long-term. With our results, we are the first to show that field-realistic applications of N-nitroguanidine neonicotinoids can significantly impact natural soil fauna communities, which might have implications for soil ecosystem functioning.

Sublethal pesticide exposure in non-target terrestrial ecosystems: From known effects on individuals to potential consequences on trophic interactions and network functioning.

Over the last decades, the intensification of agriculture has resulted in an increasing use of pesticides, which has led to widespread contamination of non-target ecosystems in agricultural landscapes. Plants and arthropods inhabiting these systems are therefore chronically exposed to, at least, low levels of pesticides through direct pesticide drift, but also through the contamination of their nutrient sources (e.g. soil water or host/prey tissues). Pesticides (herbicides, acaricides/insecticides and fungicides) are chemical substances used to control pests, such as weeds, phytophagous arthropods and pathogenic microorganisms. These molecules are designed to disturb specific physiological mechanisms and induce mortality in targeted organisms. However, under sublethal exposure, pesticides also affect biological processes including metabolism, development, reproduction or inter-specific interactions even in organisms that do not possess the molecular target of the pesticide. Despite the broad current knowledge on sublethal effects of pesticides on organisms, their adverse effects on trophic interactions are less investigated, especially within terrestrial trophic networks. In this review, we provide an overview of the effects, both target and non-target, of sublethal exposures to pesticides on traits involved in trophic interactions between plants, phytophagous insects and their natural enemies. We also discuss how these effects may impact ecosystem functioning by analyzing studies investigating the responses of Plant-Phytophage-Natural enemy trophic networks to pesticides. Finally, we highlight the current challenges and research prospects in the understanding of the effects of pesticides on trophic interactions and networks in non-target terrestrial ecosystems.

Characterization of Springtail (Arrhopalites caecus) for Use in Soil Ecotoxicity Testing.

Springtails (subclass: Collembola) represent one of the most extensively studied invertebrate groups in soil ecotoxicology. This is because of their ease of laboratory culture, significant ecological role, and sensitivity to environmental contaminants. Folsomia candida (family: Isotomidae) is a globally widespread parthenogenetic species that is prevalent in laboratory toxicity testing with springtails. Conversely, Arrhopalites caecus (family: Arrhopalitidae), a parthenogenic globular springtail species, remains untested in soil ecotoxicology. This species is found in diverse habitats, including cave systems and forest leaf litter, and has a global distribution. The sensitivity of A. caecus to environmental contaminants, such as neonicotinoid insecticides, as well as its life history and optimal culturing conditions, are largely unknown. The present study describes the establishment of a pure A. caecus laboratory culture and characterization of its life cycle and culturing conditions. We assessed the sensitivity of A. caecus to various insecticides, including exposures to the neonicotinoid thiamethoxam in soil and through a novel feeding assay as well as to clothianidin and cyantraniliprole in spiked soil exposures. In 7- and 14-day exposures to thiamethoxam in agricultural soil, the 50% lethal concentration (LC50) values were determined to be 0.129 mg/kg dry weight and 0.010 mg/kg dry weight, respectively. The 14-day LC50 for exposure to thiamethoxam via spiked food was determined to be 0.307 mg/kg dry weight. In addition, the 28-day 50% effect concentration for inhibition of juvenile production from cyantraniliprole exposure in the same soil type was 0.055 mg/kg dry weight. Challenges encountered in using this species included susceptibility to mite infestation and low adult survival rates in the 28-day cyantraniliprole test. Environ Toxicol Chem 2024;43:1820-1835. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Exposure to teflubenzuron reduces drought tolerance of collembolans.

Chitin synthesis inhibitors (CSIs) are commonly used insecticides compromising cuticle formation and structure in arthropods. Arthropods rely on intact cuticles to maintain water balance and cellular homeostasis to survive in different weather conditions. We hypothesized that physiological impacts of CSIs may make arthropods more vulnerable to harsh environmental conditions, such as extreme heat, cold or drought. The aim of this study was to investigate if pre-exposure to teflubenzuron (a common CSI) would influence Folsomia candida's (Collembola: Isotomidae) sensitivity to natural stressors. Here, we exposed adult collembolans to teflubenzuron through food for two weeks, then survivors were immediately divided into three groups for subsequent acute heat, cold, and drought exposure. After acute exposure to these natural stressors, the collembolans were moved to optimal conditions for a one-week recovery period during which their survival, time to regain reproduction, and egg production were examined. We analyzed the interaction between effects of teflubenzuron and natural stressors using a multiplicative model. No interaction between effects of teflubenzuron and heat was observed in any test endpoints. A synergistic interaction between effects of teflubenzuron and cold was observed in the time to regain reproduction. Both survival and egg production, on the other hand, showed synergistic interaction between effects of teflubenzuron and drought, as well as a tendency for longer reproduction recovery times. Our results suggest that pre-exposure to teflubenzuron reduces drought tolerance in F. candida, while its impact on heat or cold tolerance is minor or absent. This study is among the first to explore the combined effects of CSI and natural stressors on soil arthropods, providing more insight on potential risks posed by such chemicals in the environment.

Thermal adaptation affects the temperature-dependent toxicity of the insecticide imidacloprid to soil invertebrates.

Terrestrial ectotherms are vulnerable to climate change since their biological rates depend on the ambient temperature. As temperature may interact with toxicant exposure, climate change may cause unpredictable responses to toxic stress. A population's thermal adaptation will impact its response to temperature change, but also to interactive effects from temperature and toxicants, but these effects are still not fully understood. Here, we assessed the combined effects of exposure to the insecticide imidacloprid across the temperatures 10-25 °C of two populations of the Collembola Hypogastrura viatica (Tullberg, 1872), by determining their responses in multiple life history traits. The con-specific populations differ considerably in thermal adaptations; one (arctic) is a temperature generalist, while the other (temperate) is a warm-adapted specialist. For both populations, the sub-lethal concentrations of imidacloprid became lethal with increasing temperature. Although the thermal maximum is higher for the warm-adapted population, the reduction in survival was stronger. Growth was reduced by imidacloprid in a temperature-dependent manner, but only at the adult life stage. The decrease in adult body size combined with the absence of an effect on the age at first reproduction suggests a selection on the timing of maturation. Egg production was reduced by imidacloprid in both populations, but the negative effect was only dependent on temperature in the warm-adapted population, with no effect at 10 °C, and decreases of 41 % at 15 °C, and 74 % at 20 °C. For several key traits, the population best adapted to utilize high temperatures was also the most sensitive to toxic stress at higher temperatures. It could be that by allocating more energy to faster growth, development, and reproduction at higher temperatures, the population had less energy for maintenance, making it more sensitive to toxic stress. Our findings demonstrate the need to take into account a population's thermal adaptation when assessing the interactive effects between temperature and other stressors.

Toxicity mechanisms of plastic nanoparticles in three terrestrial species: antioxidant system imbalance and neurotoxicity.

The detrimental impacts of plastic nanoparticles (PNPs) are a worldwide concern, although knowledge is still limited, in particular for soil mesofauna. This study investigates the biochemical impact of 44 nm polystyrene PNPs on three soil models-Enchytraeus crypticus (Oligochaeta), Folsomia candida (Collembola) and Porcellionides pruinosus (Isopoda). Exposure durations of 3, 7 and 14 days (d) were implemented at two concentrations (1.5 and 300 mg kg-1 PNPs). Results revealed PNPs impact on the activities of the glutathione-dependent antioxidative enzyme, glutathione S-transferase (GST) and on the neurotransmitter acetylcholinesterase (AChE) for all three species. Catalase (CAT) played a minor role, primarily evident in F. candida at 300 mg kg-1 PNPs (CAT and GST response after 14 d), with no lipid peroxidation (LPO) increase. Even with the antioxidant defence, P. pruinosus was the most sensitive species for lipid oxidative damage (LPO levels increased after 7 d exposure to 300 mg kg-1 PNPs). Significant AChE inhibitions were measured already after 3 d to both PNP concentrations in F. candida and E. crypticus, respectively. Significant AChE inhibitions were also found in P. pruinosus but later (7 d). Overall, the toxicity mechanisms of PNPs involved antioxidant imbalance, being (mostly) the glutathione-associated metabolism part of that defence system. Neurotoxicity, linked to AChE activities, was evident across all species. Sensitivity to PNPs varied: P. pruinosus > F. candida ≅ E. crypticus. This pioneering study on PNPs toxicity in soil invertebrates underscores its environmental relevance, shedding light on altered biochemical responses, that may compromise ecological roles and soil ecosystem fitness.

Exploring the Relationship Among Lipid Profile Changes, Growth, and Reproduction in Folsomia candida Exposed to Teflubenzuron Over Time.

The integration of untargeted lipidomics approaches in ecotoxicology has emerged as a strategy to enhance the comprehensiveness of environmental risk assessment. Although current toxicity tests with soil microarthropods focus on species performance, that is, growth, reproduction, and survival, understanding the mechanisms of toxicity across all levels of biological organization, from molecule to community is essential for informed decision-making. Our study focused on the impacts of sublethal concentrations of the insecticide teflubenzuron on the springtail Folsomia candida. Untargeted lipidomics was applied to link changes in growth, reproduction, and the overall stress response with lipid profile changes over various exposure durations. The accumulation of teflubenzuron in organisms exposed to the highest test concentration (0.035 mg a.s. kg-1 soil dry wt) significantly impacted reproductive output without compromising growth. The results suggested a resource allocation shift from reproduction to size maintenance. This hypothesis was supported by lipid shifts on day 7, at which point reductions in triacylglycerol and diacylglycerol content corresponded with decreased offspring production on day 21. The hypermetabolism of fatty acids and N-acylethanolamines on days 2 and 7 of exposure indicated oxidative stress and inflammation in the animals in response to teflubenzuron bioaccumulation, as measured using high-performance liquid chromatography-tandem mass spectrometry. Overall, the changes in lipid profiles in comparison with phenotypic adverse outcomes highlight the potential of lipid analysis as an early-warning tool for reproductive disturbances caused by pesticides in F. candida. Environ Toxicol Chem 2024;43:1149-1160. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Chronic Effects of an Insect Growth Regulator (teflubenzuron) on the Life Cycle and Population Growth Rate of Folsomia candida.

Current standard toxicity tests on nontarget soil invertebrates mainly focus on the endpoints survival and reproduction. Such results are likely insufficient to predict effects at higher organizational levels, for example, the population level. We assessed the effects of exposure to the pesticide teflubenzuron on the collembolan Folsomia candida, by performing a full life-cycle experiment exposing single individuals via contaminated food (uncontaminated control and 0.2, 0.32, 0.48, 0.72, 1.08, and 1.6 mg/kg dry yeast). Several life-history traits were considered by following the growth and development of newly hatched individuals over a period of 65 days. We assessed survival, body length, time to first oviposition, cumulative egg production, and hatchability of eggs. A two-stage model was applied to calculate the population growth rate (λ) combined with elasticity analysis to reveal the relative sensitivity of λ to the effects of teflubenzuron on each life-history parameter. Body length was the least sensitive life-history parameter (median effective concentration = 1.10 mg teflubenzuron/kg dry yeast) followed by time to first oviposition (0.96 mg/kg), survival (median lethal concentration = 0.87 mg/kg), cumulative egg production (0.32 mg/kg), and egg hatchability (0.27 mg/kg). Population growth decreased with increasing concentrations of teflubenzuron (λ = 1.162/day in control to 1.005/day in 0.72 mg/kg dry yeast, with populations going extinct at 1.08 and 1.6 mg/kg dry yeast). Elasticity analysis showed that changes in juvenile survival had a greater impact on the population growth rate compared with the other life-history traits. Our study provides a comprehensive overview of individual-level effects of long-term exposure to teflubenzuron and integrates these effects to assess the potential risk to collembolan populations. Environ Toxicol Chem 2024;43:1173-1183. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Biotic Ligand Modeling for the Effect of Major Cations on the Uptake of Cadmium in Folsomia candida Exposed in a Sand-Solution Medium.

Biotic ligand modeling (BLM) approaches are already applied to predict the bioavailability and possible risk of metals in surface water, but need further development for soils. The present study investigated the effect of major cations (Ca2+, Mg2+, Na+, K+, and H+) on cadmium bioaccumulation in the springtail Folsomia candida. To avoid the complexity of real soils and enable control of elemental speciation in the exposure medium, the animals were exposed to different cadmium concentrations in an inert quartz sand-solution medium. Accumulation of cadmium in the animals was measured after 7 days exposure at different cation concentrations. Among the cations, only Ca2+ significantly affected the uptake of cadmium in the springtails. Mg2+ also had higher effects compared with other selected cations. Using a BLM approach, the uptake of cadmium in the animals predicted by taking into account both Ca2+ and Mg2+ activities correlated well with the measured values (R2 = 0.68). The final estimated conditional binding constants for cadmium (log KCd-BL), Ca (log KCa-BL), and Mg (log KMg-BL) of 1.06, 2.14, and 1.23 L/mol, respectively, were in agreement with previously reported values. The match between predicted and measured uptake data confirms the applicability and usefulness of the BLM for predicting the bioavailability of cadmium to springtails and opens the way for its application in soil. Environ Toxicol Chem 2024;43:1090-1096. © 2024 SETAC.

Diatomaceous Earth for Arthropod Pest Control: Back to the Future.

Nowadays, we are tackling various issues related to the overuse of synthetic insecticides. Growing concerns about biodiversity, animal and human welfare, and food security are pushing agriculture toward a more sustainable approach, and research is moving in this direction, looking for environmentally friendly alternatives to be adopted in Integrated Pest Management (IPM) protocols. In this regard, inert dusts, especially diatomaceous earths (DEs), hold a significant promise to prevent and control a wide range of arthropod pests. DEs are a type of naturally occurring soft siliceous sedimentary rock, consisting of the fossilized exoskeleton of unicellular algae, which are called diatoms. Mainly adopted for the control of stored product pests, DEs have found also their use against some household insects living in a dry environment, such as bed bugs, or insects of agricultural interest. In this article, we reported a comprehensive review of the use of DEs against different arthropod pest taxa, such as Acarina, Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera, Ixodida, Lepidoptera, when applied either alone or in combination with other techniques. The mechanisms of action of DEs, their real-world applications, and challenges related to their adoption in IPM programs are critically reported.

In vitro acaricidal activity of essential oil and crude extracts of Laurus nobilis, (Lauraceae) grown in Tunisia, against arthropod ectoparasites of livestock and poultry: Hyalomma scupense and Dermanyssus gallinae.

The current study assayed the toxicity of Laurus nobilis essential oil and crude extracts obtained using solvents of increasing polarity (cyclohexane, acetone and ethanol), on two ectoparasites of veterinary importance, i.e., Hyalomma scupense and Dermanyssus gallinae. The major components detected in bay laurel essential oil were dominated by 1.8-cineole (46.56 %), α-terpinenyl acetate (13.99 %), sabinene (7.69), α-pinene (5.75), linalool (5.50), methyleugenol (5.36 %) and ß-pinene (3.97). The highest total phenolic and flavonoids contents were present in the ethalonic extract of L. nobilis leaves at an amount of 152.88 mg gallic acid equivalents per gram of dry weight (GAE/g DW) and 21.77 mg quercetin equivalent per gram of dry weight (QE/g DW), respectively. In vitro acaricidal effects of essensial oil and crude extract of L. nobilis against H. scupense were ascertained by adult immersion test of engorged females (AIT) and larval packet test (LPT) compared with a reference drug amitraz. The essential oil exhibited strong acaricidal activity against tick engorged female and inhibition of hatching eggs. After 24 h of exposure, at the highest tested concentration (100 mg/mL) essential oil induced 90.67 % mortality of H. scupense larvae (LC50 = 10.69 mg/mL). Otherwise, essential oil exhibited high acaricidal activity compared to extracts, and among the extract, the ethanolic extract revealed the highest acaricidal efficacy (81.27 % female mortality). Results from mite contact toxicity showed that essential oil and extracts from L. nobilis were toxic to D. gallinae. Bay essential oil was both more toxic to mites, and faster in exerting this toxicity than other tested crude extracts. L. nobilis essential oil concentration leaded to enhance mortality of D. gallinae reaching the highest (100 %) mortality at 12 h with a concentration of 320 mg/mL. While, ethanolic extract acheived this rate after 24 h of exposure at same concentration. Cyclohexanic extract showed weak acaricidal activity.

Beauvericin potentiates the activity of pesticides by neutralizing the ATP-binding cassette transporters in arthropods.

Multi-drug resistance is posing major challenges in suppressing the population of pests. Many herbivores develop resistance, causing a prolonged survival after exposure to a previously effective pesticide. Consequently, resistant pests reduce the yield of agricultural production, causing significant economic losses and reducing food security. Therefore, overpowering resistance acquisition of crop pests is a must. The ATP binding cassette transporters (ABC transporters) are considered as the main participants to the pesticide efflux and their neutralization will greatly contribute to potentiate failed treatments. Real-Time PCR analysis of 19 ABC transporter genes belonging to the ABCB, ABCC, ABCG, and ABCH revealed that a broad range of efflux pumps is activated in response to the exposure to pesticides. In this study, we used beauvericin (BEA), a known ABC transporters modulator, to resensitize different strains of Tetranychus urticae after artificial selection for resistance to cyflumetofen, bifenazate, and abamectin. Our results showed that the combinatorial treatment of pesticide (manufacturer's recommended doses) + BEA (sublethal doses: 0.15 mg/L) significantly suppressed the resistant populations of T. urticae when compared to single-drug treatments. Moreover, after selective pressure for 40 generations, the LC50 values were significantly reduced from 36.5, 44.7, and 94.5 (pesticide) to 8.3, 12.5, and 23.4 (pesticide + BEA) for cyflumetofen, bifenazate, and abamectin, respectively. While the downstream targets for BEA are still elusive, we demonstrated hereby that it synergizes with sub-lethal doses of different pesticides and increases their effect by inhibiting ABC transporters. This is the first report to document such combinatorial activity of BEA against higher invertebrates paving the way for its usage in treating refractory cases of resistance to pesticides. Moreover, we demonstrated, for the first time, using in silico techniques, the higher affinity of BEA to ABC transformers subfamilies when compared to xenobiotics; thus, elucidating the pathway of the mycotoxin.

Assessing single effects of sugarcane pesticides fipronil and 2,4-D on plants and soil organisms.

The continuous growth in global population since the beginning of the 20th century result in the necessity of food and energy provision favoring the intensive use of agricultural products such as pesticides. Although pesticides are important to prevent losses in the conventional chemically based agriculture, they frequently present side effects, which goes against agricultural production. The use of pesticides cause direct and indirect effects to soil organisms unbalancing essential soil processes (e.g. primary production, organic matter decomposition, nutrient cycling). Under tropical conditions, very little is known regarding the effects of pesticides to terrestrial organisms. Hence, the aim of the present study was to assess the ecotoxicological effects of the herbicide DMA® 806 BR (active ingredient: 2,4-D) and the insecticide Regent® 800 WG (active ingredient: fipronil), on terrestrial plant species (the dicot Raphanus sativus var. acanthioformis and the monocot Allium cepa), and soil invertebrates (the collembolan Folsomia candida and the enchytraeid Enchytraeus crypticus), using natural (NS) and artificial soils (TAS). For both pesticides, negative effects on non-target species were observed at concentrations lower than the doses recommended to prevent pests in sugarcane fields. For both soils, the dicot species was the most affected by the herbicide (R. sativus > A. cepa > F. candida > E. crypticus) and the collembolan species was the most affected by the insecticide (F. candida > E. crypticus = R. sativus = A. cepa). Although the order of the organisms' sensitivity for both pesticides was the same in both soils, results showed that the extent of the effects was soil dependent. Considering the ecologically relevant concentrations tested, and their severe effects to non-target organisms, it may be concluded that the use of fipronil and 2,4-D under recommended conditions may pose a risk to the terrestrial environment.

Effect of macrocyclic lactones on nontarget coprophilic organisms: a review.

Macrocyclic lactones are frequently used dewormers in livestock farms around the world. Due to their wide spectrum of action against nematodes and arthropods and their practicality of application at very low doses, their use has become massive since their discovery. These compounds are eliminated in a large percentage in the feces of animals, causing adverse effects on coprophilic fauna. Several research groups around the world have been devoted to evaluating these effects on this fauna. The aim of this review is to register the adverse effects of the concentrations in which macrocyclic lactones are eliminated in the feces of domestic animals and the importance of the coprophilic and edaphilous fauna on the degradation of the feces of the animals. The documented data shows that the use of macrocyclic lactones has a high toxicological risk for the different species that colonize the dung, thus causing an adverse effect on its disintegration and its subsequent incorporation into the soil. Even so, more studies at the regional level and their standardization are necessary to make the comparison between different areas possible.

Dynamics of canopy-dwelling arthropods under different weed management options, including glyphosate, in conventional and genetically modified insect-resistant maize.

The use of genetically modified varieties tolerant to herbicides (HT varieties) and resistant to insects (Bt varieties) in combination with application of a broad-spectrum herbicide such as glyphosate could be an effective option for the simultaneous control of weeds and pests in maize. Nevertheless, the possible impact of these tools on nontarget arthropods still needs to be evaluated. In a field study in central Spain, potential changes in populations of canopy-dwelling arthropods in Bt maize under different weed management options, including glyphosate application, were investigated. Canopy-dwelling arthropods were sampled by visual inspection and yellow sticky traps. The Bt variety had no effect on any group of studied arthropods, except for the expected case of corn borers-the target pests of Bt maize. Regarding the effects of herbicide regimes, the only observed difference was a lower abundance of Cicadellidae and Mymaridae on yellow sticky traps in plots not treated with pre-emergence herbicides. This effect was especially pronounced in a treatment involving two glyphosate applications. The decrease in Cicadellidae and Mymaridae populations was associated with a higher density of weeds in plots, which may have hindered colonization of the crop by leafhoppers. These differences, however, were only significant in the last year of the study. The low likelihood of the use of glyphosate- and herbicide-tolerant varieties for weed control triggering important effects on the nontarget arthropod fauna of the maize canopy is discussed.

Effects of Silver Nanoparticles and Ions Exposure on the Soil Invertebrates Folsomia candida and Enchytraeus crypticus.

The aim of the study was to assess the effects of silver nanoparticles (AgNPs1 = 2.7 d·nm, AgNPs2 = 6.5 d·nm) and silver nitrate (AgNO3) on Enchytraeus crypticus and Folsomia candida using toxicity tests (OECD Guideline 220, 232). A 28-day chronic toxicity study was performed to evaluate the reproduction and mortality rate. E. crypticus reproduction was more sensitive to AgNO3 with a 28dEC50 of 86.40 (62.52-119.4) mg·kg-1 dry weight (d.w.) compared to AgNPs1 (28dEC50 = 119.3 (60.4-235.6) mg·kg-1 d.w). Similarly, the reproduction of F. candida was inhibited the most by AgNO3 with a 28dEC50 of 126.2 (104.2-152.9) mg·kg-1 d.w. followed by AgNPs1 (28dEC50 = 158.7 (64.05-393.2) mg·kg-1 d.w.) and AgNPs2 (28dEC50 = 206.4 (181.9-234.1) mg·kg-1 d.w.). No mortalities were observed for tested soil invertebrates exposed to AgNPs at concentrations up to 166 mg·kg-1 d.w. of AgNPs1 and 300 mg·kg-1 d.w. of AgNPs2, respectively. It was found that silver ions are more toxic in comparison with AgNPs.