Search Results (50)

Azoxystrobin, a widely used strobilurin fungicide, poses a potential risk to aquatic ecosystems due to its frequent detection in surface waters. Although its toxicity to non-target organisms has been extensively studied under standardized conditions, few investigations have considered how environmental factors can modulate the adverse effects of this chemical. In this study, we examined the toxicity of azoxystrobin to zebrafish (Danio rerio) embryos under different pH (5, 7, 9) and temperature (21 °C, 26 °C, 31 °C) conditions. Embryos were exposed to azoxystrobin concentrations ranging from 0 to 1000 μg/L, and endpoints such as survival, hatching rate, heart rate, malformations, developmental delay, and Hsp70 expression were assessed over 96 h post-fertilization. Our results demonstrate that azoxystrobin induces significant malformations (including edema, eye, tail, and spinal defects) and developmental delays at 1000 μg/L across all environmental conditions. Furthermore, both pH and temperature were found to modulate azoxystrobin toxicity: elevated temperature and alkaline pH partly alleviated mortality at high concentrations. The hsp70 expression patterns revealed complex interactions between the effects of the chemical and environmental factors. These findings highlight the importance of incorporating environmental variables into ecotoxicological risk assessments of pesticides to better reflect realistic exposure scenarios and potential ecological impacts. Full article

Strobilurins are a prominent class of fungicides capable of entering aquatic environments via runoff and leaching from the soil. Findings from previous studies suggest that strobilurins are highly toxic in aquatic environments, and evidence of acute developmental toxicity and altered behavioral responses have been emphasized. The objective here was to determine the effects of a new strobilurin, metyltetraprole (MTP), on zebrafish using developmental endpoints, gene expression, and behavioral locomotor assays. We hypothesized that MTP would cause developmental toxicity and induce hyperactivity in zebrafish (Danio rerio). To test this, developing zebrafish embryos/larvae were exposed to environmentally relevant levels of MTP (0.1, 1, 10, and 100 µg/L) until 7 days post-fertilization. Survival percentages did not differ among the treatment groups. No change in reactive oxygen species production was detected, but two genes involved in the mitochondrial electron transport chain (mt-nd3 and uqcrc2) were altered in abundance following MTP exposure. Moreover, the highest concentration (100 µg/L) of MTP caused notable hyperactivity in the zebrafish in the visual motor response test. Overall, results from this study increase our knowledge regarding sub-lethal effects of MTP, helping inform risk assessment for aquatic environments. Full article

Cell-based test methods with a phenotypic readout are frequently used for toxicity screening. However, guidance on how to validate the hits and how to integrate this information with other data for purposes of risk assessment is missing. We present here such a procedure and exemplify it with a case study on neural crest cell (NCC)-based developmental toxicity of picoxystrobin. A library of potential environmental toxicants was screened in the UKN2 assay, which simultaneously measures migration and cytotoxicity in NCC. Several strobilurin fungicides, known as inhibitors of the mitochondrial respiratory chain complex III, emerged as specific hits. From these, picoxystrobin was chosen to exemplify a roadmap leading from cell-based testing towards toxicological predictions. Following a stringent confirmatory testing, an adverse outcome pathway was developed to provide a testable toxicity hypothesis. Mechanistic studies showed that the oxygen consumption rate was inhibited at sub-µM picoxystrobin concentrations after a 24 h pre-exposure. Migration was inhibited in the 100 nM range, under assay conditions forcing cells to rely on mitochondria. Biokinetic modeling was used to predict intracellular concentrations. Assuming an oral intake of picoxystrobin, consistent with the acceptable daily intake level, physiologically based kinetic modeling suggested that brain concentrations of 0.1–1 µM may be reached. Using this broad array of hazard and toxicokinetics data, we calculated a margin of exposure ≥ 80 between the lowest in vitro point of departure and the highest predicted tissue concentration. Thus, our study exemplifies a hit follow-up strategy and contributes to paving the way to next-generation risk assessment. Full article

Unlike many other fungicides, strobilurins are applied several times during the growing season for prophylactic purposes, thus heightening the risk of environmental contamination. In the EU, the dimoxystrobin approval period lasted for 17 years. It has been classified as moderately toxic to birds and highly toxic to earthworms, and it is suspected to be carcinogenic to humans. However, it is still commercialized in several countries. The effects of dimoxystrobin are still largely underexplored, with only three studies reporting sublethal alterations in fish. Here, we evaluated for the first time the effects of dimoxystrobin on zebrafish liver after short-term exposure (96 h) to two sublethal and environmentally relevant concentrations (6.56 and 13.13 μg/L), providing evidence of morphological, functional, and ultrastructural modifications. We revealed severe alterations encompassing three reaction patterns: circulatory disturbance, regressive and progressive changes, which also showed a dose-dependent trend. Furthermore, we revealed that dimoxystrobin induced a significant increase in lipid content, a decrease in glycogen granules and affected the defensive response against oxidative stress through a significant downregulation of SOD and CAT. The information presented here demonstrates that the hazardous properties of dimoxystrobin may result from several pathological events involving multiple targets. Our results also emphasize the importance of the combined use of morphological, ultrastructural and functional investigation in ecotoxicological studies. Full article

Honeybee larvae and pupae form the cornerstone of colony survival, development, and reproduction. Azoxystrobin is an effective strobilurin fungicide that is applied during the flowering stage for controlling plant pathogens. The contaminated nectar and pollen resulting from its application are collected by forager bees and impact the health of honeybee larvae and pupae. The current study evaluated the survival, development, and physiological effects of azoxystrobin exposure on the larvae and pupae of Apis mellifera worker bees. The field-recommended concentrations of azoxystrobin were found to suppress the survival indices and lifespan in the larval as well as pupal stages; moreover, the rates of the survival and pupation of larvae as well as the body weights of the pupae and newly-emerged adult bees were significantly reduced upon long-term exposure to azoxystrobin. In addition, azoxystrobin ingestion induced changes in the expression of genes critical for the development, immunity, and nutrient metabolism of larvae and pupae, although the expression profile of these genes differed between the larval and pupal stages. Results indicated the chronic toxicity of azoxystrobin on the growth and development of honeybee larvae and pupae, which would affect their sensitivity to pathogens and other external stresses during the development stage and the study will provide vital information regarding the pollination safety and rational use of pesticides. Full article

In Brazil, coffee leaf rust (CLR), caused by the fungus Hemileia vastatrix, was first detected in Coffea arabica in January of 1970 in southern Bahia. Now widespread across all cultivation areas, the disease poses a significant threat to coffee production, causing losses of 30–50%. In this context, the objective of this study was to identify and quantify the different classes of occurrence of CLR in areas apt and restricted to the cultivation of Arabica coffee in Brazil for a more informed decision regarding the cultivar to be implanted. The areas of climatic aptitude for Arabica coffee were defined, and then, the climatic favorability for the occurrence of CLR in these areas was evaluated based on climatic data from TerraClimate from 1992 to 2021. The apt areas, apt with some type of irrigation, restricted, and with some type of restriction for the cultivation of Arabica coffee add up to 16.34% of the Brazilian territory. Within this 16.34% of the area of the Brazilian territory, the class of climatic favorability for the occurrence of CLR with greater representation is the favorable one. Currently, the disease is controlled with the use of protective and systemic fungicides, including copper, triazoles, and strobilurins, which must be applied following decision rules that vary according to the risk scenario, and according to the use of resistant cultivars. This study provides a basis for choosing the most suitable cultivars for each region based on the degree of CLR resistance. Full article

Due to their multi-purpose use and, in many cases, lower requirements and financial outlays for cultivation, oats are an interesting crop. However, fungal diseases may contribute to significant declines in grain yields and quality. The aspects that may potentially influence this matter of fact include weather conditions. The aim of the study was to determine the severity of diseases caused by fungi in oat cultivation during the vegetation season. The next goal was to assess the efficacy of the selected active ingredients (a.i.) of fungicides from the chemical groups of triazoles and strobilurins in selected diseases’ control under various meteorological conditions. All of the fungicides were applied in the form of a spray treatment to reduce the severity of the diseases in the cultivation of different oat varieties. Husked and naked oat varieties were used. The health status of the oat plants was determined on the basis of a macroscopic evaluation of plants performed in accordance with the proper methodology. Field experiments were carried out under different weather conditions, which varied over the years during which the trials were conducted. Statistically significant differences were found in the reduction in infection for F and F1 leaves with D. avenae and P. coronata in comparison to the control treatment, regardless of the a.i. used. The use of a.i. tebuconazole (250 g/L), a.i. epoxiconazole (125 g/L), a.i. azoxystrobin (250 g/L) and a.i. picoxystrobin (250 g/L) enabled a reduction in the severity of oat helmintosporiosis in all years of the study for all the varieties analyzed. The efficacy was 72.4%, 74.2%, 71.5%, and 73.1%, respectively. Higher efficacy in reducing P. coronata was found in comparison with D. avenae. The obtained research results confirm the satisfactory efficacy of the above-mentioned active substances in reducing the fungi D. avenae and P. coronata. Full article

The causal agent of tomato leaf mold, Cladosporium fulvum, is prevalent in greenhouses worldwide, especially under high humidity conditions. Despite its economic impact, studies on antifungal agents targeting C. fulvum remain limited. This study evaluates biocontrol agents (BCAs) as alternatives to chemical controls for managing this disease, alongside the strobilurin fungicide azoxystrobin. From a Moroccan collection of potential BCAs, five bacterial isolates (Alcaligenes faecalis ACBC1, Pantoea agglomerans ACBC2, ACBP1, ACBP2, and Bacillus amyloliquefaciens SF14) and three fungal isolates (Trichoderma spp. OT1, AT2, and BT3) were selected and tested. The in vitro results demonstrated that P. agglomerans isolates reduced mycelial growth by over 60% at 12 days post-inoculation (dpi), while Trichoderma isolates achieved 100% inhibition in just 5 dpi. All bacterial isolates produced volatile organic compounds (VOCs) with mycelial inhibition rates ranging from 38.8% to 57.4%. Likewise, bacterial cell-free filtrates significantly inhibited the pathogen’s mycelial growth. Greenhouse tests validated these findings, showing that all the tested isolates were effective in reducing disease incidence and severity. Azoxystrobin effectively impeded C. fulvum growth, particularly in protective treatments. Fourier transform infrared spectroscopy (FTIR) analysis revealed significant biochemical changes in the treated plants, indicating fungal activity. This study provides valuable insights into the efficacy of these BCAs and azoxystrobin, contributing to integrated management strategies for tomato leaf mold disease. Full article

Pseudostellaria heterophylla (or Taizishen in Chinese), a medicinal, edible, and ornamental Chinese herb, is seriously affected by leaf spot disease (LSD). Oligochitosan is a natural agricultural antibiotic that is produced via the degradation of chitosan, which is deacetylated from chitin; pyraclostrobin is a broad-spectrum and efficient strobilurin fungicide. In this work, the ability of pyraclostrobin, oligochitosan, and their formula to manage P. heterophylla leaf spot disease and their role in its resistance, leaf photosynthesis, agronomic plant traits, root growth, and root quality were studied. The results show that the joint application of oligochitosan and low-dosage pyraclostrobin could control LSD more efficiently, with control effects of 85.75–87.49% compared to high-dosage pyraclostrobin or oligochitosan alone. Concurrently, the application of this formula could more effectively improve the resistance, leaf photosynthesis, agronomic plant traits, root yield, and medicinal quality of P. heterophylla, as well as reduce the application of pyraclostrobin. This finding suggests that 30% pyraclostrobin suspension concentrate (SC) 1500-time + 5% oligosaccharin aqueous solutions (AS) 500-time diluent can be recommended for use as a feasible formula to manage LSD and reduce the application of chemical pesticides. Full article

The use of strobilurin fungicides in agriculture has increased steadily during the past 25 years, and although strobilurins have minimal water solubility, they regularly appear in surface waters, at times in concentrations approaching toxic levels for aquatic life. The present study examined concentrations of strobilurin fungicides in designated trout streams draining an agricultural watershed in southeastern Minnesota, USA, where fungicides may have contributed to a recent fish kill. Water samples (n = 131) were analyzed for the presence of five different strobilurin fungicides (azoxystrobin, fluoxastrobin, picoxystrobin, pyraclostrobin, trifloxystrobin). Samples were collected via grab and automated sampling during baseflow and stormflow events throughout an entire crop-growing season from sites on each of the three forks of the Whitewater River. Detection frequencies for the five strobilurins ranged from 44 to 82%. Fluoxastrobin and pyraclostrobin concentrations were above known toxic levels in 3% and 15% of total samples analyzed, respectively. The highest concentrations were detected in mid-summer (mid-June to mid-August) samples, coincident with likely strobilurin applications. Lower concentrations were present in water samples collected during the nonapplication periods in spring and fall, suggesting groundwater–stream interactions or steady leaching of fungicides from watershed soils or stream sediments. Further study is required to determine strobilurin concentrations in sediments, soils, and groundwater. Better tracking and guidance regarding strobilurin use is necessary to adequately protect aquatic life as fungicide use continues to increase. Full article

Melipona scutellaris is a Brazilian stingless bee that is important for pollinating wild flora and agriculture crops. Fungicides have been widely used in agriculture, and floral residues can affect forager bees. The goal of our study was to evaluate the effects of sublethal concentrations of pyraclostrobin on the midgut ultrastructure of M. scutellaris forager workers. The bees were collected from three non-parental colonies and kept under laboratory conditions. The bees were orally exposed continuously for five days to pyraclostrobin in syrup at concentrations of 0.125 ng a.i./µL (FG1) and 0.005 ng a.i./µL (FG2). The control bees (CTL) were fed a no-fungicide sucrose solution, and the acetone solvent control bees (CAC) received a sucrose solution containing acetone. At the end of the exposure, the midguts were sampled, fixed in Karnovsky solution, and routinely processed for transmission electron microscopy. Ultrastructural analysis demonstrated that both the fungicide concentrations altered the midgut, such as cytoplasmic vacuolization (more intense in FG1), the presence of an atypical nuclear morphology, and slightly dilated mitochondrial cristae in the bees from the FG1 and FG2 groups (both more intense in FG1). Additionally, there was an alteration in the ultrastructure of the spherocrystals (FG1), which could be the result of cellular metabolism impairment and the excretion of toxic metabolites in the digestive cells as a response to fungicide exposure. The results indicate that ingested pyraclostrobin induced cytotoxic effects in the midgut of native stingless bees. These cellular ultrastructural responses of the midgut are a prelude to a reduced survival rate, as observed in previous studies. Full article

Fungicides are widely used in agriculture for crop protection. Succinate dehydrogenase inhibitors (SDHIs) and strobilurins inhibit mitochondria electron transport chain (ETC) in fungi, by blocking complex II and complex III, respectively. Questions regarding their selectivity of action for fungi have been raised in the literature, and we previously showed that boscalid and bixafen (SDHIs) alter the mitochondrial function of human hepatocytes. Here, we analyzed the impact of the exposure of human hepatocytes to pyraclostrobin, a fungicide belonging to the class of strobilurins. Using electron paramagnetic resonance (EPR), we observed a decrease in oxygen consumption rate (OCR) and an increase in mitochondrial superoxide levels after 24 h exposure to 0.5 µM concentration. As a consequence, the content in ATP amount in the cells was reduced, the ratio reduced/oxidized glutathione was decreased, and a decrease in cell viability was observed using three different assays (PrestoBlue, crystal violet, and annexin V assays). In addition, as SDHIs and strobilurins are commonly associated in commercial preparations, we evaluated a potential “cocktail” toxic effect. We selected low concentrations of boscalid (0.5 µM) and pyraclostrobin (0.25 µM) that did not induce a mitochondrial dysfunction in liver cells when used separately. In sharp contrast, when both compounds were used in combination at the same concentration, we observed a decrease in OCR, an increase in mitochondrial superoxide production, a decrease in the ratio reduced/oxidized glutathione, and a decrease in cell viability in three different assays. Full article

Fungi represents a rich repository of taxonomically restricted, yet chemically diverse, secondary metabolites that are synthesised via specific metabolic pathways. An enzyme’s specificity and biosynthetic gene clustering are the bottleneck of secondary metabolite evolution. Trichoderma harzianum M10 v1.0 produces many pharmaceutically important molecules; however, their specific biosynthetic pathways remain uncharacterised. Our genomic-based analysis of this species reveals the biosynthetic diversity of its specialised secondary metabolites, where over 50 BGCs were predicted, most of which were listed as polyketide-like compounds associated clusters. Gene annotation of the biosynthetic candidate genes predicted the production of many medically/industrially important compounds including enterobactin, gramicidin, lovastatin, HC-toxin, tyrocidine, equisetin, erythronolide, strobilurin, asperfuranone, cirtinine, protoilludene, germacrene, and epi-isozizaene. Revealing the biogenetic background of these natural molecules is a step forward towards the expansion of their chemical diversification via engineering their biosynthetic genes heterologously, and the identification of their role in the interaction between this fungus and its biotic/abiotic conditions as well as its role as bio-fungicide. Full article

Despite the major role of non-chemical treatments in integrated plant protection, fungicides often need to be applied as a crop protection treatment in sugar beet farming. They should be used based on a good understanding of the requirements and effectiveness of the active ingredients. In 11-year field experiments, the effect that one and three foliar applications of fungicides containing various active ingredients (triazoles, benzimidazoles, strobilurines) had on sugar beet root yields was assessed, depending on various thermal and rainfall conditions. It was found that in eight of the 11 years, foliar application of fungicides increased yields compared to unprotected plants, and three foliar treatments during the growing season were more effective than a single application. The negative correlation of the root yield of fungicidally protected plants with total June rainfall was weaker than the same relationship for unprotected plants. At the same time, the positive correlation between the yield of fungicidally protected sugar beets and average June air temperature was stronger than the same relationship for unprotected plants. The research results indicate the need to conduct long-term field experiments and to continuously improve integrated production principles for sugar beet, especially regarding the rational use of pesticides. Full article

Soybean is a widespread crop in semi-arid regions of China, where soil salinity often increases and has a significant harmful impact on production, which will be a huge challenge in the coming years. Salicylic acid (SA) and pyraclostrobin are strobilurin-based bactericides (PBF). Under rainfall-harvesting conditions in covered ridges, the exogenous application of SA and PBF can improve the growth performance of soybeans, thereby reducing the adverse effects of soil salinity. The objectives of this research are to evaluate the potential effects of SA and PBF on soybean growth in two different regions, Harbin and Daqing. A two-year study was performed with the following four treatments: HCK: Harbin location with control; SA1+PBF1: salicylic acid (5 mL L⁻¹) with pyraclostrobin (3 mL L⁻¹); SA2+PBF2: salicylic acid (10 mL L⁻¹) with pyraclostrobin (6 mL L⁻¹); DCK: Daqing location with control. The results showed that in the Harbin region, SA2+PBF2 treatment reduced the evapotranspiration (ET) rate, increased soil water storage (SWS) during branching and flowering stages, and achieved a maximum photosynthesis rate. Moreover, this improvement is due to the reduction of MDA and oxidative damage in soybean at various growth stages. At different growth stages, the treatment of Harbin soybean with SA2+PBF2 significantly increased the activity of CAT, POD, SOD, and SP, while the content of MDA, H₂O₂, and O₂⁻ also decreased significantly. In the treatment of SA2+PBF2 in Harbin, the scavenging ability of free H₂O₂ and O₂⁻ was higher, and the activity of antioxidant enzymes was better. This was due to a worse level of lipid-peroxidation which successfully protected the photosynthesis mechanism and considerably increased water use efficiency (WUE) (46.3%) and grain yield (57.5%). Therefore, using plastic mulch with SA2+PBF2 treatment can be an effective water-saving management strategy, improving anti-oxidant enzyme activities, photosynthesis, and soybean production. Full article