Single Pesticide Research Articles

Reaction pathways, kinetics and toxicity assessment during the photocatalytic degradation of glyphosate and myclobutanil pesticides: Influence of the aqueous matrix

Assessment of reaction pathways, kinetics and water toxicity during the photocatalytic degradation of glyphosate and myclobutanil pesticides has been performed in different aqueous matrices of increasing complexity, from the single pesticides to the mix of their commercial formulations. Using Aeroxide® TiO2-P25 as reference UV-A (Ultraviolet A) light photocatalyst, the ability of photocatalysis to degrade glyphosate and myclobutanil pesticides in water was evidenced independently of the aqueous matrix complexity, complete mineralization into CO2, phosphate and chloride ions being achieved. Further, an unusual volcano-like TOC evolution profile resulting from the proposed glyphosate degradation pathway was observed whatever the aqueous matrix. Increasing the water matrix complexity from single pesticides to the commercial formulation mix reduced the degradation kinetics and consequently extended the time necessary for complete mineralization but, did not influence the overall pesticide fate profiles. This behavior was associated to the competitive adsorption of the organic matter onto the catalyst and to the presence of ions and inorganic matter. The co-presence of glyphosate and to lesser extent of Roundup® formulation additives strongly impacted the myclobutanil fate profile, due to preferential adsorption/degradation of glyphosate. By contrast, despite the impact in the degradation pathway, the inorganic additives of the Systhane® formulation influenced less both the myclobutanil removal duration and the TOC removal than the glyphosate pesticide and its organic additives from Roundup® do. The treatment allowed for most of the cases a strong reduction of acute toxicity to aquatic invertebrate test organisms (D. magna) whatever the water matrix complexity, while the ecotoxicity was reduced by half for the complex formulation mix.

The association between estimated dietary pesticide residue risk index and mortality in a population-based cohort

TPS 633: Health effects of pesticides, Johan Friso Foyer, Floor 1, August 27, 2019, 3:00 PM - 4:30 PM Background/Aim: Pesticides residues are regularly detected in foods and there is a concern that this might pose a risk to the consumer, but epidemiological evidence is almost lacking. The aim of the present study was to assess the association between dietary exposure to pesticide residues and mortality in a large population-based prospective cohort of women and men. Methods: Food consumption was assessed through a 96-item food frequency questionnaire (FFQ) at baseline (1997) in 69,498 participants (36,546 men and 32,952 women), aged 45–83 years. The pesticide residues measured 1996-1998 in foods on the Swedish market (fruits, vegetables and cereals) were obtained via the monitoring program at the National Food Agency. For each food item, we summed the ratios of each single pesticide residue concentration / acceptable daily intake present in that food, accounting for edible parts and cooking preparations. A pesticide residue risk index was then estimated based on the FFQ for each participant. Multivariable-adjusted hazard ratios (HR) with 95% confidence intervals (CI), were estimated using Cox regression. Results: A total of 16,776 deaths occurred throughout 2014 of which 5,421 were caused by cancer and 6,338 by cardiovascular disease (CVD). Comparing extreme quartiles, the highest category of the dietary pesticide residue risk index, after confounding adjustments – including the Mediterranean diet score, was not associated with cancer mortality in women, HR, 0.90 (95% CI, 0.79-1.02); while an inverse association was observed among men, 0.85 (0.77-0.98). The corresponding results for CVD mortality were HRs, 0.86 (95% CI, 0.77-0.96) and 0.85 (95% CI, 0.77-0.94), respectively. Conclusions: We observed no indications that exposure to pesticide residues was associated with increased mortality. The beneficial effect of plant food consumption seems to override any potential negative consequences related to pesticide residues at the exposure levels present during the study period.

Resistance to a chemical pesticide increases vulnerability to a biopesticide: Effects on direct mortality and mortality by predation

Pesticide mixtures are increasingly used to fight pest species that developed resistance to pesticides. To assess the pesticide control efficiency and to reduce ecological damage to non-target species, it is important to quantify the effect of these mixtures and compare them with the effect of their single pesticides on pest species, non-target species and their predator-prey interactions. We studied the effects of the chemical pesticide chlorpyrifos (CPF), the biopesticide Bacillus thuringiensis israelensis (Bti) and their mixture both on the direct mortality and on the mortality by predation. We focused on larvae of a CPF-resistant and a non-resistant strain of the vector mosquito Culex quinquefasciatus and its predator, the pygmy backswimmer Plea minutissima. In the CPF-Bti mixture, both pesticides interacted antagonistically for direct mortality. Exposure to the mixture caused equal direct mortality and equal mortality by predation in both strains. As expected, exposure to CPF resulted in less direct mortality and less mortality by predation in the CPF-resistant mosquito strain compared to the non-resistant strain. Notably, Bti caused a higher mortality in the mosquito larvae of the CPF-resistant strain compared to the non-resistant strain. Furthermore, the predator killed more mosquito larvae of the resistant strain compared to the non-resistant strain when exposed before to Bti alone. These observations identify a novel cost of resistance to a chemical pesticide in terms of increased vulnerability to a biopesticide.

Persistence and processing effects in reduction of residues of β-cyfluthrin + imidacloprid and its metabolite in hot pepper

ABSTRACT Now a days, farmers prefer to use Premix Formulations instead of single pesticide for the control of insects and pests. Large number of premix formulations are available in the market, Solomom OD (β-cyfluthrin 90 + imidacloprid 210) is the preferred one in hot pepper. Thus, the present research was done to monitor the leftover and effect of household processing in reduction of premix formulation with its toxic metabolites in hot pepper. Quantification of leftovers in hot pepper fruits was done by using two analytical instruments viz., gas chromatography-tandem mass spectrometry (GC-MSMS) in SCAN/MRM mode with a triple Quadrupole analyser and high-performance liquid chromatography (HPLC) using diode array detector. The limit of quantification (LOQ) for β-cyfluthrin was 0.05 mg kg−1, and for imidacloprid and its metabolite 6-chloronicotinic acid (6-CNA) was 0.01 mg kg−1, respectively. Based on Maximum Residue Limit (MRL) value by Food Safety and Standard Authority of India (FSSAI), the safe waiting period suggested was 3rd day for β-cyfluthrin and 1st day for imidacloprid. Residues of β-cyfluthrin and imidacloprid were persisted up to 7 days in proposed dose (PD) and 10 days in double the proposed dose (DPD) after final spray. No residues of 6-CNA were detected in hot pepper at any stage. Frying after washing was found effective in decreasing the residues when compared to washing alone with plain water. Imidacloprid shows more per cent reduction (87.75–91.49%) in frying after washing when compared to β-cyfluthrin (76.29–84.01%). Red hot pepper and soil collected at 30 days (harvest time) after final spray were found free from pesticide contamination at all test doses.

Effects of organophosphate pesticides on siderophore producing soils microorganisms

Abstract The aim of the current study was to evaluate the effects of four organophosphate pesticides on the siderophores producing soil microorganisms or plant growth promoting rhizobacteria (PGPR). Individual effects of acephate, glyphosate, monocrotophos and phorate as well as in combinations of two were tested against the five siderophore producing soils microorganisms viz, Pseudomonas fluorescens (NCIM-5096), Rhizobium leguminosarum (NCIM-2749), Bacillus brevis (NCIM-2532), Azotobacter vinelandii (NCIM-2821), and Salmonella typhimurium (NCIM-2501). The dose dependent effect was observed for the siderophore production assay. The effects of combinations were found to be more significant as compared to single pesticide(s). The overall sequence of adverse effect of the four pesticides on the siderophore production observed was: phorate > acephate > monocrotophos > glyphosate which was linear with the toxicity of pesticides. Further, it was noticed that PGPR strain Pseudomonas fluorescens (13–66%) was the least affected by the pesticides under study and Salmonella typhimurium (20–75%) was the most affected PGPR strain. The overall order of adverse effect of pesticides on the PGPR strains was as: Bacillus brevis (19–80%) > Salmonella typhimurium (20–75%) > Rhizobium leguminosarum (21–72%) > Azotobacter vinelandii (22–81%) > Pseudomonas fluorescens (13–66%). In combination, applications of Acpt + Phor have shown more adverse effects as compared to other combinations. Combination of Gly + Mono has no or least adverse effects on the PGPR strains. Present study may contribute to understand the role of siderophores and siderophores producing microorganisms in the metal ion uptake and risk associated with the applications of pesticides.

Metabolism of triflumuron in the human liver: Contribution of cytochrome P450 isoforms and esterases

Triflumuron (TFM) is a benzoylurea insecticide commonly used in Tunisian agriculture and around the world to control crop pests and flies as a promising alternative to conventional insecticides for its arthropod specificity and low toxicity. From the evidence available in animal models, it can be expected that the metabolism of TFM is catalyzed by cytochrome P450 (CYP) and esterases. However, no data are available on human metabolism of TFM with regards to phase I metabolism and CYP isoform specificity. Hence, this manuscript describes experimental investigations to underpin in vitro phase I TFM metabolism in human samples for the first time. TFM biotransformation by recombinant human CYPs was characterized, then human liver microsomes (HLM) and chemical specific inhibitors have been used to identify the relative contribution of CYPs and esterases. Our results showed that all CYP isoforms were able to metabolize TFM with different affinity and efficiency. The relative contribution based both on the kinetic parameters and the CYP hepatic content was 3A4 > >2C9 > 2C8 > 2A6 > 1A2 > 2B6 > 2D6 > 2C19 > 2C18 > 1A1 at low TFM concentration, whilst at high TFM concentration it was 1A2 > >2C9 = 3A4 = 2A6 > 2C19 > 2B6 = 2C8 > 2D6 > 1A1 > 2C18. Experiments with HLMs confirmed the involvement of the most relevant CYPs in the presence of specific chemical inhibitors with a catalytic efficiency (Cliapp) lower by an order of magnitude compared with recombinant enzymes. Esterases were also relevant to the overall TFM kinetics and metabolism, with catalytic efficiency higher than that of CYPs. It is foreseen that such isoform-specific information in humans will further support in silico models for the refinement of the human risk assessment of single pesticides or mixtures.

A Correction Method of Mixed Pesticide Content Prediction in Apple by Using Raman Spectra

In the study, a new correction method was applied to reduce error during Raman spectral detection on mixed pesticide residue in apples. Combined with self-built pesticide residues detection system by Raman spectroscopy and the application of surface enhancement technology, rapid real-time qualitative and quantitative analysis of deltamethrin and acetamiprid residues in apples could be applied effectively. In quantitative analysis, compared with the intensity value of characteristic peaks of single pesticide with same concentration, the intensity value of characteristic peaks of the two pesticides decreased after mixing the pesticides, which affected the results severely. By comparing the difference in the intensity of characteristic peaks of single and mixed pesticides, a correction method was proposed to eliminate the influence of pesticides mixture. Characteristic peak intensity values of gradient concentration pesticide from 100 mg·kg−1 to 10−3 mg·kg−1 and Lagrangian interpolation were applied in the correction method. And a smooth surface was applied to describe the correction coefficient of characteristic peak intensity. Through detecting the characteristic peak intensity values of the mixed pesticide, correction coefficient would be obtained. Then real values of the peak intensity of pesticides and the content of each component of the mixed pesticide would be acquired by the correction method. Correlation coefficient of model validation exceeded 0.88 generally and Root Mean Square Error also decreased obviously after correction, which proved the reliability of the method.

In situ localization of micropollutants and associated stress response in Populus nigra leaves

Micropollutants and emerging organic contaminants (EOCs) have been widely studied in terms of persistance, removal, human risk assessment, toxicology, etc. Mass spectrometry imaging (MSI) offers the possibility of following the fate of a single pesticide in a plant leaf or a drug in the whole body of an animal, organ by organ. However, the admissibility of chronic low doses of complex mixtures for the ecosystem has not been assessed. How do micropollutants diffuse in the environment? How do living organisms cope with chronic exposure to a low dose of diverse micropollutants? Is there a cocktail effect or a chance for hormesis? Combining mass spectrometry imaging (MSI) and targeted and nontargeted liquid chromatography coupled to mass spectrometry (LC-MS), we attempt to answer these questions. We investigate the diversity of micropollutants at the exit of a water treatment facility, their diffusion in sludge and black poplar (Populus nigra), and their impact on a living organism. We reveal a specific tissue localization of micropollutants in peripheral leaf tissues, and an associated stress response from the plant, with stress hormones and tissue degradation markers induced in the plant growing near the water efflux.

Comparison of different monitoring methods for the measurement of metaldehyde in surface waters

Metaldehyde is recognised as an emerging contaminant. It is a powerful molluscicide and is the active compound in many types of slug pellets used for the protection of crops. The application of pellets to land generally takes place between August and December when slugs thrive. Due to its high use and physico-chemical properties, metaldehyde can be present in the aquatic environment at concentrations above the EU Drinking Water Directive limit of 100 ng L−1 for a single pesticide. Such high concentrations are problematic when these waters are used in the production of drinking water. Being able to effectively monitor this pollutant of concern is important. We compared four different monitoring techniques (spot and automated bottle sampling, on-line gas chromatography/mass spectrometry (GC/MS) and passive sampling) to estimate the concentration of metaldehyde. Trials were undertaken in the Mimmshall Brook catchment (Hertfordshire, UK) and in a feed in a drinking water treatment plant for differing periods between 17th October and 31st December 2017. This period coincided with the agricultural application of metaldehyde. Overall, there was a good agreement between the concentrations measured by the four techniques, each providing complementary information. The highest resolution data was obtained using the on-line GC/MS. During the study, there was a large exceedance (500 ng L−1) of metaldehyde that entered the treatment plant; but this was not related to rainfall in the area. Each monitoring method had its own advantages and disadvantages for monitoring investigations, particularly in terms of cost and turn-a-round time of data.

Lymphocytes DNA damages and exposure to chlorpyrifos, deltamethrin, penconazole, copper oxicloride

Purpose: The evaluation of the association between different exposure to pesticides and different types of comet images among a group of 26 recruited subject.Material and methods: We have recruited 26 subjects (farmers and not farmers). They were submitted to a blood drawing of 10 mL and a questionnaire was administered to investigate personal habits and work history. By means of the comet assay it was assessed the oxidative DNA damage of peripheral lymphocytes by pesticides in the exposed and non-exposed workers.Result: The data measured by means of the comet were log transformed and the associations (odds ratios – ORs) with the single pesticides were calculated. The regression analysis shows a significant dose effects relationships between the Intensity Score of pesticides exposures tail moment (TM) and other measured parameters. Insecticides TM OR = 17.00 [1.47 – 196.41]. This relationship is independent from the smoking habits.Conclusions: TM values higher than the 75° percentile were significantly associated with the exposure to particular insecticides such as chlorpyriphos, deltamethrin and with other pesticides (near the statistical significance).

Endogenous and exogenous biomarker analysis in terrestrial phase amphibians (Lithobates sphenocephala) following dermal exposure to pesticide mixtures.

Pesticide mixtures are frequently co-applied throughout an agricultural growing season to maximize crop yield. Therefore, non-target ecological species (e.g., amphibians) may be exposed to several pesticides at any given time on these agricultural landscapes. The objectives of this study were to quantify body burdens in terrestrial phase amphibians and translate perturbed metabolites to their corresponding biochemical pathways affected by exposure to pesticides as both singlets and in combination. Southern leopard frogs (Lithobates sphenocephala) were exposed either at maximum or 1/10th maximum application rate to single, double, or triple pesticide mixtures of bifenthrin (insecticide), metolachlor (herbicide), and triadimefon (fungicide). Tissue concentrations demonstrate both facilitated and competitive uptake of pesticides when in mixtures. Metabolomic profiling of amphibian livers identified metabolites of interest for both application rates, however; magnitude of changes varied for the two exposure rates. Exposure to lower concentrations demonstrated down regulation in amino acids, potentially due to their being utilized for glutathione metabolism and/or increased energy demands. Amphibians exposed to the maximum application rate resulted in up regulation of amino acids and other key metabolites likely due to depleted energy resources. Coupling endogenous and exogenous biomarkers of pesticide exposure can be utilized to form vital links in an ecological risk assessment by relating internal dose to pathophysiological outcomes in non-target species.

Auxin Herbicides and Pesticide Mixtures in Groundwater of a Canadian Prairie Province.

Groundwater samples were collected from piezometers and water table wells in both dryland and irrigated agricultural regions of Alberta, Canada, to examine the occurrence of pesticide mixtures. Fourteen current-use pesticides and two historical compounds were detected over a 3-yr sampling period. Pesticide mixtures were detected in ∼3% of the groundwater samples, and the frequency of detection increased from spring (1.5%) to summer (3.8%) and fall (4.8%). Pesticide mixtures always consisted of at least one of two auxin herbicides: 2,4-dichlorophenoxyacetic acid (2,4-D) or 2-methyl-4-chlorophenoxyacetic acid (MCPA). 19% of all samples contained a single pesticide, with auxin herbicides 2,4-D (7.3%), MCPA (4.4%), and clopyralid (3.9%) being most prevalent. We detected 2,4-D predominantly in the fall (72% of 2,4-D detections) and less in spring and summer (28%). We detected MCPA mostly in summer (85% of MCPA detections) and less in spring and fall (15%). Clopyralid was more evenly detected across spring (30%), summer (25%), and fall (45%). Since the auxin herbicides above are typically applied in summer, results suggest that each herbicide may have different mobility and persistence characteristics in prairie soils. Guidelines for Canadian Drinking Water Quality have been set for a range of individual pesticides, but not for pesticide mixtures. If Canada is to establish such guidelines, this study demonstrates that auxin herbicides should be prioritized. In addition, only 7 of the 16 compounds detected in this study have established maximum acceptable concentrations (MACs), excluding clopyralid, which was detected in all three sampling years.

Ecological risk assessment of pesticide residues in arable soils of the Czech Republic

Currently used pesticides (CUPs) represent one of the largest intentional inputs of potentially hazardous compounds into agricultural soils. Subsequently, pesticide residues (PRs) and their transformation products (TPs) persist in agricultural soils, occurring in diverse mixtures of compounds in various concentrations. In this study, measured environmental concentrations (MECs) of CUP residues and TPs, originated from previous growing seasons in agricultural soils of the Czech Republic, were used to characterize the environmental risk for agroecosystems. Toxicity exposure ratios (TERs) were calculated using predicted no-effect concentrations (PNECs) and MECs in order to identify single pesticide residues risk to in-soil invertebrates and microorganisms. Ecological risk assessment (ERA) for the mixtures of pesticide residues at each monitored site was assessed using a risk quotient (RQ) method and considering concentration addition among components in the mixtures. The compilation of ecotoxicity data to derived PNECs for in-soil organisms clearly showed data gaps mainly for triazine and chloroacetanilide TPs. In addition, chronic toxicity data for in-soil invertebrates at different trophic levels are not available for 30% of monitored CUPs. The ERA revealed that pesticide residues in soil pose a risk at 35% of the sites (RQ ≥ 1). Among measured pesticides, epoxiconazole, atrazine-2-hydroxy, carbendazim, dimoxystrobin, terbuthylazine and difenoconazole were the main contributors to the overall pesticide mixture toxicity. The measured levels of epoxiconazole together with the frequent presence in soils represent a risk for the agroecosystems. Further assessment of higher tiers of ERA should be considered and prioritized in the pesticides risk management.

Pesticide residue survey of pollen loads collected by honeybees (Apis mellifera) in daily intervals at three agricultural sites in South Germany.

In agricultural landscapes honeybees and other pollinators are exposed to pesticides, often surveyed by residue analysis of bee bread. However, bee bread is a mixture of pollen pellets of different plants collected over a longer time period. Therefore, pesticide content in the hive varies with plant species and time of pollen collection. Hence, the analysis of bee bread is an approximate approach to gain information on detailed pesticide exposure during the agronomic active season. As high-resolution data is missing, we carried out a pesticide residue survey over five years (2012–2016) of daily collected pollen pellets at three agricultural distinct sites in southern Germany. 281 single day pollen samples were selected and subjected to a multi-pesticide residue analysis. Pesticide contaminations of pollen differed between the sites. Intensive pesticide exposure can be seen by high pesticide concentrations as well as a high amount of different pesticides detected. During the five years of observation 73 different pesticides were found, of which 84% are characterized as non-harmful to honeybees. To estimate pesticide risks for honeybees, the pollen hazard quotient (PHQ) was calculated. Even though pesticides were detected in sublethal concentrations, we found substances not supposed to be exposed to honey bees, indicating the necessity for further improvement of seed treatments and increasing awareness of flowering shrubs, field margins and pesticide drift. Additionally, an in-depth analysis of nine pollen samples, divided into sub-fractions dominated by single plant species, revealed even higher concentrations in single crops for some pesticides. We give precise residue data of 1,657 single pesticide detections, which should be used for realistic laboratory and field tests.

Effect of soil fumigants on degradation of abamectin and their combination synergistic effect to root-knot nematode.

BackgroundRoot-knot nematode (Meloidogyne spp., RKN) causes a disease that significantly reduces the yield of greenhouse cucumber crops year after year. Chemical control based on a single pesticide is now unreliable mainly due to pest resistance. Fumigant and non-fumigant pesticide combinations can potentially result in effective and economic RKN control.ResultsCombining the insecticide abamectin (ABM) with fumigants dazomet (DZ) or chloropicrin (CP) significantly extended the half-life of ABM by an average of about 1.68 and 1.56 times respectively in laboratory trials, and by an average of about 2.02 and 1.69 times respectively in greenhouse trials. Laboratory experiments indicated that all the low rate ABM combination treatments controlled RKN through a synergistic effect. ABM diffused into the nematode epidermis more rapidly when ABM was combined with DZ and CP, giving effective nematode control and an increase cucumber total yield, compared to the use of these products alone. ABM combined with CP or DZ produced significantly higher total cucumber yield than when these products were used alone.ConclusionsA low concentration of ABM combined with DZ in preference to CP would be an economic and practical way to control nematode and soilborne fungi in a greenhouse producing cucumbers.

Body weight and hematological changes induced by chronic exposure to low levels of chlorpyrifos and deltamethrin combination in rats: the effect of alpha-lipoic acid

The study was aimed at evaluating the effect of the combination of low levels of chlorpyrifos (CPF) and deltamethrin (DLT) on body weight and hematological parameters in Wistar rats, and the effect of alpha-lipoic acid (ALA). Male Wistar rats were divided into six groups of eight each. Group I (S/oil) was given soya oil at 2 ml kg−1; group II (ALA) received ALA at 60 mg kg−1. Group III (DLT) received DLT at 6.25 mg kg−1 [1/20th median lethal dose (LD50)], while group IV (CPF) was given CPF at 4.75 mg kg−1 (1/20th LD50). Rats in group V (CPF+DLT) received the combination of CPF and DLT, while rats in group VI (ALA+CPF+DLT) were pretreated with ALA at 60 mg kg−1 and then co-exposed to CPF and DLT, 45 min later. The regimens were administered once daily by gavage for 4 months. Co-exposure to CPF and DLT caused significant (P < 0.05) changes in body weight and some hematological parameters (red blood cell (RBC), hemoglobin (Hb), packed cell volume (PCV), and neutrophil/lymphocyte ratio (NLR)). Pretreatment with ALA did not significantly ameliorate most of the alterations induced by the pesticide combination. It was concluded that co-exposure to CPF and DLT caused more adverse effect on body weight and some hematological parameters than single pesticide exposure; pretreatment with ALA at 60 mg kg−1 did not significantly ameliorate the changes induced by the pesticide co-exposure.

Association between pesticides use and incidence of diffuse large B cell lymphoma (DLBCL).

1570Background: Some studies have linked pesticide exposure to risk of developing cancers. However, these studies were limited to single or few pesticides. We analyze association between incidence ...

GC-MS/MS determination and ecological risk assessment of pesticides in aquatic system: A case study in Hooghly River basin in West Bengal, India

A liquid-liquid extraction (LLE) for water and modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for sediment combined with gas chromatography-tandem mass spectrometry (GC-MS/MS) detection in multiple reaction monitoring (MRM) mode was standardized for determination of 31 pesticides. Performance characteristics for the selected pesticides were acceptable according to European Commission's (EC) guidelines for method validation (recovery 70–120%, RSD <20% and R2 value ≥ 0.99). River, pond and tubewell water and river sediment samples (64 nos.) were collected from Hooghly River basin in West Bengal, India during 2014–2016. About 42% of the samples showed the presence of 19 pesticides with the highest loading of total pesticides (T-pesticides) in river water (3.01 ng mL−1) followed by sediment (1.25 ng g−1), pond (0.40 ng mL−1) and tubewell (0.02 ng mL−1) water. The non-agricultural OC (organochlorine) insecticides were detected in all river water and sediment samples mainly due to HCHs (hexachlorocyclohexane) from old source and fresh use of DDTs (dichlorodiphenyltrichloroethane) in local areas. No OC insecticides were detected in pond and tubewell water. Maximum residues of some recommended pesticides in agriculture were obtained in pond water. Most of the river water samples (93.7%) were in excess of EC limit (0.50 ng mL−1) of T-pesticides for drinking followed by pond water samples (56.2%). Tubewell water samples were free from T-pesticide threat but exceeded the EC limit (0.10 ng mL−1) for single pesticide in case of chlorpyrifos only. Ecological risk on aquatic animals was observed for OCs in river and chlorpyrifos in pond aquatic ecosystem.

Single and mixture toxicity of strobilurin and SDHI fungicides to Xenopus tropicalis embryos

The decline in amphibian populations is a critical threat to global biodiversity, and pesticide pollution is considered as one of the major factors. Although effects of single pesticides on amphibians have been documented, toxicological interactions prevailing in mixtures of pesticides have not been well elucidated. Strobilurin and succinate dehydrogenase inhibitor (SDHI) fungicides are new types of commonly used pesticides. In this study, effects of three strobilurins (pyraclostrobin, trifloxystrobin and azoxystrobin), two SDHIs (isopyrazam and bixafen), and their mixtures on X. tropicalis embryos were fully investigated. Results showed that exposure to individual fungicides induced lethal and teratogenetic effects; and malformed embryos displayed similar phenotypes including microcephaly, hypopigmentation, somite segmentation and narrow fin. Exposure to two strobilurins or two SDHIs at equitoxic concentrations caused additive or synergetic effects at environmentally relevant concentrations. TU for mixtures of isopyrazam and bixafen was 0.53 and 0.30 for lethal and teratogenic toxicity, respectively. Finally, binary mixtures of strobilurins and SDHIs also exhibited additive or synergetic effects on amphibian embryos. Overall, these results reveal that the mixtures of multiple fungicides caused a higher incidence of lethality and teratogenicity of amphibian embryos, compared to a single fungicide at the corresponding doses. Our findings provide important data about the ecotoxicology of agricultural fungicides on non-target organisms, which is useful for guiding management practices for pesticides.

Surface tension and spreading coefficient of single-and mix-pesticide solutions with aerial spraying organosilicone adjuvant

Abstract: Recently, unmanned aerial vehicles (UAVs) have been widely used to spray pesticides to control diseases and pests of many crops. During the process of pesticide application by UAV spraying, aerial spraying tank-mix adjuvants are usually mixed with pesticide solution to improve the efficiency of pesticides. Preventing pesticides depositing in off-target area is important in enhancing pesticide utilization. Improving the wetting and spreading of pesticides is one of the most important ways to reduce pesticide droplets running off from the target. This study is focusing on the effects of aerial spraying tank-mix organosilicone adjuvant (OA) on surface tension and spreading coefficient of pesticide solutions. Six pesticide solutions used alone and mixed together of different concentrations are prepared under field application conditions. Surface tension and spreading coefficient of the solution with and without OA were measured, respectively. The results show that OA could significantly lower surface tension and increase spreading coefficient of pesticide solutions regardless of solution concentrations. OA with concentration higher than critical micelle concentration (CMC) could not further decrease surface tension, but still could significantly increase spreading coefficient of the solution. For solutions with single pesticide belongs to different formulations, the minimum needed concentration of OA is different due to formulation type. The minimum concentration of OA for solution of suspension concentrate and aqueous solution (0.5‰-0.7‰) is lower than that of solutions of emulsifiable concentrate (EC) (2.0‰-5.0‰). For solutions of several pesticides mixed together, the minimum concentration of OA is related to the number of EC formulation in the solution. For pesticide solutions containing one EC formulation, the minimum concentration of OA is 2.0‰; for pesticide solutions containing two or three EC formulation, the minimum concentration of OA is recommended to be 5.0‰-10.0‰. These results suggest that the concentration of OA needed for pesticide solution should be evaluated before field application considering pesticide belonging to different formulations mixing together for application. Keywords: aerial spraying adjuvant, organosilicone, surface tension, spreading coefficient DOI: 10.33440/j.ijpaa.20210401.159 Citation: Meng Y H, Wang M M, Wang Z G, Hu H Y, Ma Y. Surface tension and spreading coefficient of single-and mix-pesticide solutions with aerial spraying organosilicone adjuvant. Int J Precis Agric Aviat, 2021; 4(1): 6–13.