Concentrations Of Esfenvalerate Research Articles

Ultra-low esfenvalerate exposure may disrupt interspecific competition

Field and mesocosm studies repeatedly show that higher tier processes reduce the predictive accuracy of toxicity evaluation and thus their value for pesticide risk assessment. Therefore, understanding the influence of ecological complexity on toxicant effects is crucial to improve realism of aquatic risk assessment. Here we investigate the influence of repeated exposure to ecologically realistic concentrations of esfenvalerate on the two similarly sensitive species Daphnia magna and Culex pipiens in a food limited and highly competitive environment. We show that significant perturbations in population development are only present at 100 ng/L (close to the EC50). In contrast, interspecific competition between species is already reduced at 0.1 ng/L (≤ 3 orders of magnitude below the acute lethal EC50). We conclude that extremely low, environmentally relevant concentrations can disrupt species interactions. This toxicant mediated alteration of competitive balances in ecological communities may be the underlying mechanism for shifts in species distribution at ultra-low pesticide concentrations. A realistic risk assessment should therefore consider these processes in order to predict potential pesticide effects on the structure of communities.

Swimming under Pressure: The Sub-Lethal Effects of a Pesticide on the Behaviour of Native and Non-Native Cypriniformes Fish

River ecosystems are exposed to a multitude of stressors, including increasing pesticide run-off driven by precipitation and irrigation. Pyrethroids are the fourth major group of insecticides in use worldwide and have extremely negative effects on aquatic fauna. In this study, we aimed to assess the effects of an acute 2 h sub-lethal exposure to different levels of the pyrethroid esfenvalerate on the swimming behaviour of two Cypriniformes species: the native Iberian barbel (Luciobarbus bocagei) and the non-native invasive bleak (Alburnus alburnus). The experimental set-up consisted of previous exposure to three esfenvalerate concentrations (control, 1.2 (low), and 2.0 (high) μg/L) before being stocked in a three-artificial-flume-channel mesocosm for behavioural trials through direct observation. Monitored behaviours included (i) routine activity, (ii) shoal cohesion, and iii) boldness. Significant differences in fish behaviour were detected for the native species (barbel), as individuals spent significantly more time holding position (i.e., resting) in the control (44.9%) than in the high esfenvalerate concentration (25.2%). Concordantly, control barbels were also found to perform more directional changes than the ones exposed to high esfenvalerate concentrations. Behavioural changes were also found for boldness, measured by the proportion of fish attempts to negotiate the upstream ramp, which were significantly higher in the control (37.4%) and in the high concentration (41.5%) compared to the low one (21.1%). Finally, regarding shoal cohesion of the barbel, it was tighter in the control (81.3%) than in the low- (70.5%) and high- (71.1%) esfenvalerate treatments. For the invasive bleak, there were no significant differences in any of the behavioural traits upon previous exposure to an increasing esfenvalerate concentration. This experimental study demonstrated that even short-term exposure to the pyrethroid esfenvalerate was sufficient to alter the behaviour of a native Cypriniformes fish species while not affecting the non-native species. This may confer greater competitive advantages to non-native fish species in the context of global changes.

Dose-dependent stress response of esfenvalerate insecticide on common carp (Cyprinus carpio): Evaluating blood parameters and gene expression

Esfenvalerate is a pyrethroid insecticide used primarily in the agriculture sector for insect management. Esfenvalerate is effective against a wide range of harmful insects, including flies, cockroaches, locusts, and many other types of bugs. It is also known that esfenvalerate has toxic effects on aquatic organisms and poses significant environmental concerns. In this study, the aim is to subchronically examine the effects of sublethal concentrations of esfenvalerate insecticide on common carp (Cyprinus carpio) by assessing changes in blood parameters and resulting gene expression. For this purpose, common carp (Cyprinus carpio) were divided into 5 groups and exposed to 0.025, 0.05, 0.1, and 0.15 μg/L concentrations of esfenvalerate for a period of 14 days. Blood and liver tissue samples were collected from the fish that underwent weight and length measurements. The effects on gene expression levels of immune, antioxidant, and stress-related genes in the liver tissue, including SOD, GST, Cortisol receptor, HSP70, H+−ATPase, Na+/K+−ATPase, Catalase, and GpX, were evaluated, as were the hematological and serum biochemical parameters. Significant decreases were observed in the levels of hematocrit, hemoglobin, erythrocytes, triglycerides and total protein and catalase, H+−ATPase, and GpX gene expression. Glucose, cholesterol, alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase (LDH) and alkaline phosphatase (ALP), SOD, Cortisol receptor, Na+/K+−ATPase gene expression levels increased. As a result, it has been revealed that esfenvalerate insecticide causes oxidative stress in carp at all dose ranges.

Ultra-low Esfenvalerate concentrations increase biomass and may reduce competitiveness of Daphnia magna populations

Aquatic communities are frequently exposed to pesticides at sublethal concentrations, known to affect fitness parameters such as feeding, reproduction and population growth. Beside adverse effects, beneficial responses to toxicants at low concentrations may also occur. Positive effects, however, are thought to involve trade-offs. To identify such trade-offs, we quantified the population level effects on Daphnia magna during population carrying capacity in laboratory nanocosms after exposure to a single pulse of the pyrethroid insecticide esfenvalerate, including ultra-low concentrations ≤1/30 EC50. Population abundance and biomass were monitored 3 times per week for 3 months using a non-invasive imaging technique. High concentrations ≥1/10 EC50 resulted in reduced fitness endpoints. In contrast, ultra-low concentrations in the range of 0.01 μg/L significantly increased the population abundance of small (+160 %), medium (+130 %) and large organisms (+340 %) and their combined biomass (+200 %) during the 2 months after exposure. During the first five days after exposure to 0.01 μg/L and 0.03 μg/L esfenvalerate, population biomass increased by 0.1 mg/day while staying constant in the controls. While high control mortality makes firm conclusions about population responses of D. magna to esfenvalerate difficult, we hypothesize that population increases at ultra-low concentrations may be due to a hormetic response, where reduced intraspecific competitiveness is the trade-off that enables this response.

Ultra-Low Esfenvalerate Concentrations Increase Biomass and Reduce Competitiveness of Daphnia Magna Populations

Ultra-Low Esfenvalerate Concentrations Increase Biomass and Reduce Competitiveness of Daphnia Magna Populations

The pyrethroid esfenvalerate induces hypoactivity and decreases dopamine transporter expression in embryonic/larval zebrafish (Danio rerio).

Esfenvalerate is a pyrethroid insecticide used widely for agricultural and residential applications. This insecticide has been detected in aquatic environments at concentrations that can induce sub-lethal effects in organisms. In this study, zebrafish embryos were used to examine the effects of environmentally-relevant concentrations of esfenvalerate on development and behavior. It was hypothesized that esfenvalerate exposure would impair locomotion due to its effects on the central nervous system. We also measured mitochondrial bioenergetics and the expression of genes (dopamine system) as putative mechanisms of locomotor impairment. Concentrations of 0.02, 0.2 and 2μg/L esfenvalerate did not induce significant mortality nor deformity in zebrafish, but there was an acceleration in hatching time for zebrafish exposed to 2μg/L esfenvalerate. As an indicator of neurotoxicity, the Visual Motor Response (VMR) test was conducted with 5, 6, and 7 dpf zebrafish after continuous exposure, and higher concentrations were used (4 and 8μg/L esfenvalerate) to better discern age-and dose dependent responses in behavior. Experiments revealed that, unlike the other stages, 6 dpf larvae showed evidence for hypo-activity with esfenvalerate, suggesting that different stages of larval development may show increased sensitivity to pyrethroid exposure. This may be related to age-dependent maturation of the central nervous system. We hypothesized that reduced larval activity may be associated with impaired production of ATP and the function of mitochondria at earlier life stages, however dramatic alterations in oxidative phosphorylation were not observed. Based on evidence that dopamine regulates behavior and studies showing that other pyrethroids affect dopamine system, we measured transcripts involved in dopaminergic signaling. We found that dopamine active transporter was down-regulated with 0.2μg/L esfenvalerate. Lastly, we comprehensively summarize the current literature (>20 studies) regarding the toxicity of pyrethroids in zebrafish, which is a valuable resource to those studying these pesticides. This study demonstrates that esfenvalerate at environmentally-relevant levels induces hypoactivity that are dependent upon the age of the zebrafish, and these behavioral changes are hypothesized to be related to impaired dopamine signaling.

Energetic costs and biochemical biomarkers associated with esfenvalerate exposure in Sericostoma vittatum

Pyrethroid insecticides have been used for decades and their worldwide market continues to increase, despite their high toxicity to non-target insects. Recent studies reveal that it is essential to investigate the secondary mechanisms of action of type II pyrethroids to understand their cellular effects on invertebrates. The aim of this study was to evaluate the lethality, behaviour and physiological alterations and energetic costs in caddisfly larvae exposed to environmentally relevant concentrations of esfenvalerate (ESF). ESF caused both mortality and feeding inhibition of exposed caddisfly larvae: nominal ESF 96 h LC50 was 2.29 μg/L; feeding activity was impaired at concentrations equal or above 0.25 μg/L. At the cellular level, glutathione-S-transferase (GST) activity was increased on caddisfly larvae exposed to 0.25 and 0.5 μg/L ESF, which might contribute to prevent oxidative damage since levels of lipid peroxidation (LPO) were not altered. The energy budget of exposed caddisfly larvae was impaired by exposure to 0.25 μg/L ESF since sugar and protein contents decreased, while a decline of energy consumption was observed. The analysis of feeding, energy reserves and consumption data through structural equation modelling (SEM) allowed to quantify the direct and indirect effects of ESF exposure on bioenergetics of caddisfly larvae. SEM analysis showed a strong negative direct influence of ESF onto feeding activity, sugars content and energy consumption, highlighting a significant positive relationship between sugars and protein contents. These results show that energy expenditure is related to oxidative defense mechanisms induced by ESF stress that may lead to deleterious effects on growth and development.

Testing the time-scale dependence of delayed interactions: A heat wave during the egg stage shapes how a pesticide interacts with a successive heat wave in the larval stage

Under global change organisms are exposed to multiple, potentially interacting stressors. Especially interactions between successive stressors are poorly understood and recently suggested to depend on their timing of exposure. We particularly need studies assessing the impact of exposure to relevant stressors at various life stages and how these interact. We investigated the single and combined impacts of a heat wave (mild [25 °C] and extreme [30 °C]) during the egg stage, followed by successive exposure to esfenvalerate (ESF) and a heat wave during the larval stage in damselflies. Each stressor caused mortality. The egg heat wave and larval ESF exposure had delayed effects on survival, growth and lipid peroxidation (MDA). This resulted in deviations from the prediction that stressors separated by a long time interval would not interact: the egg heat wave modulated the interaction between the stressors in the larval stage. Firstly, ESF caused delayed mortality only in larvae that had been exposed to the extreme egg heat wave and this strongly depended upon the larval heat wave treatment. Secondly, ESF only increased MDA in larvae not exposed to the egg heat wave. We found little support for the prediction that when there is limited time between stressors, synergistic interactions should occur. The intermediate ESF concentration only caused delayed mortality when combined with the larval heat wave, and the lowest ESF concentrations only increased oxidative damage when followed by the mild larval heat wave. Survival selection mitigated the interaction patterns between successive stressors that are individually lethal, and therefore should be included in a predictive framework for the time-scale dependence of the outcome of multistressor studies with pollutants. The egg heat wave shaping the interaction pattern between successive pesticide exposure and a larval heat wave highlights the connectivity between the concepts of ‘heat-induced pesticide sensitivity’ and ‘pesticide-induced heat sensitivity’.

Effects of the Pyrethroid Esfenvalerate on the Oligochaete, Lumbriculus variegatus.

Esfenvalerate is a neurotoxic pyrethroid insecticide widely used for agricultural and residential purposes and is considered toxic to nontarget organisms such as fish and aquatic invertebrates. In this study, we evaluated the toxicity of esfenvalerate on the aquatic oligochaete Lumbriculus variegatus. In the acute test, organisms showed visible signs of stress but no LC50 value could be determined. In the 28-day chronic test, a significant decrease in reproduction was observed with a NOEC value of 0.25 µg/kg and a LOEC value of 2.34 µg/kg. As for biomass per worm, a significant decrease was also observed with a NOEC value of 2.34 µg/kg and a LOEC value of 36.36 µg/kg. Reproductive impairment and reductions in biomass of L. variegatus exposed to environmentally realistic concentrations of esfenvalerate observed in laboratory tests suggests potential deleterious effects of this pyrethroid on oligochaete natural populations.

Sub-lethal toxicity of environmentally relevant concentrations of esfenvalerate to Chironomus riparius

Integrative studies focused on sub-organismal responses to pyrethroid exposure are important to understand life history responses. In this study, the ecotoxicological effects of esfenvalerate (ESF) on Chironomus riparius were assessed using five biochemical biomarkers related to neurophysiological function (acetylcholinesterase) and oxidative stress (catalase; glutathione-S-transferase; total glutathione and lipid peroxidation). In addition, effects on cellular energy allocation were assessed and all results were compared with organismal level responses (larval growth, emergence and sex ratio). Exposure to sub-lethal concentrations of ESF caused the failure of C. riparius antioxidant defenses (inhibition of catalase activity and decreased levels of total glutathione), which was reflected as oxidative damage. C. riparius energy budget was decreased by exposure to ESF due to an increased energy consumption. Life cycle tests showed that exposure to ESF impaired C. riparius developmental rates and increased male:female ratios, thereby confirming its toxicity and potential population level effects at environmentally relevant concentrations.

Interactive effects of pesticide exposure and habitat structure on behavior and predation of a marine larval fish.

Coastal development has generated multiple stressors in marine and estuarine ecosystems, including habitat degradation and pollutant exposure, but the effects of these stressors on the ecology of fishes remain poorly understood. We studied the separate and combined effects of an acute 4h sublethal exposure of the pyrethroid pesticide esfenvalerate and structural habitat complexity on behavior and predation risk of larval topsmelt (Atherinops affinis). Larvae were exposed to four nominal esfenvalerate concentrations (control, 0.12, 0.59, 1.18μg/L), before placement into 12L mesocosms with a three-spine stickleback (Gasterosteus aculeatus) predator. Five treatments of artificial eelgrass included a (1) uniform and (2) patchy distribution of eelgrass at a low density (500shootsperm(2)), a (3) uniform and (4) patchy distribution of eelgrass at a high density (1,000shootsperm(2)), and (5) the absence of eelgrass. The capture success of predators and aggregative behavior of prey were observed in each mesocosm for 10min of each trial, and mortality of prey was recorded after 60min. Exposure to esfenvalerate increased the proportion of larvae with swimming abnormalities. Surprisingly, prey mortality did not increase linearly with pesticide exposure but increased with habitat structure (density of eelgrass), which may have been a consequence of compensating predator behavior. The degree of prey aggregation decreased with both habitat structure and pesticide exposure, suggesting that anti-predator behaviors by prey may have been hampered by the interactive effects of both of these factors.

A New Multi-cell Exposure System for Continuous Tracking of Daphnia Behavior for Toxicity Assessments

For several years, video tracking systems have been developed to analyze alterations in the swimming behavior of daphnia to provide early signals of chemical stress. However, these systems have limited testing abilities that do not allow for a systematic analysis of the robustness of behavioral endpoints. With recent advances in behavior tracking technology, we were able to develop a new behavioral analysis multi-cell exposure system named “Multi-DaphTrack” with a high-throughput testing capacity for assessing the behavioral response of Daphnia magna. The insecticide esfenvalerate was chosen as chemical model and tested on daphnid neonates at several concentrations for 48 h to (i) evaluate the performance of this new system and (ii) compare the sensitivity of our new multi-cell system with the standard immobilization assay and the Bbe®Daphnia Toximeter. Overall, the results demonstrated that our new “Multi- DaphTrack” system can detect significant behavioral effects of esfenvalerate at concentrations as low as 0.14 μg/L from a minimum of 1 h of exposure. Similar rapid behavioral effect trends were observed with the Bbe®Daphnia Toximeter. The behavior proved to be more sensitive than the standard immobilization endpoint. Significant behavioral changes were observed at the esfenvalerate concentrations that occur in contaminated rivers from agricultural areas in Europe and North America. Our results indicate that the “Multi-DaphTrack” system represents a powerful and convenient tool for the assessment of c and water quality

Esfenvalerate toxicity to the cladoceran Ceriodaphnia dubia in the presence of green algae, Pseudokirchneriella subcapitata

The presence of phytoplankton, like other particulate organic matter, can interfere with the effects of hydrophobic contaminants such as pyrethroid pesticides. However, the reduction or elimination of toxicity by algae added as food during testing is not taken into account in standard US EPA whole effluent toxicity (WET) zooplankton tests. On the other hand, WET test conditions may overestimate toxicity of such compounds in highly productive surface waters with high concentrations of detritus and other particulate matter. In addition, WET tests do not measure impaired swimming ability or predator avoidance behavior as an indicator of increased mortality risk. This study used a modified version of the US EPA WET Ceriodaphnia dubia acute test to investigate the effects of phytoplankton on toxicity of the pyrethroid insecticide, esfenvalerate. Animals were exposed simultaneously to different concentrations of esfenvalerate and green algae (Pseudokirchneriella subcapitata). Mortality and predation risk were recorded after 4 and 24 h. Algae at or below concentrations specified in the WET protocol significantly reduced mortality. Regardless, organisms exposed to esfenvalerate were unable to avoid simulated predation in the presence of algae at any concentration. After 12 h, esfenvalerate adsorbed to algae represented 68-99 % of the total amount recovered. The proportion of algae-bound insecticide increased with algal concentration indicating that conclusions drawn from toxicity tests in which algae are added as food must be interpreted with caution as the dissolved fraction of such hydrophobic contaminants is reduced. Additionally, our results strongly suggest that the EPA should consider adding ecologically-relevant endpoints such as swimming behavior to standard WET protocols.

Susceptibility of Oriental Fruit Moth (Lepidoptera: Tortricidae) to Two Pyrethroids and a Proposed Diagnostic Dose of Esfenvalerate for Field Detection of Resistance

Laboratory colonies of oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), were reared on 'Gala' apples (Malus pumila Mill.) and lima bean (Phaseolus lunatus L.) diet. Neonates were placed on wheat germ diet containing a range of concentrations of esfenvalerate or lambda-cyhalothrin; mortality was assessed after 96 h. For a long-term laboratory colony, LC50 values of esfenvalerate and lambda-cyhalothrin were 0.35 and 0.12 ppm, respectively, for progeny of insects reared on apples. For a colony established from Calhoun Co., IL, in 2007, LC50 values of esfenvalerate and lambda-cyhalothrin were 0.37 and 0.10 ppm, respectively, for progeny of insects reared on apples. LC50 values of these insecticides did not differ significantly for either colony when progeny of insects reared on lima bean diet were tested. We observed no consistent evidence of pyrethroid resistance in the Calhoun colony after laboratory culture for 21-23 generations. We described the dose-response relationship for esfenvalerate applied topically in 1 microl of acetone to male moths from the long-term laboratory colony and estimated the LD99 to be 0.022 microg per moth. Application of 0.022 microg of esfenvalerate per moth to approximately 600 male moths from two putatively susceptible populations resulted in mean survivorship approximately equal to the expected level of 1.0%. Application of the same dose to 374 field-captured moths from two Calhoun Co. orchards with histories of pyrethroid use resulted in mean survivorship of 9.4 and 82%. We propose that 0.022 microg of esfenvalerate in 1 microl of acetone can be used as a diagnostic dose for monitoring pyrethroid resistance in oriental ruit moth in the field.

Effectiveness of the standard evaluation method for hydraulic nozzles employed in stored grain protection trials

In stored grains, smaller depositions and great variation with respect to theoretical insecticide doses are frequently found. The objective of this work was to study the effectiveness of the standard method (ISO 5682/1-1996) employed to evaluate hydraulic nozzles used in stored corn and wheat grain protection experiments. The transversal volumetric distribution and droplet spectrum of a model TJ-60 8002EVS nozzle were determined in order to calibrate a spraying system for an application rate of 5 L/t and to obtain theoretical concentrations of 10 and 0.5 mg/kg of fenitrothion and esfenvalerate, respectively. After treatment, the corn and wheat grains were processed and deposition was analyzed by gas chromatography. The type of grain did not have any influence on insecticide deposition and was dependent upon insecticide only. The insecticide deposits on the grains only reached 42.1 and 38.2% of the intended theoretical values for fenitrothion and esfenvalerate concentrations, respectively. These results demonstrate the ineffectiveness of the standard evaluation method for hydraulic nozzles employed in stored grain protection experiments.

Expression of immune-regulatory genes in juvenile Chinook salmon following exposure to pesticides and infectious hematopoietic necrosis virus (IHNV)

Impairment of fish immune function as a consequence of polluted aquatic environments can result in changes in susceptibility to disease. In this study, we investigated the effects of two widely used insecticides, chlorpyrifos (CP) and esfenvalerate (EV), and a pathogen, infectious hematopoietic necrosis virus (IHNV), singly and in combination, on survival and cytokine (Mx protein, IL-1β, TGF-β and IGF-1) expression in juvenile Chinook salmon. Fish were exposed for 96 h to sublethal concentrations of CP (3.7 μg L −1) or EV (0.08 μg L −1), allowed to recover in clean water for seven days, then exposed to IHNV (6.4 × 10 5 TCID 50 mL −1) for 1.5 h. Mortality was recorded daily, and spleen and anterior kidney samples were collected on day 4 (after CP or EV treatment), day 20 and day 60 (after CP or EV treatment and subsequent IHNV exposure) of the experiment. Significant mortality after 60 days was observed following exposure to EV (17%) or IHNV (20%), and prior insecticide exposure did not synergize the acute effects of pathogen treatment. By day 4, exposure to CP as well as EV led to a significant decrease of Mx protein and IL-1β expression; by day 20, EV-exposed fish significantly overexpressed IL-1β. Mx protein transcription was up-regulated in spleen and kidney of all IHNV-exposed fish groups by day 20. All but one treatment (EV) led to significantly decreased IGF-1 transcription in spleen on days 20 and 60, whereas a short-term increase was seen after CP exposure (day 4). In kidney, decreases of IGF-1 transcription were less pronounced. TGF-β transcription was up-regulated in CP/IHNV and EV/IHNV exposure groups. Our results indicate that CP and EV alter the expression of cytokines, but this did not negatively affect the ability of fish to survive a subsequent exposure to IHNV. Induced TGF-β transcription indicated that the combined stressors affected fish in a synergistic manner, but the consequences are unknown. Increased transcription of Mx protein was a reliable indicator of virus exposure.

EFFECTS OF DIETARY ESFENVALERATE EXPOSURES ON THREE AQUATIC INSECT SPECIES REPRESENTING DIFFERENT FUNCTIONAL FEEDING GROUPS

Given the chemical properties of synthetic pyrethroids, it is probable that compounds, including esfenvalerate, that enter surface waters may become incorporated into aquatic insect food sources. We examined the effect of dietary esfenvalerate uptake in aquatic insects representing different functional feeding groups. We used three field-collected aquatic insect species: A grazing scraper, Cinygmula reticulata McDunnough (Ephemeroptera: Heptageniidae); an omnivorous filter feeder, Brachycentrus americanus Banks (Trichoptera: Brachycentridae); and a predator, Hesperoperla pacifica Banks (Plecoptera: Perlidae). Laboratory-cultured algae were preexposed for 24 h to esfenvalerate concentrations of 0, 0.025, 0.05, and 0.1 microg/L and provided to two C. reticulata age classes (small and final-instar nymphs). Reduction in small nymph growth was observed following three weeks of feeding on algae exposed to 0.05 and 0.1 microg/L of esfenvalerate, and the highest dietary exposure reduced egg production in final-instar nymphs. The diet for B. americanus and H. pacifica consisted of dead third-instar Chironomus tentans larvae preexposed for 24 h to esfenvalerate concentrations ranging between 0.1 and 1.0 microg/L. Consumption of larvae exposed to 0.5 to 1.0 microg/L of esfenvalerate caused case abandonment and mortality in B. americanus caddisfly larvae. Although H. pacifica nymphs readily consumed esfenvalerate-exposed larvae, no adverse effects were observed during the present study. Furthermore, no evidence of esfenvalerate-induced feeding deterrence was found in any of the species tested, suggesting that aquatic insects may not be able to distinguish between pyrethroid-contaminated and uncontaminated food sources. These findings indicate that feeding deterrence is not a factor in regulating aquatic insect dietary exposures to synthetic pyrethroids.

A system to evaluate the performance of hydraulic nozzles used in stored grain preotection trials

We developed a system to evaluate the performance of hydraulic nozzles used in stored corn and wheat grain protection experiments. An insecticidal mix was used as test fluid to determine the transversal volumetric distribution and droplets spectrum of a model TJ-60 8002EVS hydraulic nozzle. A mobile application system was built to apply a rate equivalent to 5 L t-1 and obtain theoretical concentrations of 10 and 0.5 mg kg-1 of fenitrothion and esfenvalerate, respectively. The corn and wheat grains were spread out as a fine layer. Three glass slides (0.1 × 0.05 m) were placed on the top surface of the grains to ensure that the intended application rate was achieved. After treatment, the deposits on both matrices were analyzed by gas chromatography. The fenitrothion deposit was higher than esfenvalerate, and the deposit on wheat was higher than on corn grains (P < 0.05). The deposits on the glass slides reached values of 100 and 93% of the intended theoretical fenitrothion and esfenvalerate concentrations, respectively. Deposits on the grains were lower than on the glass slides, with values of 64 and 52% of the intended theoretical fenitrothion and esfenvalerate concentrations, respectively. The results obtained demonstrate a high effectiveness of the method for evaluation of the performance of hydraulic nozzles when an insecticidal mix is used as test fluid. The factors that influenced insecticide deposition on glass slides and on grains are discussed in the present work.

Effects of the pyrethroid esfenvalerate on life‐cycle traits and population dynamics of Chironomus riparius—importance of exposure scenario

Field populations of aquatic organisms, particularly those inhabiting flowing waters, likely are exposed to short pulses of pesticides following periods of spray drift, surface runoff, or drain flow. In the present study, we investigated the effect of pulse exposures of a pyrethroid insecticide, esfenvalerate, on survival, development, and reproduction of the midge, Chironomus riparius. The first experiment was designed to simulate the exposure of settling larvae to a waterborne pulse of esfenvalerate. A second experiment simulated exposure of larvae entering a sediment that had been exposed previously to a waterborne pulse of esfenvalerate. A third experiment simulated exposure of sediment-inhabiting larval populations to a waterborne pulse of esfenvalerate and examined whether population density influenced the response of C. riparius. Our results indicate that even very brief (i.e., 1-h) exposures to environmentally realistic concentrations of esfenvalerate during early larval life can have measurable effects on larval survival and developmental rates. For those individuals that survived a pulse exposure early in life, however, there appeared to be no lasting effects of esfenvalerate on their subsequent egg laying or egg viability. Thus, brief exposure to environmentally realistic concentrations of pesticides can have measurable effects on freshwater invertebrate populations, but whether such effects occur depends on the details of the exposure regime. In addition, population density may influence the responses of life-cycle traits and, thereby, population-level impacts of pesticides.

Innovative uses of vegetated drainage ditches for reducing agricultural runoff

Vegetated agricultural ditches play an important role in mitigation of pesticides following irrigation and storm runoff events. In a simulated runoff event in the Mississippi (USA) Delta, the mitigation capacity of a drainage ditch using the pyrethroid esfenvalerate (Asana XL) was evaluated. The pesticide was amended to soil prior to the runoff event to simulate actual runoff, ensuring the presence of esfenvalerate in both water and suspended particulate phases. Water, sediment, and plant samples were collected temporally and spatially along the drainage ditch. Even with mixing of the pesticide with soil before application, approximately 99% of measured esfenvalerate was associated with ditch vegetation (Ludwigia peploides, Polygonum amphibium, and Leersia oryzoides) three hours following event initiation. This trend continued for the 112 d study duration. Simple modeling results also suggest that aqueous concentrations of esfenvalerate could be mitigated to 0.1% of the initial exposure concentration within 510 m of a vegetated ditch. Observed field half-lives in water, sediment, and plant were 0.12 d, 9 d, and 1.3 d, respectively. These results validate the role vegetation plays in the mitigation of pesticides, and that ditches are an indispensable component of the agricultural production landscape.