Side-effects of pesticides on ground-dwelling predatory arthropods in arable ecosystems

The effects of above ground applications of pesticides in field crops on the epigeal predator fauna in the Lake Yssel polders in The Netherlands was assessed during a 20-month period by means of pitfall trapping in 17 commercially farmed fields and in one experimental field. The pesticides used during this period were the herbicides 2,4-D-amine and MCPA/MCPP and the insecticides deltamethrin, fenitrothion, and bromophos-ethyl. Deposition of the spray on the soil was determined. Bioassays were carried out in the fields in two cases. Of the taxa identified, i.e. staphylinids, carabids and spiders, the erigonid and linyphiid spiders appeared to be sensitive to the three insecticides. Long-term effects, however, could not be demonstrated. No effect was observed from the herbicide applications. Fields which were mechanically treated against weeds had a lower species diversity than chemically treated fields. Ploughing had a detrimental effect on the spiders. The effect of deltamethrin appeared to depend on weather conditions. At higher temperatures the effect was stronger than at lower temperatures, and no effects could be observed under rainy conditions. A guild of five species, i.e. Erigone atra, E. dentipalpis, Oedothorax apicatus, Meioneta rurestris and Bathyphantes gracilis, is recommended as an indicator for early detection of side-effects of insecticides on the epigeal predator fauna.     

A multi-step bioassay to assess the effect of the deltamethrin on the parasitic wasp Aphidius ervi

Insecticides are widely used for crop protection. Effectiveness of pesticides and beneficial arthropods in an Integrated Pest Management (IPM) program requires a full understanding of how specific pesticides alter natural enemy effectiveness. This may require evaluation of chemicals at different life stages of the insect considered, on different physiological and behavioural components, and also on population dynamic components such as recolonization capacities after a pesticide treatment. Aphidius ervi Haliday (Hymenoptera: Braconidae) is an aphid parasitoid commonly used for the biological control of aphid populations. In this work, our aim was to assess the effects of deltamethrin (pyrethroid) treatments on this parasitoid using a multi-step bioassay. We evaluated its effects on parasitoid emergence, adult survival and longevity, and host searching. Two exposure methods were used, topical and spray, to evaluate impact of the deltamethrin field rate (6.25ga.i./ha) and also to compare the methods of exposure. A four-armed olfactometer was used to investigate effect of deltamethrin on host searching behaviour. When applied at the rate of field exposure, deltamethrin reduced the adult longevity but not the rate of emergence from mummies. Effects varied between the two exposure methods. Two indices were defined: the "population survival index" to measure capacity of parasitoids to recolonize a treated field and the "reproductive potential" to estimate the reduction in reproduction as a function of longevity decrease. These indices predicted effects of deltamethrin on A. ervi in terms of mortality and reduction of recolonization capacities. However, adults that survived residual exposure to deltamethrin retained their ability to orient to host odours. The implications of results in IPM and interest of the methodology used are both discussed.     

Unexpected effects of sublethal doses of insecticide on the peripheral olfactory response and sexual behavior in a pest insect

Pesticides have long been used as the main solution to limit agricultural pests, but their widespread use resulted in chronic or diffuse environmental pollutions, development of insect resistances, and biodiversity reduction. The effects of low residual doses of these chemical products on organisms that affect both targeted species (crop pests) but also beneficial insects became a major concern, particularly because low doses of pesticides can induce unexpected positive—also called hormetic—effects on insects, leading to surges in pest population growth at greater rate than what would have been observed without pesticide application. The present study aimed to examine the effects of sublethal doses of deltamethrin, one of the most used synthetic pyrethroids, known to present a residual activity and persistence in the environment, on the peripheral olfactory system and sexual behavior of a major pest insect, the cotton leafworm Spodoptera littoralis. We highlighted here a hormetic effect of sublethal dose of deltamethrin on the male responses to sex pheromone, without any modification of their response to host-plant odorants. We also identified several antennal actors potentially involved in this hormetic effect and in the antennal detoxification or antennal stress response of/to deltamethrin exposure.     

Optimization of a methodology for the simultaneous determination of deltamethrin,permethrin and malathion in stored wheat samples using dispersive liquid–liquid microextraction with solidification of floating organic drop and HPLC-UV

The purpose of this study was to investigate common pesticides in stored wheat at Kermanshah province's silos in Iran. A simple, inexpensive, reliable and environmentally friendly method based on dispersive liquid–liquid microextraction with solidification of floating organic drop was developed. The analytical characteristics of the method were determined. Also, various parameters such as the materials of the silos, types of ownerships of the silos, geographic orientation of silo locations and climatic conditions of silo locations on pesticide residues in studied wheat samples were investigated. Among all the studied parameters, the climatic conditions of silo locations showed the highest influence on pesticide residues in wheat samples. Generally, 61.2% of the samples had pesticide levels below the method detection limits and 38.8% of the total samples had at least one of the understudied pesticides. Also, 13.9% of the samples had deltamethrin residues, 16.7% of the samples had permethrin, 22.2% of the samples had malathion, 11.1% of the samples had both permethrin and malathion and 2.8% of the samples had both deltamethrin and malathion. The results revealed that the residues of deltamethrin and malathion were lower than the standard level announced by European Union regulation and only three samples contained permethrin higher than Europe standard level.     

Environmental pesticide distribution in horticultural and floricultural periurban production units

The environmental pesticide distribution on non-target systems (soil, drift and agricultural plastics) during the application step at small periurban production units, was studied in open field and greenhouses, for different crops (tomato, lettuce, broccoli, strawberry and flowers) using different pesticides (endosulfan, procymidone, chlorothalonil, chlorpyrifos and deltamethrin). In all cases, soil was the most exposed non-target system. For greenhouses, a general pesticide distribution was found of approximately 2/3 for crop, 1/4 for soil and 1/20 for plastic, of the total amount applied. In horticultural open fields, although the distribution was very dependent on the crop size and type, soil was also the most exposed non-target subsystem. Pesticide drift seems not to be significant in these production units, whilst pesticide accumulation on agricultural plastics reached up to 45% of the total applied, for polyethylene mulching in strawberry fields.     

Combined effects of deltamethrin, temperature and salinity on oxidative stress biomarkers and acetylcholinesterase activity in the black tiger shrimp (Penaeus monodon)

This study aimed to investigate the interactions of two abiotic factors (temperature and salinity) and deltamethrin (pyrethroid pesticide) exposure on some oxidative stress biomarkers as well as on acetylcholinesterase activity (AChE) in hepatopancreas, gills and muscle of black tiger shrimp (Penaeus monodon). A combination of three temperatures (24, 29 and 34 °C), two salinities (15 and 25 ppt), and the absence or presence of 0.1 μg L⁻¹ deltamethrin was applied on shrimp during 4 d under laboratory conditions. Lipid peroxidation level (LPO) and glutathione S-transferase activity (GST) were not affected by combined effect of temperature, salinity and deltamethrin in any of the studied tissues. Deltamethrin impaired other tested oxidative stress biomarkers, i.e. total glutathione (tGSH), catalase (CAT), glutathione peroxidase (GPx). tGSH level significantly increased in hepatopancreas due to deltamethrin exposure mainly at 34 °C, while pesticide effects on tGSH and CAT activity in gills were influenced by both temperature and salinity. In addition, GPx activity in hepatopancreas decreased after deltamethrin treatment mainly at 24 °C. Finally, AChE in muscle was strongly inhibited by deltamethrin at all tested temperatures and salinities. These novel findings demonstrate that interactions between abiotic factors and a commonly used pesticide exposure should be taken into account when analyzing some widespread biomarkers in black tiger shrimp.     

Persistence of deltamethrin and cypermethrin on wheat and sweetclover

Residues of cypermethrin and deltamethrin in wheat herbage and grain and deltamethrin in sweetclover herbage were determined. Cypermethrin was applied at 28 g/ha to wheat and the residues on the herbage declined exponentially from 3.74 ppm immediately after spraying to 0.20 ppm 27 days after spraying. No cypermethrin residues were detected in the grain. Deltamethrin was applied at 6 g/ha to wheat and the residues on the herbage declined exponentially from 0.70 ppm immediately after spraying to 0.05 ppm 27 days after spraying. No deltamethrin residues were detected in the grain. Deltamethrin was applied to sweetclover at 3, 4, 5, 10, and 16 g/ha. Residues on the herbage declined exponentially from 0.10, 0.16, 0.22, 0.40 and 0.70 ppm immediately after spraying to 0.02, 0.03, 0.04, 0.15 and 0.18 ppm 5 days after spraying, respectively.     

Persistence of deltamethrin and cypermethrin on wheat and sweetclover

Abstract

Residues of cypermethrin and deltamethrin in wheat herbage and grain and deltamethrin in sweetclover herbage were determined. Cypermethrin was applied at 28 g/ha to wheat and the residues on the herbage declined exponentially from 3.74 ppm immediately after spraying to 0.20 ppm 27 days after spraying. No cypermethrin residues were detected in the grain. Deltamethrin was applied at 6 g/ha to wheat and the residues on the herbage declined exponentially from 0.70 ppm immediatly after spraying to 0.05 ppm 27 days after spraying. No deltamethrin residues were detected in the grain. Deltamethrin was applied to sweetclover at 3, 4, 5, 10, and 16 g/ha. Residues on the herbage declined exponentially from 0.10, 0.16, 0.22, 0.40 and 0.70 ppm immediatly after spraying to 0.02, 0.03, 0.04, 0.15 and 0.18 ppm 5 days after spraying, respectively.     

Effects of droplet density and concentration on the efficacy of bacillus thuringiensis and carbaryl against gypsy moth larvae (Lymantria dispar L.)

Abstract

The feeding behavior of gypsy moth larvae exposed to two pesticide deposits (Bt and carbaryl) on oak leaf disks was monitored to determine the relationships between its efficacy and application parameters (droplet density and pesticide concentration). A range of pesticide concentrations and droplet densities (from 9 to 149 droplets/cm²) was used to simulate high and low application rates produced by different methods of application in the field.

The LD₅₀ and the LC₅₀, appeared to be affected by the spatial distribution of the deposit on the leaf surface. Both Bt and carbaryl showed a decreasing LD₅₀ at increasing time after spray. The LD₅₀ of Bt decreased from 14.1 BIU/liter to 3.1 BIU/Iiter between 48 and 144 hours after spray. The results show that feeding inhibition by Bt is more closely related to concentration than to droplet density and dose per unit area with the highest feeding inhibition occurring at 10 BIU/liter at 9 droplets/cm². With carbaryl, an increase in both concentration and droplet density was necessary to cause a decrease in leaf area eaten by larvae.     

The effect of fluorescent tracers on droplet spectrum,viscosity, and density of pesticide formulations

The most important factor affecting efficacy and drift of pesticide applications is the droplet spectrum. To measure pesticide drift, researchers utilize fluorescent tracers to rapidly quantify spray deposition. Although fluorescent tracers have been used for more than 50 years, no experiments have been performed on the effect they have on the properties of pesticide formulations (density and viscosity) or droplet spectrum, which affect the drift of pesticides. Therefore, we examined the effect of an oil- and water-based tracer on the volume median diameter (VMD), viscosity, and density of oil- and water-based pesticide formulations. In addition, we experimentally fit and demonstrate the utility of using distributions to characterize pesticide droplet spectra. The addition of tracers to both water- and oil-based formulations did not significantly alter the VMD, viscosity, and density. Lognormal distributions provided the best fit for the water- and oil-based formulations with and without tracer. Our results demonstrated that the addition of oil- and water-based tracers do not significantly alter pesticide formulations properties and droplet spectrum, and most likely do not alter the movement of pesticide droplets in the environment.     

Buffer zone widths for honeybees from ground and aerial spraying of insecticides

The relative field hazards of insecticides to honeybees have been estimated by considering intrinsic toxicity levels and field application rates. This approach is extended here to a consideration of buffer zones downwind of sprayed areas by estimating the distance at which bees would encounter an LD(50) dose from spray drift. 'LD(50) distances' are determined for both ground and aerial spraying of ground crops in Britain using published data on spray deposition under various weather conditions. For ground spraying at low wind speeds (< or =3 m s(-1)), this zone of risk is up to 5 m for the great majority of compounds. Aerial spraying in unstable atmospheric conditions appears to produce drift deposits of about the same order of magnitude as from ground spraying at wind speeds of about 4 m s(-1), with maximum LD(50) distances of < or =40 m for chlorpyrifos, fenitrothion and triazophos. For aerial spraying in stable atmospheric conditions these distances would be much greater. Pieris brassicae larvae are contrasted with honeybees in their relative sensitivities to insecticides and consequent LD(50) distances.     

The greenhouse work environment: a modifier of occupational pesticide exposure?

Abstract

Greenhouses are enclosed structures which have various characteristics that enhance crop productivity, but the implications for workers’ pesticide exposure and uptake are not well understood. A narrative literature review was conducted to explore the mechanism/s of interactions between greenhouse characteristics and occupational pesticide exposure. Using a “work”, “worker” and “workplace” conceptual framework, the greenhouse environment (hot and humid microclimate, limited space and dense crop arrangements) combines with work characteristics (high work and pesticide use intensity, multi-tasking, predominantly manual spraying techniques and quick reentry to treated farms) to potentially increase occupational pesticide exposure, compared with open field farming. Greenhouse environments, are variable but have been shown to influence pesticide availability, route, pathways and frequency of exposure, deposition and distribution on a worker’s body as well as use and performance of exposure control methods. Training programs can emphasize the differences in exposure potential between greenhouse and open field farming. Development of tailored guidelines for exposure control strategies to better suit the level of uniqueness of greenhouse agriculture seems warranted.     

A validated 2-D diffusion–advection model for prediction of drift from ground boom sprayers

Correct field drift prediction is a key element in environmental risk assessment of spraying applications. A reduced order drift prediction model based on the diffusion–advection equation is presented. It allows fast assessment of the drift potential of specific ground boom applications under specific environmental wind conditions that obey the logarithmic wind profile. The model was calibrated based on simulations with a validated Computational Fluid Dynamics (CFD) model. Validation of both models against 38 carefully conducted field experiments is successfully performed for distances up to 20 m from the field edge, for spraying on flat pasture land. The reduced order model succeeded in correct drift predictions for different nozzle types, wind velocities, boom heights and spray pressures. It used 4 parameters representing the physical aspects of the drift cloud; the height of the cloud at the field edge, the mass flux crossing the field edge, the settling velocity of the droplets and the turbulence. For the parameter set and range considered, it is demonstrated for the first time that the effect of the droplet diameter distribution of the different nozzle types on the amount of deposition spray drift can be evaluated by a single parameter, i.e., the volume fraction of droplets with a diameter smaller than 191 μm. The reduced order model can be solved more than 4 orders of magnitude faster than the comprehensive CFD model.     

Influence of input uncertainty on prediction of within-field pesticide leaching risks

Previous research has suggested that pesticide losses at the field scale can be dominated by a small proportion of the field area. The objective of this study was to investigate whether site-specific applications (i.e. avoiding high-risk areas) at the field scale can contribute to a reduction of pesticide leaching despite uncertainty in the underlying model-based leaching risk map. Using a meta-model of the dual-permeability model MACRO, the annual average pesticide leaching concentrations were estimated for 162 sample sites on a 47 ha field. The procedure was repeated for different scenarios describing different patterns of spatial variation of degradation half-lives and the partition coefficient to soil organic carbon. To account for interpolation uncertainty, maps of predicted pesticide leaching risk were produced by the method of sequential Gaussian simulation. The results of the case study show that larger reductions of predicted leaching were achieved by site-specific application than by that of a comparable uniform dose reduction. Hence, site-specific-applications may be a feasible method to reduce pesticide leaching at the field-scale providing that the model approach gives reasonable estimates of the spatial pattern of pesticide leaching.     

Characterizing the uncertainty of pesticide leaching in agricultural soils

A Monte-Carlo numerical simulation procedure for making regional assessments of pesticide leaching has been developed. This procedure uses probability density functions for organic matter, field capacity, and wilting point developed from information on approximately 3000 soils. Variations in climatic conditions were incorporated by random selection of yearly rainfall data. The procedure was demonstrated for aldicarb applied to corn grown in Ohio. A total of 2000 parameter sets were evaluated using the unsaturated zone model PRZM. The simulation results indicated that convergence of the 90th, 95th, and 99th percentiles for movement past 0.3, 0.6, 0.9, and 1.5 m was obtained after 500 simulations. The relative uncertainty associated with these percentiles was approximately 50% after 1500 simulations. The downward movement of aldicarb residues was most sensitive to changes in field capacity. These simulations, coupled with additional soil-specific simulations, indicated no significant movement of aldicarb residues beyond 1.8 m for applications to Ohio corn.     

Atmospheric loss of pesticides above an artificial vineyard during air-assisted spraying

A procedure to assess pesticide emission to the air and characterise possible air pollution sources was carried out using a tracer dye and 2 mm PVC lines during air-assisted spraying of an artificial vineyard. Three experiments were performed to evaluate the method feasibility, quantify upward movements of sprayed droplets and investigate the influence of microclimatic variables on pesticide emission. During each experiment two test series were carried out with two droplet size distributions (very fine and fine spray, according to the BCPC classification). The amount of sprayed liquid collected at 2.5 m above ground varied between 9.0% and 10.7% of the total dose applied for very fine spray and between 5.6% and 7.3% for fine spray. In stable atmospheric conditions the spray drifted along the mean wind direction over the crop whereas in unstable conditions the sprayed liquid plume was larger, with a greater amount of material sent to higher levels. A statistical model based on a simple multiple regression featuring droplet characteristics and microclimatic variables (wind speed, temperature, stability parameter and relative humidity) provided a robust estimate of spray loss just above the crop, with an acceptable determination coefficient (R²=0.84). This method is therefore suitable for quantifying spray drift and provides a way to study the influence of several variables on the amount of pesticide released into the atmosphere by air-assisted spraying, with suitable accuracy.     

Seasonal variations in cholinesterase activity, nerve conduction velocity and lung function among sprayers exposed to mixture of pesticides

Pesticide spraying operation is associated with the increased risk of adverse health effects among sprayers who do not follow safe farm work practices. A study was conducted among pesticide sprayers in North India to evaluate the clinical and subclinical variations in their vital health parameters before and after the pesticide spraying season. Blood cholinesterase levels, pulmonary function test, nerve conduction velocity and self-reported symptoms were studied among 18 eligible and consenting male sprayers. Mean acetylcholinesterase activity was reduced by 55 % in the post-exposure assessment (P?<?0.001) as compared to pre-exposure levels. Mean forced expiratory volume in 1 s was 20 % lower in the post-exposure assessment as compared to the pre-exposure level (P?<?0.05). No significant change was observed in the motor and sensory nerve conduction velocity in the median nerve of sprayers before and after the spraying activity. Also, no significant variation was observed with respect to self-reported symptoms except weakness in arms and legs (P?<?0.05). The significant decline in lung function and acetylcholinesterase level after pesticide exposure reflects the strongly negative effect of exposure to pesticides during spraying activity. More longitudinal studies among pesticide sprayers must be undertaken to further substantiate the cause–effect relationship between pesticide exposure and its subclinical effects. There is a strong necessity to minimise the exposure through the use of personal protective equipment in pesticide sprayers.     

Beyond selectivity: Are behavioral avoidance and hormesis likely causes of pyrethroid-induced outbreaks of the southern red mite Oligonychus ilicis?

Secondary pest outbreak is a counterintuitive ecological backlash of pesticide use in agriculture that takes place with the increase in abundance of a non-targeted pest species after pesticide application against a targeted pest species. Although the phenomenon was well recognized, its alternative causes are seldom considered. Outbreaks of the southern red mite Oligonychus ilicis are frequently reported in Brazilian coffee farms after the application of pyrethroid insecticides against the coffee leaf miner Leucoptera coffeella. Selectivity favoring the red mite against its main predatory mites is generally assumed as the outbreak cause, but this theory has never been tested. Here, we assessed the toxicity (and thus the selectivity) of deltamethrin against both mite species: the southern red mite and its phytoseid predator Amblyseius herbicolus. Additionally, behavioral avoidance and deltamethrin-induced hormesis were also tested as potential causes of red mite outbreak using free-choice behavioral walking bioassays with the predatory mite and life-table experiments with both mite species, respectively. Lethal toxicity bioassays indicated that the predatory mite was slightly more susceptible than its prey (1.5×), but in more robust demographic bioassays, the predator was three times more tolerant to deltamethrin than its prey, indicating that predator susceptibility to deltamethrin is not a cause of the reported outbreaks. The predator did not exhibit behavioral avoidance to deltamethrin; however insecticide-induced hormesis in the red mite led to its high population increase under low doses, which was not observed for the predatory mite. Therefore, deltamethrin-induced hormesis is a likely cause of the reported red mite outbreaks.     

Copper modulates non-enzymatic antioxidants in the freshwater fish Channa punctata (Bloch) exposed to deltamethrin

The assessment of the ecotoxicological risks caused by pesticides to ecosystems are based on data on the toxicity and effects of pesticide preparations to non-target organisms like fish. Deltamethrin is a widely used pesticide based on pyrethroids, which is reported to be extremely toxic to fish species. Modulatory effect of copper pre-exposure (10 ppb) on deltamethrin (0.75 microg l-1)-induced oxidative stress was investigated in freshwater fish Channa punctata (Bloch). Non-enzymatic antioxidants were studied as biomarkers of exposure to deltamethrin and possible protection afforded by copper pre-exposure. Glutathione levels were reduced significantly (P<0.05) in liver of copper-acclimatized deltamethrin-exposed group when compared with deltamethrin-exposed groups. The total thiol levels of copper-acclimatized deltamethrin-exposed group was significantly lowered (P<0.01) in liver when compared with deltamethrin-exposed group, while non-protein thiol levels recorded a significant (P<0.01) increase in liver of copper-acclimatized deltamethrin-exposed group when compared with deltamethrin-exposed group. The lipid peroxidation levels of copper-acclimatized deltamethrin-exposed groups were significantly lowered (P<0.01) in liver when compared with deltamethrin-exposed group. Deltamethrin is known to induce toxic responses by generating reactive oxygen species and to neutralize its toxic effect various non-enzymatic antioxidants were found to be modulated thus implicating their role as biomarkers in pollution control programmes.     

A simulation procedure for groundwater quality assessments of pesticides

A procedure is described for making regional assessments of pesticide residue loadings and movement in groundwater underneath and downgradient from treated fields. A Monte-Carlo numerical simulation technique is used to generate model parameters for both the unsaturated and saturated zones. Simulations are performed using the Pesticide Root Zone Model linked to a simple groundwater solute transport model.The procedure is useful for evaluating the potential for producing pesticide residues in drinking water wells before actual field applications are made. Appropriate land management options, including restrictions on pesticide application, also can be developed using this procedure.The procedure was used to assess aldicarb levels in northeastern North Carolina groundwater resulting from application of the pesticide to peanuts. Probability density functions for selected soil characteristics were developed using a direct-access soils information data base. Probability density functions for selected groundwater characteristics were developed from available data for the study area. Simulation results indicated that mass fluxes to groundwater exceeded 0.01 and 0.1 kg ha⁻¹ approximately 6.9 and 1.0 percent of the time, respectively. No fluxes exceeded 0.1 kg ha⁻¹ at a distance of 60 m downgradient in any of the cases evaluated.