Effect of nozzle selection on deposition of thiamethoxam in Actara® spray drift and implications for off-field risk assessment

Simulated Drift of Dicamba and Glyphosate on Coffee Crop

Weed management in areas adjacent to coffee plantations makes herbicide drift a constant concern, especially with the use of nonselective products such as dicamba. The objective of this study was to evaluate the phytotoxic effects of the herbicide dicamba alone and mixed with glyphosate as a result of simulated drift in a coffee-producing area. The study was conducted in duplicate at two different coffee cherry development stages. The study was performed with a randomized block design and a 2 × 5 + 1 factorial scheme with four replications using two herbicide spray solutions (dicamba and dicamba + glyphosate) and five low doses (0.25; 1; 5; 10; and 20%). Additionally, a control treatment without herbicide application was also employed. In this study, we evaluated the phytotoxic damage and biometric and productive parameters. Visual damages were observed with the use of dicamba and dicamba + glyphosate doses reduced by 0.25% to 5% in the first days after application. The main symptoms were new leaf epinasty, changes in the internodal distance, and plagiotropic branch curvature. Low doses led to reduced plant height and branch length. The treatments did not reduce productivity and performance but altered the physical classifications of grains.

Weak evidence base for bee protective pesticide mitigation measures

Pesticides help produce food for humanity's growing population, yet they have negative impacts on the environment. Limiting these impacts, while maintaining food supply, is a crucial challenge for modern agriculture. Mitigation measures are actions taken by pesticide users, which modify the risk of the application to nontarget organisms, such as bees. Through these, the impacts of pesticides can be reduced, with minimal impacts on the efficacy of the pesticide. Here we collate the scientific evidence behind mitigation measures designed to reduce pesticide impacts on bees using a systematic review methodology. We included all publications which tested the effects of any pesticide mitigation measure (using a very loose definition) on bees, at any scale (from individual through to population level), so long as they presented evidence on the efficacy of the measure. We found 34 publications with direct evidence on the topic, covering a range of available mitigation measures. No currently used mitigation measures were thoroughly tested, and some entirely lacked empirical support, showing a weak evidence base for current recommendations and policy. We found mitigation measure research predominantly focuses on managed bees, potentially failing to protect wild bees. We also found that label-recommended mitigation measures, which are the mitigation measures most often applied, specifically are seldom tested empirically. Ultimately, we recommend that more, and stronger, scientific evidence is required to justify existing mitigation measures to help reduce the impacts of pesticides on bees while maintaining crop protection.

Theoretical and experimental studies on the oil-based emulsion spray

Oil-based emulsion is a common herbicide formulation in agricultural spray, and its atomization mechanism is different from that of water spray. In this paper, a theoretical model based on the characteristics of spray sheets was proposed to predict the spray droplet size for oil-based emulsion spray. An image processing method was used to measure droplet size distributions for different spray pressures and nozzle configurations, and the measured results were used to validate the theoretical model. The results show that oil-based emulsion spray is characterized by the web structure constituted by perforations. The liquid originally occupied by spray sheets eventually gathers in these web structures. The proposed theoretical model is based on the size of the nozzle exit, the angle of spray sheets, and the perforation number in the web structure, which are relatively easy to obtain. The theoretical droplet size is in inverse proportion to the square root of the perforation number in the web structure while in proportion to the square root of the area of the nozzle exit. The captured images of spray sheets and the measured droplet size distribution show consistency with the theoretical prediction. The difference between theoretical results and measured volumetric median diameter is less than 10% for different spray pressures and nozzles.

Effect of oil-based emulsion on air bubbles in the spray sheet produced through the air-induction nozzle

BACKGROUND

The air-induction spray featured by air bubbles involved in the spray sheet has attracted great attention in applications of agricultural spray due to its advantages of alleviating spray drift and promoting deposition. The objective of the presented study is to deepen the understanding of the mechanism of the air-induction spray through elucidating the effect of sprayed liquid on characteristics of air bubbles in the spray sheet.

RESULTS

The air bubbles with relatively large sizes are stable for a long time span. As velocity of the water spray increases from 6.85 m s^-1 to 17.87 m s^-1 , average size of the air bubbles decreases from 383.21 μm to 236.47 μm. With the introduction of organosilicone surfactant, the surface tension of the sprayed liquid decreases from 67.38 mN m^-1 to 31.32 mN m^-1 ; accordingly, average size of the bubbles decreases from 383.21 μm to 160.9 μm. Compared to aqueous solutions spray, the oil-based emulsion spray is responsible for relatively small average size of air bubbles as the surface tension and spray velocity are respectively similar.

CONCLUSION

Low drainage rate of the bubble lamella contributes to high stability of large air bubbles. The decrease of the average size of air bubbles is responsible for small volumetric median diameter of oil-based emulsion spray compared with water spray. Besides the increase of the spray velocity and the decrease of the surface tension, the Marangoni effect caused by dynamics of oil droplets at air-liquid interface also contributes to the decrease of average size of air bubbles. © 2022 Society of Chemical Industry.

Characterization of field-scale spray drift deposition and non-target plant biological sensitivity: a corn herbicide (mesotrione/s-metolochlor) case study

BACKGROUND

This work reports a combined, field-scale spray drift deposition and plant bioassay study for a pre-mixture of the herbicides mesotrione and s-metolachlor. Wind direction data and field dimensions were used to evaluate the potential for spray drift to bypass downwind sampling devices. Variability in resulting spray drift across downwind distances was assessed alongside wind speed measured at on-site weather stations. Measured wind angles were used to geometrically adjust traveled drift particle distances and enabling isolation of wind direction impact from wind speed. Further, the use of single and multiple in-field monitoring locations was compared to quantify the benefit of higher-resolution meteorological sampling.

RESULTS

Generally, increased wind speed resulted in significantly greater herbicide deposition at distances proximal to the edge of the spray zone. According to the drift deposition curves that included wind speed data from single and multiple onsite weather stations, trials with relatively higher wind speeds were associated with greater spray drift deposition at relatively close sampling distances downwind from the application area. Only marginal improvement of linear mixed-effects model fit was observed when including data from three weather stations, compared to the fit from a single weather station or absence of weather data in the model. Using tomato and lettuce plant bioassay species, the overall no-effect distance was 3.0 m (10 ft).

CONCLUSION

Results from this study are informative to refine pesticide risk assessment for non-target plants and indicate that a single weather station is sufficient to capture potential influential effects from wind speed and direction on spray drift. © 2022 Society of Chemical Industry.

Passive Sampling as a Tool to Assess Atmospheric Pesticide Contamination Related to Vineyard Land Use

The massive use of pesticides in agriculture has led to widespread contamination of the environment, particularly the atmospheric compartment. Thirty-six pesticides, most used in viticulture, were monitored in ambient air using polyurethane foams as passive air samplers (PUF-PAS). Spatiotemporal data were collected from the samplers for 10 months (February–December 2013), using two different sampling times (1 and 2 months) at two different sites in a chateau vineyard in Gironde (France). A high-volume active air sampler was also deployed in June. Samples were extracted with dichloromethane using accelerated solvent extraction (ASE) (PUFs from both passive and active) or microwave-assisted extraction (MAE) (filters from active sampling). Extracts were analyzed by both gas and liquid chromatography coupled with tandem mass spectrometry. A total of 23 airborne pesticides were detected at least once. Concentrations in PUF exposed one month ranged from below the limits of quantification (LOQs) to 23,481 ng PUF−1. The highest concentrations were for folpet, boscalid, chlorpyrifos-methyl, and metalaxyl-m—23,481, 17,615, 3931, and 3324 ng PUF−1. Clear seasonal trends were observed for most of the pesticides detected, the highest levels (in the ng m−3 range or the µg PUF−1 range) being measured during their application period. Impregnation levels at both sites were heterogeneous, but the same pesticides were involved. Sampling rates (Rs) were also estimated using a high-volume active air sampler and varied significantly from one pesticide to another. These results provide preliminary information on the seasonality of pesticide concentrations in vineyard areas and evidence for the effectiveness of PUF-PAS to monitor pesticides in ambient air.

Current use pesticides in soil and air from two agricultural sites in South Africa: Implications for environmental fate and human exposure

Concerns about the possible negative impacts of current use pesticides (CUPs) for both the environment and human health have increased worldwide. However, the knowledge on the occurrence of CUPs in soil and air and the related human exposure in Africa is limited. This study investigated the presence of 30 CUPs in soil and air at two distinct agricultural sites in South Africa and estimated the human exposure and related risks to rural residents via soil ingestion and inhalation (using hazard quotients, hazard index and relative potency factors). We collected 12 soil and 14 air samples over seven days during the main pesticide application season in 2018. All samples were extracted, purified and analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry. In soils, nine CUPs were found, with chlorpyrifos, carbaryl and tebuconazole having the highest concentrations (up to 63.6, 1.10 and 0.212 ng g^-1, respectively). In air, 16 CUPs were found, with carbaryl, tebuconazole and terbuthylazine having the highest levels (up to 25.0, 22.2 and 1.94 pg m^-3, respectively). Spatial differences were observed between the two sites for seven CUPs in air and two in soils. A large dominance towards the particulate phase was found for almost all CUPs, which could be related to mass transport kinetics limitations (non-equilibrium) following pesticide application. The estimated daily intake via soil ingestion and inhalation of individual pesticides ranged from 0.126 fg kg^-1 day^-1 (isoproturon) to 14.7 ng kg^-1 day^-1 (chlorpyrifos). Except for chlorpyrifos, soil ingestion generally represented a minor exposure pathway compared to inhalation (i.e. <5%). The pesticide environmental exposure largely differed between the residents of the two distinct agricultural sites in terms of levels and composition. The estimated human health risks due to soil ingestion and inhalation of pesticides were negligible although future studies should explore other relevant pathways.

Spray drift deposition comparison of fluorimetry and analytical confirmation techniques

Tracer dyes are often used as surrogates to characterize pesticide spray drift and it is assumed that they accurately reflect analytical measurement of active ingredients; however, the validity of this assumption remains inconclusive. Consequently, the influence of measurement technique on the magnitude of deposition of spray drift was investigated using spray drift samples evaluated by traditional analytical techniques (HPLC-MS/MS) and fluorimetry (1,3,6,8-pyrene-tetra sulfonic acid tetrasodium salt dye tracer). The experiment was conducted in a low-speed wind tunnel under controlled meteorological conditions. The herbicide mesotrione was sprayed through three spray air induction nozzles (anvil deflector flat fan TTI11004; flat fan AI11004; flat fan AIXR11003). Spray drift deposition samples were collected using stainless steel discs pairs placed side by side in the center of the wind tunnel at distances of 5, 10, 20, 30, and 40 ft (1.5, 3.1, 6.1, 9.1, and 12.2 m) from the spray nozzle. The analytical technique determined pesticide concentration on one disc per pair, and the other was evaluated by fluorimetry. The experimental results, analyzed using the linear split-split plot model, revealed that median deposition concentrations were 15% higher using the tracer dye fluorescence method relative to the analytical method, potentially due in part to procedural recovery inefficiencies of the analytical method (the mean overall procedural recovery result and RSD was 87% ± 6.4% (n = 12). This relationship was consistent and held true for the three nozzle types at all distances within the wind tunnel. © 2021 Society of Chemical Industry.