Validation Testing of Drift Reduction Technology Testing Protocol

Advancements in both application hardware (e.g., nozzles and spray assist devices) and spray property modification products have led to a number of products that are specifically designed to maximize the on-target deposition and minimize off-target movement of spray droplets. Testing protocols are being developed to objectively measure spray drift reduction from a wide range of drift reduction technologies (DRTs) including spray nozzles, sprayer modifications, spray delivery assistance, spray property modifiers (adjuvants), and/or landscape modifications. Using a DRT evaluation protocol, the objectives of this work were to study the effects of different air speeds on droplet size from different spray nozzles and spray solutions and to further evaluate the effects of differences in liquid and air temperature on droplet size at the different air speeds tested. Measured spray droplet size was significantly affected by changes in airspeed with the DV0.5 increasing by ∼30–100 μm and the percent of spray volume less than 200 μm decreasing by 50 % or more as the tunnel airspeed was increased from 0.5 to 6.7 m/s (1 to 15 miles per hour), depending on the spray solution, spray nozzle, and air speed. The data also showed a lesser influence of temperature differential between the spray solution and ambient air, with the differences seen most likely resulting from changes in spray solution physical properties with the changes in liquid temperature. Most importantly, this study demonstrated that a reference nozzle evaluated under the same conditions resulted in the reduction in driftable fines while the DRT remained constant across all conditions tested.

Improvements in pesticide drift reduction technology (DRT) call for improving liability provisions to offer incentives for adoption

Pesticide spray drift represents an important exposure pathway that may cause illness among orchard workers. To strike a balance between improving spray coverage and reducing drift, new sprayer technologies are being marketed for use in modern tree canopies to replace conventional axial fan airblast (AFA) sprayers that have been used widely since the 1950s. We designed a series of spray trials that used mixed-effects modeling to compare tracer-based drift volume levels for old and new sprayer technologies in an orchard work environment. Building on a smaller study of 6 trials (168 tree rows) that collected polyester line drift samples (n = 270 measurements) suspended on 15 vertical masts downwind of an AFA sprayer application, this study included 9 additional comparison trials (252 tree rows; n = 405 measurements) for 2 airblast tower sprayers: the directed air tower (DAT) and the multi-headed fan tower (MFT). Field-based measurements at mid (26 m) and far (52 m) distances showed that the DAT and MFT sprayers had 4-15 and 35-37% less drift than the AFA. After controlling for downwind distance, sampling height, and wind speed, model results indicated that the MFT [-35%; 95% confidence interval (CI): -22 and -49%; P < 0.001] significantly reduced drift levels compared to the AFA, but the DAT did not (-7%; 95% CI: -19 and 6%; P = 0.29). Tower sprayers appear to be a promising means by which to decrease drift levels through shorter nozzle-to-tree canopy distances and more horizontally directed aerosols that escape the tree canopy to a lesser extent. Substitution of these new technologies for AFA sprayers is likely to reduce the frequency and magnitude of pesticide drift exposures and associated illnesses. These findings, especially for the MFT, may fit United States Environmental Protection Agency's Drift Reduction Technology (DRT) one-star rating of 25-50% reduction. An 'AFA buyback' incentive program could be developed to stimulate wider adoption of new drift-reducing spray technologies. However, improved sprayer technologies alone do not eliminate drift. Applicator training, including proper sprayer calibration and maintenance, and application exclusion zones (AEZs) can also contribute to minimizing the risks of drift exposure. With regard to testing DRTs and establishing AEZs, our study findings demonstrate the need to define the impact of airblast sprayer type, orchard architecture, sampling height, and wind speed.

With changing climate and farmland ecological conditions, pest outbreaks in agricultural landscapes are becoming more frequent, increasing the need for improved crop production tools and methods. UAV-based agricultural spraying is anticipated to be an important new technology for providing efficient and effective applications of crop protection products. This paper reviews and summarizes the status of the current research and progress on UAV application technologies for plant protection, and it discusses the characteristics of atomization by unmanned aircraft application systems with a focus on spray applications of agrichemicals. Additionally, the factors influencing the spraying performance including downwash airflow field and operating parameters are analyzed, and a number of key technologies for reducing drift and enhancing the application efficiency such as remote sensing, variable-rate technologies, and spray drift models are considered. Based on the reviewed literature, future developments and the impacts of these UAV technologies are projected. This review may inspire the innovation of the combined use of big data analytics and UAV technology, precision agricultural spraying technology, drift reduction technology, swarm UAV cooperative technology, and other supporting technologies for UAV-based aerial spraying for scientific research in the world. Keywords: UAV, plant protection, spraying technology, drift reduction, pesticide efficacy, spraying model, big data analytics DOI: 10.25165/j.ijabe.20211401.5714 Citation: Chen H B, Lan Y B, Fritz B K, Hoffmann W C, Liu S B. Review of agricultural spraying technologies for plant protection using unmanned aerial vehicle (UAV). Int J Agric & Biol Eng, 2021; 14(1): 38–49.

The EPA's proposed Drift Reduction Technology (DRT) low-speed wind tunnel evaluation protocol was tested across a series of modified ASAE reference nozzles. Both droplet size and deposition and flux volume measurements were made downwind from the nozzles operating in the tunnel at airspeeds of 1 m∕s and 2.5 m∕s, following the prescribed protocol. Overall, the data followed anticipated trends with a few unanticipated results observed, which could be addressed in future iterations of the protocol. There were some difficulties meeting the proposed protocol data quality requirements. Refined quality requirements would address this with no detrimental effect to the overall data set. Major concerns, at this point, are the feasibility of the overall protocol as well as the applicability of the final collected data. The protocol was tailored such that the collected data would directly input into a dispersion model (most likely WTDISP). However, not having access to such a model puts into question the validity and practicality of the protocol in its present form. Given the time requirements, which require approximately nine times that of the high speed protocol (90 min versus 10 min, unpublished data), there is a definite need to modify the existing protocol to insure equitable implementation of the overall DRT program.

The use of unmanned aerial vehicles (UAVs) for the application of plant protection products (PPPs) in paddy fields is becoming increasingly prevalent worldwide. Despite its growing usage, UAV spraying for rice pest control faces practical challenges, including limited canopy penetration, uneven deposition, and significant spray drift. This study investigated the impact of two tank-mix adjuvants, Wonderful Rosin (Adjuvant-1) and Tiandun (Adjuvant-2), at six volume concentrations, on the spray liquid's physicochemical properties, spray drift, plant deposition, and the biological efficacy of rice insecticides using a quadrotor UAV sprayer. The physicochemical characteristics of the spray liquid influenced spray performance and biological efficacy. Incorporating Adjuvant-1 and Adjuvant-2 led to a decrease in surface tension and contact angle while increasing the viscosity of the spray solution. These alterations in surface tension and viscosity contributed to an optimized droplet size distribution, reduced spray drift, enhanced deposition uniformity and penetration, and improved control efficacy against the rice planthopper in UAV applications. The highest control efficacy was observed at a concentration of 0.5%, showing an improvement of 35.12% (Adjuvant-1) and 20.23% (Adjuvant-2) over applications without tank-mix adjuvant 7 days after treatment. The judicious selection of tank-mix adjuvants for UAV PPP applications can significantly enhance spray performance and biological efficacy in controlling rice insects. This study's findings offer valuable insights for integrating tank-mix adjuvants into UAV spraying applications. © 2024 Society of Chemical Industry.

Pesticide spray drift and risk assessment using unmanned aerial vehicle (UAV) sprayer and traditional electric knapsack sprayer (EKS).

Assessing the deposition and canopy penetration of nozzles with different spray qualities in an oat (Avena sativa L.) canopy

Gear Up/Throttle Down (GUTD) and Inward Only strategies represent potential alternatives to conventional airblast applications to reduce spray drift. This study evaluates Inward Only and a modified version of GUTD in almonds, the largest US tree crop, at the recommended hull split treatment timing for control of navel orangeworm (NOW), the key almond insect pest. Conventional treatment produced the most drift (15.6% of total bifenthrin load), while the GUTD and Inward Only treatments produced only 7.6 and 9.7% respectively. For all methods, 92-94% of the drift was found in the first 15.2 m downwind of the orchard. NOW control was lower for the Inward Only treatment compared with the GUTD and conventional treatments. NOW control was consistently lower at 4.88 m height relative to 2.44 m in all treatments, reflecting the reduced deposition higher in the tree canopy recorded in deposition samples. While Inward Only treatments reduced spray drift relative to the conventional application method, poorer control of NOW, the key insect pest of almonds, in the Inward Only treatment would likely limit its voluntary use by growers. However, GUTD holds promise for use at the hull split treatment timing to address spray drift. © 2016 Society of Chemical Industry.

The most widespread method for weed control and suckering in vineyards is under-row band herbicide application. It could be performed for weed control only (WC) or weed control and suckering (WSC) simultaneously. During herbicide application, spray drift is one of the most important environmental issues. The objective of this experimental work was to evaluate the performance of specific Spray Drift Reducing Techniques (SDRTs) used either for WC or WSC spray applications. Furthermore, spray drift reduction achieved by buffer zone adoption was investigated. All spray drift measurements were conducted according to ISO22866:2005 protocol. Sixteen configurations deriving from four nozzle types (two conventional and two air-induction—AI) combined with or without a semi-shielded boom at two different heights (0.25 m for WC and 0.50 m for WSC) were tested. A fully-shielded boom was also tested in combination with conventional nozzles at 0.25 m height for WC. Ground spray drift profiles were obtained, from which corresponding Drift Values (DVs) were calculated. Then, the related drift reduction was calculated based on ISO22369-1:2006. It was revealed that WC spray applications generate lower spray drift than WSC applications. In all cases, using AI nozzles and semi-shielded boom significantly reduced DVs; the optimum combination of SDRTs decreased spray drift by up to 78% and 95% for WC and WSC spray application, respectively. The fully-shielded boom allowed reducing nearly 100% of spray drift generation. Finally, the adoption of a cropped buffer zone that includes the two outermost vineyard rows lowered the total spray drift up to 97%. The first 90th percentile model for the spray drift generated during herbicide application in vineyards was also obtained.

IntroductionWhile the integrated rice-crayfish (Procambarus clarkii) farming system (IRCFS) is widely developing in China, the widespread use of Unmanned Aerial Spraying Systems (UASS) to protect rice from pests has led to potential pesticide risk for the crayfish in IRCFS. Therefore, it is crucial to examine UASS’s spray deposition and drift in IRCFS.MethodIn this study, we used the oligonucleotide sequence-tracking / dot-blotting (OSTDB) method to trace pesticide spraying. We collected detailed data not only on spray loss in the paddy fields, but also on spray drift in the breeding ditches caused by upwind and downwind spray areas. Additionally, pesticide residues in the breeding ditches were measured using LC-MS/MS by collecting water samples after pesticide application.ResultsThe data analysis indicated that the spray loss in the paddy field was significantly greater than that in the breeding ditches. The spray drift in the breeding ditches, caused by the upwind spray area, was seven times higher than that originating from the downwind spray area. Furthermore, the results also revealed that the bulk flow between the paddy fields and the breeding ditches contributed a substantial amount of pesticide residue to the water body in the breeding ditches. In addition, we investigated the acute toxicities of common insecticides using in paddy fields, including thiamethoxam (THI), chlorantraniliprole (CHI), THI·CHI-Mix and THI·CHI-WG.DiscussionThe results demonstrated that the spray losses and spray drift from UASS spray applications of these pesticides in IRCFS would not cause acute toxicity or death in crayfish. These findings provide important materials for establishing pesticide application standards and guiding the field testing of droplet deposition and drift in IRCFS.

The Environmental Protection Agency (EPA) Office of Pesticide Programs (OPP) is participating in Organization For Economic Cooperation and Development (OECD) workgroups to update OECD guidelines number 201 (aquatic algal toxicity), number 208 (terrestrial plant toxicity), and to develop a new yet unnumbered guideline for the aquatic macrophyte Lemna spp. The EPA participants have presented the 850 series EPA guidelines and existing American Society for Testing and Materials (ASTM) guidelines to the OECD workgroups for their consideration. Under the existing North Atlantic Free Trade Agreement (NAFTA), the EPA is harmonizing plant toxicity tests and nontarget plant risk assessment methods with the Pest Management Regulatory Agency (PMRA), Canada. A pesticide regulatory workshop was recently held at the EPA to share information with Mexican government pesticide regulators. The OECD guidelines are focusing on pesticide and toxic substances, whereas NAFTA harmonization efforts to date are primarily for methods used to evaluate pesticides. While some of the plant tests are similar for toxic substances and pesticides, statutes and risk assessment methods are different.

Pesticide spray drift has been a worldwide concern in terms of potential environmental pollution and ecosystem damage. This study defined the main drift reduction agent (DRA) characteristics that help to understand the drift formation process in agricultural spraying. Seven various DRAs and water were evaluated. Three solutions were created based on the following materials: calcium dodecylbenzenesulfonate, benzenesulfonic acid, C10-13-alkyl derivatives, and calcium salt. Drift measurements were performed by means of the open circuit-type wind tunnel and in the field under conditionally controlled conditions. Air-injector flat spray nozzles and standard flat spray nozzles were used during trials. The spray pressure was 4.0 bar. Solutions were sprayed at different wind speeds (from 2 m s−1 to 10 m s−1, increasing every 2 m s−1). Studies have shown that wind speed and nozzle design have the greatest influence on spray drift. For all DRA solutions studied, the standard flat spray nozzles resulted in ground spray drift, both in the wind tunnel and in the field, which was about two times higher than that of air-injector flat spray nozzles. The spraying of water and all DRA solutions with the air-injector flat spray nozzle showed that all new solutions statistically significantly reduced the drift both in the tunnel and in the field. Ground-drift studies in the wind tunnel showed a trend towards a less intense drift reduction in DRA droplets with increasing wind speed. With DRA7e, the drift can be reduced by up to 56% (at a wind speed of 4 m s−1) and up to 30% (at 10 m s−1). The effect of the solutions on the reduction in spray drift is significantly lower when spraying with standard flat spray nozzles. Spray drift can then be reduced by up to 30% (at a wind speed of 4 m s−1) and up to 12% (at 10 m s−1) for DRA7e.

Pesticide spray drift, which is the movement of pesticide by wind to any location other than the intended area, is hazardous to human, animal, food safety and environmental health. It is not possible to completely eliminate spray drift during spraying with field crop sprayers, but spray drift can be reduced by developing new technologies. The most common methods to reduce spray drift are carrying the droplets to the target with air-assisted spraying, electrostatic spraying, preferring air induction nozzles and boom shields. With these methods, it is not possible to make a change on the sprayer depending on the wind intensity during spraying. In this study, a novel servo-controlled spraying system was designed and developed to change the nozzle orientation angle in the reverse direction of the wind current to reduce the ground spray drift in real time and automatically in a wind tunnel. The displacement in the spray pattern (Dc ) was used as a ground drift indicator for each nozzle to evaluate the spray drift. The developed system, operated by LabVIEW software, calculated different nozzle orientation angles depending on nozzle types, wind velocities and spraying pressures. Orientation angles calculated for different test conditions achieved in reduction were up to 49.01% for XR11002 nozzle, 32.82% for AIXR11002 nozzle and 32.31% for TTJ6011002 nozzle at 400 kPa spray pressure and 2.5 m s-1 wind velocity. The developed system, which has a self-decision mechanism, calculated the nozzle orientation angle instantaneously according to the wind velocity. It has been observed that the adjustable spraying nozzle system, sprayed with high precision towards the wind in the wind tunnel, and the developed system have advantages compared to conventional spraying systems. This article is protected by copyright. All rights reserved.

Real time canopy density validation using ultrasonic envelope signals and point quadrat analysis