Agricultural Spray Applications Research Articles

DROPLET SIZE DISTRIBUTION PARAMETERIZATION FOR FLAT FAN SPRAYS OF AGRICULTURAL TANK MIXTURES

In agricultural spray application of pesticides, the volumetric droplet size distribution (VDSD) critically influences the efficacy of the application as well as the risk of off-target spray deposition. It is critical to have accurate predictions of the VDSD for development of new agrochemicals and spray nozzles. VDSD parameterization and subsequent prediction is complicated in agrochemical sprays by the unique geometries of the nozzles employed, which typically do not have clearly evident hydraulic diameters and vary in size, as well as by the effects of active herbicides and adjuvants on the spray. Herein, scaling based on conservation of energy is utilized to develop a relationship predicting the VDSD for flat fan sprays used in agrochemical application with agrochemical products. To examine the proposed scaling relationship, we made measurements of VDSDs using laser diffraction interferometry for agriculturally relevant tank mixtures, including active pesticides and both emulsion-forming and rheology-modifying drift control adjuvants, sprayed with complex geometry, flat fan nozzles typical of field application. We show that for three distinct nozzle types and three tank mixtures (nine combinations), VDSDs can be normalized by the Sauter mean diameter (<i>D<sub>32</sub></i>), and normalized distributions collapse for given nozzle type-spray tank mix combination. Subsequently, we show for all test combinations that the Sauter mean diameter normalized by the nozzle hydraulic diameter (<i>D<sub>H</sub></i>) scales with the ratio of product of tank mix surface tension and hydraulic diameter divided by the nozzle pressure drop, with a scaling exponent of 1/3.

Predicting the Aerial Application of Dispersant Onto an Oil Spill

Abstract The release of dispersant from an aircraft onto an oil spill is simulated using the AGDISPpro computer model, to develop a better understanding of how aircraft type, spray systems, and meteorological conditions affect the prediction of surface deposition. This model, originally developed for predicting the aerial release of pesticides for agricultural spray applications, is ideally suited to simulate the effects of aircraft type and flight condition/configuration, spray system arrangement, wind speed and direction, temperature and relative humidity (evaporation), release height, and spray application rate when spraying an oil spill. Predictions of droplet trajectories from the aircraft to the surface, drop size distributions at the release height, and deposition profiles are compared to two historical datasets for the Lockheed C-130, from field studies conducted in 1982 and 1993. This article shows that model accuracy improves from R2 = 0.411 to 0.827 with the earlier data, to R2 = 0.885 to 0.968 with the later data, most probably because of a better understanding of nozzle locations in the 1993 data. Model accuracy also appears improved when the aircraft flies in an in-wind direction, a configuration strongly recommended in the available literature.

Analysis of the Influence of Different Parameters on Droplet Characteristics and Droplet Size Classification Categories for Air Induction Nozzle

Droplet characteristics are identified as essential factors in agricultural spray application. The aims of this study were to analyse the influence of spray parameters on droplet characteristics and to determine possible candidate sprays that would produce the same droplet size categorizations as the American Society of Agricultural and Biological Engineers (ASABE) standard S-572.1 for air induction nozzles (AINs). Six different orifice sizes of the Billericay Farm Services (BFS) air induction (AI) flat fan hydraulic nozzles (the air bubblejet) were examined at different spray pressures (200 kPa, 300 kPa, 400 kPa, 500 kPa, 600 kPa and 700 kPa) and concurrent air velocities (2 m/s, 3 m/s, 4 m/s and 5 m/s). The influences of spray parameters on the droplet characteristics were analysed using analysis of covariance (ANCOVA) and analysis of variance (ANOVA). Results showed that: (1) The values of droplet characteristics and the results of ANOVA were significantly different before and after eliminate the influence of dynamic surface tension (DST) on droplet characteristics by ANCOVA; (2) (a) the reduction rates of the droplet diameter sizes decreased with increasing spray pressure; (b) air velocities of 2 m/s and 5 m/s resulted in smaller droplets reports, and air velocities of 3 m/s and 4 m/s are more suitable for agricultural spray applications; (c) a larger nozzle orifice size not always result in a larger droplet size and (3) Fine, Medium, Coarse, Very Coarse and Extremely Coarse droplet classification categories as the ASABE S-572.1 standard categorizations were determined to classify AINs.

The relations of leaf area index with the spray quality and efficacy of cotton defoliant spraying using unmanned aerial systems (UASs)

Leaf area index influences on the spray quality and efficacy, and has relationships with the spray quality and efficacy in agricultural spray application. The aim of the present study was to sought the relations of LAI with the spray quality and efficacy of cotton defoliant spraying using unmanned aerial systems (UASs). A TRAC-II instrument was used to measure the LAI of cotton plants. Three different types of UASs with different spray volume rates (48 L·ha−1, 72 L·ha−1 and 96 L·ha−1), flight altitudes (1.5 m, 2.0 m and 2.5 m), and flight speeds (1 m·s−1, 2 m·s−1 and 3 m·s−1) were tested. Results showed the following: (1) There were exponential relationships between LAI and droplet deposition at volume rates of 48 L·ha−1, 72 L·ha−1 and 96 L·ha−1. There were cubic relationships between LAI and cotton defoliation rate at volume rates of 48 L·ha−1, 72 L·ha−1 and 96 L·ha−1. (2) The multiple regression model between LAI and volume rate, and droplet deposition was D = −0.02896 − 0.08055 L + 0.01226 V, the R2 and RMSE values of the training and test sets were 0.81 and 0.08, and 0.83 and 0.07, respectively. The multiple regression model between LAI and volume rate, and cotton defoliation was C = 100.8524 − 4.0617 L + 0.05482 V, the R2 and RMSE values of the training and test sets were 0.72 and 0.17, and 0.75 and 0.06, respectively.

Development of droplet characteristics prediction models for air induction nozzles based on wind tunnel tests

Nozzle flowrate and spray pressure are two of the most important factors influencing on droplet characteristics. With the aim to develop prediction models for air-induction nozzles (AINs), a series of Billericay Farm Services (BFS) AINs with different orifice diameters in combination with tap water were tested. 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa and 0.7 MPa of spray pressures and 2 m/s, 3 m/s, 4 m/s and 5 m/s of air speeds were setup. Based on the wind tunnel tests data, prediction models with input variables of nozzle flowrate and spray pressure and output variables of Dv0.1, Dv0.5, Dv0.9, %<150 µm (proportion of spray volume contained in droplets with diameter below 150 µm), relative span (RS) and coefficient of variation (CV) of Dv0.5 were developed. The developed models were validated based on wind tunnel experimental data. Results showed that: for Dv0.1, Dv0.5, Dv0.9 and %<150 µm, R2 were equal to 0.768, 0.823, 0.868 and 0.811, indicating that the predictive ability for these four parameters were strong. For RS and CV, R2 were equal to 0.100 and 0.113, respectively, indicating that the predictive ability for these two parameters were poor. The models developed in the present study are helpful for facilitating the use of AIN in agricultural spray application. Keywords: prediction model, agricultural spray application, droplet characteristics, AIN, laser diffraction DOI: 10.25165/j.ijabe.20191206.5014 Citation: Liao J, Hewitt A J, Wang P, Luo X W, Zang Y, Zhou Z Y, et al. Development of droplet characteristics prediction models for air induction nozzles based on wind tunnel tests. Int J Agric & Biol Eng, 2019; 12(6): 1–6.

Effect of insecticide formulation and adjuvant combination on agricultural spray drift

Loss of crop protection products when agricultural spray applications drift has economic and ecological consequences. Modification of the spray solution through tank additives and product formulation is an important drift reduction strategy that could mitigate these effects, but has been studied less than most other strategies. Therefore, an experimental field study was conducted to evaluate spray drift resulting from agricultural ground applications of an insecticide formulated as a suspension concentrate (SC) and as a wettable powder (WP), with and without two adjuvants. Droplet sizes were also measured in a wind tunnel to determine if indirect methods could be substituted for field experimentation to quantify spray drift from these technologies. Results suggest that spray drift was reduced by 37% when comparing the SC to the WP formulation. As much as 63% drift reduction was achieved by incorporating certain spray adjuvants, but this depended on the formulation/adjuvant combination. The wind tunnel data for droplet spectra showed strong agreement with field deposition trends, suggesting that droplet statistics could be used to estimate drift reduction of spray solutions. These findings can be used to develop a classification scheme for formulated products and tank additives based on their potential for reducing spray drift.

Dermal and Inhalation Exposure of Workers during Control of Oak Processionary Moth (OPM) by Spray Applications.

The caterpillars of the oak processionary moth (OPM) form stinging hairs, which release an irritant poison. They cause skin and eye irritation and sometimes even breathing difficulties and allergic reactions. OPM is mainly controlled by spraying insecticides. Insecticides applied for protection of human health must be authorized under the Biocidal Products Regulation (BPR) (EU) No 528/2012. In order to assess safety of professional use, which is a key requirement for the authorization, a risk assessment based on exposure estimation has to be performed. However, no exposure data specific for OPM control was available until now. Existing models for agricultural spray applications such as Agricultural Operator Exposure Model cover different spray patterns and equipment and were therefore considered too unreliable for assessment of OPM control. We have studied dermal and inhalation exposure of certified pest control operators resulting from spraying DimilinTM 80 WG suspensions with vehicle-mounted spraying (VMS) and with handheld spraying (HHS) devices for control of OPM. Exposure resulting from these applications, from weighing and portioning of the granular product and from cleaning of contaminated spraying devices was studied. Dermal exposure was investigated by whole body dosimetry using disposable chemical protective coveralls and cotton gloves as samplers. Inhalation exposure was measured using personal air samplers. The active substance diflubenzuron was quantified by gas chromatography-mass spectrometry with positive chemical ionization and by high-performance liquid chromatography for dermal and inhalation measurements, respectively. The exposure was dominated by the dermal pathway. HHS results in considerably higher operator exposure than VMS. Comparison with data from typical agricultural spraying applications revealed that OPM control results in much higher exposure of operators for both, vehicle-mounted and handheld equipment. Comprehensive data on potential dermal and inhalation exposure is presented in this article, along with typical figures for handled and applied amounts of product and respective task durations. This data is suitable for risk assessments in regulatory frameworks such as the European BPR.

Development of droplet characteristics prediction models for air induction nozzles based on wind tunnel tests

Nozzle flowrate and spray pressure are two of the most important factors influencing on droplet characteristics. With the aim to develop prediction models for air-induction nozzles (AINs), a series of Billericay Farm Services (BFS) AINs with different orifice diameters in combination with tap water were tested. 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa and 0.7 MPa of spray pressures and 2 m/s, 3 m/s, 4 m/s and 5 m/s of air speeds were setup. Based on the wind tunnel tests data, prediction models with input variables of nozzle flowrate and spray pressure and output variables of Dv0.1, Dv0.5, Dv0.9, %<150 µm (proportion of spray volume contained in droplets with diameter below 150 µm), relative span (RS) and coefficient of variation (CV) of Dv0.5 were developed. The developed models were validated based on wind tunnel experimental data. Results showed that: for Dv0.1, Dv0.5, Dv0.9 and %<150 µm, R2 were equal to 0.768, 0.823, 0.868 and 0.811, indicating that the predictive ability for these four parameters were strong. For RS and CV, R2 were equal to 0.100 and 0.113, respectively, indicating that the predictive ability for these two parameters were poor. The models developed in the present study are helpful for facilitating the use of AIN in agricultural spray application. Keywords: prediction model, agricultural spray application, droplet characteristics, AIN, laser diffraction DOI: 10.25165/j.ijabe.20191206.5014 Citation: Liao J, Hewitt A J, Wang P, Luo X W, Zang Y, Zhou Z Y, et al. Development of droplet characteristics prediction models for air induction nozzles based on wind tunnel tests. Int J Agric & Biol Eng, 2019; 12(6): 1–6.

Application of Ultrasonic Anemometer Array to Field Measurements of the Downwash Flow of an Agricultural Unmanned Helicopter

Abstract. Unmanned helicopters are widely used in agricultural spray applications; however, there is a lack of high-accuracy field data on the complex downwash flows caused by such helicopters to support efficient spraying. Therefore, we aimed to collect high-accuracy reference data by developing an ultrasonic anemometer array and related software to measure the downwash flow velocity field of a common agricultural unmanned helicopter (Copterworks AF-25B) during outdoor hovering and forward flight. Differential GPS and image scaling were used to determine the exact position and velocity of the helicopter to ensure repeatability of the tests. When the hovering height of the rotor above the ground plane was y/R = 2.5 (where y is the height above ground level and R is the radius of the rotor), the maximum downwash velocity reached 7 m s-1 at x/R = 0.5 (where x is the radial distance from the axis of the rotor). In addition, we obtained the spatial distribution of the turbulence kinetic energy. The attached flow velocity in the near-ground boundary layer increased radially and reached a maximum of 3 m s-1 at x = 3.6 m, after which it decreased. Comparatively, the maximum downwash velocity during forward flight occurred between x/R = 0.5 and 1.5 and was only about 3 m s-1, which was less than half the maximum downwash velocity while hovering. In addition, the circulation flow below the rotor tips had a velocity of 1.5 m s-1. The downwash flow lasted more than 1 s as the helicopter passed over a given point on the ground, the downwash velocity decreased from 3 m s-1 to 1.5 to 2.5 m s-1, and the symmetry of the flow field was not maintained. This study is the first application of an ultrasonic anemometer array to measure the airflow around an unmanned helicopter and provides high-accuracy field data that can be used as a reference for future indoor and simulation studies. Keywords: Agricultural unmanned helicopter, Downwash flow velocity field, Forward flight, Hovering, Ultrasonic anemometer.

Development and Preliminary Evaluation of an Integrated Individual Nozzle Direct Injection and Carrier Flow Rate Control System for Pesticide Applications

Abstract. Direct injection systems for agricultural spray applications continue to present challenges in terms of commercialization and adoption by end users. Such systems have typically suffered from lag time and mixing uniformity issues, which have outweighed the potential benefits of keeping chemical and carrier separate or reducing improper tank-mixed concentration by eliminating operator measurements. The proposed system sought to combine high-pressure direct nozzle injection with an automated variable-flow nozzle to improve chemical mixing and response times. The specific objectives were to: (1) integrate a high-pressure direct nozzle injection system with variable-flow carrier control into a prototype for testing, (2) assess the chemical metering accuracy and proper mixing at different combinations of injection valve frequency and duty cycle along with chemical pressure, and (3) assess the ability of the control system to ensure proper chemical dilutions and concentrations in the nozzle effluent resulting from step changes in target application rates. Laboratory experiments were conducted using the combined system. Results of these experiments showed that the open-loop control of the injectors could provide a means of accurately metering the chemical concentrate into the carrier stream. Chemical injection rates could be achieved with an average error of 5.4% compared to the target rates. Injection at higher duty cycles resulted in less error in the chemical concentration predictions. Discrete Fourier transform analysis showed that the injection frequency was noticeable in the nozzle effluent when the injector was operated at 3.04 MPa and 5 Hz (particularly at lower duty cycles). Increasing the injection pressure and operating frequency to 5.87 MPa and 7 Hz, respectively, improved mixing, as the injection frequency component was no longer noticed in the effluent samples. The variable-flow nozzle was able to maintain appropriate carrier flow rates to achieve product label chemical concentrations. In one case, the maximum allowable concentrate was exceeded, although the nozzle was able to recover in 0.5 s. Steady-state errors ranged from 2.5% to 7.5% for chemical concentrations compared to the selected chemical to carrier ratio (0.03614). This test scenario represented an application rate of 4.68 L ha-1 with velocity increases from 4.0 to 7.1 m s-1 and decreases from 7.1 to 4.0 m s-1, which were typical of the example field application data. Keywords: Pesticides, Precision agriculture, Spraying equipment, Variable-rate application.

Assessing the Fate of an Aromatic Hydrocarbon Fluid in Agricultural Spray Applications Using the Three-Stage ADVOCATE Model Framework.

Components of emulsifiable concentrates (ECs) used in pesticide formulations may be emitted to air following application in agricultural use and contribute to ozone formation. A key consideration is the fraction of the ECs that is volatilized. This study is designed to provide a mechanistic model framework for estimating emissions of an aromatic hydrocarbon fluid used in ECs based on the results of spray chamber experiments that simulate fate as the fluids become subject to volatilization, sorption to soil, and biodegradation. The results indicate the need to treat the volatilization losses in three stages: (i) losses during spraying, (ii) losses up to 12 h after spraying in which the soil is coated with the ECs, and (iii) subsequent longer term losses in which the ECs become increasingly sorbed and subject to biodegradation. A mass balance model, the agrochemical derived volatile organic compound air transfer evaluation (ADVOCATE) tool, is developed, treating the ECs as seven hydrocarbon component groups, to estimate the volatilization and biodegradation losses using parameters fitted to empirical data. This enables losses to be estimated for each hydrocarbon component under field conditions, thereby providing a basis for improved estimation of ozone formation potential and for designing ECs that have lower emissions.

Presence of organophosphorus pesticide oxygen analogs in air samples

A number of recent toxicity studies have highlighted the increased potency of oxygen analogs (oxons) of several organophosphorus (OP) pesticides. These findings were a major concern after environmental oxons were identified in environmental samples from air and surfaces following agricultural spray applications in California and Washington State. This paper reports on the validity of oxygen analog measurements in air samples for the OP pesticide, chlorpyrifos. Controlled environmental and laboratory experiments were used to examine artificial formation of chlorpyrifos-oxon using OSHA Versatile Sampling (OVS) tubes as recommended by NIOSH method 5600. Additionally, we compared expected chlorpyrifos-oxon attributable to artificial transformation to observed chlorpyrifos-oxon in field samples from a 2008 Washington State Department of Health air monitoring study using non-parametric statistical methods. The amount of artificially transformed oxon was then modeled to determine the amount of oxon present in the environment. Toxicity equivalency factors (TEFs) for chlorpyrifos-oxon were used to calculate chlorpyrifos-equivalent air concentrations. The results demonstrate that the NIOSH-recommended sampling matrix (OVS tubes with XAD-2 resin) was found to artificially transform up to 30% of chlorpyrifos to chlorpyrifos-oxon, with higher percentages at lower concentrations (<30 ng m−3) typical of ambient or residential levels. Overall, the 2008 study data had significantly greater oxon than expected by artificial transformation, but the exact amount of environmental oxon in air remains difficult to quantify with the current sampling method. Failure to conduct laboratory analysis for chlorpyrifos-oxon may result in underestimation of total pesticide concentration when using XAD-2 resin matrices for occupational or residential sampling. Alternative methods that can accurately measure both OP pesticides and their oxygen analogs should be used for air sampling, and a toxicity equivalent factor approach should be used to determine potential health risks from exposures.

DIRECT INJECTION TECHNIQUE FOR BIO-PESTICIDE SPRAY

Chemical pesticides have been used in agriculture and horticulture for several decades as a brute force method of achieving pest control. As a result, the persistence of some of these chemicals has left a long-lasting impact on the environment and non-target organisms. Pollution, pest resistance, and possible implications to cancer and diseases are a few such impacts. Modern pest control is shifting away from reliance on persistent chemical pesticides in favor of a more integrated approach to pest management. Applied biological pest control is an important component in an Integrated Pest Management (IPM) program. The main objective of the current research is reducing the organism damage due to these individual mechanisms in conventional agricultural spray application system by using the direct injection of bio-pesticide. The tequniche of biopesticied (Bacillus Thuringiensis . BT) was constructed and developed in Agriculture engineering dept. kafr El.sheikh University. The result indicate the mean values of B.T. spores for direct injection and Albuz B nozzle were 4×106, 6×107 and 8x107 at operating pressure 250 kPa, 150 kPa and 100 kPa respectively. Further more, the values of B.T. at the same operating pressure for indirect sprayer were 1×105, 4×105 and 8x105 at operating pressure 250 kPa, 150 kPa and 100 kPa respectively

Microencapsulated Clomazone: Formulation Stability, Tank Mix Volatility, and Solvent Effects

Abstract Clomazone is microencapsulated and sold in the U.S. as a dispersion in water, a capsule suspension (CS), under the name Command®®Command is a trademark of FMC Corporation. 3ME herbicide. Our encapsulated formulation reduces the volatility of the active ingredient when it is applied to the soil surface in a typical agricultural spray use. The commercialized formulation was selected from among hundreds of encapsulated formulations for its ability to reliably control volatility. Many of the rejected formulations did not control volatility, and it was only through a careful optimization of the encapsulation process that we came to our selection. As part of our formulation development process, we developed a laboratory volatility assessment method for use in screening formulations. This method determined the volatility following a soil application and normalized the volatility of the encapsulated formulations to that of the older Command 4EC herbicide formulation. Our optimized formulation was introduced to the market in 1996 to control volatility. A sample of the first production batch of commercial clomazone 3CS formulation, which had been stored at room temperature and regularly assessed for ten years, continues to provide excellent control of volatility. This indicates that the capsules have remained intact and functional, and that the proportion of clomazone in the capsule, versus outside, has not changed as the formulation aged. When these capsules are diluted in water, some clomazone slowly diffuses out of the capsules. This release is limited by the water solubility of clomazone. Even for excessive residence times in the spray tank, the volatility from the soil surface increased only slightly and was well within the acceptable range, for dilutions used for agricultural spray application. Improper addition of solvents and surfactants to the formulation can provide a phase where the clomazone is soluble, and this solubility will extract clomazone from the capsules. Under these conditions the volatility of the product increased so that it was similar to an unencapsulated formulation. In contrast, addition of other herbicides or spray additives to the spray tank mix had little impact on the volatility.

Caffeine for reducing bird damage to newly seeded rice

The economic impact of blackbirds can be severe to rice producers in the United States. One approach to managing this damage is the application of bird-deterrent chemical to the crop. Previous pilot trials suggested that caffeine offered potential as a safe, economical bird repellent. In this study, cage feeding trials with female red-winged blackbirds and male brown-headed cowbirds confirmed that a treatment rate of 2500 ppm caffeine on rice seed reduced consumption as much as 76%. Trials with mixed species blackbird flocks in a 0.2-ha flight pen resulted in just 4% loss of caffeine-treated rice compared to 43% loss of untreated rice. Field trials of a 10,000 ppm caffeine treatment in Louisiana revealed >90% of caffeine-treated rice seed remained unconsumed on days 2 and 3 of the study whereas blackbirds consumed >80% of the untreated seed. As a rice seed treatment to deter blackbirds, caffeine appears to be effective, economical and environmentally safe, although additional aquatic toxicity testing is desirable. Improvements in formulation will be needed to make the compound practical for general agricultural spray applications and to extend the adherence of caffeine to rice seeds in field conditions.

Mapping leaf surface landscapes.

Leaf surfaces provide the ecologically relevant landscapes to those organisms that encounter or colonize the leaf surface. Leaf surface topography directly affects microhabitat availability for colonizing microbes, microhabitat quality and acceptability for insects, and the efficacy of agricultural spray applications. Prior detailed mechanistic studies that examined particular fungi-plant and pollinator-plant interactions have demonstrated the importance of plant surface topography or roughness in determining the outcome of the interactions. Until now, however, it has not been possible to measure accurately the topography--i.e., the three-dimensional structure--of such leaf surfaces or to record precise changes in patterns of leaf surface elevation over time. Using contact mode atomic force microscopy, we measured three-dimensional coordinates of upper leaf surfaces of Vaccinium macrocarpon (cranberry), a perennial plant, on leaves of two age classes. We then produced topographic maps of these leaf surfaces, which revealed striking differences between age classes of leaves: old leaves have much rougher surfaces than those of young leaves. Atomic force microscope measurements were analyzed by lag (1) autocorrelation estimates of leaf surfaces by age class. We suggest that the changes in topography result from removal of epicuticular lipids and that the changes in leaf surface topography influence phylloplane ecology. Visualizing and mapping leaf surfaces permit detailed investigations into leaf surface-mediated phenomena, improving our understanding of phylloplane interactions.

Organosilicone surfactant performance in agricultural spray application: a review

Summary: Résumé: ZusammenfassungThe effects of organosilicone surfactants on the physico‐chemical properties of spray solutions, and on foliar uptake and field performance of agrochemicals are reviewed. Aqueous solutions of organosilicone surfactants frequently have lower equilibrium surface tensions (down to 20 mN m−1) than conventional surfactants. Dynamic surface tension of silicone surfactants, however, is not consistently lower than that of conventional surfactants. On leaf surfaces of many plant species spray droplets containing organosilicone surfactants spread completely. Organosilicone surfactants are ineffective in lowering surface tension when mixed with most conventional surfactants. However, poly‐alkylene oxide surfactants do not interfere with surface tension lowering by organosilicone surfactants. Some organosilicone surfactants degrade rapidly in acidic or alkaline spray solutions and degradation adversely affects performance. Generally, organosilicone surfactants increase foliar uptake and field performance of agrochemicals more rapidly, but final uptake is not consistently different from conventional surfactants. Frequently, mass flow of the spray solution through open stomata accounts for rapid enhancement of uptake and performance. The studies reviewed suggested that some organosilicone surfactants may offer advantages over conventional surfactants, but require some precautions if their full potential is to be utilized. Revue: les tensio‐actifs de type organosilicone dans la pulvérisation phytosanitaire Les effets des tensio‐actifs de type organosilicone sur les propriétés physicochimiques des bouilles de pulvérisation, ainsi que sur la pénétration foliaire et l'efficacité au champ des produits phytosanitaires, sont examinés. Les solutions aqueuses de tensio‐actifs organosilicones ont souvent des tensions superficielles à l'équilibre plus basses (20 nN m−1) que celles des tensio‐actifs conventionnels. Ce n'est cependant pas toujours le cas de leur tension superficielle dynamique. Sur la surface foliaire de beaucoup d'espèces végétales, les gouttelettes contenant des organosilicones s'étalent complètement. Les tensio‐actifs organosilicones perdent leur faculité de baisser la tension superficielle lorsqu'ils sont mélangés à la plupart des tensio‐actifs conventionnels. Cette restriction ne concerne pas les tensio‐actifs de type polyalkylène oxyde. Certains tensio‐actifs organosilicones se dégradent rapidement si la bouillie est acide ou alcaline, ce qui affecte leur efficacité. En général, ils accélèrent la pénétration foliaire et l'efficacité au champ des produits phytosanitaires mais la pénétration finale n'est pas différente de celle quiest obtenue avec des adjuvants conventionnels. Souvent, la pénétration de la bouillie par l'ouverture stomatique rend compte de l'augmentation de pénétration et d'efficacité. Certains surfactants organosilicones pourraient offrir des avantages par rapport aux tensio‐actifs conventionnels mais qu'ils demandent certaines précautions pour que leur potentiel soit pleinement exprimé. Möglichkeiten des Einsatzes von Silikon‐Tensiden in Formulierungen und Spritzlösungen Es wird ein überblick über den Einfluß von Silikon‐Tensiden auf die physikochemischen Eigenschaften von Spritzbrühen, die Blattaufnahme und die Wirkung von Agrarchemikalien gegeben. Wäßrige Lösungen von Silikon‐Tensiden haben oft eine niedrigere Gleichgewichtsoberflächenspannung (20 mN m−1) als solche herkömmlicher Tenside. Die dynamische Oberflächenspannung ist mit Silikon‐Tensiden jedoch nicht immer niedriger als mit herkömmlichen. Auf den Blattflächen vieler Pflanzenarten spreizen Spritztröpfchen von Lösungen mit Silikon‐Tensiden vollständig. Werden Silikon‐Tenside mit herkömmlichen Tensiden gemischt, so sind die Lösungen weniger oberflächenaktiv als die reiner Silikon‐Tenside. Lediglich in Mischungen mit Polyalkylenoxid‐Tensiden bleibt die niedrige Oberflächenspannung der Silikon‐Tenside erhalten. Einige Silikon‐Tenside zerfallen in saurer oder basischer Spritzbrühe schnell, wodurch ihre Wirkung beeinträchtigt wird. Der Zusatz von Silikon‐Tensiden beschleunigt zwar allgemein die Blattaufnahme und Wirkung von Agrarchemikalien, doch unterscheidet sich die insgesamt aufgenommene Dosis oft nicht von der mit herkömmlichen Tensiden. Die schnellere Aufnahme und Wirkung ist in vielen Fällen auf das Eindringen der Spritzbrühe durch offene Stomata ins Blattgewebe zurückzuführen. Silikon‐Tenside können gegenüber herkömmlichen Tensiden in einigen Situationen Vorteile bieten, wenn ihre spezifischen Eigenschaften beim Einsatz berücksichtigt werden.