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The quantity and quality of spray deposition are fundamental for improving pesticide performance in plant pests. This study evaluated how spray droplet size (1) and spray nozzle type (2) affect the quantity and quality of spray deposition on peanut plants at the vegetative and reproductive growth stages. Two greenhouse experiments were performed on peanut plants at the V1 and R1 growth stages. Experiment 1 treatments included three droplet sizes: medium (flat fan XR 11002), very coarse (TT 11002), and extremely coarse (AIXR 11002). Experiment 2 treatments were five spray nozzles: hollow cone (TXA 8002 VK), twin flat fan (TTJ60 11002), air induction flat fan (AIXR 110025), drift guard twin flat fan (DGTJ60 11002), and extended range flat fan (XR 11003). Spray deposition values were determined using a solution of brilliant blue dye sprayed by a CO2-pressurized backpack sprayer. The medium droplet size provided higher spray deposition on peanut plants at the V1 and R1 growth stages. Increasing the droplet size from medium to extremely coarse reduces spray deposition at the V1 growth stage. Spray deposition uniformity increased as droplet size increased at the V1 growth stage. The spray uniformity decreased at the R1 growth stage as the droplet size increased. The flat fan XR 11003 (medium droplet) and hollow cone nozzle TXA 8002 VK (fine droplet) provided a higher spray deposition on peanut plants at both growth stages. The spray nozzles that provide a higher spray deposition did not perform well on spray uniformity. [ABSTRACT FROM AUTHOR]

BACKGROUND: A suite of plant retention spray models has been developed to simulate spray retention using virtual surfaces (either single leaves or whole plants) and their outputs compared with experimental data for the equivalent spray scenarios. RESULTS: The results for a single formulation (0.1% v/v lecithin mixture in water) and difficult to wet plant species Chenopodium album L (common lambsquarters) are presented. They include experimental observations with single leaves, as well as simulations of virtual impaction events, conducted to provide for the first time estimates of f (the proportion of theoretical impact drop diameter at shatter). With this factor prescribed, multi‐plant simulations using a range of nozzle types and droplet sizes (volume mean diameter (VMD) range 241 to 530 μm) are compared with equivalent experimentally determined spray retention by real plants. The simulations demonstrated that impaction resulted predominantly in shatter with the production of daughter droplets, and that retention is mainly due to re‐capture of these droplets. Overall the simulations show the same trends as experimental retention results from different nozzle applications, but at best predicted retention results were 68% to 79% of experimental percentage retention, depending on plant spacing. CONCLUSIONS: Retention is the result of some primary drop capture but predominantly by recapture of shatter droplets as the modelling illustrates. The value of f affects the droplet shatter outcome and can result in fewer, more energetic daughter droplets, or more droplets but with lower energies. However, this effect alone cannot explain the discrepancy between actual and simulated results. Possible operational influences are discussed. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Rattail fescue (Vulpia myuros (L.) C.C. Gmel.) is a self-pollinating winter annual grassy weed of winter annual crops. The problems with V. myuros are mostly associated with no-till cropping systems where glyphosate application before sowing or emergence of the crop is the most important control measure. Ineffective V. myuros control has been reported following glyphosate applications. Experiments were performed to study the effectiveness of glyphosate on V. myuros, and determine the causes of the lower performance of glyphosate on V. myuros compared to other grass weeds. Estimated GR50 values demonstrated that V. myuros was less susceptible to glyphosate than Apera spica-venti regardless of the growth stage. Within each species, glyphosate efficacy at different growth stages was closely related to spray retention. However, the low susceptibility to glyphosate in V. myuros was not caused by lower retention as previously suggested. A significantly lower shikimic acid accumulation in V. myuros compared to A. spica-venti was associated with a higher activity of the EPSPS enzyme in V. myuros. Nevertheless, the relative responses in EPSPS activity to different glyphosate concentrations were similar in the two grass species, which indicate that EPSPS from V. myuros is as susceptible to glyphosate as EPSPS from A. spica-venti suggesting no alternation in the binding site of EPSPS. The results from the current study indicate that V. myuros is less susceptible to glyphosate compared to A. spica-venti, and the low susceptibility of V. myuros is caused by an increased EPSPS enzyme activity.

Study of the potential for the use of controlled droplet application (CDA) upon cereal crops. A review. Introduction. Controlled droplet application (CDA) has the advantage both of the reduction in the span of droplet size distribution and in the volume of liquid applied, in comparison with conventional hydraulic nozzles. Literature. This review investigates the potential for the use of CDA relative to hydraulic nozzles within the early stages of weed control (2-3 leaves). The studies reviewed examine spray retention, linking the droplet characteristics (size, velocity and direction) of spray liquids with the architecture, density and wettability of the foliage. These studies show that the use of droplets of 300 µm, combined with an appropriate adjuvant and applied with a 60° forward-angled spray, led to the enhanced depositing of liquids on upright surfaces. Assessment of the reduced volumes applied by both application techniques was based on the mean, the variation coefficient and the deposition coverage. However, these results cannot be generalized, due to the different operative settings in which the spray application techniques were employed. Regarding the risk of drift to the side, the drift potential of droplets generated horizontally by CDA nozzles is greater than that of the conventional technique with a downward orientation of spray. The drift potential increases as the wind velocity increases and the volume median diameter (DV50) decreases. Conclusions. New settings of CDA nozzles in terms of DV50 and the direction of spray may address the challenge of precision agriculture. Innovative ways to apply pesticides, based on CDA, must be explored in order to avoid the sensitivity to wear of the teeth in spray applicators and to obtain a narrower droplet-size distribution.

Conyza bonariensis, C. canadensis and C. sumatrensis are problematic weeds in citrus orchards and olive trees in southern Spain. The aim of this work was to determine the efficacy of glufosinate in these species, and also to establish a suitable growing stage for application in C. bonariensis. For this purpose, dose-response and spray retention assays were carried out in susceptible biotypes of C. bonariensis, C. canadensis and C. sumatrensis at the rosette stage (BBCH 14-15). Additionally, the ED50 and spray retention at two later growth stages were determined in C. bonariensis. Results at rosette stage (BBCH 14-15) showed an ED50 of 0.216 in the case of C. bonariensis; 0.058 for C. canadensis and 0.090 L ha-1 for C. sumatrensis. The spray retention values did not show any significant differences between the three species at rosette stage. In C. bonariensis, at the second stage of its growth (10-15 cm in height), the ED50 obtained was 0.517 and 1.297 L ha-1 for the third stage (with formed capitula). Also, the spray retention in the second and third stage was of 0.44 and 0.38 mL of glufosinate g-1 of dry weight, respectively. These species treated in an early developmental stage are more susceptible to glufosinate herbicide.

Retention of sprays on plants is a critical component influencing the effectiveness of agrichemical applications. Previous simulations of s pray retention by plants gave poor agreement for hard-to-wet species when compared with actual measured retention. A new model is developed here that accounts for: species wettability, impaction angle, droplet bounce, partial retention on shatter, a variable time to shatter, and the number of daughter droplets produced. The aim of this study was to compare predictions from the new model with data obtained by spraying five mixtures via five nozzles onto easy-to-wet cotton ( Gossypium hirsutum L.), and hard-to-wet wheat ( Triticum aestivum L.) and fat hen ( Chenopodium album L.). The new model correctly predicts retention to be highest on cotton and lowest on wheat. The trend in both measured data and the model predictions is for retention to decrease with increasing droplet size, on all three plant species. Formulation is correctly predicted to have little influence on retention by easy-to-wet cotton plants and to enhance retention by the harder-to-wet wheat and fat hen plants. The parameters that describe partial retention on shatter and variable time to shatter have a substantial influence on retention, as they affect primary or secondary droplet capture. A better understanding of the kinetic energy effects and the interactions between the formulation and the leaf surface are needed to refine their input values. [ABSTRACT FROM AUTHOR]

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A model predicting the spray droplet interception and retention by a single virtual plant has been developed. The model was based on three main experimental inputs: the 3D architecture of a barley plant, the spray quality and the droplet impact behavior. Two contrasted formulation scenarios, limits of the common range covered by pesticide application in terms of surface tension, were tested by changing the droplet behavior at impact in the model. Simulations were undertaken for studying the variability of spray retention resulting from spray quality, applied volume and plant size for a difficult-to-treat target. Results showed that the spray retention efficiency ranged from 6.8% to 96.6% of a theoretical full adhesion scenario, where all intercepted droplets were captured, according to spray quality for the two formulation scenarios tested. Average retention increased with increasing spray fineness, applied volume per hectare and plant size. Variability of deposits, evaluated using the coefficient of variation of simulated retentions, was found to be a function of the mean droplet density according to CV∝N −0.68 , where CV is the coefficient of variation and N the number of droplet per square centimeter. Variability was also found to be a function of the plant size according to a relation CV∝S −0.5 , where S is the total leaf area of the plant model. The variability of deposits increased with decreasing spray fineness, applied volume per hectare and plant size because of the reduced number of droplets contributing to retention. Wetting properties greatly influenced retention but surprisingly poorly influenced the variability of deposits. Such a modeling approach that is capable of an independent investigation of the influence of various parameters on spray retention can be used to improve understanding of application methods and adjuvants that could help minimizing development of resistance in problematic weed species. [ABSTRACT FROM AUTHOR]

Soybeans are often sprayed to prevent significant yield loss from damage by insect pests and plant diseases. Understanding interactions of spray droplet reactions on soybean plant surfaces can lead to development of improved application strategies to enhance efficacy of pesticides. In this research, dynamics of impact and spread of water droplets of 185 to 693 ²m at 1.85 to 6.4 m s-1 impact speeds and 28° to 75° impact angles on two soybean leaf surface orientations (horizontal and 30° inclination) were investigated with two high-speed digital video cameras and a mono-sized droplet generator under laboratory-controlled conditions. Within the test ranges of the variables, droplet rebound was not observed after impact on leaf surfaces, while droplets larger than 300 ²m were observed to slide on the 30° inclined surface. Droplet spread factors increased with droplet diameters and impact speeds but decreased with impact angles. Isoline distributions of droplet spread factors on a horizontal surface were established to provide visual observations for estimating spray coverage areas with different droplet impact speeds and impact angles. At similar impact speeds and angles, droplet spread factors on inclined leaf surfaces were greater than those on horizontal surfaces. These discoveries elucidate that careful selection of controllable spray parameters to maximize droplet spread area and retention on soybean plants is possible for efficient soybean spray applications with minimal amounts of spray mixtures. [ABSTRACT FROM AUTHOR]

Spray retention, i.e. the overall capture of spray droplets by plants on initial or subsequent impact, and after loss due to run-off, is an important stage in the spray application process as droplet losses may result in reduced efficacy, economic loss, and environmental contamination. The aim of this exploratory study is to determine whether a new method based on calculating the volumetric proportions per impact type, i.e. adhesion, rebound and shatter, can be used to predict spray retention. These volumetric proportions are calculated based on logistic regression models, derived from vision-based droplet characteristics and impact assessments, and laser-based spray characteristics. The advantages and limitations of such a method are explored. The volumetric proportions per impact type on a horizontal, synthetic hydrophobic surface were determined for four different nozzles (XR 110 01 VS flat-fan nozzle, XR 110 04 VS flat-fan nozzle, XR 110 08 VS flat-fan nozzle and AI 110 08 VS air-induction nozzle) under controlled realistic conditions, and compared to the results of a retention test. The volumetric proportions of adhesion were much lower than the relative retentions, indicating that a considerable amount of rebound and shatter also contributed to final retention. The method should thus be improved by including the droplets retained after first impact and the retained proportions of partial droplet fragmentation but it is nevertheless considered a promising technique. [ABSTRACT FROM AUTHOR]

Research in precision spraying investigates the means to reduce the amount of herbicide applied by directing droplets more accurately towards the weeds. The trend in the development of spot spraying equipment is an increase of the spatial resolution and new actuators that are able to target very small areas. However, there is a lack of methods for assigning rates of herbicides relating target to optimal droplet features. A wide range of droplet impact angles occurs during the spray application process because of droplet trajectories and the variability of leaf orientation. In this study, laboratory experiments were conducted to highlight the effect of surface orientation on droplet impact outcomes (adhesion, rebound or splashing) on two very difficult-to-wet surfaces: an artificial surface with a regular roughness pattern and an excised black-grass leaf with an anisotropic roughness pattern. Measurements were performed for different surface orientations with a high-speed camera coupled with backlighting LED. Droplets of two formulations (distilled water and distilled water + a surfactant) were produced with a moving flat-fan hydraulic nozzle to obtain a wide range of droplet sizes and velocities, which were measured by image analysis. Increasing surface angle reduces surface area available for droplet capture. Droplet impact behaviors are then modified since surface tilt induces a tangential velocity component at impact and, consequently, a reduction of the normal component. Impact modifications have also been observed due to the anisotropic roughness pattern of a black-grass leaf. The integration of droplet-surface interaction information offers a significant way to further improve the precision spraying efficiency by considering the optimal droplet size, speed and ejection angle depending on the target surface and architecture. [ABSTRACT FROM AUTHOR]

AGDISP uses canopy structure and collection efficiency to model canopy interception but assumes droplets that intercept a leaf surface are retained at that point and do not bounce or shatter. This behavior is not the case for many plant species, particularly species that are moderately to very difficult to wet, for which canopy deposition would be overestimated with this assumption. This article summarizes the initial implementation of process-based models for spray droplet bounce and shatter within an experimental build of AGDISP in order to predict spray retention within plant canopies. Spray simulations were run for formulations ranging in surface tension, applied to three species (wheat, canola, and capsicum) with different wettabilities and leaf orientations, and using the AGDISP ground model with and without the retention model, to evaluate the impact of the retention model on canopy deposition within AGDISP The model outputs were also compared to previously determined tracksprayer results. The current AGDISP canopy deposition (interception) model was unable to fully account for differences in retention due to the spray formulation used or species studied Incorporation of the process-driven models for bounce and shatter allowed these differences to be predicted. Over the three species and four formulations studied, there was good agreement (Pearson's correlation coefficient = 0.9308, p = 0.0000, indicating an almost certain correlation) between predicted and experimentally determined retention. Considerable work is still required to make this approach practical. However, this article illustrates that the ability to model retention is important for many crops (and weeds) and that the approach outlined herein is an effective adjunct to the current AGDISP interception model. [ABSTRACT FROM AUTHOR]

Abstract: Recent advances in the area of the wetting of leaf areas are reviewed with particular emphasis on their relation to agrochemical application. Areas reviewed include leaf wax composition, leaf wetting and superhydrophobicity, agrochemical deposit formation and spray retention. It is thought that most progress has been made in the area of leaf wetting through the work on lotus leaves. In the area of spray retention, factors such as plant type, spray solution properties and weathering of the plants are found to be keys. Recent progress in the modelling of spray retention is also discussed. [Copyright &y& Elsevier]

Abstract: Laboratory and field experiments were carried out with apples (Malus x domestica Borkh.) cv. ‘Golden Reinders’, to assess the efficacy of sodium salt of carboxymethyl ether of cellulose (0.5%, CMC) as an adjuvant for Ca spray formulations containing either Ca-chloride or Ca-propionate as active ingredient (120 or 250mM Ca). This additive significantly increased the retention of Ca-containing solutions by the apple skin and prolonged the process of drying of the solution at room temperature. Four days after immersion of apples in 0.5% CMC plus CaCl2 or Ca-propionate solutions (120 and 250mM Ca) significant Ca increases were recorded in the peel and cortex of treated fruits. Application to apple trees of in-season sprays containing 250mM CaCl2 plus 0.05% Tween 20, Ca-propionate (120 and 250mM Ca) plus 0.5% CMC or 250mM CaCl2 plus 0.5% CMC had no impact on fruit yield and quality, but significantly limited the rate of bitter pit incidence during the following 3-month cold-storage period. Evidence is provided that addition of appropriate adjuvants to Ca sprays can favour the distribution of Ca into the apple fruit and helps to reduce the incidence of Ca-related disorders over the postharvest cold-storage period. [Copyright &y& Elsevier]

Fractal analysis can provide a unique mathematical tool to quantify the geometry of irregular and complex plant canopies. This study demonstrated that a single numerical fractal dimension (FD) value derived from an image taken from above the plant canopy could differentiate between and rank the canopies of a range of plant species. We also investigated the influence of canopy architecture and surface characteristics on spray retention. Multiple regressions were used to derive mathematical relationships and develop a spray retention model. It was discovered that the FD value can successfully be used to replace the statistically generated plant morphological factor (Mp4) used in a previous retention model, with the major advantage being that the retention model now only involves variables that can be readily measured. There is an excellent relationship ( R2 = 0.99) between actual spray retention per plant (μL) and that predicted by the model incorporating the FD. The spray retentiveness of the plant species studied was ranked using a numerical index based on plant canopy architecture and surface characteristics. [ABSTRACT FROM AUTHOR]

The article focuses on the factors that affect retention and efficacy of disease-management products on field and horticultural crops. It says that disease development on vertical tissues of plants can affect yield and quality, but spray coverage and retention are frequently too low to reduce infection success. It concludes that the efficacy of foliar-applied disease-management products and other pesticides can be improved through optimizing spray application parameters.

The influence of application volume on the efficacy of clodinafop-propargyl and fenoxaprop-P-ethyl on cultivated oats ( Avena sativa) was studied in the glasshouse. Both herbicides were more efficacious when applied in 75 L ha−1 than in 300 L ha−1, with 11002 and 11006 nozzles respectively. However, when the same two volume rates were created by varying the speed of a 11003 nozzle, clodinafop-propargyl efficacy was not affected by application volume, whereas fenoxaprop-P-ethyl remained more efficacious at 75 L ha−1. This suggests that in the first experiment, fenoxaprop-P-ethyl efficacy was affected by changes in both spray quality and concentration, whereas only the former influenced clodinafop-propargyl efficacy. The hypothesis that the fenoxaprop-P-ethyl formulation was more influenced by concentration than clodinafop-propargyl was supported by dynamic surface tension studies and measures of active ingredient retention by oat plants. Within the practically relevant concentration range considered, surface activity of clodinafop-propargyl remained low, with little influence on herbicide retention. In contrast, depending on the concentration, surface activity of fenoxaprop-P-ethyl was below or above levels that were critical for its retention. Although these differences may not be as apparent in the field as in the glasshouse, our study certainly indicates that both clodinafop-propargyl and fenoxaprop-P-ethyl are herbicides favoured by low application volumes. [ABSTRACT FROM AUTHOR]

The aim of this work was to examine the effect of liquid properties on spray retention in a range of situations representative of practical pesticide application. Liquids with different physical properties were sprayed with conventional flat-fan and air-induction nozzles onto outdoor-grown wheat plants (Triticum aestivum L cv Axona) at growth stages between GS 22 and GS 35. Since total retention is affected by leaf surface as well as plant growth stage and canopy density, the experiments included spraying both single leaves and groups of plants with different canopy densities. Retention on whole plants was strongly influenced by plant growth and canopy properties. Individual leaf surfaces were not as water-repellent as was found previously for younger indoor-grown plants, reducing the effect of dynamic surface tension on retention. This, combined with the increased probability of droplets hitting foliage in a denser canopy, gave reduced differences in retention between liquids when compared with similar measurements made previously on younger plants. With a leaf area index greater than 7, retention on whole plants was almost independent of liquid. Air-induction nozzles gave lower levels of retention than flat-fan nozzles, with this difference greatest when spraying high dynamic surface tension liquids and at low crop densities. [ABSTRACT FROM AUTHOR]

Rattail fescue (Vulpia myuros (L.) C.C. Gmel.) is a self-pollinating winter annual grassy weed of winter annual crops. The problems with V. myuros are mostly associated with no-till cropping systems where glyphosate application before sowing or emergence of the crop is the most important control measure. Ineffective V. myuros control has been reported following glyphosate applications. Experiments were performed to study the effectiveness of glyphosate on V. myuros, and determine the causes of the lower performance of glyphosate on V. myuros compared to other grass weeds. Estimated GR50 values demonstrated that V. myuros was less susceptible to glyphosate than Apera spica-venti regardless of the growth stage. Within each species, glyphosate efficacy at different growth stages was closely related to spray retention. However, the low susceptibility to glyphosate in V. myuros was not caused by lower retention as previously suggested. A significantly lower shikimic acid accumulation in V. myuros compared to A. spica-venti was associated with a higher activity of the EPSPS enzyme in V. myuros. Nevertheless, the relative responses in EPSPS activity to different glyphosate concentrations were similar in the two grass species, which indicate that EPSPS from V. myuros is as susceptible to glyphosate as EPSPS from A. spica-venti suggesting no alternation in the binding site of EPSPS. The results from the current study indicate that V. myuros is less susceptible to glyphosate compared to A. spica-venti, and the low susceptibility of V. myuros is caused by an increased EPSPS enzyme activity. [ABSTRACT FROM AUTHOR]