Conventional Hydraulic Nozzles Research Articles

Aerial application methods control spider mites on corn in Kansas, USA.

The Banks grass mite, Oligonychus pratensis (Banks), and two-spotted spider mite, Tetranychus urticae Koch, are important chelicerae herbivores on irrigated corn in Kansas, USA. They cause loss of foliage, stalk breakage, kernel shrinkage and yield loss. Aerial application methods were evaluated to control spider mites in a commercial corn field in August, 2017, near Hoxie, Kansas. Dimethoate (0.56kg active ingredient/ha) and Lorsban Advanced (1.05kg active ingredient/ha) mixed with a nonionic surfactant, Traverse (0.25% v/v), were aerially applied using conventional flat-fan hydraulic nozzles at 28.1L/ha and aerial electrostatic nozzles at 9.3L/ha. To assess spray droplet spectra of the aerial application methods, water sensitive paper samplers were deployed at the whorl of husk leaves at the tip of the ear before aerial spray treatments were applied. Spray droplet spectra were quantified using commercial image analysis software. Treatment efficacy was assessed both objectively and subjectively. Objective efficacy evaluation incorporated the use of an active multispectral optical sensor via spectral analysis of the midrib regions of corn leaves on the abaxial surface where spider mites reside. Subjective damage ratings based upon in-field spider mite movement observations were scored by professional crop scouting consultants. Results of objective spectral analysis and subjective damage ratings indicated that both the conventional and electrostatic nozzles with 283 and 210-µm spray droplet 'volume median diameter' (VMD) at 28.1 and 9.3 L/ha, respectively, controlled spider mites compared to an untreated check.

The effect of air velocity and proximity on the charging of sprays from conventional hydraulic nozzles

Conventional nozzles where hydraulic pressure is used to form the spray, are widely used in agricultural spraying. In many cases they rely on air assistance to efficiently convey the spray droplets to the target. The addition of a further depositing force based on electrostatic charging can significantly improve deposition, particularly on the shaded or hard-to-reach surfaces. The positioning of induction-charging electrodes close to nozzle outlets was investigated. In the laboratory the charging of a conventional flat-fan hydraulic nozzle was investigated. Optimal spacings were found when a high ambient air velocity was used to prevent charged droplets depositing on the electrodes and their insulated mountings. The moving air also dried them continuously, thereby prevented leakage. The results show that a current of 13.9 μA per nozzle was attainable for a spray pressure of 400 kPa with a liquid flow rate of 0.45 l min −1 and droplet spectrum with a 115 μm volume medium diameter (VMD). This is equivalent to a charge-to-mass ratio of 1.85 mC kg −1 . These high currents and high charging levels were achieved by using air velocities > 10 m s −1 . Laboratory tests showed that the spacing between nozzles could be too small, reducing the level of charge per nozzle. A field sprayer was designed with nozzles using a higher flow rate than those investigated in the laboratory. Field tests of the prototype sprayer in a commercial vineyard showed that electrostatic charging improved the deposition of droplets containing a fluorescent tracer by 200 and 500% on the leaf undersides and the rear of grape clusters, respectively. Core findings of the study : • Air velocity is very important when charging spray generated by hydraulic nozzles. • High-air velocity may facilitate charge level of more than 1.8 mC kg −1 for such spraying. • This level is substantially higher than those previously reported for conventional nozzles. • This charging substantially improved deposition on hard-to-reach surfaces in field tests.

Ground-based spectral reflectance measurements for evaluating the efficacy of aerially- applied glyphosate treatments

Aerial application of herbicides is a common tool in agricultural field management. The objective of this study was to evaluate the efficacy of glyphosate herbicide applied using aircraft fitted with both conventional and emerging aerial nozzle technologies. A weedy field was set up in a randomised complete block experimental design using three replicates. Four aerial spray technology treatments, electrostatic nozzles with charging off, electrostatic nozzles with charging on, conventional flat-fan hydraulic nozzles and rotary atomisers, were tested. To evaluate the glyphosate efficacy and performance of aerial spray technologies, spectral reflectance measurements were acquired using a ground-based sensing system for all treatment plots. Three measurements were taken at 1, 8, and 17 days after treatment (DAT). The statistical analyses indicated that glyphosate applied with different methods killed the weeds effectively compared to untreated areas at 17 DAT. Conventional flat-fan nozzles and rotary atomisers performed better than the electrostatic nozzles with charging off. There was no evidence to show that the electrostatic nozzle performed better with charging on or charging off. The results could provide applicators with guidance equipment configurations that can result in herbicide savings and optimised applications in other crops.

Aerial Application Methods for Increasing Spray Deposition on Wheat Heads

Fusarium head blight (FHB) is a major disease of wheat and barley in several small grain production areas in the United States and, as such, the development and evaluation of aerial application technologies that enhance the spray deposition of fungicides, is critical to its management. This research was initiated to assess aerial spray technologies in an effort to increase spray deposits on wheat heads. Conventional hydraulic nozzles at two spray rates and two droplet sizes along with rotary atomizer and electrostatic treatments were investigated. Based on results from collectors and visual analysis the optimal spray treatment for deposition on wheat heads was hydraulic nozzles at 18.7 L/ha and a 350-m droplet volume mean diameter. The results from this study provide guidance for aerial fungicide applications for increased deposition on wheat heads.

Coverage and Drift Produced by Air Induction and Conventional Hydraulic Nozzles Used for Orchard Applications

A conventional, axial-flow, air-blast orchard sprayer was used to make applications to the outside row of a semi-dwarf apple block. Fluorescent tracer was applied at the same rate using either disc-core nozzle sets or air-induction nozzles fitted with flat-fan tips. The experiment included measuring the percent area of spray coverage on leaves after three variations in spray application method. Each of the variations used a different type of nozzle on the same conventional, axial-fan orchard sprayer. The three nozzle variations were a Spraying Systems D3-25 nozzle set, a Spraying Systems D4-25 nozzle set, and a TurboDrop 02 (TD02) air-induction nozzle set. Canopy spray deposits, downwind sedimentation, and airborne spray losses were also measured following treatment on the inside half of the outside row using D4-25 nozzles or TD02 nozzles. The small droplet spectrum D3-25 nozzle set produced the highest leaf surface coverage on both upperside and underside surfaces at 2.0 and 3.0 m heights in the canopy. The upperside leaf surface coverage produced by the D3-25 nozzle was only somewhat greater than the TD02 nozzle. It was, however, significantly higher than the D4-25 nozzle set at the 3.0 m height. Conversely, the underside leaf surface coverage produced by the D3-25 was significantly greater than the TD02 nozzle set at both 2.0 and 3.0 m heights and not statistically different from the D4-25 nozzle set at the lower sampling height. There were relatively few differences in canopy spray deposits between the D4-25 and TD02 nozzle sets. The TD02 treatment produced the lowest downwind sedimentation deposits on targets 8 to 32 m from the edge of the orchard. The D4-25 produced approximately three times higher deposits up to 9 m above the ground than the TD02 treatment on passive nylon screens located 8 m downwind from the edge of the orchard. The D4-25 treatment produced significantly higher airborne deposits on elevated, high-volume, air sampler filters out to 64 m. At 128 m, sedimentation and airborne deposits were similar for the D4-25 and TD02 treatments.

Field Evaluation of Application Variables and Plant Density for Bell Pepper Pest Management

Bell peppers are a valuable vegetable crop in the U.S. Management of pepper insects and diseases relies on chemical control options. Because there are relatively few chemical options available for pepper pest management, it is critical to make efficacious application of pesticides. Foliar spray coverage and spray retention in the middle and bottom of bell pepper canopies were compared using fluorescent dyes and food coloring, respectively. Several delivery systems were evaluated, including air-induction and twin-fan nozzles, air-assisted delivery with conventional hydraulic nozzles, and pneumatic atomization nozzles producing electrically charged sprays. Plant spacing between and within rows was evaluated in the second year of the application trial. Travel speeds of 6.4 and 12.9 km h-1 were also evaluated. Faster travel speeds did not significantly affect spray retention in twin-row canopies. The electrostatic sprayer produced the greatest differences in deposits between the middle and bottom of the canopy. Although there was no more than a 25 cm difference between leaves sampled from the middle and bottom canopy locations, spray retention on foliage in the bottom canopy locations had significantly lower retention than the middle canopy for almost all sprayer types. Despite differences in atomization characteristics, the performance of the twin-fan nozzle and the air-induction nozzle treatments were similar. Air-assisted delivery provided no advantage in the amount of spray retained on the foliage, but it produced more desirable spray quality on foliage and resulted in more spray retained on whole fruit.

AERIAL APPLICATION METHODS FOR INCREASING SPRAY DEPOSITION ON WHEAT HEADS

Fusarium head blight (FHB) is a major disease of wheat and barley in several small grain production areas in the United States and, as such, the development and evaluation of aerial application technologies that enhance the spray deposition of fungicides, is critical to its management. This research was initiated to assess aerial spray technologies in an effort to increase spray deposits on wheat heads. Conventional hydraulic nozzles at two spray rates and two droplet sizes along with rotary atomizer and electrostatic treatments were investigated. Based on results from collectors and visual analysis the optimal spray treatment for deposition on wheat heads was hydraulic nozzles at 18.7 L/ha and a 350-m droplet volume mean diameter. The results from this study provide guidance for aerial fungicide applications for increased deposition on wheat heads.

Pedestrian sprayers: equipment for ultra‐low and very‐low volume spraying1

Plant protection products often need to be applied to small areas, inaccessible to vehicular equipment, hence the need for manually carried equipment. While there are lever‐operated knapsack and compression sprayers using conventional hydraulic nozzles, reduced‐volume applications have been developed in combination with the use of rotary atomizers to provide a narrow droplet spectrum. Most of the initial development of these hand‐carried battery‐operated spinning disc sprayers was for their use in the semi‐arid tropics to apply insecticides to cotton in the absence of plentiful water supplies. This continues to be the main market for these sprayers, although the trend recently has been away from oil‐based ultra‐low volume formulations to very‐low volume spraying (typically 5‐1 5 litre ha1) of water‐based formulations to reduce costs and allow greater flexibility in choice of insecticide in integrated pest management programmes. Changes in equipment design have been made to suit this change in spray volume and formulation. Air‐assisted sprayers have also been used in glasshouses. Subsequent development of rotary atomizers operated at slower speeds has led to the equipment being used for herbicide application. especially in forestry and urban situations where low weight of equipment and drift reduction have been important considerations. Formulations prepacked in containers to connect directly to the sprayers have been used to reduce operator contamination.

Spraying Technologies for Cotton: Deposition and Efficacy

Three electrostatic sprayers and a controlled droplet application technique were compared to conventional hydraulic nozzles in cotton. Deposition on dorsal and ventral leaf surfaces, and efficacy in terms of whitefly control, were used to assess performance. Application method had minimal influence on the level of insect control obtained. None of the sprayers provided consistently greater deposition on ventral leaf surfaces, the region where whiteflies feed. Variation in deposition through the plant canopy was considerable for all of the sprayers. This indicates that application methods evaluated here did not provide uniform deposition under commonly encountered field conditions.

Deposition and efficiency of herbicide sprays in sugar beet with twin-fluid, low-drift and conventional hydraulic nozzles

Four low-drift nozzles working at various pressures, one twin-fluid nozzle at two liquid and air pressures and two conventional flat-fan nozzles were compared with respect to spray deposition and herbicidal efficacy. Measurements of spray deposit on oats ( Avena sativa) and white mustard ( Sinapis alba) using a tracer showed that conventional nozzles were superior to the other nozzle types in most settings. Low-drift nozzles in the majority of settings and the twin-fluid nozzle at low pressures gave poor deposition on oats. Deposition on white mustard was greater than on oats and differences between spray methods small, although highly variable with the twin-fluid nozzle. Herbicide applications in sugar beet fields did not reveal any difference in weed control or crop vigour between the spray methods, but weed counts were affected by the dose level applied. The design of spray application experiments is discussed.

Glyphosate efficacy on eastern Canadian forest weeds. Part II: deposit–response relationships and crop tolerance

First-season herbicide efficacy and crop tolerance results are presented for a range of glyphosate (VISION®) rates (0–1.00 kg acid equivalent per hectare) aerially applied with two different dispersal systems (AU5000 Micronairs® and conventional hydraulic nozzles). Derivative-free nonlinear regression was used to model post-treatment raspberry cover (Rubusidaeus L. var. strigosus (Michx.) Maxim.) as an exponentially decreasing function of chemical deposit (R2 = 0.87). Similar methods were used to model post-treatment crown area as a function of chemical deposit and pretreatment crown area for pin cherry (Prunuspensylvanica L.f.) (R2 = 0.92), red maple (Acerrubrum L.) (R2 = 0.79), white birch (Betulapapyrifera Marsh.) (R2 = 0.93), elderberry (Sambucuspubens Michx.) (R2 = 0.85), and aspen (Populustremuloides Michx.) (R2 = 0.96). Acceptable first-season control (>60% cover reduction) of raspberry, pin cherry, elderberry, and aspen was achieved with rates of deposit ≥0.50 kg acid equivalent per hectare. Red maple and white birch crown area reduction averaged 60% at the highest rate tested (1 kg acid equivalent per hectare). Significant differences in efficacy attributable to the different dispersal systems were found only for pin cherry: the Micronair system resulted in 30% greater efficacy on one of the four blocks tested (P < 0.0001). On this particular block, characterized by unstable weather conditions during treatment, both systems produced significantly greater efficacy than observed on the other blocks for all species studied except aspen (P < 0.01). No significant differences were detected in black spruce (Piceamariana (Mill.) B.S.P.) health patterns in areas treated with the two different application systems (P = 0.780). Crop trees in untreated areas declined in health relative to trees in treated areas (P < 0.001).

Glyphosate efficacy on eastern Canadian forest weeds. Part I: experimental design and on-target deposit

Experimental methods and resulting on-target deposit data are presented for an operational field trial designed to evaluate glyphosate (Vision®) efficacy using two different dispersal systems (AU5000 Micronairs® and conventional hydraulic nozzles). A range of glyphosate rates (0, 0.25, 0.50, 0.75, and 1.00 kg acid equivalent per hectare) was aerially applied in a randomized complete block design to four cutover sites in New Brunswick. Formulation, tank-mix, droplet, and chemical analyses were conducted to quantify actual on-target deposit for each treatment. Data for the calibrated portion of each swath suggested that the Micronair system produced a slightly narrower drop-diameter spectrum (0–677 μm, volume median diameter = 300 μm) than the hydraulic system (0–1085 μm, volume median diameter = 425 μm). Analysis of variance and orthogonal contrasts indicated that on-target deposit for the Micronair system (average accountability = 71%) was not significantly different from that of the hydraulic system (average accountability = 82%) for three of four rates tested. Unrepresentative meteorological and site conditions affecting Micronair treatments in two blocks resulted in reduced deposit for the treatment of 1.00 kg acid equivalent per hectare. Substantial variability within treatments was observed for both dispersal systems (41 and 47% coefficient of variation for Micronair and hydraulic systems, respectively). Overall, results suggest no significant differences between the two dispersal systems (as calibrated) in terms of on-target deposit efficiency or variability. Both on-target droplet density and chemical deposit data reflected differences associated with blocks. This fact highlights the need for further studies on meteorological and operational factors on deposit.

Effects of nozzle size, travel speed and air assistance on deposition on artificial vertical and horizontal targets in laboratory experiments

Small horizontal and vertical targets were placed in the swath of a Hardi Twin air-assisted crop sprayer and sprayed indoors with a variety of conventional hydraulic nozzles with and without air assistance and at differing travel speeds. With conventional spraying, deposition was improved on vertical targets with high travel speed and small droplet-size spectra, whereas deposition on horizontal targets was relatively unaffected by the configuration used. Air assistance changed this behaviour, by generally enhancing deposition markedly and reducing variability. The scope for reducing application volumes is discussed.

Interception and persistence of parathion and fenvalerate on cotton plants as a function of application method

Parathion (O,O-diethyl O-4-nitrophenyl phosphorothioate) and fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] were applied by controlled droplet applicators (CDAs) and conventional hydraulic nozzles in refined soybean oil, soybean oil + water, or water, to mature cotton plants (Gossypium hirsutum L.) as ULV (ultra-low volume, < 5 litre ha−1), VLV(very low volume, 5-50 litre ha−1), or LV(low volume, 50–200 litre ha−1) carrier rates. The use of CDA or soybean oil applied as ULV and VLV sprays did not produce greater deposition or persistence for either insecticide during the 49-h test period following application. In general, insecticide persistence was greatest when applied with water or soybean oil + water as LV sprays using the conventional TX8 hydraulic nozzle.

Depositional Characteristics of Charged and Uncharged Droplets Applied by an Orchard Air Carrier Sprayer

ABSTRACT MASS-TRANSFER of fluorescent tracer onto front-sides and backsides of targets deployed throughout a large-scale grid was determined for comparison between charged and uncharged spray from air-atomizing electrostatic nozzles and uncharged spray from conventional hydraulic nozzles. Depending on target location, electrostatically charged spray achieved deposition increases ranging from 1.5 to 2.4-fold over uncharged droplets from the same air-atomizing induction-charging nozzles. The highest electrodeposition benefit was achieved on target backsides. Deposition of charged droplets did not surpass that achieved with 370 jum VMD (volume median diameter) droplets from conventional hydraulic orchard spraying nozzles. Suggested improvements to the electrostatic system included lowering the per-nozzle liquid flowrate to 160 mL/min to facilitate a 4-fold increase in droplet charging.

Air-Assist, Air-Foil, and Air-Curtain Sprayers

Air-assist nozzles that use pneumatic energy to help atomize the spray liquid were reviewed. These nozzles use larger orifices than conventional hydraulic nozzles for low-volume applications. By changing the air pressure, various droplet sizes can be produced without changing nozzle tips. Several systems use air to transport the atomized spray to specific target sites. Various air volumes and velocities have been evaluated in these systems. Preliminary research indicated that air can improve canopy penetration and can cover the entire plant more uniformly. Undersides of leaves can be treated easier with air-assist systems compared to conventional applications with hydraulic nozzles.

Worker Exposure to a Herbicide Applied With Ground Sprayers in the United Kingdom

This study was designed to measure potential dermal and respiratory exposure of agricultural workers during the application of a typical herbicide, 2,4-dichlorophenoxy acetic acid, with five types of application equipment commonly used in the United Kingdom. The workers were monitored during filling and loading operations and during spray application. Potential dermal exposure was higher during mixing and loading all tractor-powered sprayers than during spraying. Potential dermal exposure from tractor-powered sprayers fitted with conventional hydraulic nozzles was lower than from knapsack sprayers, with exposure from a tractor-powered sprayer fitted with controlled-droplet application equipment intermediate in this regard. There was no difference in potential dermal exposure between tractor-mounted and tractor-drawn sprayers fitted with conventional hydraulic nozzles. The hands were the most highly exposed part of the body during mixing and loading operations for all sprayers, and during spraying with tractor-powered sprayers. The lower legs of the workers were exposed principally when knapsack sprayers were used. For all five sprayers, potential respiratory exposure, where detectable at all, was negligible compared with potential dermal exposure.

Worker exposure to a herbicide applied with ground sprayers in the United Kingdom.

This study was designed to measure potential dermal and respiratory exposure of agricultural workers during the application of a typical herbicide, 2,4-dichlorophenoxy acetic acid, with five types of application equipment commonly used in the United Kingdom. The workers were monitored during filling and loading operations and during spray application. Potential dermal exposure was higher during mixing and loading all tractor-powered sprayers than during spraying. Potential dermal exposure from tractor-powered sprayers fitted with conventional hydraulic nozzles was lower than from knapsack sprayers, with exposure from a tractor-powered sprayer fitted with controlled-droplet application equipment intermediate in this regard. There was no difference in potential dermal exposure between tractor-mounted and tractor-drawn sprayers fitted with conventional hydraulic nozzles. The hands were the most highly exposed part of the body during mixing and loading operations for all sprayers, and during spraying with tractor-powered sprayers. The lower legs of the workers were exposed principally when knapsack sprayers were used. For all five sprayers, potential respiratory exposure, where detectable at all, was negligible compared with potential dermal exposure.

The effect of leaf shape on the deposition of spray droplets in rice

Paddy rice is usually sprayed with different types of conventional hydraulic nozzles and application rates. Spray droplets are more easily captured by the tip of rice leaves; this phenomenon was therefore studied with rice plants in a settling tower so that deposition of droplets occurred under controlled conditions. Further tests were carried out in rice fields by dirferent methods. The deposition rate was generally higher at the leaf tip compared with other parts, whether the leaf was vertical, pointing downwards at an angle of 60 degrees, horizontal or in a normal position. Similar results could be obtained if leaf-like water-sensitive paper strips were used instead of a natural rice leaf. The deposition and distribution pattern found on field rice leaves confirmed these results. Deposits on water-sensitive papers of different widths (2–25 mm) showed fewer droplets as the target width increased.

Deposition and Biological Efficacy of Electrostatically Charged and Uncharged Sprays in Cereal Crops1

Cereal crops were sprayed with conventional hydraulic nozzles (2501/ha), electrostatic hydraulic nozzles (66 l/ha), spinning discs (aqueous 5 l/ha and oil 2 l/ha) and ICI « Electrodyn » nozzles (1 and 2 l/ha). The ULV sprays were applied with or without air assistance. An experimental triazole fungicide was applied with fluorescent tracer and control of RhynchospoHum secalis in barley and Erysiphe graminis in wheat was compared with deposit data. The two high volume spray systems performed well with no significant differences in disease control or deposition between charged and uncharged modes at 66 l/ha. The spinning disc and « Electrodyn » systems performed well with air assistance but, without air, deposition was uneven and disease control inferior. The «Electrodyn» system often produced the largest total deposits but, without air, assistance spray deposition was concentrated mainly in the upper plant parts. The results indicate that under suitable conditions application volumes as low as 1 l/ha can be as effective biologically as high volumes when the same amount of fungicide per hectare is used. Relationships between spray distribution within cereals and sites for pest and disease attack are discussed with regard to different methods of application.