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A mathematical model was developed to predict orifice wear rate for fan-pattern, spray nozzles. Variables affecting nozzle wear rate in the model are usage time, spray pressure, initial orifice size, effective coefficient of friction between orifice wall and fluid, orifice material, and the fluid. Spray-pattern measurements for new and worn orifices verified that wear mainly increased minor-axis length of the elliptical orifice with very little wear at the ends of the major axis. There was good agreement between predicted and measured flow rate increases for worn orifices with various materials and nominal capacities for up to about 38% increase in flow rate relative to new orifices. Both the model and experiments indicated nozzle wear rate increased with usage time, spray pressure, effective coefficient of friction between nozzle orifice wall and fluid, and ratio of major to minor axis of the elliptical orifice.

A BASIC language computer program (DRIFTSIM) was developed to rapidly estimate the mean drift distances of discrete sizes of water droplets discharged from atomizers on field sprayers. This program interpolates values from a large database of drift distances originally calculated with a flow simulation program (FLUENT). The simulations of drift distances up to 200 m (656 ft) included temperatures (10° to 30° C; 50° to 86° F), discharge heights (0 to 2.0 m; 0 to 6.56 ft), initial downward droplet velocities (0 to 50 m/s; 0 to 164 ft/s), relative humidities (10 to 100%), wind velocities (0 to 10.0 m/s; 0 to 32.8 ft/s), droplet sizes (10 to 2000 mm), and 20% turbulence intensity. The program requires about 15.5 Mb of disk space. Variables can be either in metric or English units and input can be either individual droplet sizes or size classes with portion of volume in each class.

Precise modulation of nozzle flow rates is a critical measure to achieve variable-rate spray applications. An electronic flow rate control system accommodating with microprocessors and pulse width modulation (PWM) controlled solenoid valves was designed to manipulate the output of spray nozzles independently to match tree structures which would be detected with a wide-range laser scanning sensor. The PWM signals to control nozzle flow rates were generated by the microprocessors based on laser sensor detections. Multi-channel driver and protection circuits for activating solenoid valves were developed to modulate variable-rate outputs in real time. An embedded computer PC/104 along with a touch screen was used to process control algorithms and to fulfill communications between the operator and the control system. Laboratory tests demonstrated that the flow rate control system was able to achieve linear nozzle outputs with the duty cycle of PWM-controlled solenoid valves.

Capability to control both liquid and air flow rates based on tree structures would be one of the advantages of future variable-rate orchard and nursery sprayers. Air jet velocity distributions from an air assisted, five-port sprayer which was under the development to achieve variable-rate functions were measured at various heights above the ground and various distances from nozzle outlets. The air jet velocity was controlled by changing the sprayer fan inlet diameter. Air jet initial region length, transition length and expansion angle from five-port nozzles were calculated with an air jet model. The interaction point between adjacent air jets from the five-port nozzles was also determined from the air jet expansion angle. Air velocities at the sprayer travel speed ranging from 0 to 8.0 km/h were measured with a constant temperature anemometer system coupled with hot-film sensors. Air jets expanded at 50° angle and interacted at 0.027 from the nozzle outlets. When the sprayer travel speed was 0 km/h, the axial air velocity increased as the fan inlet diameter increased while it decreased in the hyperbola function with the increase of distance from the nozzle outlets. When the sprayer was on the move, due to the air entrainment and air jet diversity, the peak air velocity decreased with the increase of distance from nozzle outlets. The peak air velocity also increased slightly as the fan inlet diameter increased but the increase scale was not as great as the increase scale of the fan inlet diameter. There were little variations in the peak air velocity with the travel speed and measurement height, confirming the sprayer was able to discharge uniform air profiles to achieve variable air flow rates by controlling the fan inlet diameter.

A system was developed to investigate droplet dynamic impact and retention on leaf surfaces. The system consisted of a uniform droplet generator, two high speed digital video cameras, a constant speed track, a leaf holder, and a cool light source. The droplet generator produced mono-sized droplets ranging from 100 to 1,800 µm with a controllable speed. The video cameras were able to capture images at the speed of 40,000 frames per second with the resolution of 512×512 pixels. The track was used to mount and drive the droplet generator at a constant speed ranging from 1.6 to 10 km/h. The leaf holder could support leaves with different inclinations and distances from the droplet generator. With a commercially available 3-D image analytical software, the system was able to determine the dynamics of droplet impact, rebound and retention on hairy and waxy leaves when droplet diameter, droplet discharge speed, droplet discharge height, nozzle travel speed, leaf surface orientation, and spray formulation were the variables.

The drift distances of water droplets from field sprayers were determined for several variables with a computational fluid dynamics computer program. The simulation variables for drift distances up to 200 m included: droplet size (10 to 2000 mm), wind velocity (0.5 to 10.0 m/s), initial droplet velocity (0 to 50 m/s), discharge height (0.25 to 4.0 m), temperature (10 to 30 C), relative humidity (10 to 100%), and 20% turbulence intensity. Except at low temperature and high relative humidity, all 50-mm-diameter and smaller droplets completely evaporated before depositing 0.5 m below the point of discharge for all simulated conditions. Drift distances increased with increasing wind velocity and discharge height, but decreased with increasing initial downward droplet velocity for 100-mm-diameter and larger water droplets. Changes in ambient temperature and relative humidity had much greater influence on drift distances of water droplets less than 100-mm-diameter than on 200-mm-diameter and larger droplets.

In spray application, reflection (rebound) and wetting difficulty can hinder droplet retention by plant surfaces. Surfactants are usually added to formulations to help overcome these problems, but are sometimes ineffective. Some workers have found dynamic surface tension (DST) to be more reliable than equilibrium surface tension (EST) as a measure of surfactant effectiveness. Diffusion-controlled surfactant adsorption generally produces the quickest surface tension reductions as newly generated interfaces age. A diffusion model was developed for DST of three surfactants representing those commonly used in agrochemical formulations: Tween 20, Triton X-100, and Triton X-405. A bulk-solution diffusion model was developed which, together with the DST model indicated apparent diffusive surface-layer thicknesses of a few micrometers. Apparent diffusion coefficients were determined from DST data obtained by oscillating-jet and maximum bubble pressure methods for aqueous solutions. Good agreement of the models with DST data indicated that adsorption processes for the surfactants were diffusion-controlled. Surface ages required to achieve EST for the surfactants were greater than time intervals observed for droplet deformation and recovery in impaction.

Variable-rate application is an effective way for nursery and orchard growers to reduce pesticide use and potential contaminations to the environment. To realize this goal, an intelligent air-assisted sprayer implementing a high speed laser scanning sensor (LIDAR) was developed to vary spray output of each individual nozzle to match target tree needs in real time. Each nozzle was coupled with a pulse width modulation (PWM) solenoid valve to achieve variable rates based on the occurrence and canopy characteristics of the target, such as height, width and foliage density as determined by LIDAR. A unique density algorithm was developed to calculate foliage density by mapping the surface roughness of the canopy during the spray application. A back pressure control unit was integrated into the system to minimize the pressure fluctuation due to frequent changes in nozzle flow rates. Delay time between the sensor detection of the canopy and the nozzle activation was determined with a high-speed video camera. Laboratory tests demonstrated that the design criteria of the experimental sprayer were acceptable for performing variable rate functions.

Most chemical applications in orchards and ornamental nurseries are not target-oriented, resulting in significant loss of pesticides and contamination of the environment. To avoid over- and under-application of chemicals, sprayers must be designed to apply the appropriate amount of pesticide based on the tree canopy characteristics such as tree height, width, volume, and foliage density. A precision air-assisted sprayer with variable flow rate of individual nozzles was tested for treating ornamental nursery and fruit trees. The sprayer was developed using a modified conventional air-assisted orchard sprayer by implementing a laser scanner to detect canopy characteristics, five-port air-assisted nozzles coupled with pulse width modulation (PWM) solenoid valves to deliver spray, and an automatic flow rate controller to minimize pressure fluctuation. Sprayer treatments included the new precision sprayer, the same precision sprayer without the intelligent control activated and a conventional, axial flow, air blast sprayer in an apple orchard at three different growing stages. Measurements were made for spray deposition and coverage inside canopies, losses on the ground and beyond target trees, and airborne drift downwind from the target trees. Compared to conventional sprayers, the variable-rate sprayer produced relatively uniform spray coverage and deposition inside canopies, and reduced spray volume by 47% to 73% with significantly less off-target losses on the ground, through gaps between trees, and in the air.

Measurements of micro-variations in plant stem diameter are potentially useful to optimize irrigation decision support systems that are based on plant physiological responses. However, for this technology to be suitable for field applications, problems associated with stem softness and micro variations in the stem diameter due to water potential changes must be resolved. A real-time, non-destructive measuring system that uses a miniature ultrasonic linear actuator to precisely measure the deformation of stem surface was developed. The actuator employs a specially designed probe capable of a 0.8 µm travel per step and a 0.083 N maximum push force to avoid deforming the soft stem during the measurement. The travel motion of the probe is controlled with a custom-designed microcontroller. The plant stem was held in place by a fixture designed for the probe to precisely sense the contact of the stem surface. Tests with different plants under laboratory conditions verified the system accuracy and reliability, and provided prospects for the technology to be used for optimizing water utilization during plant growth.

Adjuvants can improve pesticide application efficiency and effectiveness. However, quantifications of the adjuvant-amended pesticide droplet actions on foliage, which could affect application efficiencies, are largely unknown.Droplet evaporation rates and spread on waxy or hairy leaves varied greatly with the adjuvant types tested. On waxy leaves, the wetted areas of droplets containing crop oil concentrate (COC) were significantly smaller than those containing modified seed oil (MSO), non-ionic surfactant (NIS) or oil surfactant blend (OSB), whereas the evaporation rates of COC-amended droplets were significantly higher. On hairy leaves, COC-amended droplets remained on top of the hairs without wetting the epidermis. When the relative concentration was 1.50, the wetted area of droplets with NIS was 9.2 times lower than that with MSO and 6.1 times lower than that with OSB. The wetted area increased as the adjuvant concentration increased. MSO- or OSB-amended droplets spread extensively on the hairy leaf surface until they were completely dried.These results demonstrated that the proper concentration of MSO, NIS or OSB in spray mixtures improved the homogeneity of spray coverage on both waxy and hairy leaf surfaces and could reduce pesticide use. This article is a US Government work and is in the public domain in the USA.

Adjuvants have been used to improve pesticide application efficiency and effectiveness for many years. However, knowledge on quantitative reactions of adjuvant-amended pesticide droplets on foliage is lacking. Evaporation rate and wetted area of 500 µm droplets with four different adjuvants on waxy and hairy leaves were measured inside an environment-controlled chamber. The adjuvants included Crop Oil Concentrate (COC), Modified Seed Oil (MSO), Nonionic Surfactant (NIS), and Oil Surfactant Blend (OSB). Droplet evaporation rate and spread on either waxy or hairy leaves varied greatly with the type of adjuvants. On waxy leaves, droplets containing COC had significantly smaller wetted area than those containing MSO, NIS or OSB while the evaporation rate was opposite. On hairy leaves, droplets containing COC remained on top of hairs and did not reach the epidermal surface of leaves. When the relative concentration was 1.50, the wetted area of droplets with NIS was 9.2 times lower than that with MSO and 6.1 times lower than that with OSB. The wetted area increased as the concentration increased. Droplets with MSO or OSB spread extensively on the hairy leaf surface until they dried completely. Results of this study demonstrated that addition of MSO, NIS or OSB into spray mixtures with proper concentrations improved homogeneity of spray coverage on both waxy and hairy leaf surfaces, leading to pesticide reduction strategies.

New variants of wheat pathogens are emerging in various countries for which there is no known resistance. The current movement of these pathogens suggests that their incursion into the US is imminent. The objective of this work was to identify effective application parameters to apply fungicides for protecting against wheat head scab and stem rust infection. Field trials were designed to evaluate the effect of spray volume, spray quality, and air assistance on the fate of spray on sections of a wheat plant most susceptible to infection. Following application of a fluorescent tracer tank mix, plant samples were collected from each of ten plants in each replicate for each treatment. Plant sections sampled included Heads, Flag Leaf, Flag Leaf +1, and the Stem between the Head and Flag Leaf +1. There were no significant differences between treatments in the amount of spray on the stem sections. Significant differences between treatments were observed for the amount of spray found on Head and Leaf sections. Directing the spray and air stream 30° forward increased deposits of Medium spray quality droplets on the Head sections but reduced deposits on the more horizontal Flag leaves. Spray coverage measured on targets with a vertical and cylindrical shape to simulate the wheat head target also increased when the air/spray stream was directed 30° forward compared to a vertical delivery. These results demonstrate that different application parameters may be required depending on the specific section of the wheat plant that requires protection.

A computer program (Fluent“) was evaluated for use in modeling the drift of spray droplets delivered by atomizers. A uniform-size droplet generator and wind tunnel were also used to determine drift distances for various droplet sizes, wind velocities and other operating conditions. Drift distances determined experimentally for droplet sizes ranging from 148 to 424 mm diameter and wind velocities ranging from 0.5 to 6.2 m/s agreed well with distances predicted by the computer program.

A computer program was used to determine the effects of several variables on drift distances of spray droplets. Variables were initial droplet size, velocity and height of discharge, wind velocity, turbulence intensity and relative humidity, and volatility of the liquid. For relative humidity and wind velocity ranges of 20-80% and 0.5-4.0 m/s, all water droplets 50 µm diameter and smaller that were directed downward with initial velocity of 20 m/s either completely evaporated or drifted farther than 6 m before depositing 0.5 m below point of discharge. With 20 m/s initial droplet velocity, 2.0 m/s wind velocity (20% turbulence intensity) and 60% relative humidity, 100 and 200 µm diameter droplets deposited at mean distances from point of discharge of 2.6 and 0.13 m respectively. Drift distances of water droplets as large as 200 µm diameter were influenced by initial droplet velocity and height of discharge. Experimental data verified the accuracy of the computer program in predicting drift distances of water droplets.

Foliar diseases like apple scab result in significant economic losses to growers each year. Assessment in past studies involved only macroscopic disease ratings. More complete knowledge of the fate and behavior of fungicide has been needed to reduce pesticide use with less off-target contamination. Field studies were conducted in a production nursery for over 4 years. A moderately susceptible cultivar of ornamental crabapple, Malus spp. cv “Candied Apple”, was sprayed with a fungicide using two sprayer/nozzle configurations. The fungicide used in this study was Mankocide, combination of Cu(OH)2 and mancozeb that permitted electron beam analysis (EBA) identification based on the presence of Cu, MN and Zn in the molecule and formulation. EBA was conducted using a cold field emission scanning electron microscopy and energy dispersive x-ray microanalyzer. Fresh leaf samples were placed on sticky stubs after each fungicide treatment. The presence or absence of fungal conidia and fungicide residue were measured. EBA permitted direct visualization and identification of the pathogens, morphologically, and chemical characterization of fungicide present. EBA was useful to quantify disease control related to fungicide coverage, sprayer configuration and treatment efficacy. SCANNING 31: 24–27, 2009. Published 2009 by Wiley Periodicals, Inc.

Handgun applications are popular general purpose greenhouse sprayers. However, there are few recommendations on how to use them to treat plant benches. Handgun applications made from one side can also result in significant differences in deposits between the side of the plant facing the spray stream and the opposite side. The objectives of this research were to determine how handgun spraying and broadcast applications using twin-fan sprays and air-assistance affect underleaf spray deposits. A bench-top trial was conducted using a mature poinsettia canopy in a

Leaf surfaces are often altered when attacked by various insects and diseases. To evaluate the effect of droplet deposition on pesticide application efficiency, evaporation and deposit pattern formation of single droplets deposited at various locations on waxy leaves were investigated under controlled conditions. The locations on leaves included the intervenial area, midrib and secondary vein on both adaxial and abaxial surfaces. Tests were conducted with 300 and 600 µm droplets containing water and a nonionic surfactant. The ambient temperature was 25oC and relative humidity was 60%. Evaporation time and wetted area of droplets varied with where droplets deposited on leaf surfaces. The difference in evaporation time of 300 µm droplets without the surfactant on the intervenial area, midrib and secondary vein of adaxial surface was 30% while the difference in wetted area was 39%. The wetted area was significantly larger on the adaxial surfaces than on the abaxial surface but the evaporation time between both surfaces was not significantly different. For the whole leaf, the average evaporation time of 300 µm droplets was decreased by 44% and the average wetted area was increased by 202% when 0.25% nonionic surfactant was added into the spray solution. The total mean evaporation time increased 279% and the total mean wetted area increased 166% without the surfactant, 452% and 229% with the surfactant when the droplet diameter was changed from 300 to 600 µm. The largest spread area of droplets was appeared on the midrib of adaxial surface with the surfactant. The 300 µm droplets had longer evaporation time per droplet volume and greater wetted area per droplet volume than the 600 µm droplets. Increased pesticide application efficiency could be achieved with smaller droplets containing the surfactant to enhance the droplet spreading at different positions on waxy leaves.

It is wide foreground that aerial electrostatic spraying technology is applied for prevention and cure pests in agriculture and forestry. In the field of agriculture aviation, there are some advantages about helicopter such as flight convenience and realizing pesticide spraying in low-altitude flying. Be aimed at using R44 helicopter which is made in USA Robinson company, an aerial electrostatic spaying system was designed including aerial nozzles, high-voltage power supply and inlay cylinder acicular induction charging device which can makes spraying droplets more uniformly and droplets charging more effectively and fully. Some experimental studies about aerial electrostatic spraying set were introduced and conducted on the electrostatic spraying system assembled in the R44 helicopter. These experiments included the effective spraying breadth, droplets deposition characteristics and droplets drift and so on. The electrostatic spraying can make coverage rate of target increase 12 droplets / cm2 compared with the non-electrostatic spraying. In action of helicopter propeller disturbing, droplets could be found on the back of the spraying target. By the effects of the electrostatic field, the effective spray breadth of R44 helicopter reached 36m, and droplets drift decreased obviously. The results of the studies showed that electrostatic spraying could produce uniform and fine droplets with better droplet adhesion and distribution, higher depositing efficiency, lower environmental contamination, lower pesticide application rate and aerial spray can improve efficiency for prevention and cure pests in agriculture and forestry. Combined electrostatic spraying with aerial spraying technology will take an important role for prevention and cure pests.

Appropriate adjuvant selection for pesticide applications is central to improve spray performances on waxy leaves and to reduce off-target losses. Evaporation and deposition patterns of 500 µm sessile droplets with five classes of adjuvants on five different waxy plants were investigated. Droplets generated with a single droplet generator were deposited on target leaves placed in a controlled environmental chamber at 60% relative humidity and 25oC temperature. Adjuvants tested were two types of oil-based Crop Oil Concentrate (COC) and Modified Vegetable Oil (MSO), two types of surfactant Nonionic Surfactant (NIS) and Silicone Surfactant, and a type of mixture Oil Surfactant Blend (OSB), plus the water-only droplets for comparison purposes. The Silicone Surfactant was removed from the test because its various properties were inconsistent with time. The five waxy plants were difficult-to-wet with the water contact angle greater than 90o. The single water-only droplets did not spread with time and formed extremely tiny wetted areas on the leaf surface. The addition of the adjuvant to the spray solution significantly reduced the contact angle and increased the wetted area, but the change varied with the plant specie and the adjuvant class. In general, the MSO and NIS had obvious effects on enhancing droplet spread and maintaining the droplet in solution on the waxy leaf surface. The residual pattern of droplets after evaporation was formed with “coffee ring”. Droplets with oil-based adjuvants had more uniform residual pattern than the droplet with the surfactant adjuvant. Results of this study demonstrated that selection of the appropriate class of adjuvants can significantly influence deposit formation on the waxy plants leading to effectiveness of agrochemicals.

Evaporation time and wetted area of single droplets sizing from 246 to 886 µm at relative humidity (RH) ranging from 30 to 90% were measured with sequential images under controlled laboratory conditions. Droplets were placed inside an environmental-controlled chamber under a stereoscope and a high definition digital camera. The spray mixtures used to form droplets included different combinations of water, a polymer drift retardant, a surfactant, and two insecticides. The droplet evaporation was investigated on the surfaces of crabapple leaf surfaces, hydrophilic and hydrophobic glass slides, respectively. Adding surfactant into spray mixtures greatly increased droplet wetted area while droplet evaporation time was greatly reduced. For a 343 µm droplet on the crabapple leaf at 60% RH, the evaporation time decreased from 70 to 50 s and the wetted area increased from 0.366 to 0.890 mm2 after the surfactant was added into the spray mixture containing water and insecticide. Adding the drift retardant into the spray mixture slightly increased the droplet evaporation time and decreased the droplet coverage area. Also, changing the target surface from the hydrophilic slide to the hydrophobic slide greatly increased the droplet coverage area and reduced the droplet evaporation time. Increasing RH could increase the droplet evaporation time greatly but did not change the coverage area. The droplet evaporation time and coverage area increased exponentially as the droplet size increased.

Canopy penetration and thorough coverage are important when applying foliar fungicides to soybeans for the control of rust. The purpose of this study was to examine how spray application rate and spray droplet size affect the efficacy of soybean rust applications. Four treatments were examined: a medium droplet spectrum applied at 47 L/ha (5 GPA) and at 140 L/ha (15 GPA), and a very coarse droplet spectrum applied at 47 L/ha (5 GPA) and at 140 L/ha (15 GPA). Applications were made to soybeans planted with 91 cm (36 inch) row spacing in the R5 growth stage. Spray coverage, deposition, soybean rust severity, and yield were measured to evaluate the effectiveness of these treatments. Spray coverage was measured on Kromekote paper positioned in the upper and lower parts of the canopy. Deposition was measured using a dye and Mylar plates positioned in the upper and lower parts of the canopy. The very coarse droplet spectrum at 140 L/ha (15 GPA) had the highest coverage and deposition in both the upper and lower canopy. Overall the very coarse droplet spectrum performed better than the medium droplet spectrum. There was no difference among the treatments in soybean rust severity or yield. All the treatments had significantly lower soybean rust severity than an untreated control, and all but the very coarse droplet spectrum at 140 L/ha (15 GPA) had a significantly higher yield than the untreated control.

Using a nonionic, alkyl polyoxyethylene surfactant (X-77) in aqueous solutions, sessile droplet spreading, pinning, evaporation, contraction, and post-evaporation deposits are characterized. X-77 is widely used in the agricultural field as a spreader/adherent, intended to optimize pathenogenic agent coverage. Using a single droplet size under monitored temperature conditions, we control humidity, substrate hydrophobicity, and surfactant concentration to mimic varying agricultural conditions. For hydrophilic surfaces, the droplet spreads, reaching and retaining a maximum, stationary size. At this stage, a ring accretion occurs at the maximum spread diameter. During the final stage, the water film retracts, resulting in deposition of small islands of surfactant residue inside the ring. At lower concentrations of surfactant, we discover ring formations that break-up into "ring islands" at late-stage evaporation, accompanied by a distribution of the smaller islands in the interior portion of the substrate contact area. These are promoted by higher relative humidity. At higher concentrations, only a solid ring of surfactant remains, post-evaporation. Increasing surfactant concentration tends to increase the mean of the interior island size and to broaden the overall island size distribution. On sufficiently hydrophobic surfaces, surfactant-laden droplets do not evidence pinning, ring formations, or post-evaporation interior islands. Interestingly, lower humidity increases spreading at higher surfactant concentrations. Such pattern formations of surfactant deposit are reported for the first time and are of significance in projecting how surfactants such as X-77 distribute pesticides or other chemicals on leaf surfaces.

Greenhouse pesticide labels lack specific recommendations on the spray volume and spray droplet sizes which will provide the most efficacious pest management. A greenhouse trial was established to determine differences in spray retention in a poinsettia canopy between applications using three different spray volumes and three different spray qualities using single nozzle handgun applicators. For the same areas of the canopy, there were few differences in spray deposit between treatments. Fronts and upper areas of the canopy received more deposits than the backs and lower areas of the canopy. There were no significant differences in recovery of fungicide from leaves between treatments. The high volume application produced the highest deposits on artificial targets across all spray qualities. There were no significant differences in overall spray deposit between the low and medium volume treatments.

Pesticide spray applications in nurseries are usually implemented in the very early morning to avoid chemical exposures to regular workers and to prevent potential drift to nearby residential areas. Conventional sprayers cannot efficiently apply pesticides to many container ornamental crops due to the special planting circumstance. A cannon air jet sprayer was investigated in an effort to use optimal spray techniques to effectively control pest insects or diseases for container ornamental crops. Air velocity, spray deposition, spray coverage and spray spot density on artificial targets inside and outside hydrangea plants at two heights across the spray swath were evaluated and correlated. Treatments included three flow rates, three travel speeds, and two different nozzle settings. Under the calm weather conditions, the cannon air jet sprayer could provide fairly uniform spray distributions across the 24 m spray swath.

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 μm 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 μm 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.

Summary Fungicides manufactured to control soybean rust are effective; however, successful control of this disease will mostly depend on proper application methods. Spray coverage and deposition from 10 application equipment/spray nozzles were analysed. In general, the spray treatments with air assistance were more effective in spraying rust fungicides than the treatments with the conventional boom sprayer. Spray performances from the boom sprayer with a canopy opener were very similar to the air assisted spray treatments, and were better than other treatments with the boom sprayer. Twin jet, Turbo Dual pattern and hollow cone nozzles produced lower spray performances than conventional flat fan nozzles. For treatments with the boom sprayer, medium spray quality provided higher spray coverage inside canopies than coarse and fine spray qualities. Future research will address how much fungicide inside canopies can be sufficient to control the soybean rust disease.

At the growth stage from R3 to R5, the foliage at the top of a soybean canopy takes the most part of the canopy and these top leaves cover the most area of the field. Because of the high foliage density at the top of canopy, conventional boom sprayers can hardly deliver sufficient chemical droplets to inner part of canopies. An experimental canopy opener was developed and attached on a conventional boom sprayer to increase spray deposition and coverage inside soybean canopies. The canopy opener consisted of a conduit pipe mounted on the spray boom upwind the nozzles. The conduit pipe opened the top part of canopies as the sprayer traveled to achieve better penetration of spray into lower parts of the soybean plant, where the rust infection first starts. Conventional flat fan nozzles were used for the test with the canopy opener for the application rate of 145 L/ha. Spray deposition and coverage at two heights inside canopies were determined. Treatments included three depths of the opener inside canopies, three horizontal distances of the opener from nozzles, and two nozzle sizes. A mathematical model was also developed to determine the plant deflection and traveling time so that droplets could be delivered inside canopies before the top part of canopy returning to vertical positions. Spray deposition and coverage inside canopies with the opener were also compared with a conventional boom sprayer without the opener. With the help of the canopy opener to push the top part of canopies, spray droplets had more space to reach middle and bottom of canopies, resulting in higher spray deposition and coverage on targets inside canopies.

Spray drift potential, spray coverage, droplet size, and spray pattern width for various sizes of air induction and conventional flat fan nozzles with equivalent orifice areas were investigated and compared under the laboratory conditions. Droplet sizes were measured with a laser imaging system, spray coverage on water sensitive papers (WSP) was evaluated with a boom sprayer at a constant travel speed in a greenhouse, and ground and airborne spray deposits were determined in a wind tunnel at two wind velocities (2.5 and 5 m/s). Tests were also conducted to evaluate the effect of air intake holes being closed or open on spray characteristics of air induction nozzles. With the equivalent nominal flow rate, air induction nozzles had approximately 2.1 to 2.75 times larger exit orifice areas than the conventional nozzles. With the equivalent orifice area and equal liquid flow rate, there was no significant difference in droplet size, spray pattern width, spray coverage, ground spray deposit, and airborne deposit among regular air induction nozzles, the air induction nozzles with two sealed air holes, and conventional flat fan nozzles. Spray characteristics of air induction nozzles could be achieved by conventional nozzles with the equivalent orifice size operated at the pressure below the manufacturer’s recommended pressure range.

New sprayers are needed to deliver droplets uniformly within dense nursery crops to obtain healthy and marketable plants in the nursery industry. An air-assist sprayer with five-port nozzles was developed and investigated to improve spray penetration into dense nursery canopies. Spray deposits at top, middle and bottom of canopies were characterized using fluorescence detection, and were compared at three nozzle heights in a commercial nursery field. Dynamic air velocities corresponding to the deposit sampling locations inside and outside the canopy were measured at the time when the sprayer passed over the canopies. Air jet velocity profiles from nozzle outlets to 0.79 m below the nozzles were determined experimentally and mathematically. The measured air jet velocity decreased from 40.1 to 19.4 m/s when the distance from the orifice increased from 0.33 to 0.79 m. The peak velocities at the top and middle elevations for both inside and outside the canopy decreased as the nozzle height above the ground increased, but the peak velocities at the bottom elevation for both situations were not significantly decreased as the nozzle height increased. The average period of time for dynamic air velocities higher than 1 m/s inside the canopy was 1.9 s at 2.5 cm, 3.8 s at 25 cm and 1.1 s at 46 cm. The mean spray deposit inside taxus canopies with leaf area index of 5.96 increased in an exponential function as the peak air velocity increased. The spray penetration capability and spray deposition uniformity inside taxus canopies were greatly improved with the five-port air assist sprayer.

Humid areas, such as the southeastern and midsouthern United States, have particular climate, topography, soils, cropping systems, and water sources that require special consideration when considering and implementing a subsurface drip irrigation (SDI) system. Design criteria are generally the same in humid areas as in arid or semi-arid areas, but these factors are normally different enough in value or type to result in a different system design. Irregularly shaped fields commonly found in humid areas can result in a system layout that differs greatly from a "normal" layout. Installation is best done when the soil moisture is within an optimal range, which may seriously limit installation windows in humid areas. As fewer systems have been installed in humid regions, availability of professional installers and installation equipment can be problematic. This paper presents both design and installation considerations for SDI systems, with particular emphasis placed on conditions found in humid areas. It is condensed from two publications in a series designed to provide guidance on SDI systems in humid regions in an "extension-like" format. Topics include: design criteria; pumps; filtration; chemical injection; valves; main and submain, dripline, and flush ing manifold design; instrumentation and control systems; design implementation; installation tips; and locating an installer.

Spray deposits at various elevations within crabapple trees and on the ground were investigated with an air blast sprayer equipped with conventional hollow cone nozzles, air induction nozzles, and conventional hollow cone nozzles with a drift retardant in a commercial nursery field. Airborne deposits at three elevations on sampling towers and on the ground at several distances from the sprayer were also investigated with the three spray treatments in an open area without trees. Droplet size distributions across spray patterns were measured with a laser particle/droplet image analysis system. In general, there was no significant difference for deposits within nursery tree canopies and on the ground with three different spray techniques. With the 700 L/ha application rate, which was 360 L/ha lower than the rate normally used in nursery application, the tree canopies received over 4 to 14.5 times spray deposits actually needed from the air blast sprayer with the three spray techniques, and a large portion of spray droplets deposited on the ground.

Computer simulation provides a means of determining the relative effects of various factors on spray drift while field experiments to measure spray drift have the limitation that many variables cannot be controlled. A Windows Version computer program (DRIFTSIM) was developed to rapidly estimate the mean drift distances of water droplets discharged from atomizers on field sprayers. This program interpolates values from a large data base of drift distances originally calculated for single droplets with a flow simulation program (FLUENT). The simulations of drift distances up to 200 m (656 ft) included temperatures (10-30 °C; 50-86°F), discharge heights (0-2.0 m; 0-6.56 ft), initial downward droplet velocities (0-50 m/s; 0-164 ft/s), relative humidity (10-100%), wind velocities (0-10.0 m/s; 0-32.8 ft/s), droplet sizes (10-2000 µm), droplet size distribution in Dv.1, Dv.5 and Dv.9, and 20% turbulence intensity. Variables can be either in metric or English units. For the input of droplet size distribution, drift distances are reported along with portion of volume in each class such as provided by many droplet size analyzers. The accuracy of the program FLUENT was verified with a uniform droplet generator and wind tunnel. The program indicates the relative effects of the input variables on drift distances and should, especially for large droplets, provide reasonable accuracy for many field applications.

Nursery growers are seeking new sprayers that can discharge droplets uniformly within taxus canopies to obtain healthy and marketable plants. A custom-designed five-port, air-assist sprayer was investigated to improve spray penetration into taxus canopies in a production nursery. Air velocity profiles from nozzle outlets to 0.79 m below the nozzles were determined experimentally and mathematically. Spray deposits at top, middle and bottom of canopies were characterized using fluorescence detection, and were compared with two application rates. The air velocity decreased from 40.1 to 19.4 m/s when the distance from the orifice increased from 0.33 to 0.79 m. Variations of air velocities across the same level above the ground decreased as distance from the nozzle increased. Tests indicated that increasing application rate by 34% could increase spray deposition at the bottom of canopies by 42%. Spray deposits increased as the air velocity at target positions increased.

The black vine weevil (BVW), Otiorhynchus sulcatus (Fabricius), is a major economic insect pest for growers of ornamental nursery crops and small fruits. Development of management strategies by entomologists and growers has been hampered by a lack of behavioral information on movement of BVW within agroecosystems. Although insects can be tracked using tag-and-release methods, the BVW is active primarily at night, cannot fly, and can be difficult to relocate. Harmonic radar technology has been used in entomological research and was investigated for applicability to the BVW problem. An insect-mounted, miniature transponder was developed to facilitate location in conjunction with a commercially available harmonic radar transceiver detector. The transponder powered by a 0.917 GHz signal from the detector, when detected returns a 1.834 GHz signal to the detector. The transponder consists of a Schottky barrier diode with an inductively loaded monopole antenna and is lightweight at about 27% of a BVW body mass. In field trials, insects were successfully released, relocated and recovered after several days.

Techniques are needed to ecologically monitor nursery production practices with proper use of water resource and nutrient management. An experimental system to examine water quality, irrigation efficiency and drainage from pot-in-pot nursery container production was established in a commercial nursery field. The system mainly consisted of a plot containing 50 trees planted in 50 pot-in-pot containers and irrigated with micro spray stakes; 10 drainage water measurement devices; 10 pot media moisture probes; 10 thermocouples; a weather station and a data logger. Preliminary tests indicated the system was feasible to monitor water inputs, drainage water loss, medium moisture content and temperature, leachate of nitrogen, phosphate and potassium in drainage water, rainfall and weather conditions, and tree growth in pot-in-pot nursery production.

A surface drip irrigation system was developed to irrigate peanuts in two topographic fields. Peanut pod yield, kernel size distribution, and total sound mature kernels were evaluated with two peanut varieties, two planting patterns and two drip tape lateral spacings. Test results were compared with the adjacent non-irrigated area planted with the same varieties of peanuts. Soil temperature and volumetric moisture content were measured at different locations to track soil temperature and water movement from drip tapes. The maximum soil temperature in the irrigated area was substantially lower than in the nonirrigated area. About 16 h were required for water to travel 46 cm and then hold the moisture for 14 h before decreasing after either 12.5 mm or 25 mm irrigation was applied. No significant difference (p

Although considerable research has been done on effectiveness of drift retardants for many years, answers to some questions are still unclear to applicators. Laboratory tests were conducted to evaluate drift potentials associated with off-target ground and airborne spray deposits discharged with a hollow cone nozzle spraying three different drift retardants at a high operating pressure and various wind velocities in a wind tunnel. Droplet sizes and spray widths were also determined with a laser imaging system and a portable spray patternator. At 1655 kPa pressure and 4.65 L/m flow rate, the volume median diameters of droplets from the hollow cone nozzle discharging spray mixtures containing water only, polyvinyl polymer, nonionic colloidal polymer and polyacrylamide polymer drift retardants were 201, 222, 239, and 210 μm, respectively. The major spray pattern width was not changed after drift retardants were added into the spray carrier. For the wind velocity from 1 to 5 m/s in the wind tunnel, the polyacrylamide drift retardant produced the highest airborne deposit among the three drift retardants, followed by polyvinyl, and then nonionic colloidal. Also, the polyacrylamide drift retardant produced the highest ground drift potential, followed by nonionic colloidal and then polyvinyl. According to the results from this laboratory study, both nonionic colloidal and polyvinyl polymer drift retardants reduced the drift potential compared to the spray carrier containing water only.

Nitrogen (N) is often supplied to plants in excess to minimize the possibility of encountering N deficiency that would reduce the plant quality due to leaf chlorosis and necrosis. This is not only costly, but it can reduce the quality of plants, predispose the plants to biotic stress such as Botrytisgray mold, and extend the production cycle. Several tools can be used to identify N deficiency in plants, and most are based on chlorophyll reflectance or transmittance. While sensitive when plants are experiencing N deficiency, spectral signals can saturate in an ample N supply and make it difficult to discern sufficient and supra-optimal N nondestructively. Three diverse ornamental species (begonia, Begoniacea×tuberhybrida; butterflybush, Buddlejadavidii; and geranium, Pelargonium×hortorum) were grown with a broad range of N supplied (1.8 to 58 mm) in three separate studies that resulted in a range of 1.8% to 6% tissue N concentration. Using a spectroradiometer, we measured reflectance from the whole plants twice over a period of 3 weeks. A first-derivative analysis of the data identified six wavebands that were strongly correlated to both begonia and butterflybush tissue N concentration (r2 ∼ 0.9), and two of these also correlated well to geranium N concentration. These wavebands did not correlate to chlorophyll peak absorbance, but rather blue, green, red, and far-red “edges” of known plant pigments. These wavebands hold promise for use as a nondestructive indicator of N status over a much broader range of tissue N concentration than current sensors can reliably predict.