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United States Department of Agriculture

Agricultural Research Service


Location: Application Technology Research Unit

2011 Annual Report

1a.Objectives (from AD-416)
Develop precision sprayers that can continuously match canopy characteristics to deliver agrichemicals and bio-products accurately to nursery and fruit crops. Identify and characterize factors that have the greatest impact on foliar pesticide spray application efficiency: determine how water droplets amended with spray additives, relative humidity and the morphological surfaces of leaves affect the droplet evaporation time, spread factor and residual pattern on leaves; determine how the droplet size and velocity, spray formulation, and morphological surface of leaves affect spray impact, retention and coverage. Identify and evaluate agrichemicals and bio-products that can be precisely delivered through drip irrigation systems.

1b.Approach (from AD-416)
Precision sprayers with wide range controllable flow rate, multi-jet nozzles will be developed to reduce the amount of pesticides required by matching spray characteristics to specific types of ornamental nursery and fruit trees. Fast response, high resolution, non-contact sensors will be used to detect the plant size, shape, density and position. Based on the plant structure data from the sensors, air velocity, spray application rate and number of jets will be determined to control the spray outputs as needed. All these operations will occur as the sprayer moves past the plant, providing uniform spray coverage with minimum off-target loss. Evaporation time, spread factor and chemical residual pattern area of individual droplets containing spray additives on leaves will be measured via sequential imaging under controlled conditions. Droplets will be placed inside an environmental-controlled chamber under a stereomicroscope and a high definition digital camera. A large database will then be developed including droplet evaporation time, and deposit pattern area on leaves with different surface characteristics, droplet sizes, chemical formulation components, and relative humidity conditions. A laboratory system will be developed to determine dynamic effects of spray characteristics on spray impact, retention and coverage on fine surface structure plants. All individual pesticide spray application variables will be controlled under laboratory conditions. The system contains a turntable, a mono-disperse droplet generator and uniform air carrier to deliver droplets onto leaves or selected polymer targets with defined surface properties. Droplet impact and rebound velocity will be measured with a particle/droplet laser image analysis system. A cold field emission scanning electron microscope (CFESEM) and a variable pressure scanning electron microscope will be used to determine leaf surface fine structure, droplet coverage area, residue deposit form and composition, and distribution of active ingredients on leaf target surfaces. Variables will be droplet size, droplet velocity, travel speed, type of liquid formulation, physical properties and concentration of spray additives, leaf orientation, leaf deformation, leaf wax and leaf roughness. Relationships among the spray droplet retention, distribution and coverage area on leaf surfaces with the variables will be determined and documented in a large database as a guideline to choose the optimum operational parameters. An engineering testing system for delivering agrochemicals and bio-pesticides through drip irrigation will be developed. All individual delivery variables will be controlled in the system. The distribution uniformity of agrochemicals and bio-pesticides with different physical properties and particle sizes throughout drip lines and in the soilless substrates and soil will be investigated. Tests will also include determination of emitter sizes and amounts of water needed to diffuse bio-pesticides in the soilless substrate in various size containers. A new injection unit will be developed to precisely deliver suspendable bio-pesticides through drip irrigation.

3.Progress Report
An experimental real-time variable-rate sprayer that implemented high frequency ultrasonic sensors and pulse width modulation solenoid valve-controlled spray nozzles was developed to adjust spray outputs automatically based on the liner canopy size. The accuracy of the sprayer in triggering spray against detected targets was evaluated by use of a high-speed camera. A laboratory field consisting of six different sized tree species was used to test the sprayer performance consistency. Influences of liner canopy size and sprayer travel speed on uniformity of spray deposition and coverage inside nursery liner canopies were analyzed. An experimental, real-time, variable-rate, air-assisted sprayer that implemented a high speed laser scanner sensor and portable computer was developed for ornamental nurseries and fruit trees. The accuracy of the sprayer to maintain constant droplet size distributions and constant operating pressure was evaluated under both laboratory and field conditions. Air velocity profiles at different distances to the sprayer were also determined with various travel speeds and fan inlet sizes under laboratory and field conditions. Droplet spread area and evaporation on various waxy leaves were investigated with different classes of spray additives. Tests were conducted under the controlled conditions. The magnitude of the influence of individual variables on droplet behaviors was determined. Impact, rebound and retention of mono-size droplets on various surface characteristics were investigated with high speed video cameras under laboratory-controlled conditions. Quality spray applications with half the conventionally recommended volume of carrier and dosage of active ingredients were investigated with existing spray equipment to achieve effective pest and disease control under commercial nursery production conditions. Investigations included six different air-assisted sprayers in two tests and State inspector surveys for the control of arthropod pests and plant diseases. Sprayers were optimized with properly sized nozzles and properly calibrated operating parameters. Test results were statistically analyzed and reported along with real cost benefits to producers, consumers and environment. Spray deposition and coverage at different application rates for nursery liners of different sizes were investigated to determine the optimal spray application rates. Experiments were conducted on two and three-year old red maple liners. A traditional hydraulic sprayer with vertical booms was used to apply the spray applications. A mathematical model was developed to estimate the spray application rate required for different tree liner heights and to minimize excessive chemical use in rapidly growing tree liners. A portable scanning system was developed that could quickly evaluate spray deposit distribution and coverage area on deposit collectors. The system is integrated with a handheld business card scanner, deposit collectors, a laptop computer, and original software package entitled “DepositScan”. The accuracy of the system was verified with various nominal size spots through a stereoscopic microscope.

1. Optimal spray application rates for ornamental nursery liner production. Production of liners is an essential process for providing abundant bareroot stocks for the ornamental nursery industry to beautify our environment. Liners are one to three-year old young trees grown in nurseries prior to being transplanted to fields or containers where they continue growing into larger, market-ready shade trees. They are normally planted densely and grow rapidly during a growing season, which can aggravate the severity and incidence of insect infestations and diseases. In response to an onset of pest infestations and diseases, spray applicators must make decisions within a very narrow time window on how much pesticide and spray volume is needed for economical control. ARS researchers at Wooster, Ohio quantified the amount of spray deposition and coverage inside ornamental nursery liner canopies from an over-the-row frame vertical boom sprayer, determined its optimal application rates, and established a spray rate model for different size liners. Growers are now using the research findings to increase spray application efficiency, minimize potential environmental contamination due to over application of pesticides, maximize the effectiveness of pest management strategies, and achieve real cost savings for their liner production.

2. Capability of patch antennas in a portable radar system to track insects. Every year insect pests cause substantial economic losses to agricultural and forest crops. To develop more effective pest control measures and limit their spread, data on the dispersal and behavioral patterns of these insects are needed to help develop control and management strategies. ARS researchers at Wooster, Ohio and The Ohio State University researchers investigated the performance of their newly developed entomological radar tracking system as a potential tool to study insect behavior, migration, and population. The system was light and had low power consumption. This technology has a great potential to be used for tracking agricultural and forest insects and even animals.

3. Comprehensive application technology and strategy to reduce pesticide use. Pesticide applications are critical to ensure healthy, unblemished ornamental nursery plants. However, conventional spray application practices only suggest for the modification of carrier volume for preparations of spray mixtures, but not the amount of active ingredients per unit area. ARS researchers at Wooster, Ohio have tested their strategies of using half-rate applications of pesticides and judicious adjustments of air-assisted sprayers in commercial nurseries. They demonstrated that growers could use their existing spray equipment to reduce pesticide and water use by 50% with properly changing spray nozzles at no extra cost and still achieve the effective pest and disease control. This equals to doubling the pesticide application efficiency with reduced pesticide costs, reduced health risk to applicators, and diminished adverse impact to the environment. Other benefits accrued with this approach included increased operational efficiency (the area sprayed is doubled, the frequency and travel time required for the tank refilling times are reduced) and reduced costs for energy consumption and for new equipment, as well as reduced risk of pesticide exposure of workers. By using the half-rate practice, growers reported savings of over $200-$500 per acre.

4. Development of variable-rate sprayer for nursery liner applications. Growing liners is a specialized business for some ornamental nurseries. These liners are young trees that are grown in densely planted rows for two to three years and then sold to other nurseries who then transplant and grow them to market size. Because of their rapid growth in a confined space, pesticide applications are needed to protect them from insect pests and diseases. However, variations in tree size and varieties invariably confound spray applications and over-applications of pesticide are always possible. ARS researchers at Wooster, Ohio developed an experimental intelligent sprayer using ultrasonic sensors and pulse-width modulated spray nozzles to deliver real-time variable-rate sprays to liners based on their canopy size. The newly developed sprayer could achieve uniform spray deposition and coverage for nursery liner applications despite variations in liner canopy size and sprayer travel speed.

5. Droplet evaporation and spread on waxy and hairy leaves. Pesticide spray application efficiency is often improved with enhanced droplet adhesion on leaf target surfaces which is achieved by the addition of adjuvants to spray mixtures. Use of pesticide will be reduced resulting in effective pest control if the active ingredients in droplets uniformly spread out and remain on the target area. ARS researchers at Wooster, Ohio and The Ohio State University researchers determined the fate of water droplets amended with different classes of adjuvants at various concentrations on plant leaves. They clearly demonstrated the fact that the use of adjuvants could greatly improve the homogeneity of sprayed pesticides to increase the coverage area on waxy and hairy leaves, thereby offering possibilities of reduced pesticide usage, and leading to economic benefit to the farmer and reduced risk of contamination of the environment by pesticides. Growers, extension educators and chemical companies in the U.S. and other countries are using the research findings to increase pesticide application efficiency.

Review Publications
Jeon, H., Zhu, H., Derksen, R.C., Ozkan, H., Krause, C.R. 2011. Evaluation of ultrasonic sensors for the variable rate tree liner sprayer development. Computers and Electronics in Agriculture. 75(1):213-221. DOI:10.10161j.compag.2010.11.007.

Xu, L., Zhu, H., Ozkan, E., Bagley, B., Krause, C.R. 2011. Droplet evaporation and spread on waxy and hairy leaves associated with type and concentration of adjuvants. Pest Management Science. 67:842-851. DOI: 10.1002/ps.2122.

Zhu, H., Salyani, M., Fox, R.D. 2011. A portable scanning system for evaluation of spray deposit distribution. Computers and Electronics in Agriculture. 76(1):38-43.

Zhu, H., Psychoudakis, D., Brazee, R.D., Thistle, H.W., Volakis, J.L. 2011. Capability of patch antennas in a portable harmonic radar system to track insects. Transactions of the ASABE. 54(1):355-362.

Zhu, H., Grewal, P.S., Reding, M.E. 2011. Development of a desiccated cadaver delivery system to apply entomopathogenic nematodes for control of soil pests. Applied Engineering in Agriculture. 27(3):317-324.

Zhu, H., Altland, J.E., Derksen, R.C., Krause, C.R. 2011. Optimal spray application rates for ornamental nursery liner production. HortTechnology. 21(3):367-375.

Jeon, H., Tian, L.F., Zhu, H. 2011. Robust crop and weed segmentation under uncontrolled outdoor illumination. Sensors. 11(6)6270-6283.

Last Modified: 4/20/2014
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