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United States Department of Agriculture

Agricultural Research Service


Location: Application Technology Research Unit

2009 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
A precision air-assisted sprayer implementing an automatic variable rate control system is in the process of development for fruit trees and ornamental nurseries. A high speed laser scanner was investigated to detect gaps between trees, and measure tree characteristics. Interfaced program between laser and computer was developed to determine the tree size and shape. Ultrasonic sensors were evaluated for the development of variable-rate sprayers to apply pest control agents for liner nurseries. Durability and detection stability of the sensors were tested under the conditions of winter storage and field spray application. A laboratory system was developed for evaluation of droplet evaporation and residual pattern on leaves. Experiments were conducted under controlled conditions to investigate effects of droplet size, relative humidity, and physical property of sprays on evaporation and on the deposition coverage of single droplets on waxy and hairy leaf surfaces. The sprays included different combinations of water, a nonionic colloidal polymer drift retardant, a nonionic surfactant, insecticides and fungicides. Reduced rate applications of chemicals for control of insect and disease in nursery production were investigated in nurseries in Ohio and Kentucky. Leaf samples were collected and assessed for insect and disease damage for the half-rate and full-rate chemical trials. A portable scanning system, “DepositScan,” was developed to quickly evaluate the deposition quality of pesticide spray applications. In operation, the system first scans samples with a handheld business card scanner, and then reports individual droplet sizes, their distribution, total numbers, and percentage of coverage areas. The analysis of a spray deposition sample is completed in less than 30 seconds even under field conditions. The software is available to the public without charge, and can be downloaded from the website (

1. Investigation of the fate of pesticide droplets on targets. Extensive research has been conducted to achieve accurate delivery of chemical droplets. However, the fate of chemical droplets after deposition on leaf surfaces has not been studied to determine how that consequence might reduce pesticide use. Evaporation time and the area wetted by a single pesticide droplet on waxy or non-waxy surfaces leaves were investigated under controlled conditions and for various droplet size, relative humidities and chemical formulations. Evaporation time and the wetted area of droplets affected the distribution of pesticides on targets with different surface characteristics. To obtain the optimal biological effect and reduce pesticide use, pesticide dosage and spray techniques should be used differently for different leaf surfaces.

2. Optimizing pesticide application rate technology for nursery production. Use of traditional settings in air-assisted sprayers in nursery applications resulted in excessive spray deposition inside tree canopies and loss of spray mixtures to the ground and air. Half-rate application of pesticides with various adjustments of air-assisted sprayers was investigated in nurseries. Adaptations by nursery growers of the recommendations developed in this study have resulted in half the usage of pesticides for pest and disease controls in nursery shade tree plants. By using the half-rate technology, growers safeguarded the environment due to pesticide applications and reported savings of over $200-$500 per acre.

3. Development of a handy helper scanning system to optimize pesticide spray applications. Inaccurate application of pesticides on target areas causes serious spray drift and off-target loss problems, resulting in excessive pesticide use, poor food safety, environmental contamination and hazards to workers. A portable scanning system, DepositScan was developed to quickly evaluate the deposition quality of pesticide spray applications. The use of DepositScan will improve accuracy of pesticide spray applications. The software for DepositScan is available to the public without charge, and can be downloaded from the website ( To execute the DepositScan software, users need a laptop computer and a handheld business card scanner which can be purchased from any office supply stores or the internet. DepositScan is a tool that farmers can use to optimize equipment settings, techniques, and practices. For extension educators, DepositScan can help train applicators to accurately apply chemicals on targets. For manufacturers, it can accelerate the process for new pesticide formulations and pesticide spraying equipment. It can also help researchers determine factors that influence spray application technology. DepositScan has considerable potential to minimize off-target loss including spray drift, and impact pesticide spray application efficiency and efficacy.

4. Investigation of optimal spray techniques for nursery applications. Unusual planting configurations limit efficient pesticide use in pest control for many container-grown ornamental crops. The parameters (maximum spray range, uniformity of spray deposition, coverage and the air velocity throughout the spray swath) from a wide-swath air jet sprayer for container-grown crops were determined. Nursery growers can now identify optimal spray techniques to effectively control pest insects or diseases for the crops planted with this type of special circumstances.

5.Significant Activities that Support Special Target Populations
The floral and nursery grower industry needs timely weather data to aid decision making in crop management and protection. This information also benefits small farms and nurseries with less than $250,000 annual gross receipts. Research weather stations have been developed and upgraded cooperatively with OSU/OARDC and commercial nurseries in northern Ohio. Web pages have been developed to report charts on wind speed and azimuth, solar radiation, atmospheric temperature and relative humidity, precipitation, leaf wetness, barometric pressure, soil temperatures, soil moisture contents at depths from 10 to 100 cm below the soil surface, and interrelationships among variables related to leaf wetness. In addition to application technology research, data and summaries are available in real time to the grower industry via web sites to aid in crop management and protection decisions and irrigation scheduling.

6.Technology Transfer

Number of Web Sites Managed1
Number of Other Technology Transfer2

Review Publications
Yu, Y., Zhu, H., Ozkan, H.E. 2008. Evaporation of Pesticide Droplets under Various Relative Humidity Conditions. Journal of ASTM International. 6(1):1-8.

Zhu, H., Brazee, R.D., Fox, R.D., Derksen, R.C., Ozkan, H.E. 2008. Development of a Canopy Opener to Improve Spray Deposition and Coverage Inside Soybean Canopies -- Part 1: Mathematical Models to Assist Opener Development. Transactions of the ASABE. 51(6):1905-1912.

Zhu, H., Derksen, R.C., Ozkan, H.E., Reding, M.E., Krause, C.R. 2008. Development of a Canopy Opener to Improve Spray Deposition and Coverage Inside Soybean Canopies -- Part 2: Opener Design with Field Experiments. Transactions of the ASABE. 51(6):1913-1921.

Zhu, H. 2009. DepositScan, a Scanning Program to Measure Spray Deposition Distributions. Software and User Manual Public Release. Available:

Last Modified: 4/24/2014
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