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United States Department of Agriculture

Agricultural Research Service


Location: Application Technology Research Unit

2010 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
Residue patterns and evaporation time of single droplets that incorporated four classes of adjuvants on five different waxy plants were investigated under the controlled conditions. Droplets were generated with a single-droplet generator and deposited on target leaves placed in an environmentally-controlled chamber at 60% relative humidity and 25 ºC ambient temperature. Droplets with oil-based adjuvants had more uniform residual distribution in the deposition patterns than droplets with the surfactant adjuvant. Evaporation and deposit pattern formation of single droplets deposited at various locations on waxy leaves were investigated under controlled conditions. The leaf locations included the interveinal area, midrib and secondary vein on both adaxial and abaxial surfaces. Tests were conducted with two sizes of droplets containing water and a nonionic surfactant. A light weight system was developed to deliver infected desiccated cadavers carrying entomopathogenic nematodes into the soil. The system mainly consists of a metering unit, an air pressure source, a cadaver scraper, a custom-designed cadaver container, tension adjustment devices, double disk soil opener, a discharge tube, a packer wheel, and a press/drive wheel. Laboratory and field tests were conducted to verify the system delivery accuracy. 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 was developed that could quickly evaluate spray deposit distribution and coverage area on deposit collectors such as water sensitive paper. After scanning the collectors, individual droplet sizes, their distributions, total droplet number, and percentage of area coverage are displayed on the computer screen and saved in a spreadsheet. A series of tests to evaluate durability and detection stability of an ultrasonic sensor was carried out under cold weather exposure, wind, dust, travel speed, air temperature and spray cloud conditions. A strategy to configure the sensor with spray nozzles was developed to reduce root mean square errors. A real-time variable-rate experimental sprayer was developed to reduce pesticide usage by coinciding spray outputs with canopy sizes. Srayer performances including accuracy of spray timing and spray modulation as well as percent spray coverage inside tree canopies were evaluated under both laboratory and field conditions. A precision air-assisted sprayer implementing an automatic variable rate control system is in the process of development for ornamental nurseries and fruit trees. 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. Laboratory and field tests were conducted to verify the accuracy of spray controller timing and modulation. A laboratory system was developed for evaluation of droplet impact, rebound and retention on leaves.

1. Adjuvant effects on behaviors of pesticide droplets on waxy leaves. Pesticide applications have ensured a bountiful supply of high quality crops, but the public has concerned about its increased use and its effects on worker safety, environmental contamination, and adverse impacts on a vulnerable ecosystems. Residue patterns of single droplets and their evaporation time in four classes of adjuvants on five different waxy plants were determined under the controlled conditions. Results of this study demonstrated that the use of an appropriate class of adjuvants significantly improved droplet deposition on waxy leaves and the effectiveness of pesticides, and is critical to the process to reduce off-target losses.

2. Behavior of droplets amended with or without surfactants at different sites of waxy leaf surfaces. Although numerous studies have been conducted to accurately deliver chemical droplets on targets, the behavior of chemical droplets after their deposition on leaf surfaces largely remains unknown. Our studies under controlled conditions on the rate of evaporation and residue formation from single droplets amended with or without surfactants and depositied at various locations on waxy leaves provided answers to this challenging question. This study demonstrated that the ratio between the coverage area and the amount of spray required at different sites of waxy leaves was increased by the use of surfactants and offered the possibilities of reduced spray application rates and increased application efficiency.

3. Desiccated cadaver delivery system for application of entomopathogenic nematodes to control soil pests. Root-feeding larvae are important economical pests of crops and require control measures. However, the use of conventional pesticides has raised concerns over potential contamination to the environment. Consequently, biological control agents, which are considered safer and offer environmentally-friendly advantages, have been promoted as an alternative approach. Entomopathogenic nematodes when harbored within desiccated cadavers are more capable as a control measure of root-feeding larvae. In this study, a crop seed planter was modified to determine whether irregular-shaped, fragile and nematode-infected desiccated cadavers could be effectively delivered into the soil at a desired rate and depth as the seed planter traveled continuously along a row. Laboratory and field tests demonstrated that, although feasible, to improve accuracy of the seed planter, metering plates must be specifically designed for this system to discharge desiccated cadavers at different rates.

4. Optimization of technologies for pesticide application rates in nursery production. Traditional settings of air-assisted sprayers for nursery applications often result in excessive spray deposition inside tree canopies and exacerbate off target losses. Since 2005, we have annually tested our strategies of using half-rate applications of pesticides and judicious adjustments of air-assisted sprayers in commercial nurseries. Adaptations by nursery growers of the half-rate technology have resulted in overall reduction in pesticide usage. By using the half-rate technology, growers not only reduced the use of pesticides, but also safeguarded the environment and reported savings of over $200-$500 per acre.

5. A handy helper scanning system to quickly evaluate spray deposition. Inaccurate pesticide applications on target areas cause serious spray drift and off-target loss problems, and result in excessive use of pesticides, compromise food safety, contaminate the environment and are a hazard to workers. Prevention of over- or under-spray applications on intended targets requires a system that can rapidly measure spray coverage and provide spray quality feedback information. “DepositScan”, a portable scanning system, was developed that quickly evaluated spray deposition and coverage on deposit collectors. The software for DepositScan is available to the public without charge, and can be downloaded from our website. DepositScan is a tool for farmers, extension educators, researchers and manufacturers to increase pesticide delivery accuracy, minimize off-target loss, and improve pesticide spray application efficiency and efficacy.

6. Detection of nursery liner canopies with ultrasonic sensors. Ornamental nursery liners (or seedlings) grow quickly during a growing season. The limited capabilities of conventional sprayers to compensate for the rapid growth of liners with the proper amount of sprays are responsible for much of the inaccurate pesticide applications. Traditional ultrasonic sensors coupled with variable-rate sprayers cannot evaluate small tree liners. Thus, sensors in advanced sprayers that automatically adjust spray outputs based on canopy sizes are needed. Our newly designed detecting system implementing fast detection ultrasonic sensors for high travel speeds satisfied the requirements for durability and measurement stability under field conditions. This new generation of detecting technologies has made advanced variable-rate sprayers for tree liner application a reality.

7. A real-time variable-rate sprayer for nursery liner applications. Pesticide applications on ornamental nursery tree liners with conventional sprayers to control pests and diseases are excessive. A real-time, variable-rate experimental sprayer where spray outputs coincided with canopy sizes was developed to reduce pesticide usage. In laboratory tests, the experimental sprayer reduced the average application rates by 59 to 75%, and demonstrated that pesticide usage could be greatly reduced when variable-rate spray applications are determined by canopy sizes and occurrences. The potential use of the sprayer could be extended to other fruit crops including vineyards.

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.

Review Publications
Wang, X., Zhu, H., Reding, M.E., Locke, J.C., Leland, J.E., Derksen, R.C., Spongberg, A.L., Krause, C.R. 2009. Delivery of Chemical and Microbial Pesticides from Drip Irrigation Emitters. Applied Engineering in Agriculture. 25(6):883-893.

Yu, Y., Zhu, H., Frantz, J., Reding, M.E., Chan, K.C. 2009. Evaporation and Coverage Area of Pesticide Droplets on Hairy and Waxy Leaves. Biosystems Engineering. 104:324-334.

Yu, Y., Zhu, H., Derksen, R.C., Krause, C.R. 2009. Evaporation and Deposition Coverage Area of Droplets Containing Insecticides and Spray Additives on Hydrophilic, Hydrophobic and Crabapple Leaf Surfaces. Transactions of the ASABE. 52(1):39-49.

Xu, L., Zhu, H., Ozkan, E., Thisle, H. 2010. Evaporation Rate and Development of Wetted Area of Water Droplets with and without Surfactant at Different Locations on Waxy Leaf Surfaces. Biosystems Engineering. 106: 58-67.

Xu, L., Zhu, H., Ozkan, E., Bagley, B., Derksen, R.C., Krause, C.R. 2010. Adjuvant Effects on Evaporation Rates and Wetted Area of Droplets on Waxy Leaves. Transactions of the ASABE. 53(1): 13-20.

Zhu, H., Yu, Y., Ozkan, H. 2010. Influence of Spray Formulation and Leaf Surface Structure on Droplet Evaporation and Wetted Area. Aspects of Applied Biology. 99:333-340.

Last Modified: 4/23/2014
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