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United States Department of Agriculture

Agricultural Research Service

Research Project: BIOLOGICAL, MICROCLIMATE, AND TRANSPORT PROCESSES AFFECTING PEST CONTROL APPLICATION TECHNOLOGY

Location: Application Technology Research Unit

2013 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:
The spray performance of newly developed laser-sensor guided precision sprayer was tested in a laboratory plot, three commercial nursery fields and a vineyard, and was compared with the conventional spray applications. Spray deposition and coverage inside canopies were measured with nylon screens and water sensitive papers to determine the spray quality on target trees. In the laboratory plot, tests were conducted with three travel speeds, two size nozzles and six different tree species of different sizes on the same row. In the first commercial nursery field, tests were conducted with six different sizes of five tree species in two rows and three travel speeds. In the second nursery field, tests were conducted with four similar size trees of the same variety in two rows and three travel speeds to compare spray quality with a constant-rate application. In the third nursery field, tests were conducted in two plots with different widths of multi rows. One plot had four rows of sterling silver linden trees and the other plot had six rows of red oaks. In the vineyard, tests were conducted for the 10 year old red wine grape plants. Spray deposition samples were collected on the trunk, in the front, the middle and the back of three plant canopies as well as gaps between two plants.

Field efficacy tests were conducted to evaluate the control of aphids and powdery mildew with our newly developed air-assisted precision sprayer in four commercial nurseries in Ohio, Oregon and Tennessee. The control efficiency was also compared between the new sprayer and conventional constant-rate sprayers. These tests will be continued for the next three years.

Dispersion and evaporation of single droplets amended with four different classes of spray adjuvants on five weed surfaces were investigated. Tests were conducted under the controlled conditions to identify the best class of adjuvants and optimal concentrations to control these weeds. Evaporation rates of three types of pheromones at four ambient air temperatures and three relative humidities were measured under controlled environmental conditions.

Dynamic processes of droplet impact, rebound and retention on various types of leaf surfaces were accessed with three-dimensional images. Five motion processes of droplets after they impacted on waxy and hairy leaf surfaces were observed and quantitatively analyzed with a 3-D image program.


4.Accomplishments
1. Development of a precision air-assisted sprayer for tree crop production. Trees in nurseries and orchards have great variations in shapes, sizes, canopy densities and gaps between in-row trees. The variability requires future sprayers to be flexible to spray the amount of chemicals that can match tree structures. ARS researchers at Wooster, Ohio developed a variable-rate air-assisted sprayer implementing high-speed laser scanning technology to achieve these requirements. Field tests demonstrated that the new variable-rate sprayer produced significantly more consistent spray deposit and coverage inside tree canopies than the conventional sprayers, consequently resulting in less off-target loss and less pesticide use. Therefore, use of the new sprayer to deliver pest control agents will bring great benefits to growers economically and environmentally.

2. Air velocity distributions inside canopies from the precision air-assisted sprayer. Future precision air-assisted variable-rate sprayers should have a capability to control both liquid and air flows to match tree canopy structures. ARS researchers at Wooster, Ohio established a feasible and economic approach with adjusting fan inlet diameters to achieve the variable air rate function for new precision sprayers used in orchard and nursery applications. With this function, sprayers will be able to control the amount of air flow as needed to prevent crops from either over sprayed or under sprayed, and to minimize excessive off-target losses to the air and ground, resulting in preservation of air, water, and soil quality and sustainable ecosystems.

3. A system developed for investigation of dynamic droplet impaction and deposition formation on leaves. The need to elucidate droplet dynamic impaction and deposition formation on leaf surfaces to increase the biological control efficiency has been recognized for many years, but recent reports do not address this problem due to lack of scientific methodologies. ARS researchers at Wooster, Ohio developed a three-dimensional sophisticated system for analyses of dynamic droplet impaction, rebound and deposition formation on leaves. The system was able to manipulate variable droplet sizes, impact speeds and impact angles to independently test the dynamic impaction of droplets on different types of leaves with different spray solutions under controlled experimental conditions. This accomplishment would provide insights into pesticide droplet impaction and deposition formation on plant leaf surfaces to bridge the gaps of knowledge between the spray application technologies and biological control effectiveness. These underlying mechanisms are necessary to advance pesticide spray application technologies and strategies to increase effectiveness and reduce pesticide waste.

4. Tree growth with various fertilizer applications in container production. Because of vast varieties and species in nurseries, scientific guidelines are lacking for growers to improve their nutrition practices based on their specific production circumstance. Fertilizer practices with topdressing, incorporating and liquid feeding methods can cause substantial labor cost and excessive nutrient runoff loss. To provide solutions to this problem, ARS researchers at Wooster, Ohio investigated various fertilizer practices and nutrient applications for container-grown trees and established a scientific guideline for container production. Following this nutrition application strategy, growers will be able to maximize the one-year growth of container-grown trees, shorten tree production time, and save labor costs.


Review Publications
Gimenes, M., Zhu, H., Raetano, C., Oliveira, R. 2013. Dispersion and evaporation of droplets amended with adjuvants on soybeans. Crop Protection Journal. 44:84-90.

Bartzanas, T., Kacira, M., Zhu, H., Karmaker, S., Tamimi, E., Katsoulas, N., Lee, I.B., Kittas, C. 2013. Computational fluid dynamics applications to improve crop production systems. Computers and Electronics in Agriculture. 93:151-167.

Gu, J., Zhu, H., Ding, W. 2012. Unimpeded air velocity profiles of air-assisted five-port sprayer. Transactions of the ASABE. 55(5):1659-1666.

Guler, H., Zhu, H., Ozkan, H.E., Ling, P. 2013. Characterization of hydraulic nozzles for droplet size and spray coverage. Atomization and Sprays. 22(8):627-645.

Zhu, H., Zondag, R., Merrick, J., Demaline, T., Jeon, H.Y., Krause, C.R., Locke, J.C. 2013. Fertilizer applications for container-grown ornamental tree production. Journal of Environmental Horticulture. 31(2):68-76.

Chen, Y., Zhu, H., Ozkan, E. 2012. Development of variable-rate sprayer with laser scanning sensor to synchronize spray outputs to tree structures. Transactions of the ASABE. 55(3):773-781.

Zhu, H., Wang, X., Reding, M.E., Locke, J.C. 2011. Distribution of chemical and microbial pesticides delivered through drip irrigation systems. In: Stoytcheva, M. editor. Pesticides - Formulations, Effects, Fate. Rijeka, Croatia:InTech. p 155-180.

Last Modified: 12/19/2014
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