ARS | Publication request: A portable scanning system for evaluation of spray deposit distribution

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 29, 2011
Publication Date: May 10, 2011
Repository URL: http://hdl.handle.net/10113/50052
Citation: 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.

Interpretive Summary: The effect of pesticide on the environment is a major concern throughout the world. Typical spray applications generally provide over sprays to accessible parts of the target canopy and under sprays to hard-to-reach parts of the foliage. If sprays are applied uniformly throughout the canopy, significant reduction in the amount of applied active ingredient can be achieved without diminishing pest control. The quality of spray application is usually measured by collectors (e.g. water sensitive paper) attached to selected target areas or leaves and inspected after spraying. In this research, an easy-to-use and small portable device using a pixel recognition scanning technique was developed to measure spray quality under various working conditions. The device can quickly scan spray deposits on collectors, calculate spray coverage data, and demonstrate distributions of spray coverage during spray experiments or at grower field days. This enables users to obtain the spray quality feedback information quickly with a baseline required for effective control of insects or diseases and minimize off-target loss.

Technical Abstract: Preventing over- or under–spray applications on intended targets require a system to rapidly measure spray coverage and provide spray quality feedback information. A portable scanning system was developed that could quickly evaluate spray deposit distribution and coverage area on deposit collectors such as water sensitive paper or Kromekote® card. The system is integrated with a handheld business card scanner, deposit collectors, a laptop computer, and a custom-designed software package entitled “DepositScan”. The software is composed of a set of custom plug-ins that are used by an image-processing program (ImageJ) to produce a number of measurements suitable for describing spray deposit distribution. The program worked with the handheld business card scanner to scan spray deposits on the collectors. After scanning the collectors, individual droplet sizes, their distributions, total droplet number, droplet density, amount of spray deposits, and percentage of spray coverage are displayed on the computer screen and saved in a spreadsheet. Spots smaller than 23.9 µm are ignored by DepositScan when 2400 dpi resolution was used. Observations of nominal size spots through a stereoscopic microscope verified the accuracy of the system, and demonstrated that because of pixel limitations, the accuracy of any image-processing program using the pixel recognition technique would decrease as the spot sizes decrease. The portable scanning system offers a convenient solution for on-the-spot evaluation of spray quality under various working conditions. Key words: DepositScan; Droplet density; Droplet distribution; Image analysis; Imaging instrumentation; Spray coverage; Spray quality.