Ground Cover Supplement : GC Supplement - Spray application 2016
19 Applicator toolbox TA BLE 1 A selection of the data produced comparing the percent coverage measured by four of the image-analysis systems tested. Nozzle used Operating pressure (kPa) Percent coverage on water-sensitive paper (WSP)* SnapCard Image J Deposit Scan Droplet Scan 110--01 450 49 60 60 75 110--03 300 49 53 53 71 110--06 200 51 53 52 75 80--08 250 43 44 43 50 65--10 200 48 50 49 65 * As this is only a selection from the original data set the levels of statistical signifcance are not included. SOURCE: UNIVERSITY OF QUEENSLAND CENTRE FOR PESTICIDE APPLICATION AND SAFETY. MODIFIED FROM AN ARTICLE BY FERGUSON, JC ET AL (2016), PEST MANAGEMENT SCIENCE (IN PRESS) it was difficult to find a consistent relationship between droplets/cm2 and efficacy, particularly when applying products with different spray qualities. Laboratory-based image-analysis systems that were available at the time seemed to provide a more consistent relationship between the percentage of the target covered and the level of control obtained. SNAPCARD APP The SnapCard app (https://www.agric. wa.gov.au/grains/snapcard-spray- app) takes WSP to a new level. The SnapCard app has been available for Android and Apple devices since 2014, and its use by growers and spray operators to measure spray deposition continues to increase. The app is the outcome of a research collaboration between the entomology group at the Department of Agriculture and Food, Western Australia, and the University of WA's (UWA) applied entomology program, which was supported by funding from the Council of Grain Grower Organisations. The GRDC also provided funding to UWA for the employment of an entomology professor. The SnapCard app can be used to predict and measure spray coverage on WSP. While the predictions, which are based on agronomic variables, weather conditions and sprayer set-up, serve as a useful guide with which to compare measurements. Perhaps the most powerful function of the SnapCard app RESEARCHERS ZOOM IN ON DROPLET BEHAVIOUR Several factors influence what a spray droplet does when it strikes the target surface. Depending on the droplet size, droplet velocity, chemical properties of the spray solution and the characteristics of the leaf surface, the droplet may adhere, bounce or shatter and possibly be recaptured. Researchers in Australia and New Zealand (funded by the Australian Research Council and some commercial companies) are mathematically modelling what happens during the spraying of plants. Researchers from the University of Queensland, Queensland University of Technology, Plant Protection Chemistry New Zealand and SciCon Scientific Consultants have pooled their knowledge and research expertise to quantify what happens to spray droplets at the leaf surface, particularly when the parameters that influence their deposition are changed. “It has turned out to be a lot more complicated than we first thought,” says Jerzy Zabkiewicz, from SciCon Scientific Consultants in New Zealand. “However, the main factors that influence what happens to the droplets after they impact on the leaf are the droplet velocity, spray formulation and the characteristics of the leaf surface itself.” Combining all of these factors to produce a virtual model of the spraying process relied on sophisticated modelling of what happens from the time that the droplets exit the nozzle to when they first impact on the leaf surface, and then what happens to them in the milliseconds after impact. This research is continuing towards developing decision-support tools for industry to predict droplet retention levels on selected targets More information: Jerzy Zabkiewicz, SciCon Scientifc Consultants, firstname.lastname@example.org, email@example.com The SnapCard app is simple to download and use, and can help to measure the level of spray coverage achieved. is the measurement tool itself, which provides the user with a measurement of the percentage of the WSP covered. In a recent University of Queensland study comparing some of the image- analysis systems available to measure spray deposits, results obtained from the SnapCard app supported results from laboratory-based equipment, which is often expensive and difficult to use in the field. Results obtained from this study (Table 1) show the percent coverage on WSP as measured using a range of image-analysis systems. The nozzles and operating pressures used in this study were the American Society of Agricultural and Biological Engineers reference nozzles, which are used to determine the spray-quality classification for nozzles according to standard 572.1. While the estimates of percentage coverage measured with SnapCard were marginally lower for 110-01 nozzle outputs than those measured by other instruments, there was good agreement with other instruments for the range OVER TIME THIS RECORD CAN BECOME A VALUABLE TOOL, ESPECIALLY WHEN THE INFORMATION IN THE SPRAY RECORDS ALLOWS FOR DIRECT COMPARISON BETWEEN HOW THE APPLICATION WAS MADE AND THE RESULTS THAT WERE OBTAINED.
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