Towards the optimisation of Coarse sprays to reduce drift and improve efficacy in Australian cropping systems

Abstract

The optimisation of Coarse sprays for control of insects, weeds, and diseases in agriculture involves understanding how those technologies are classified and selected for use. Coarse sprays are the focus of this thesis, because Coarse is a spray size classification that balances adequate coverage, while reducing pesticide spray drift. Spray drift is detrimental, and by selecting coarser droplet sprays, spray drift can be minimised. The initial research study in this thesis sought to identify the repeatability of each nozzle type by randomly selecting five units to test consistency of droplet size measurements across nozzle type.The optimisation of Coarse sprays involves understanding differences that separate uniform technologies, especially when uniform nozzles of the same droplet size classification category are selected. When using plants and efficacy studies alone to quantify spray coverage, specific coverage values are difficult to determine. This consideration prompted studies with artificial collectors to quantify droplet coverage and provide the droplet distribution across the collector to help aid in technology selection. Results from these studies showed that nozzles which produced the same spray quality based on the droplet size distribution did not result in similar coverage across collector types. Nozzles that resulted in the highest coverage were further studied in the subsequent chapters.The optimisation of Coarse sprays involves understanding how sprays move within plant canopies. Consistent spray coverage that is evenly distributed throughout the canopy is necessary to control pest populations that negatively affect yield. As applicators are switching to coarser sprays to reduce risk and liability of pesticide spray drift, concerns about efficacy loss are increasing. Results showed that droplet number densities were inversely related to the droplet size produced by the nozzles, yet coverage was influenced more by application volume rate than droplet size.The optimisation of Coarse sprays involves ensuring that measurement methods and techniques are precise for the selection of the best technologies. A freely available smartphone application (app), SnapCard was developed to provide for in-field analysis of spray collectors. Results from this study showed consistent agreement between Image J and the new app, SnapCard, both of which were used consistently in this study. 3 The optimisation of Coarse sprays requires using novel techniques for characterising sprays, notably artificial collectors. The use of artificial collectors for spray characterisation is well accepted, but there is no literature to bridge the knowledge gap to understand how each major artificial collector type differs. Using all collector types (water sensitive paper, Kromekote ® and Mylar ® ) in tandem was useful to properly characterise the sprays, in addition to helping to quantify the differences between each collector type for coverage and droplet number density analyses.An optimal Coarse spray should not drift in ...

Effect of sprayer parameters and wind speed on spray retention and soil deposits of pesticides: Case of artichoke cultivar

“…In order to improve D f and reduce D s , the droplet size spectrum should be increased by selecting a different nozzle type (NT), reducing operating pressure (P) or increasing the nozzle size (S). Several other researchers obtained the same conclusions (Creech et al 2015;Ferguson 2016) and some have even observed that the efficacy with coarser droplets is as good as with finer droplets (Shaw et al 2000). However, the droplet size increase should not exceed 400 µm (medium spray quality) as a limit of droplet run-off on the foliage (Ozkan 2016).…”

Analysis of the Influence of Different Parameters on Droplet Characteristics and Droplet Size Classification Categories for Air Induction Nozzle

“…Spray pressures of 200 kPa, 300 kPa, 400 kPa, 500 kPa, 600 kPa and 700 kPa and air velocities of 2 m/s, 3 m/s, 4 m/s and 5 m/s were set up. The XR 11003VS was also measured by a method consistent with the ASABE S-572.1 standard in the same laboratory, and it has been used as the ASABE reference nozzle in international spray studies [24][25][26]. The criteria of the size classes were provided by a set of certified reference nozzles.…”

Deposition of Pesticide to the Soil and Plant Retention During Crop Spraying: The Art State

“…The extraction coefficient is generally higher for artificial targets, except for the Brilliant Blue tracer, for filter paper collector, lower than the limit (80%) of extraction established by (ANVISA, 2008) for validation of the analytical methods. The use of artificial collectors for spray characterization is well known using all collector types was useful to properly characterize the sprays and to quantify the differences between each collector type for coverage and droplet density (Ferguson, 2016).…”