High-speed imaging use to predict spray retention on barley leaves

Measuring spray retention by plant leaves was the aim of many experiments in plant protection researches. Different methods have been used to measure spray proportion retained on vegetative surfaces, such as chemical methods using dyes and other methods using image analysis. We conducted Laboratory studies in order to validate the effectiveness of using high-speed imaging method developed by Massinon and Lebeau (2012a) to replace chemical analysis by spectrofluorometry. Measurements were performed with a high speed camera coupled with a retro-LED lighting. Sizes and velocities of the drops were extracted by image analysis and drop impact behaviours were determined by the operator. Drops were produced with a flat-fan nozzle mounted on a movable ramp. Two surfactants (Break Thru 5240 and Li700) were sprayed to highlight the effect of the reduction of surface tension. Sprays contained a fluorescent tracer for the chemical analysis, fluorescein. Relative volume proportions were computed within of an energy scale based on the Weber number. Results of high-speed imaging were compared to those of the chemical analysis by spectrofluorometry.