Comparative analysis of the Potter Tower and a new Track Sprayer for the application of residual sprays in the laboratory

Abstract

Abstract Efforts to evaluate the residual efficacy of new IRS formulations have identified limitations with the industry standard laboratory sprayer, the Potter Spray Tower (PT). Calibrating the PT can be time-consuming, and the dosing of surfaces may not be as accurate nor uniform as previously assumed. To address these limitations the Micron Horizontal Track Sprayer with Spray Cabinet (TS) was developed to provide higher efficiency, ease of operation, and deposition uniformity equal to or better than the PT. A series of studies showed that deposition volumes could be accurately calibrated for both spray systems. However, the uniformity of spray deposits was higher for the TS compared to the PT. Less than 12% of the volume sprayed using the PT reaches the target surface, with the remaining 88% unaccounted for, presumably vented out of the fume hood or coating the internal surfaces of the tower. In contrast, the TS deposits the majority of the spray on the floor of the spray chamber, with the rest contained therein. The total sprayed surface area in one run of the TS is 1.2 m2, and the operational zone for spray target placement is 0.7 m2, meaning that 58% of the applied volume deposits onto the targets. The TS can treat multiple surfaces (18 standard 15x15 cm tiles) in a single application, whereas the PT treats one surface at a time and a maximum area of around 0.0225m2. An assessment of the time taken to perform spraying, including the setup, calibration and cleaning, showed that the cost of application using the TS was around 25–35× less per tile sprayed. A standard operating procedure (SOP) for calibration and use of both the Potter Tower and Track Sprayer are presented. Overall, the TS represents a significant improvement over the PT in terms of the efficiency and accuracy of IRS formulation applications onto test substrates and offers a useful additional tool for researchers and manufacturers wanting to screen new active ingredients or evaluate the efficacy of IRS or other sprayable formulations for insect control.