Spray characterization of aerosol delivery systems for use in stored product insect facilities

Authors: ASUNCION, FEI XYZA - Kansas State University; Brabec, Daniel - Dan; Casada, Mark; MAGHIRANG, RONALDO - University Of Illinois; Arthur, Franklin; Campbell, James - Jim; ZHU, KUN YAN - Kansas State University; Martin, Daniel - Dan

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2020
Publication Date: 11/20/2020
Citation: Asuncion, F.B., Brabec, D.L., Casada, M.E., Maghirang, R.G., Arthur, F.H., Campbell, J.F., Zhu, K., Martin, D.E. 2020. Spray characterization of aerosol delivery systems for use in stored product insect facilities. Transactions of the ASABE. 63(6):1925-1937. https://doi.org/10.13031/trans.14010.
DOI: https://doi.org/10.13031/trans.14010

Interpretive Summary: Aerosol insecticides are widely used for controlling stored product insects inside food facilities, but limited information is available on the effectiveness of these treatments. Knowing the spray characteristics of the equipment to be used and understanding how key factors influence the application are crucial to maximizing the effectiveness of aerosol applications. Important factors in achieving an effective aerosol application are size, number, and concentration of aerosol droplets; airflow pattern; and droplet distribution. We determined the spray characteristics of the following application systems: Hurricane ES, Fogmaster Jr, and a compressed gas cylinder with two types of manifolds and two types of nozzles (solid stream and fan). Results showed that the spray systems differed in spray characteristics that are likely to impact insecticide efficacy. The handheld sprayers generated significantly larger droplets and more variable droplet size distributions than the compressed gas sprayer systems. With larger droplets produced, the handheld sprayers had lower spray coverage area and lower efficacy than the compressed gas sprayers. The average deposition was not significantly different between the two manifolds for the compressed gas sprayers. The amount of deposition from spraying at high dosage was significantly higher than the amount from spraying at low dosage. Higher pressure was produced in the plume by the nozzles with the compressed gas sprayer systems as compared with the handheld sprayers. Between the two nozzles, the circular nozzle generally had higher plume pressure, but the ellipsoidal nozzle had a wider spray plume. The tapered spray pattern produced by the ellipsoidal nozzle produced more uniform distribution across the entire sprayed surface. Results of this study will be used to improve spray techniques for controlling stored product insects and to improve testing methods in large-scale spray testing in a flour mill. Further research will be conducted to compare the spray systems in a grain processing facility.

Technical Abstract: Aerosol insecticides, including pyrethrin, can be used as methyl bromide replacements to control stored product insects inside flour mills and rice mills. The effectiveness of aerosol application for insect control requires knowing the spray characteristics of the equipment to be used and understanding factors that influence the effectiveness of insecticide application. The objectives of this study, as part of efforts to optimize aerosol applications, were to evaluate the characteristics of six aerosol delivery systems (two handheld sprayers and compressed gas sprayer system fitted with two types of manifolds and two types of nozzles), estimate the dispersion and deposition of aerosol in a simulated stored product facility, and determine how the dispersion and deposition are affected by the characteristics of the sprayers. Results showed that the spray systems differed significantly in spray characteristics, which could affect insecticide efficacy. The compressed gas sprayers generated significantly smaller droplets, more uniform droplet size distribution, higher spray coverage and efficiency than the handheld sprayers. The fan nozzle produced significantly smaller droplets than the solid stream nozzle. While the type of manifold had no significant effect on deposition, higher aerosol dosage and spray time resulted in significantly higher deposition. Results of this study will be used to improve spray techniques for stored product insect control, to validate computational fluid dynamics modeling of aerosol application, and to improve testing methods in large-scale spray testing inside commercial facilities.