CROP PROTECTION AND PRODUCTION STRATEGIES FOR HORTICULTURAL CROPS
Location: Application Technology Research Unit
Title: Comparison of Handgun and Boom Spray Delivery Systems for Greenhouses
Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: March 10, 2009
Publication Date: June 21, 2009
Citation: Derksen, R.C., Ranger, C.M., Canas, L.A., Locke, J.C., Zhu, H., Krause, C.R. 2009. Comparison of Handgun and Boom Spray Delivery Systems for Greenhouses. ASABE Annual International Meeting, June 21-24, 2009, Reno, Nevada. ASABE Paper #97453.
Consumers seek out high quality, blemish free ornamental plants driving the many pest management decisions. Greenhouse structures pose unique pest management challenges that limit application equipment choices. Interior support structures as well as small walkways and alleys limit the size of equipment and maneuverability. The objective of this research was to determine differences in performance between different sprayers used to treat mature poinsettias and differences in the fate of the spray within the canopy with the aim to determine which techniques produced highest spray retention on the underside of leaves. A bench-top trial was conducted using a mature poinsettia canopy in a greenhouse. Sprayer treatments were used to apply a tank mix of BSF fluorescent tracer. Spray retention was measured on nylon screen targets fixed to the underside of leaves in the upper and lower part of the canopy. Treatments included a handgun used to apply different spray volumes at different pressures and a twin-fan and an air-assisted delivery broadcast treatments. Despite the relatively short distance between the upper and lower canopy sampling sites on the poinsettia plants in this study, significant differences in under-leaf spray deposits were noted by elevation for most treatments. Statistically, there were no significant differences between treatments at either canopy elevation. Greater variability in mean spray deposits were noted at the upper canopy elevation compared to the lower canopy elevation. Overall, spray volume, as changed by application speed of the handgun treatment, did not significantly affect spray deposit at either canopy location. Increasing operating pressure by a factor of four did significantly change the atomization characteristics and droplet velocity of the handgun spray stream and resulted in higher mean deposits in the upper canopy, but they were not significantly greater than the mean deposits of the lower pressure handgun treatments. Higher operating pressure also did not improve canopy penetration and underside leaf spray deposits. While air-assistance with a flat fan nozzle inclined at 30° increased mean deposits over a non-air-assist boom treatment, the results were not significantly different. Overall, variability of results within some of the treatments was quite high. The high pressure handgun treatment produced the greatest variability across target plants. Broadcast applications with the TwinJet nozzles and the Air-assist treatment produced lower spray deposit variability. Deposit variability could be important in terms of ensuring uniform results, especially if contact materials are being applied or if plant injury to sensitive ornamental plants could result from over application. Producers will benefit from means to make more uniform applications and applying more predictable amounts of treatments in the target area.
Handgun applications are popular general purpose greenhouse sprayers. However, there are few recommendations on how to use them to treat plant benches. Previous experience demonstrates that handgun applications made from one side can also result in significant differences in deposits between the side of the plant facing the spray stream and the opposite side. The objectives of this research were to determine how handgun spraying and broadcast applications using twin-fan sprays and air-assistance affect under-leaf spray deposits. A bench-top trial was conducted using a mature poinsettia canopy in a greenhouse. Sprayer treatments were used to apply tank mixes of pesticides and fluorescent tracer. Nylon screen targets were secured to the underside of leaves in the upper and lower part of the canopy. Trials revealed significant differences between the amount of spray found on upper and lower canopy target areas. Handgun nozzle pressure was a more significant factor in depositing material on the underside of leaves than changing application rate. A Twin Jet Boom system using dual-orifice nozzles did not treat undersides of leaves differently from the handgun applications. The Air-assist treatment with flat fan nozzles produced the highest mean deposits on the underside of leaves in the lower canopy area but overall there were no statistical differences in lower canopy deposits between treatments. These results demonstrate the difficulty ornamental producers have targeting pesticide placement in the canopy like the undersides of leaves lower in the canopy. The variability in spray deposits observed on foliage demonstrates the potential for significant variability in pest management.