Influence of Spray Application Technique on Spray Deposition in Greenhouse Ivy Pot Plants Grown on Hanging Shelves

As a result of the decreasing availability of authorized plant protection products, adequate pest control becomes more difficult in many ornamental crops and almost no information is available about the optimization of spray application techniques in ornamental crops. Yet, spray boom systems-instead of the still predominantly used spray guns-might improve crop protection management in greenhouses considerably. Application rate, nozzle type, and configuration will influence the spray deposition and, as such, its efficiency. In this study, spray deposition in ivy pot plants [Hedera algeriensis cv. Montgomery, Hibb.], grown on hanging shelves in greenhouses, was compared with a traditional spray gun with a disc-core nozzle and a manually pulled trolley equipped with two vertical spray booms. The sprayings with the spray gun were performed at an application rate of 8500 L.ha(-1). For the vertical spray boom system, two different reduced application rates (2500 and 5000 L.ha(-1)) with five different combinations of nozzle type, size, and pressure for each application rate were investigated. This research underlined that, besides the application rate, also the spray application equipment used has an important effect on the spray depositions. Nozzle type, size, and pressure on the vertical spray boom system only had a minor effect on the spray deposition. Although the spray gun performed well on the easily accessible crop zone with the runners, its performance in the more dense main crop zone was inferior. With 240% more sprayed liquid (8500 L.ha(-1)) and chemicals, the realized depositions in this crop zone were not significantly different from the ones obtained with the vertical spray boom system applying only 2500 L.ha(-1). Spraying at 5000 L.ha(-1), the vertical spray boom system achieved a 82.9% higher overall spray deposition in the main crop canopy zone compared with the spray gun at an application rate of 8500 L.ha(-1). For the sprays applied with the vertical spray boom system, doubling the application rate resulted in equally higher spray depositions, except for the inner canopy deposition for which higher application rates were more effective.