Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/10/2007
Publication Date: 2/1/2008
Citation: Zhu, H., Zondag, R.H., Derksen, R.C., Reding, M.E., Krause, C.R. 2008. Influence of Spray Volume on Spray Deposition and Coverage Within Nursery Trees. Journal of Environmental Horticulture. 26(1):51-57.
Interpretive Summary: The conventional air blast sprayer is one of the most commonly used sprayers to apply pesticides in ornamental nursery crops. Many nursery growers have used one sprayer to cover a wide variety of crop shapes and sizes, and they have been misled that better spray coverage can be obtained with the spray volume at the point that the target areas are saturated. Without scientific spray application guidelines, most target areas of nursery crops are over sprayed, resulting in high production cost and potential environmental contamination. In this study, the relationship between spray application rate and deposition-coverage on target areas of nursery crabapple trees from a conventional air blast sprayer was investigated. Estimation of the application rate with the traditional fruit tree row volume method for nursery trees could cause extremely excessive spray deposits on target areas. Conventional air blast sprayers have many advantages to spray short nursery trees but are not the best method to achieve uniform spray deposition and coverage of pesticides for tall nursery trees. For tall nursery trees, other spray systems such as tower sprayers should be used to discharge uniform spray deposition and coverage across the tree height inside canopies.
Technical Abstract: Information on better utilizing air blast sprayers to obtain high pesticide spray application efficiency in nursery tree production is needed. Foliar spray deposition and coverage at different heights inside crabapple tree canopies were investigated for an air blast sprayer with four different application rates ranging from 230 L/ha to 900 L/ha. The spray deposition on the ground at various distances from the sprayer was also measured at the 700 L/ha application rate. Foliar deposition and coverage on targets below 2.6 m inside tree canopies increased as the application rate increased, but the increase in the coverage was much lower than the deposition. For trees taller than 2.6 m, the sprayer could not deliver uniform spray deposition and coverage across the tree height. The part of trees below 2.1 m was well covered by the spray deposits with 230 L/ha application rate while higher application rates resulted in over spray application. Less than 30% of total spray volume was deposited on target trees while over 34% of the total spray volume was lost on the ground. The tree-row volume method should include foliage density and tree-row gaps to avoid excessive estimation of spray application rates for nursery tree crops.