Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2006
Publication Date: March 1, 2006
Citation: Derksen, R.C., Krause, C.R., Fox, R.D., Brazee, R.D., Zondag, R. 2006. The Effect of Application Variables on Spray Retention, Coverage, and Ground Losses in Nursery Tree Applications. Journal of Environmental Horticulture. 24(1):45-52. Interpretive Summary: In 2003, U.S. nursery production was valued at $9.1 billion. The diversity of nursery production techniques creates special pest management problems for managers as well as their proximity to urban areas. Keeping in mind the nursery industry's needs to improve the efficiency of application techniques and to minimize its impact on the environment, a series of experiments were designed to evaluate the effect of several different application parameters on the fate of nursery tree sprays. A cross-flow (CF) fan, tower sprayer and a conventional, axial fan type of sprayer (DW) were used to treat multiple rows of four year old, multi-stem, red maple trees, and Turkish Filbert trees. Besides sprayer type, application rate, travel speed, air-assist fan speed, and fan orientation were evaluated. Food coloring applied by each application type was used to estimate deposits on leaves and ground targets. The test results showed that the conventional DW sprayer produced the highest deposits in the tree row closest to the sprayer. However, there was less variation in spray deposits across canopies for the standard CF treatment. The CF sprayer also produced deposits that covered more of the leaf area than compared to the DW treatment. Slowing the CF fan speed increased deposits in the row closest to the sprayer and reduced spray losses to the ground. Reducing the application volume or carrier rate for the CF sprayer did not significantly change spray retention in the tree row adjacent to the sprayer. Nursery managers can use these results to adjust the operation of their sprayers so that they can keep more spray on target which will reduce the total amount of pesticide needed to provide biological control and will reduce time spent making applications.
Technical Abstract: With increasing pressure to reduce operating costs and minimize the impact of their production practices on off-target areas, nursery crop producers must adapt pest management strategies to increase the efficiency and efficacy of applications. These experiments were designed to evaluate how to keep more spray material on target and reduce losses to the ground. An experimental cross-flow (CF) fan sprayer and a conventional, axial-fan, orchard sprayer (DW) were used to treat multiple rows consisting of four year old, multi-stem, red maple trees, Acer rubrum L. and Turkish Filbert trees, Corylus colurna L. Food coloring was used to estimate canopy and ground deposits and water sensitive paper was used to evaluate spray coverage. Variations in deposits and coverage across the canopies were generally smaller for the CF sprayer than the DW sprayer. The conventional, axial-fan sprayer (DW) produced the highest overall deposits in the first row adjacent to the sprayer. Reducing the DW sprayer ground speed while maintaining the application rate did not significantly change any of the measures of performance. The CF sprayer treatments produced higher coverage ratings in the second and third rows downwind from the sprayer compared to the DW treatments. These deposit and coverage results indicate that the conventional, axial-fan treatment is limited to making applications on each side of every treatment row if uniform spray deposits are required. The CF sprayer may not need to be operated down every row depending on the overall deposits and coverage needed to provide the desired biological impact. The performance of the reduced application rate CF sprayer also indicates that this sprayer design may provide equivalent or superior biological control compared to the conventional orchard sprayer while reducing the time and carrier requirements necessary to make the application.