ARS | Publication request: Influence of application equipment on deposition of spray droplets in wheat canopy

Submitted to: Aspects of Applied Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 2011
Publication Date: January 10, 2012
Repository URL: http://handle.nal.usda.gov/10113/54119
Citation: Ozkan, H.E., Paul, P.A., Derksen, R.C., Zhu, H. 2012. Influence of application equipment on deposition of spray droplets in wheat canopy. International Advances in Pesticide Applications --Aspects of Applied Biology. 114:317-324.

Interpretive Summary: The ability to provide protection across the wheat plant is important because different infections may occur on different parts of the plant canopy depending on the pathogen. Fusarium Head Blight results from fungal infection of the wheat head in the early stages of flower development. Wheat Stem Rust is caused by airborne movement of a pathogen and primarily causes infection on stems but can also cause infection on leaves. Leaf Rust is caused by a fungus that primarily infects leaves. Therefore, the same application method or equipment may not work well to protect the plant against diseases that affect different part of wheat canopy. The objective of this work was to identify effective application parameters to apply fungicides for protecting against wheat head scab and stem rust infection. Field trials were designed to evaluate the effect of spray volume, spray quality, and air assistance on the fate of spray on sections of a wheat plant most susceptible to infection. Following application of a fluorescent tracer tank mix, plant samples were collected from each of ten plants in each replicate for each treatment. Plant sections sampled included Heads, Flag Leaf, Flag Leaf +1, and the Stem between the Head and Flag Leaf +1. There were no significant differences between treatments in the amount of spray on the stem sections. Significant differences between treatments were observed for the amount of spray found on Head and Leaf sections. Directing the spray and air stream 30° forward increased deposits of Medium spray quality droplets on the Head sections but reduced deposits on the more horizontal Flag leaves. Spray coverage measured on targets with a vertical and cylindrical shape to simulate the wheat head target also increased when the air/spray stream was directed 30° forward compared to a vertical delivery. These results demonstrate that different application parameters may be required depending on the specific section of the wheat plant that requires protection.

Technical Abstract: Fungicides manufactured to control various diseases in wheat are effective; however, successful control of diseases will mostly depend on proper application methods. The ability to provide protection across the wheat plant is important because different infections may occur on different parts of the plant canopy depending on the pathogen. The objective of this work was to identify effective application parameters to apply adequate amount of fungicides for protection against spike and foliar diseases of wheat. Field trials were conducted in 2009, 2010 and 2011 to evaluate the effect of different nozzle types and spray qualities on spray coverage at three levels within the wheat canopy: at the height of the spike, flag leaf , and 30 cm below the flag leaf. Nozzles selected for this three-year study included two single flow pattern nozzles (XR 8003 and XR11003) with Fine and Medium spray qualities, and three twin-flow pattern nozzles (TJ, TTJ, TT Duo) with spray qualities of Fine, Medium and Coarse. Water Sensitive Paper cards placed vertically at spike level (vertical), at the height of the flag leaf (horizontal top), and 30 cm below flag leaf (horizontal bottom). In all three years, the mean percent spray coverage on vertical, horizontal top, and horizontal bottom targets varied from 5-15%, 18-35%, and 8-28%, respectively, across all five treatments. The three nozzles with double spray patterns outperformed the two single-flow pattern nozzles in deposition on vertical targets representing wheat spike. However, single-flow pattern nozzles produced higher coverage on bottom horizontal targets than the twin-flow nozzles. Because the drift reduction nozzles produced coverage similar to or better than nozzles that produce more driftable nozzles, using the larger droplet size nozzles may provide similar disease control and reduce the off-target impact of the applications.