Location: Application Technology Research Unit
Title: Field evaluations of application techniques for fungicide spray deposition on wheat and artificial targets Authors
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 2, 2012
Publication Date: June 1, 2012
Repository URL: http://handle.nal.usda.gov/10113/56363
Citation: Derksen, R.C., Paul, P., Ozkan, H.E., Zhu, H. 2012. Field evaluations of application techniques for fungicide spray deposition on wheat and artificial targets. Applied Engineering in Agriculture. 28(3): 325-331. Interpretive Summary: New variants of wheat pathogens are emerging in various countries for which there is no known resistance. The current movement of these pathogens suggests that their incursion into the US is imminent. The window of opportunity to protect the wheat crop is short once the diseases become a threat. The objective of this research was to determine the influence of spray quality, spray volume, and air-assisted delivery on wheat canopy penetration and deposition which could aid in selection of efficacious means for delivering fungicides to different parts of wheat canopy for effective management of diseases that may predominantly reside in hard-to-reach parts of the canopy. Evaluation of tracer residue on head, stem, and leaf tissue was used to characterize treatment effectiveness to provide a true representation of where spray was deposited on different portions of a mature wheat canopy (Stage 10.5). In general, the overall differences in the performance parameters measured were small between the two spray application rates tested (140 vs. 94 L/ha). The highest possible air outlet speed available on the Jacto sprayer (34 m/s) produced few advantages over lower outlet air speeds. Penetration to the middle of the canopy was generally not a problem for the treatments using no air-assisted delivery or the lower air outlet speed setting (18 m/s). The high air outlet speed setting did produce lower deposits on the Head and Stem sections. Angling the air/spray stream 30º forward produced higher deposits and coverage on the Head targets but the results were not significantly different from the air/spray stream with the vertical orientation. Greater spray angles may be needed to significantly improve application performance but may reduce penetration into the canopy. A Medium spray quality nozzle treatment tended to produce smaller droplet density across all targets and lower spray coverage which could reduce disease control effectiveness. These results demonstrate to growers how to better protect the safety and abundance of the wheat crop by selecting spray parameters that best target those areas of the canopy at most risk of infection.
Technical Abstract: 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. When the threat of infection is discovered, there is little time available to make multiple treatments over the vast areas of wheat production. The objective of this work was to identify effective application parameters to apply fungicides for protecting against wheat head scab and stem rust infection of a mature wheat canopy (Stage 10.5). 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 are required to optimize spray deposition depending on the specific section of the wheat plant that requires protection.