Field Evaluations of Application Techniques for Fungicide Spray Deposition on Wheat and Artificial Targets

New variants of wheat pathogens are emerging in various countries for which there is no known genetic resistance. The current movement of these pathogens suggests that their incursion into the United States is imminent. 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 spray deposition 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 (sometimes referred to as the penultimate leaf or 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 but the higher volume (140 L/ha) treatments tended to produced the highest deposits across all plant parts compared to the lower volume (94 L/ha) treatments. 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 Fine spray quality droplets on the Head sections but reduced deposits on the more horizontal Flag leaves. Spray coverage measured on artificial 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. Spray coverage also was higher for treatments made at the same spray volume and air outlet speed using a Fine quality spray nozzle compared to a Medium quality spray nozzle. These results demonstrate that different application parameters may be required depending on the specific section of the wheat plant that requires protection.