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Evaluating New Nozzles and an Air Assist Sprayer for Improving Spray Coverage and Powdery Mildew Control on Underleaf Surfaces 2000

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Principal Investigators: Margaret Tuttle McGrath, Dept. of Plant Pathology, Riverhead, Andrew Landers, Dept. Agricultural & Biological Engineering, Ithaca

Cooperators: Dale D. Moyer, Vegetable/Potato Specialist, CCE Suffolk County

Abstract: The goals of this project were to identify equipment that maximizes spray coverage on the underside of leaves of cucurbits and to determine if powdery mildew can be controlled effectively with nonsystemic fungicides when coverage is maximized. Conventional nozzles and sprayers deliver little spray material to the underside of leaves. Therefore, growers presently rely on systemic fungicides to control powdery mildew in cucurbits. Fungicide resistance is a major concern because systemic fungicides are at-risk for resistance development due to their single-site mode of action and because the powdery mildew fungus has demonstrated high potential for developing resistance. For this project, unfortunately, it was only possible to examine spray coverage because of technical problems with the sprayer. Greater coverage on both leaf surfaces was achieved with the air induction and twin jet nozzles, two novel types for a conventional hydraulic spray boom, than with the traditional flat fan, hollow cone, and cone jet nozzles. Better coverage was obtained on upper leaf surfaces with these novel nozzles than with the air assist boom; similar coverage was obtained on the underside of leaves. The differences between the novel and traditional nozzle types were not great, however, this was a limited study because it could not be started until late in the growing season. Additional research is needed to further these preliminary results and to obtain a true measure of spray coverage by examining disease control.