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Evaluating New Nozzles and an Air Assist Sprayer for Improving Spray Coverage and Powdery Mildew Control on Underleaf Surfaces 2001

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Project Leader(s): Margaret Tuttle McGrath, Plant Pathologist, Dept. of Plant Pathology, Riverhead

Andrew Landers, Pesticide Application Technology Specialist, Dept. Agricultural & Biological Engineering, Ithaca

Cooperator(s): Dale D. Moyer, Vegetable/Potato Specialist, CCE Suffolk County

Type of grant: Pheromones; biorationals; microbials; conventional pesticides

Project location(s): 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. Thus systemic fungicides are currently essential for controlling 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. Organic growers would also benefit from identification of a means to improve spray deposition as there are no systemic fungicides approved for organic production. The contact fungicide Bravo was applied using an air assist sprayer and using two novel nozzles (twin jet and air induction) and three traditional nozzles (flat fan, hollow cone, and cone jet) on a conventional boom. Parallel experiments were conducted on muskmelon and on pumpkin because these cucurbit crops have different canopies.

Neither the air assist boom nor the novel nozzles improved control achieved with Bravo applied with conventional nozzles on a hydraulic boom. Control was improved on the lower leaf surface only when systemic fungicides were also used. This study has demonstrated that it is challenging to improve spray coverage on the lower surface of muskmelon and pumpkin leaves by changing spray equipment. This may be due to their large size. However, results from one year of research cannot be considered conclusive. Considering the potential great benefit of improved spray coverage on cucurbit crops, additional research on novel nozzles and air assist application technologies is warranted. Perhaps these nozzles will be more effective used at different pressure or gallonage. If coverage can be improved sufficiently, growers will be able to reduce the quantity of pesticides used because they will not need to apply systemic fungicides as much as they now need to. Implementing the necessary changes to achieve better spray coverage will not be very costly if the novel nozzle types for a conventional boom can provide better coverage than traditional nozzle types. On the other hand, perhaps it will only be possible to achieve better coverage with novel spray application technologies on crops with smaller leaves, such as tomato.