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

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.