Efficacy evaluation of pneumatic solid set canopy delivery system to control powdery mildew (Erysiphe necator) in Washington vineyards

BACKGROUND: In this study, a previously optimized pneumatic spray delivery (PSD)-based solid set canopy delivery system (SSCDS) was compared with an airblast sprayer (grower control [GC]) for the delivery of fungicides in the management of pow- dery mildew (Erysiphe necator) in vineyards. For 2023 and 2024 growing seasons, spray coverage was quantified for each appli- cation date and treatment. Visual disease severity on clusters and leaves was assessed five times per season. The accumulated area under the disease progression curve (AUDPC) was developed from these ratings. RESULTS: Over two seasons, spray coverage for PSD-SSCDS treatment ranged from 16.7% to 32.7%, whereas GC achieved cov- erage between 39.9% and 62.9%. The average difference in maximum cluster and foliar disease severity between GC and PSD- SSCDS was 5.5% and 14.2%, respectively. CONCLUSIONS: Despite lower spray coverage in PSD-SSCDS, the accumulated AUDPC for cluster disease severity was similar to GC treatments in both growing seasons. However, foliar disease severity differed significantly, with GC showing less disease than PSD-SSCDS. These study findings indicate that optimal emitter selection is crucial for achieving enhanced spray perfor- mance and effective disease control using the PSD-SSCDS technology in vineyards. Both fungicide spray treatments effectively protected clusters from powdery mildew, indicating PSD-SSCDS as an emergent alternative spray technology.