Pheromone mating disruption of the North American grape berry moth, Paralobesia viteana, was evaluated in 2 acre vineyard plots treated by hand with GBM-SPLAT, a wax-based formulation containing 3% (v/v) sex pheromone. Droplets of 1 ml volume placed on every vineyard post provided greater than 90% disruption, compared to untreated plots, for over 10 weeks in each of two growing seasons. Evaluations of cluster infestation by P. viteana showed reduced infestation in treated plots compared to untreated plots in both years, but the reduction was not statistically significant. Additional comparisons of disruption efficiency in plots treated with varying densities and sizes of wax droplets suggest that high densities of small droplets may provide greater disruption of moth orientation than low densities of large droplets. Opportunities for future development of this technology for use in vineyards will be discussed.