Host plant effects on captures of grape berry moth, Paralobesia viteana Clemens (Lepidoptera: Tortricidae), in pheromone traps

Grape berry moth (GBM) is a key economic pest of cultivated grapes in eastern North America. This fruit feeding tortricid can be monitored with sex pheromone baited traps, but captures of male GBM decline over the course of a season as infestation increases. This limits the utility of the traps for prediction of fruit infestation and timing control measures. In separate experiments, each performed over two seasons, we sought to determine whether the density of the grape canopy or the number of fruit clusters per vine affects the number of male moths captured in monitoring traps over the season. To test the influence of canopy density, we compared male moth capture in 6m long tunnels constructed within the grape canopy to moth capture in a normal, dense canopy. Similar captures between treatments suggests canopy density does not affect moth capture. To determine whether the number of clusters per vine affects male capture, we removed either 100, 50 or 0% of the clusters in 6m x 6m vineyard plots, and compared the number of moths captured among treatments. Fewer moths were caught in plots where clusters were removed compared to plots where clusters were not removed. These results are counter to our prediction that having a denser canopy or more, ripe clusters would negatively affect male moth captures. We discuss other potential explanations for the declining captures of P. viteana through the growing season.