Behavioral ecology of the grape berry moth, Endopiza viteana Clemens, in Michigan agroecosystems

Vitis spp. are the native hosts of the grape berry moth, Endopiza viteana Clemens (Lepidoptera: Tortricidae), a primary pest of cultivated grapes throughout Eastern North America. Distribution within and between habitats in the grape agroecosystem was determined with pheromone traps placed at different heights in woods and vineyards. Moth relative abundance increased dramatically with height in woods, whereas 90.0% of moths caught in vineyards were at the canopy level. Relatively few moths (<4%) were trapped in the interface between these habitats, where grapevines are not present. Overall, results indicate that earlier suggestions of greater numbers of adult moths in vineyards at the end of the season were based on insufficient understanding of the vertical distribution of E. viteana. The distribution of this specialist insect seems to be associated with the distribution of its wild and cultivated host throughout the agroecosystem. The level of larval infestation of grape clusters and the abundance of adult male grape berry moth were compared in commercial vineyards bordered by four types of uncultivated habitat: deciduous woods, coniferous woods, a single row of trees, and grasses. Wild grapevines were surveyed at each uncultivated habitat site for their presence or absence, fruiting, and abundance. Infestation was greatest in vineyard borders near deciduous woods, and lowest near grasses. Moth abundance inside vineyards was similar irrespective of bordering habitat, but fewer moths were captured in grass borders than in borders with trees. Wild grapevines were likely to be present in any habitat, but their fruiting was most common in deciduous woods. Larval infestation in vineyards and abundance of wild grapevines and wild clusters in neighboring habitats were correlated, indicating that the presence of wild grapevines adjacent to vineyards poses a risk of increased damage by grape berry moth in vineyards. To determine whether E. viteana are moving from these wild hosts into vineyards, a mark-release-recapture study was undertaken. A total of 3,505 marked moths was released at the center of a vineyard and 850 were released inside a neighboring woodlot. From the vineyard releases, 222 moths were recaptured in the vineyard using pheromone traps and passive interception traps. Of the moths released in the woods, 24 were recaptured, 18 of them in the vineyard, indicating that inter-habitat movement occurs in this species. This is the first such study to demonstrate active flight of female and male grape berry moth, and the data suggest greater flight capacity by males. To assess the potential for passive dispersal of pupae, leaves of vines at the vineyard border and interior were painted after harvest and sampled in the succeeding spring. Recovery of leaves in adjacent woods indicated that they dispersed during the winter season. This wind-driven movement may well be the means of transportation for the overwintenng population of E. viteana in this agroecosystem.