This is the major insect pest of grape berries in the eastern United States and Canada. When vineyards are left unmanaged, up to 90 percent of the fruit often is destroyed by the larvae and the diseases facilitated by the damage inflicted upon the fruit.
Infestations vary greatly from vineyard to vineyard, from year to year, and within a vineyard.
However, infestations bordering wooded areas are most vulnerable. Grape berry moths overwinter in cocoons within folded leaves in debris on the vineyard floor and within adjacent woodlots. After emerging in the spring, the adults mate and females lay eggs on or near flowers or berry clusters. Newly hatched larvae feed upon the flowers and young fruit clusters. Larvae that hatch in June make up the first generation of grape berry moth and will mature from mid to late-July or August.