Growers need to examine flower or berry clusters for webbing before and after bloom. A protective insecticide may be needed to prevent damage in heavily invested areas. When the berries reach 3 mm in diameter, larvae begin to burrow into them. Often larvae feed successively on 2 to 3 berries. Mature first generation larvae move to a leaf where they cut out a circular flap to construct a pupation chamber.
Some larvae pupate in the fruit cluster where they have fed.
It is not unusual in Michigan to have both first and second generation larvae in the vineyard. Second generation larvae tunnel directly into the fruit and feed internally. Second generation larvae usually enter where the berries touch each other or where the berry joins the stem. The larvae feed just below the skin, but eventually the inside of the berry is attacked. Larvae feed on berries in succession and up to 7 berries may be destroyed.