Grape berry moth
Adults. The adult moths begin to emerge from overwintering pupae in mid- to late May before the blossom period of the widely planted Concord variety. Emergence of the overwintering generation peaks in mid-June and continues until mid-July. First generation adults begin to fly in late July, they peak in early August, and continue to emerge until early September.
The adult grape berry moth is small and has an inconspicuous brownish appearance. When resting it is about 6 mm long. Its wingspread is 9 to 12 mm. The forewings are gray blue at the base and become cream-colored with brown patches towards the tips. The smaller smoky-brown hindwings are hidden underneath the forewings when the moth is at rest. The body color is brown. During most of the day moths rest on the vines. Around mid- or late afternoon they become active and their rapid, zig- zag flight can be observed until after dusk.
Eggs. In early spring eggs are laid singly on buds, stems, or on newly-formed berries. Later, most eggs are deposited directly on the grape berries. Depending on temperature, eggs hatch after 4 to 8 days. The opaque white eggs are oval, scale- like, and measure only 0.7 mm across.
Larvae. The newly hatched larva is creamy white with a dark brown head and thoracic shield. As the larva grows, its body becomes greenish and eventually turns purple. The head of the mature larva is light brown but the thoracic shield remains dark colored. The mature larva measures 10 mm in length.
The first larvae in the spring feed on tender stems, blossom buds, and the newly set berries. Often they feed inside large protective webbings which can involve the entire cluster. When berries have reached about 3 mm in diameter, larvae begin to burrow into them. Second generation larvae feed only on the berries. They usually enter where berries touch each other or where the berry is joined to the stem. Once insidethe fruit, larvae feed just below the skin but eventually the inside of the berry is attacked. Often larvae feed successively on 2 to 3 berries. Up to seven berries can be destroyed by a single larva. Mature first generation larvae move to a leaf where they cut out a circular flap to construct a pupation chamber. Also, some larvae pupate in the fruit cluster where they have fed. Most fully developed second generation larvae spin down to the ground where they construct overwintering pupal cells in fallen leaves.
Pupae. The grape berry moth overwinters in the pupal stage. The pupa is 5 mm long and is either light-brown with a green shade on the abdomen or entirely dark green.
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