Grapes: Grape Berry Moth

Problem
Grapes are webbed together and to leaves. Dark green to purple worms, up to 3/8 inch long, with dark brown heads are inside the grapes. White cocoons cling to the leaves between flaps of leaf tissue.

Analysis
(Endopiza viteana)

The grape berry moth is the most serious insect pest of grapes in the East. The worms damage both green and ripening fruit by feeding on the inner pulp and seeds. They web the grapes together and to leaves with silken threads as they feed and move from cluster to cluster of grapes. One worm can injure several berries. The worms spend the winter as pupae on leaves and on the ground. The purplish brown moths emerge in late spring and lay eggs on blossom stems and small fruit. The larvae that hatch from these eggs feed on the buds, blossoms, and fruit. After 3 to 4 weeks of feeding, they cut a small bit of leaf, fold it over, and make a cocoon inside, where they pupate. Within a few weeks, adult moths emerge to repeat the cycle, this time laying eggs on ripening fruit. This second generation feeds for 3 to 4 weeks, then pupates for the winter.

Solution
Destroy infested grapes. Discontinue cultivation in late summer so that the cocoons remain on top of the ground to be cleaned up with all fallen grape leaves at the end of the season. This will reduce the number of overwintering pupae. Next year, treat the plants immediately after bloom with an insecticide containing malathion, diazinon, or carbaryl. Repeat the application 7 to 10 days later. To control the second generation, spray again in midsummer.