Paper Wasps (Hymenoptera: Vespidae)
Grape berries that become overripe and split open commonly are attacked by yellowjackets, hornets and paper wasps. These insects feed on the pulp and juice that become available when conditions leading to berry splitting are prevalent. Because these wasps are often present in clusters at harvest time, they are a nuisance to pickers. Economic damage to the crop by these stinging insects is rare.
Current pesticide recommendations may be found Here