1. Blueberry Maggot, Rhagoletis mendax (Curran)
Photos: Jerry A. Payne, USDA Ag Res. Service, Bugwood.org
Adults of the blueberry maggot are similar in size to houseflies but have white spots on their wings. They appear and begin laying eggs in the fruit just as the berries begin to turn blue.
2. Fruitworms, Grapholita packardi and Acrobasis vaccinii
The cherry fruitworm is a small pink worm with a brown head that bores a small hole in the side of the berry, usually where it touches other berries. The cranberry fruitworm (photos above) is yellow-green with a yellow head and causes damage similar to the cherry fruitworm.
3. Plum Curculio, Conotrachelus nenuphar
The plum curculio is a 1/4-inch-long, gray snout beetle that can be seen crawling about the clusters; its larvae are yellow-white, legless, and curved.