The adult plum curculio is a snout beetle with a curved snout, pits on its back and is black or gray in color with white patches. Adults usually measure 1/5 inches in length, and four humps run along the back of the beetle's wings. The larvae of this pest are white grubs that reach lengths of 1/3 inches at maturity. Adult beetles lay their eggs inside the blueberries and the larvae emerges from the fruit through exit holes.
Adult beetles injure the blueberries when they lay their eggs, making a crescent-shaped slit in the fruit. The female beetle cuts a slit in the fruit with her mouthparts, laying the eggs in the flap of fruit skin. Cutting the slit in the fruit ensures the eggs will not be crushed and destroyed. Once the larvae hatches, it bores into the fruit and ingests the contents.
Avoid planting blueberry bushes near fruit trees such as apples, peaches and pears. Plum curculio is more prevalent in blueberry bushes planted in close proximity to fruit trees.
There are insecticides labeled for the control of plum curculio in blueberry bushes. According to Ohio State University, applying insecticides at blossom drop and re-applying in 10 days can eliminate the pest. Contact your local extension office for advice on insecticidal control of plum curculio in blueberry bushes.