Bill Cissel, Extension Agent – Integrated Pest Management, University of Delaware; bcissel@udel.edu
Congratulations to Sylvie Childress for correctly identifying the ovipositioning scar and larva in the photos below as plum curculio and for being selected to be entered into the end of season raffle for $100 not once but five times. Everyone else who guessed correctly will also have their name entered into the raffle. Click on the Guess the Pest logo to participate in this week’s Guess the Pest challenge!
Guess the Pest Week #9 Answer: Plum Curculio
The plum curculio is a pest of apples, peaches, plum, and other stone fruit. The adult beetles are about ¼” in length, dark brown with patches of white, and have a protruding snout. They belong to the weevil family, commonly referred to as the snout beetles.
Adult Plum Curculio
The primary damage to fruit is caused by the ovipositioning or egg laying behavior of the female plum curculio. The females lay eggs in the developing fruit and cut a crescent shaped slit beneath each egg to prevent the rapidly growing fruit from crushing the egg. As the fruit continues to grow, the slit the female beetle cut below the egg develops into the classic, crescent shaped scar that you see in the photo above. These scars are usually only cosmetic. However, if the egg hatches, the larva will bore into the fruit, which will usually cause the fruit to drop from the tree. After a couple weeks of feeding on the fruit, the larva will exit the fruit to pupate in the soil.
In addition to the crescent shaped ovipositioning scars and fruit drop, the adult beetles will also feed on fruit, creating numerous round puncture holes in the fruit skin. It has been estimated that a single beetle will average over 100 feeding and/or puncture wounds during its lifespan.
Fun Entomology Fact: The family Curculionidae (true weevils), are the largest family of insects with the most species described worldwide.
