Plum Curculio

Conotrachelus nenuphar — the plum curculio — is one of the most economically important PEACH AND APPLE PESTS in North America and one of about 60,000 species in family Curculionidae (the snout weevils — the largest single beetle family on Earth). The species is widespread across all of eastern and central North America from southern Canada south through the eastern US to Texas. Adults are 4-6 mm long, dark brown to black with patches of lighter scales, and the species' diagnostic 'snout' weevil features: a long curved CHEWING SNOUT with mandibles at the tip (the snout is used for chewing through fruit skin during egg-laying), and the typical Curculionidae body plan with hardened elytra protecting folded flight wings. The species is the focus of major USDA Agricultural Research Service apple and stone-fruit research programs because of the dramatic economic impact on NA orchard agriculture. The species' major significance comes from the EGG-LAYING WOUND — the diagnostic 'CRESCENT-SHAPED CUT' on developing fruits. Female plum curculios make a SPECIFIC TWO-PART WOUND on each fruit they lay an egg into: (1) a CIRCULAR PUNCTURE where the egg is deposited (the female chews through fruit skin to access the developing fruit flesh, lays a single egg, then withdraws the snout); (2) a CRESCENT-SHAPED CUT just below the circular puncture (the female uses the snout to make a curved cut that ENCIRCLES THE EGG-LAYING SITE FROM BELOW). The crescent cut is thought to ISOLATE the egg-laying site and prevent the developing fruit from compressing and crushing the egg as the fruit grows. The crescent-cut signature is one of the MOST-RECOGNIZED fruit damage patterns in NA orchard agriculture and is the diagnostic field-ID feature for plum curculio damage. The species is a major economic pest of: APPLE (the most cited crop — approximately 5-15% of unprotected apples in NA orchards are damaged by plum curculio), PEACH and other STONE FRUITS (cherries, plums, nectarines, apricots), and PEAR. Damaged fruits typically drop prematurely (the developing apple or peach with a curculio larva inside falls before maturing), and surviving fruits show characteristic crescent-scarred surfaces that reduce marketability. Larvae develop inside the dropped fruit on the orchard floor over 2-3 weeks, then emerge from the fruit and pupate in the soil. Adults emerge in midsummer and feed on fruit flesh through similar puncture wounds before overwintering as adults in leaf litter for the next year. Modern integrated pest management for plum curculio includes: ground sanitation (rapid removal of dropped fruit to disrupt larval development), targeted insecticide applications timed to adult emergence, mating disruption with synthetic pheromones, and host-plant resistance breeding. Annual NA fruit losses to plum curculio total tens to hundreds of millions of dollars in damage and control costs. The species is harmless to humans (no bite, no sting) but is a major economic pest of NA orchard agriculture.