Fall Migration, Hibernation Site Selection, and Associated Winter Mortality of Plum Curculio (Coleoptera: Curculionidae) in a Quebec Apple Orchard

Abstract

In fall, >5,000 labeled (65Zn) adult plum curculio (PC), Conotrachelus nenuphar (Herbst), were released in two orchards, two woodlots, and 16 microplots in a plowed field. From orchards, most PC migrated toward high tree silhouettes at the edge of woodlots unless they occurred to the north. Most PC (83%) released within woodlots, with no directional differences in tree silhouette, migrated south. Migration was influenced by woodlot type and direction. Where woodlots had a thin litter layer, PC remained at the edge or returned to the orchard. In a field choice experiment, hibernating PC were recovered in thick litter (86%) and orchard turf (14%) plots, whereas none were found in gravel and thin litter layer plots. In field conditions, most PC hibernated within the litter layer; very few (<1%) penetrated the soil. Survival was related to preferred microhabitat type. Speed of dispersion was highest just after release in early September (3 m per insect per day) and close to zero by mid-October. Females dispersed further than males. A pathogenic fungus and bacterium were isolated from diseased PC. Nontarget organisms contaminated with 65Zn included spiders, slugs, earthworms, and birds. Implications for control and future research are discussed.