Use of several host plants with different seed maturation times by the chestnut weevil, Curculio sikkimensis (Coleoptera: Curculionidae), in mixed oak and chestnut coppice stands

Abstract

Curculio sikkimensis (Heller) (Coleoptera: Curculionidae) is a serious pest of the Japanese chestnut, Castanea crenata, because the larvae feed inside seeds. Chestnut seeds are usually harvested before the larvae leave them, meaning it is unlikely that the weevil is based in orchards. Instead, adults from neighboring woodlands likely invade orchards to oviposit. In this study, I examined host plant use and the course of development of Cu. sikkimensis in mixed oak and chestnut coppice stands to improve our understanding of weevil infestations in chestnut orchards. Females oviposited into seeds of three Quercus species and Ca. crenata, whose seed maturation times differed, over several months. The phenology of the weevil’s oviposition most closely tracked that of Quercus serrata seed maturation. Mature larvae left the seeds and burrowed into the soil, where they overwintered—in some cases for up to three winters because of prolonged diapause. Adults emerged over the course of 1 month and survived for about 2 months; such traits seem to enable this weevil to reproduce for several months. Thus, Cu. sikkimensis uses several host plants in coppice stands, and its oviposition phenology suggests that it is more dependent on Q. serrata than on Ca. crenata.