The host range of the Eucalyptus Weevil, Gonipterus "scutellatus" Gyllenhal (Coleoptera: Curculionidae), in South Africa

Introduction The Eucalyptus Weevil (Gonipterus "scutellatus" Gyllenhal) is a notorious pest of eucalypt plantations around the world, but its host range differs across its area of introduction, which may be due to it being a complex of several cryptic species. Objectives The performance of the weevil was tested on 14 Eucalyptus and one Syzygium species in the laboratory and the field in South Africa. Results The Weevil exhibited different levels of polyphagy, depending on how the host plants were presented: as bouquets or sleeved branches, in choice or no-choice combinations or in the open field. The fundamental host range in the laboratory was found to be broader than the realized host range in the field. Eucalyptus smithii was found to be the preferred host while Eucalyptus saligna and the native Syzygium myrtifolia were immune to both feeding and oviposition. Adult feeding and oviposition were more selective in the field, and the larvae were found to be less discriminating than the adults. Conclusions The weevil is shown to have a narrow host range within two sections of the subgenus Symphyomyrtus, a finding that could contribute to resolution of the taxonomy of the genus Eucalyptus. Further, it suggests that countries that already have the pest may be susceptible to introductions of additional Gonipterus species.