Within-crown distribution, attack, and germination of Curculio occidentis-damaged and Cydia latiferreana-damaged Garry oak acorns in Victoria, British Columbia, Canada

摘要

Garry oak, Quercus garryana Douglas ex Hooker (Fagaceae), is part of a unique ecosystem in British Columbia, Canada, which is rich in rare and endangered plant species. Garry oak recruitment is critical to the existence of this ecosystem, therefore, the effect of Curculio occidentis (Casey) (filbert weevil; Coleoptera: Curculionidae) and Cydia latiferreana (Walsingham) (filbertworm; Lepidoptera: Tortricidae) on acorn germination is of great interest. Together these two insects infested 80.7%, 75.1%, and 51.3% of acorns collected in 1996, 1997 (low crop years), and 1998 (high crop year), respectively. Filbertworm infestation did not vary with crown level. Filbert weevil infestation did not vary with crown level during poor crop years, but significantly more filbert weevil-infested acorns were found in the lower than the middle and upper portions of the trees during the high crop year. Severely damaged acorns did not germinate, and acorns with light to moderate feeding damage had lower germination success than undamaged acorns, but growth of germinated seedlings in the light to moderate damage category was unaffected. This study showed, for the first time, that these two insect species infested a large proportion of Garry oak acorns on the tree in British Columbia, and that light to moderate damage of the acorn has relatively low impact on seedling growth.