Damage by the pine weevil Hylobius abietis to seedlings of two native and five introduced tree species in Sweden

Abstract

There is increasing interest in using introduced species in Swedish forestry in response to climate change, but it is important to assess their resistance to native pests. Thus, we compared the extent of pine weevil feeding on two dominant native conifers, Scots pine ( L.) and Norway spruce ( (L.) Karst.), the non-host deciduous broadleaf hybrid aspen ( × Hämet-Ahti) and four introduced conifers: Douglas fir ( (Mirb.) Franco), hybrid larch ( × Coaz), Sitka spruce ( (Bong.) Carriére) and lodgepole pine ( Douglas ex Loudon). The extent of feeding damage on seedlings and its effect on their vitality were examined in a field study in south-central Sweden and a laboratory experiment, which gave largely consistent results. Generally, the species most heavily attacked by the pine weevil, in both experiments, were Douglas fir and Sitka spruce. In the field experiment pine weevils killed or severely damaged significantly higher proportions of Douglas fir and Sitka spruce seedlings (60%) than any other species except Norway spruce (49%). Among conifer seedlings the proportions of killed or severely damaged seedlings were lowest for Scots pine and hybrid larch (27%) and Lodgepole pine (36%). The results indicate that most conifer species planted on young clear-cuttings in Sweden need some kind of pine weevil protection, and the possibility that introducing new tree species might increase damage caused by pests must be considered. For instance, widespread use of hybrid aspen could reduce damage by pine weevils, but increase damage by other, untested pests or pathogens.Pinus sylvestrisPicea abiesPopuluswettsteiniiPseudotsuga menziesiiLarixmarschlinsiiPicea sitchensisPinus contorta