Double-spined bark beetle (Ips duplicatus) (Coleoptera: Curculionidae): a new host - Douglas fir (Pseudotsuga menziesii)

Spruces (Picea spp.) are considered to be the primary host trees of the double-spined bark beetle Ips duplicatus (Sahlberg, 1836), but occurrences on pines (Pinus spp.) are often reported. This paper documents the first recorded successful development of I. duplicatus on Douglas fir (Pseudotsuga menziesii) (Mirbel) Franco. Two densely infested Douglas fir trees were found in a forest dominated by Norway spruce (Picea abies) (L.) H. Karst., close to the village of ValĹĄovice (Czech Republic). Ips duplicatus is an oligophagous species that attacks different coniferous tree species but was not previously reported to develop on Douglas fir. The infestation of Douglas fir recorded in the present study was most likely promoted by a large population of I. duplicatus in the studied region combined with a local lack of primary host trees as a consequence of bark beetle outbreak.