Weak performance of the Eurasian spruce bark beetle in the non-native lodgepole pine

The North American lodgepole pine is the most used non-native tree species in Sweden. The performance of the Eurasian spruce bark beetle (Ips typogaphus) and the occurrence of other insects were recorded from bark samples from 19 I. typographus-killed lodgepole pines in central Sweden. The occurrence of blue-stain fungi and the mean radial increment were recorded from cut stem sections from 10 trees. Mean colonization density (+/- SE) per m2 bark was 331 +/- 38 for males (based on entrance holes) and 329 +/- 39 for females (maternal galleries) at 2.5 m height. The mean production of new generation I. typographus adults per m2 bark was 8.6 +/- 2.6 and mean reproductive success (daughters per mother) was 0.01 +/- 0.003. The mean density per m2 bark of the bark beetle enemies Thanasimus sp. (Coleoptera) was 2.2 +/- 2.2, Medetera spp. (Diptera) 41.8 +/- 10.3 and parasitoids 30.8 +/- 10.1. Blue-stain covered most of the surfaces of the cut stems and the annual ring widths decreased steadily during the last 20 years. The study demonstrates that I. typographus can colonize weakened lodgepole pines, but the reproductive success is very low. Ips typographus does not escape its enemies in the non-native host.