Performance of the tree-killing bark beetles Ips typographus and Pityogenes chalcographus in non-indigenous lodgepole pine and their historical host Norway spruce

Abstract

The North American lodgepole pine Pinus contorta has been planted on 660 000 ha in Sweden. We compared the performance of Ips typographus and Pityogenes chalcographus in storm-felled and standing pheromone-baited trees of the historical host species Norway spruce (Picea abies) and lodgepole pine. In the first summer after a storm, I. typographus colonized 0.2% and P. chalcographus colonized 2.4% of the storm-felled lodgepole pines compared with 31% and 25%, respectively, of the storm-felled Norway spruces. In the second summer 1.6% and 41.5% of the lodgepole pines were colonized by I. typographus and P. chalcographus, respectively. The reproductive success of I. typographus was five-fold higher in Norway spruce than in lodgepole pine. Other species colonizing lodgepole pine were Ips duplicatus, Orthotomicus proximus, Orthotomicus laricis, Monochamus sutor and Pissodes pini. The male attack densities of both bark beetle species required to overcome defences of standing pheromone-baited trees were much higher in lodgepole pine than in Norway spruce. The reproductive success of I. typographus and P. chalcographus was approximately five- and 14-fold higher, respectively, in Norway spruce than in lodgepole pine. Larvae of the most important groups of bark beetle enemies were present in both storm-felled and standing pheromone-baited lodgepole pines colonized by I. typographus and P. chalcographus. In the standing trees, the densities of enemy larvae were lower in lodgepole pine than in Norway spruce, whereas the opposite was true for storm-felled trees.