Fungal associates of five bark beetle species colonizing Norway spruce

Abstract

Fungi associated with five bark beetle species colonizing Norway spruce (Piceaabies (L.) Karst.) were isolated from beetle-inoculated logs. Ipstypographus L., an aggressive tree-killing bark beetle, was associated with a different range of blue-stain fungi than the nonaggressive Pityogeneschalcographus L., Polygraphuspoligraphus L., and Hylurgopspalliatus Gyll. The flora of the nonaggressive Ipsduplicatus Sahib. was similar to that of I. typographus. The pathogenic fungus Ceratocystispolonica (Siem.) C. Moreau, and other blue-stain fungi, were isolated in high frequency from inoculations with both Ips species. Pathogenic blue-stain fungi were absent, or isolated in low frequencies, from inoculations with the other nonaggressive beetle species. With the exception of I. duplicatus, these results support the hypothesis that aggressive bark beetles carry more pathogenic blue-stain fungi than other bark beetles and indicate that pathogenic fungi are important for aggressive bark beetles to kill trees.