Diversity of ophiostomatoid fungi associated with bark beetles (Coleoptera: Scolytidae) colonizing branches of Norway spruce (Picea abies) in southern Poland

Bark beetles (Coleoptera: Scolytidae) infesting Norway spruce trees are known to be associated with fungi, especially species of Ophiostoma sensu lato and Ceratocystis. However, very little is known about these fungi in Poland. In this study, we examined the ophiostomatoid species associated with seven species of bark beetles developing in Norway spruce (Picea abies). Fungi were isolated from the beetles and their galleries at ten sites in southern Poland. We identified a total of 2,769 fungal isolates that belong to 19 ophiostomatoid species. These 19 species included a total of 16 associations between fungi and bark beetles that had not been previously recorded. The isolated fungal species were similar to those previously reported. The species spectrum and relative abundance of fungal associates were similar in seven bark beetle species, despite some differences between species. Except for Pityophthorus pityographus, all bark beetles species were frequently associated with ophiostomatoid fungi. The most commonly encountered fungal associates of bark beetles were the following: Ophiostoma ainoae, O. bicolor, O. piceae sensu lato and Grosmannia piceiperda. The results support the hypothesis that pathogenic ophiostomatoid fungi are important for aggressive bark beetles to kill trees. The most virulent fungal associate of bark beetles, Ceratocystis polonica was most commonly associated with Ips typographus. The most frequent ophiostomatoid species isolated from the beetles and galleries of P. pityographus were O. ainoae and Graphium fimbriisporum.