Two blue-stain fungi colonizing Scots pine (Pinus sylvestris) trees infested by bark beetles in Slovakia, Central Europe

Abstract

Excessive mortality of Scots pine (Pinus sylvestris) trees has recently been observed in the Zahorska nižina lowland in western Slovakia, Central Europe. Continuous drought, bark beetles and blue-stain fungi are likely to play a crucial role in this dieback of pines in a warm sandy area. Two blue-stain fungi, Ophiostoma ips and Ophiostoma minus, were found here on Scots pine trunks infested by bark beetles. These fungi were isolated and identified based on morphological properties and DNA sequences (ITS, LSU, β-tubulin). They colonized the inner bark, phloem and blue-stained sapwood, and were recorded in the galleries of Orthotomicus longicollis and other species of this genus. The occurrence of O. minus was massive; the fungus was found to produce perithecia abundantly in dying pines. Detailed descriptions, illustrations and global distribution of the two fungal species on host pine species are provided. The records of O. ips and those of O. minus are new for the mycoflora of Slovakia. Undetermined mycophagous nematodes were found inside the perithecia of O. ips. The role of bark beetles as real and potential vectors (Ips spp., Orthotomicus spp., Tomicus spp., Hylurgus ligniperda, Hylastes sp.) of blue-stain fungi in a declining pine forest is discussed.