First Reports of Silver Fir Blue Staining Ophiostomatoid Fungi Associated with Pityokteines Spinidens

Pityokteines spinidens commonly occurs in Europe where it infests Silver fir and occasionally other conifers. Together with the two additional Pityokteines species (P. curvidens and P. vorontzowi) it has been reported as an important factor in Silver fir decline in some parts of Europe. Bark beetles are known to be associated with diverse guilds of arthropods and microorganisms of which phoretic mites and ophiostomatoid fungi are among the best-known associates. Some ophiostomatoid fungi associated with bark beetles display high levels of virulence to their host trees and they are thus suspected to aid their bark beetle vectors in overcoming the defense mechanisms of living hosts. Increased local populations of P. curvidens, P. spinidens and P. vorontzowi have been recently noted in conifer forests in various parts of Croatia, resulting in high damage levels on Silver fir. This increase in the importance of Pityokteines species as forest pests of Silver fir in Croatia, prompted research on the biology of these bark beetles species and on their mite and fungal associates. Preliminary reports of ophiostomatoid fungi associated with P. spinidens resulted from the inspections of bark beetle galleries in trees at the site Litori} (Gorski Kotar, Croatia) where severe case of Silver fir decline took place. Six ophiostomatoid fungi were isolated from the galleries of P. spinidens. These included Ceratocystiopsis minuta, Ceratocystiopsis cf. alba, Graphium cf. fimbriisporum, Ophiostoma cf. cucullatum, Ophiostoma piceae sensu lato and a Pesotum species. Ophiostoma cf. cucullatum was the most common species based on the occurrence of fungal structures in the insect galleries