The occurence of pathogens was investigated in the spruce bark beetle Ips typographus L. from three different localities in the Central Plateau of Switzerland within a five-year period. In all three localities Norway spruce (Picea abies) was attacked by I. typographus; at two localities (Forrenmoos and Tössstock) infested trees were not removed, at the third locality (Rothenburger Wald) infested trees were removed as a sanitation measure.
3073 adult I. typographus were inspected within several consecutive generations (upt to ten). Two pathogen species were identified in the beetles, i.e. the protozoan species Gregarina typographi and Chytridiopsis typographi. Beside these two pathogens fungal infections were found frequently. Nematodes occured in the gut and in the hemolymph of many beetles.
No differences were found in the spectrum of the pathogen species in beetles from the three localities. The rate of G. typographi and C. typographi infections increased within the first three generations in most cases, thereafter the number of infected beetles decreases. Infeaction rates varied between the beetles from different localities as well as between different years.