Occurrence of pathogens in the pine bark beetles Tomicus piniperda and Tomicus minor (Coleoptera, Scolytidae).

Specific topics for investigations: 1. Registration of pathogens in beetles from different locations in northern, central and southern Europe over a two year period (to take account of temporal variability). 2. Registration of pathogen occurrence in beetles emerging from trap tree logs in relation to the time of emergence. This analysis will show if all beetles (parental beetles and offspring) have the same infection rates, and allows the development of infection rates in early and late emerging specimens to be observed. A prolonged stay within the bark is presumed to raise the contact frequencies of beetles with the (horizontally transmitted) pathogens. A related topic is the implication of changes in the quality and quantity of feeding material - particularly the direct and indirect implications of differences in phloem quality caused by timber decay. 3. Pathogen frequency in beetles feeding on P. sylvestris in comparison with those feeding on P. nigra (which should give information about the influence of (host) tree species). 4. Selectivity of individual pathogen species, i.e. the comparative frequency of individual pathogen species in the two beetle species (in some cases both bark beetle species occur on the same tree).