Pathogens in Tomicus

The aim of the project is to investigate the pathogen complexes of T piniperda and T minor in Europe, with special focus on the identification and taxonomic classification of new pathogen species. Additional objectives are a study of the variability in these pathogen complexes across Europe and exploration of the relationship between this variability and changes in both the eco-geographical distribution of the bark beetle`s populations and in the pest status of these bark beetle species. Research on differences in the pathogen species spectrum has to take account of the local biology, bionomy and ecology of the bark beetles. Accordingly, T piniperda and T minor should be collected from locations in Scandinavia, central Europe and southern Europe. Trap trees must be used because no pheromone catch system is known for these two species. These pathogen complexes can only be effectively investigated through considerable investment in the preparation and display of specimens for analysis using fight and electron microscopes.

Tomicus species were collected in the two years period (1999 through 2000) at 33 locations in Europe and in the USA. Tomicus piniperda was collected at 26 locations in: Austria, Finland, Poland, Czech Republic, Hungary and USA, Tomicus minor at 12 locations in: Austria and Czech Republic and Tomicus destruens at 6 locations in: Greece and Italy. During this study new details were found on the morphology and molecular biology of Tomicus species. Precise determination of the three Tomicus species was performed by use of scanning electron microscope. Differences in hair types and in numbers of hairs were found on the antennal club and on the elytra which allowed to separate the three Tomicus species. Molecular studies of beetles brought also evidence of differences between the three Tomicus species; the mitochondrial COI revealed high sequence divergence between the three species. T. piniperda, T. minor and T. destruens proved to be monophyletic species with about 16.98-19.23% of sequence divergence. 10.344 adult beetles (6.778 T. piniperda, 2.587 T. minor, 979 T. destruens) were dissected through the two years study. During the study the description of a new microsporidian species was possible. Canningia tomici sp.n., the new microsporidium was found infecting the cells of the mid-gut, the gut muscularis, Malpighian tubules, connective tissues and gonads of adult Tomicus piniperda. Spores were uninucleated and oval. There occurred two different spore sizes: 2.8m ( 0.4m) x 1.4m ( 0.4m) and 3.8m ( 0.3m) x 2.0m ( 0.2m). The spore coat was built by an exospore and an endospore. The polar filament (four to five or five to six coils) was fixed subapically in a flat anchoring disc. The thick posterior lamellae of the binary polaroplast were asymmetric due to the lateral fixation of the polar filament. The infection was found in seven T. piniperda populations from Europe (Finland, Poland, Czech Republic, Austria) and two populations from USA. Infection rates varied in beetles from Europe from 0.4% to 12.4% and in beetles from USA: 28.0 and 33.9%. In one case the microsporidium was found in T. piniperda larvae too (one location in Finland: 1.6%; n = 189). Infection rates varied between male and female beetles, but without significant differences. Beetles of the parental generation were less infected in comparison with offspring beetles. Infected beetles never showed any externally visible symptoms. Furthermore, Gregarina sp. was found in T. minor from one location in Austria in the mid-gut lumen (0.3%). No protozoan infections were found in T. destruens. Fungal infections were found in all three Tomicus species. First preliminary experiments on artificial infection of adult T. minor were performed with Canningia tomici spore suspension, which turned out to cause successful infection.