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Notes:
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In the last two decades, stand decline and increased mortality has affected silver fir (Abies alba) forests in
the Spanish Pyrenees. Simultaneously severe occurrences of the root rot fungus Heterobasidion
annosum s.l. and of the mistletoe Viscum album have been reported. We aimed to improve the
understanding of the epidemiology of both pathogens in our region. All H. annosum isolates found on
silver fir were typed as H. abietinum. H. abietinum was more frequently observed where cuttings had
targeted fir trees rather than other species. H. abietinum fruiting bodies were observed in the most
recently cut stumps. V. album was more abundant on more dominant fir trees, and in southern aspect
stands. The number of V. album colonies in the stand correlated (R2 = 0.40) with silver fir mortality.
Stands with a high level of V. album infection tended to have a smaller percentage of basal area in species
other than silver fir, and they tended to be located on more south-facing slopes. H. abietinum was
widespread in silver fir forests of the Pyrenees. Our data suggest that, in the Pyrenees, the observed
H. abietinum incidence may represent a combination of both primary and secondary spread of the
pathogen. Favouring mixed forests should be tested as a potential control method for V. album. The
correlation between silver fir mortality and V. album infection warrants further study, as the observed
tree mortality could have occurred due to other factors than V. album, such as drought damage.
This research was partially funded by the project RTA01-071-C3-1 of the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, by the Action S3 of the project SILVAPYR (I3A-1- 57-E) and by the scholarship 2006BE00500 to Jonàs Oliva from the DURSI-GENCAT |
