Cork oak decline in Catalonia: Symptoms and related fungi

Abstract

The cork oak decline in Catalonia is characterised by low vigour of the trees. Most frequent symptoms are trunk cankers caused by fungi, trunk wounds due to bark-stripping, dieback, reduced branch growth, epicormic shooting, defoliation, low leaf surface area, and chlorosis. No significant differences in decline index were detected among trees of different diameter classes, indicating an homogeneous incidence of the disease unrelated to plant age. Moreover, there is not a clear relationship between plot orientation and decline, although the greatest percentage of diseased trees was found in southwest-facing expositions. Fifty-four fungal taxa were recorded after field surveys carried out in several cork oak forests. Several pathogenic fungi were identified: Biscogniauxia mediterranea, Botryosphaeria stevensii, Phomopsis sp., in branch and trunk; Cystodendron dryophilum, Dendrophoma myriadea, Elsinoë quercus-ilicis and Lembosia quercina, in leaves; and Armillaria sp. and Phytophthora cinnamomi, in roots. Some of these fungal species were especially abundant in the aerial parts of declined trees, thus remarking the importance of cork oak pathogens as a contributory factor to the decline of this forest species.