Serious outbreak of Holm oak decline on Caprera Island, Italy


Abstract: Since 2009 a severe decline of Holm oak trees has been observed on Caprera Island,Italy. In summer 2010, a survey was carried out to study the pathogens involved in the aetiologyof this decline event. Fungal isolates obtained from living twigs and branches of affected trees,showing sunken necrotic bark lesions and blackish exudates were identified as Botryosphaeriacorticola on the basis of morphological features and internal transcribed spacer region (ITS1-5.8S-ITS2) rDNA sequence. The occurrence of signs and symptoms caused by this pathogen wasdetected in all Holm oak stands investigated. Moreover, Phytophthora cinnamomi and other rootinfectingPhytophthora spp. were isolated from Holm oak trees showing sudden death, severebranch dieback, bleeding cankers and root rot. The results obtained suggest that invasivepathogens such as Botryosphaeria and Phytophthora species, as well as causing sudden oakdeath, could also be important contributing factors in the onset of long-term oak decline and inthe loss of biodiversity of natural and semi-natural ecosystems in the Mediterranean area.

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