Epidemiological aspects of Biscogniauxia mediterranea in declining cork oak forests in Sardinia (Italy).

Biscogniauxia mediterranea is one of the most important fungal pathogens involved in oak decline in the Mediterranean countries. In Sardinia, it has been found as endophyte in several tree and bush species of the Mediterranean maquis, and in particular on Quercus suber. This work reports the results of studies made in a declining cork oak forest in North Sardinia in order to establish the most favourable period and the optimal climatic conditions for the endophytic infections of B. mediterranea. This fungus is capable of infecting all of the plant organs throughout the whole year, although its highest frequencies were found in wetter winter periods. On the contrary, in spring and summer, when rainfall was limited or absent, the frequency was lower, even though the higher temperatures should have encouraged its growth. Indeed, the results of in vitro tests have shown that B. mediterranea is a mesophilic fungus, with marked eurythermal properties. It can grow even at temperatures near to 40°C and its ascospores can germinate at over 35°C.