Efficacy of oak endophytic fungi in controlling the infections of Botryosphaeria orticola in cork oak trees

Abstract: Botryosphaeria corticola is one of the most virulent pathogens involved in theaetiology of cork oak decline in Mediterranean countries. Its attacks are often subsequent to corkextraction and cause cankers, vascular necrosis and dieback in healthy or declining trees. Giventhe high susceptibility of cork oak to endophytic infections of B. corticola and the spread of thispathogen inside cork oak forests, suitable prevention measures, such as the application of biopesticides,should be taken in order to limit the damage. Therefore, research was carried out toevaluate in planta the bio-control activity of three oak endophytic fungi: Bionectria solani,Dictyochaeta parva and Trichoderma sp., selected for their marked antagonistic activity in vitroagainst B. corticola. The results showed that all three fungi were able, in all seasons, to colonizethe artificially damaged branch tissues of cork oak trees. Moreover, they significantly reducedboth the length of necrotic lesions and the incidence of branch mortality caused by B. corticola.The most active were Trichoderma sp. and chiefly B. solani. In the summer tests, B. solanireduced branch mortality by up to 100%. All branches inoculated only with the endophytic fungishowed no disease symptoms. These results suggested that the selected strains of B. solani andTrichoderma sp. are good candidates for developing new biological control formulations both innursery and in forest of cork oak against endophytic infections of B. corticola.