Susceptibility of cork oak (Quercus suber) to canker disease caused by Diplodia corticola: when time is of the essence

Cork is a renewable resource mainly produced in Mediterranean countries thanks to sustainable management of cork oak (Quercus suber) stands. The infection caused by the ascomycete fungus Diplodia corticola promotes the occurrence of cankers that reduce cork regeneration devaluating the stands. In this article, we tested the hypothesis that the trees are susceptible to the fungus during a limited period of time after debarking. Five mature cork oaks were subjected to eight reiterative inoculations of D. corticola (from the day of debarking to 35 days after) in an experimental plot located in Catalonia (North-Eastern Spain). The time until first symptom appearance as well as the severity of necrosis were assessed for each inoculation treatment. A generalized linear mixed model was fitted showing that the time of symptoms appearance varied among the assayed times of inoculation. In contrast to the foresters-assumed idea of high susceptibility immediately after debarking, earlier inoculations were neither related to higher severity nor to earlier occurrence of canker. This study represents the first approach to this etiological issue in cork oak canker pathosystem.