INTERACTION OF CORAEBUS OAK BORERS AND OTHER COLEOPTERANS WITH ENTOMOPATHOGENIC FUNGI

The genus Quercus plays a crucial ecological and economic role throughout the Mediterranean, particularly in Sardinia, where oak species contribute to biodiversity, carbon storage, and the production of high-value products like cork. Wood-boring beetles, especially Coraebus species (Coleoptera: Buprestidae), are posing a rising threat to Quercus forests, causing considerable damage to oak trees. The two species present in Italy are Coraebus florentinus, which causes desiccation of branches and weakening of trees at high infestations, and Coraebus undatus, which attacks cork oak phellogen layer, reducing cork quality by creating galleries imbedded into the growing cork layer. C. undatus infestations were previously rare in Sardinia, but since 2016 there has been a significant increase in damaged cork planks, notably in the northeastern regions. This research investigated the distribution, seasonal dynamics, and phenology of C. undatus to evaluate its impact on Sardinian cork production and to identify infestation hotspots. Our monitoring data revealed concentrated infestations near industrial cork storage facilities, with attacks varying in frequency and intensity between 2011 and 2021. Emergence data showed that adult beetle activity peaked in mid to late July, emphasizing the importance of seasonal control. As part of an Integrated Pest Management (IPM) framework, this research also studied the efficacy of a newly isolated strain of the entomopathogenic fungus Beauveria bassiana as a biological control agent of Coraebus species. B. bassiana had significant lethal effects on larvae, pupae, and adult beetles under laboratory conditions. In comparative experiments with other commercially available strains, B. bassiana strain UNISS22 had distinct abilities to produce increased biomass and the ability to penetrate and spread within oak plants through the lymphatic system with characteristic endophytic behaviour. In addition, the whole genome of the new strain was sequenced and annotated, revealing its own gene profile with specific adaptations to insecticidal action and endophytism. These findings suggest B. bassiana as a viable biocontrol alternative to typical chemical pesticides, which is consistent with sustainable forestry and conservation goals in sensitive Mediterranean environments. In addition, this study examined the safety profile of B. bassiana by conducting experiments on the non-target species Chrysoperla lucasina, a widespread beneficial insect predator. The results showed that B. bassiana had no significant detrimental effects on C. lucasina survival or development, suggesting that it can be used safely in field conditions without reducing beneficial insect populations. However, further research on the potential impacts of B. bassiana on non-target species is required to properly establish the ecological safety of this fungusin broader applications in oak forests. Overall, this research provides important data for the development of sustainable pest management approaches in Mediterranean Quercus forests, with a focus on eco-sustainable solutions for effective forest conservation. Keywords: Quercus, Coraebus, Beauveria bassiana, Chrysoperla lucasina, biological control, Sardinia, non-target effects