DIAGNOSTICS, EPIDEMIOLOGY, AND CONTROL OF EMERGING OOMYCETES AND PHYTOPATHOGENIC FUNGI

Climate warming constitutes a primary threat to the overall health of global forests. The impacts of climate on forest ecosystems are manifold and intricate, encompassing interplays affecting species physiology and phenology, the geographical distribution of vegetation, and biogeochemical cycles. Another consequence of climate change is the modification of ecosystem processes, e.g. the rate of litter decomposition and habitat suitability, changes that can ultimately pose a threat to the survival of species within their native ranges. All these alterations can impact forests directly or indirectly. In fact, they not only weaken trees but also enhance the reproductive success of pathogens: it has been proven that climate anomalies lead to an increased host susceptibility as well as heigthen pathogen virulence, survival rate and biomass (a high pathogen inoculum pressure lead to a higher disease rate on crops). The problem is further worsened by the introduction of alien, invasive pathogens. In fact, in such a complex scenario, with plants weakened and physiologically impaired, even microorganisms typically considered opportunistic, secondary pathogens turn into aggressive pathogens. The field investigations carried out in this study deal with some severe outbreaks and mortality events that are heavily impacting Fraxinus spp. formations in the Mediterranean area. Botryosphaeriaceae and Phytophthorae emerged as prominent species in the monitored sites, particularly the fungal pathogens Botryosphaeria dothidea, Neofusicoccum parvum, Diplodia fraxini and the oomycetes P. acerina, P. bilorbang, P. cinnamomi, P. hydropathica, P. lacustris, P. multivora, P. plurivora, P. polonica, P. pseudocryptogea, P. pseudosyringae, and P. syringae. Botryosphaeriaceae species played a significant role. The characteristic of these fungi is their opportunistic nature, seriously affecting plants when these undergo stress conditions. With ongoing global warming, climatic stressors have become more prominent and frequent, creating greater opportunities for Botryosphaeriaceae to thrive and contribute to the decline of numerous tree species. These pathogens have the capacity to spread across vast areas due to their natural dispersal abilities or can be inadvertently introduced through human activities, impacting the functioning of entire agroecosystems. The epidemic spread of these pathogens is exacerbated by the challenge of promptly identifying the true etiological agent, as various secondary or commensal microorganisms are often associated and complicate the efforts to