Forest Disease Affecting Pines in the Mediterranean Basin

Patterns of forest disease are shifting worldwide. Pine woodlands in the Mediterranean Basin deliver important functions that may be disturbed by pathogen damage. In this chapter, I briefly review general concepts with examples on how and why forest pathogens are affecting pines. The main threat is the one posed by invasive pathogens that continually enter Europe via trade of living plants. While this aspect is capturing most of the attention, more efforts should be placed on understanding the role of native pathogens that may become more aggressive under global warming. For instance, the role of pathogens driving plant-soil feedbacks in pine woodlands, as well as their role in benefitting from abiotic perturbations such as drought, fire, hail or wind, remains largely unexplored. Another risk may come from future land-use changes. Nowadays, pines cover extensive areas with minimal management. However, increasing demand for timber products may put pressure on these stands and increase the prevalence of roots rots, particularly those caused by Heterobasidion annosum. Simulation data show that stump infection by Heterobasidion can be prevented by spraying thinning stumps with spores of the biocontrol fungus Phlebiopsis gigantea. Promoting mixed stands can be beneficial too. Diplodia sapinea is another pathogen to consider given its association with drought and hail. Concerning exotics, the pine wood nematode still poses the highest risk, however new invaders such as Fusarium circinatum, Dothistroma spp. or H. irregulare require attention. Greater involvement of society and stakeholders in preventing disease is needed. Several general directions for research and some general management recommendations are provided.